A Single Subject Design to Study the Effects
of a Mental Imagery Intervention on
Basketball Free Throw Perfomance
GEOFFREY ROSS STEWART
A thesis submitted to the
School of Physical and Health Education
in conformity with the requirements
for the degree of Master of Arts
Queen's University
Kingston, Ontario, Canada
April 1997
copyright Q GeoEey Ross Stewart, April 1997
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Abstract
The history of research into the effectiveness of mental imagery as a tool for
perfonname enbancement is one of equivocal results. Singlecase research designs have
been proposed as an effective method of scaminiog the efficacy of psychological
interventions (Hrycaiko & Martin, 1996; Shambrook & Bd, 1996; Wollman, 1986). This
thesis reports the findings ofa multiplebaseline across subjects investigation to determine
the effects of an imagery intervention on fkee throw shooting performance in basketball.
Seven male interuniversity players carried out twenty-four trials m which ten fiee throws
were scored for accuracy to determine performance scores. Performance outcome results
were also recorded to determine any change in actual scoring proficiency from baseline to
intervention. Subjects underwent a basketball-specific imagery training session and were
expected to perform the imagery routine for five minutes each day following this session.
Mental training log books were used to influence adherence to the mental imagery training
program (Bull, 1991). Performance scores were plotted and evaluated using visual
inspection and split-middle regression analysis to determine changes in trend from the
pre-intervention to the post-intervention phase. Results of each analysis are equivocal
with a definite improvement in performance displayed by two subjects using both aaalytic
techniques and by three subjects under the scrutiny of either split-middle analysis or visual
inspection. Although equivocal, the results of this investigation suggest that imagery may
be effective for some athletes and that the multiplebaseline design is appropriate for
investigating the individual and group effects of psychological intewentions. Six subjects
adhered to the imagery program and reported that they considered the program effdve.
The author would like to thank John Ahinson PhD. for his help, support and
enthusiasm towards this investigation. I can't begin to appreciate how dBicuit it must be
to
supervise masters studeats with vastly different areas of interest and remain accessible
and open to new thoughts and ideas. Whout John's guidance, particularly with respect to
methodological issues, this thesis would never have come into being. I would like to
thank Dave Paskevich PhD. for his insights and help in the technical preparation of this
document. I would like to thank Chris Shambrook and Steve Bull for steering me clear of
the pitMs of their earlier work and for providing the original manuscript of their
sinqle-case design, upon which this thesis is based. I would like to thank Scott Meeson,
Brad EIarm and the members of the 1996-97 Queea's Golden Gaels men's basketball team
for their participation in, and support for, this investigation and for putting up with a
would-be sport psychologist on the bench. Finally I would like to extend a heartfelt
thanks to my parents, BP Stewart and Shelagh Gordon, who have provided me with an
inexhaustible source of support and encouragement, not only during my time as a masters
student, but throughout my twenty-sixyears.
To the Gentlasen's Club of Kingston,..CReers!
Table of Contents
1. Abstract / i
2. Acknowledgements / ii
3. Table of Contents / iii
4. Figures / v
5. Introduction / 1
6. Review of Literature / 2
A Brief History of Imagery Theory / 2
The Single Subject Design / 1 1
The Creation of an Imagery Protocol / 10
Other Basketball Related Findings / 18
Replication / 19
7. Method / 22
Sample and Experimental Design / 22
instrumentation / 24
Treatment of Data / 25
8. Results 126
Visual Inspection / 26
Replication of Effects Across Subjects / 35
Split-Middle Analysis / 38
Post-Investigation Interviews / 46
9. Discussion / 48
General Discussion / 48
Limitations of the Present Investigation / 52
Recommendations for Future Research / 55
10. References / 57
Appendix A: Imagery Script for the Basketball Free Throw / 61
Appendix B: Performance Effects Under Various Criteria for Each
Subject / 62
Vita / 63
Figures
Figure
1
Trial results for subject one. Solid vertical line indicates the point of
imagery protocol introduction, dotted horizontal lines indicate pre and post
intervention means. Each data point represents a summed score of ten f?ee
throws. Breaks in the data line indicate practices missed. 127
2
Trial results for subject two. Solid vertical line indicates the point of
imagery protocol introduction, dotted horizontal lines indicate pre and post
intwention means. Each data point represents a summed score of ten fkee
throws. Breaks in the data line indicate practices missed. / 28
3
Trial results for subject three. Solid vertical line indicates the point of
imagery protocol introduction, dotted horizontal lines indicate pre and post
intervention means. Each data point represents a summed score of ten f?ee
throws. Breaks in the data line indicate practices missed / 29
4
Trial results for subject four. Solid vertical line indicates the point of
imagery protocol introduction, dotted horizontal lines indicate pre and post
intervention means. Each data point represents a summed score of ten free
throws. The data line ends abruptIy because of a season-ending injury to
subject four./ 30
5
Trial results for subject five. Solid vertical line indicates the point of
imagery protocol introduction, dotted horizontal lines indicate pre and post
intervention means. Each data point represents a summed score of ten free
throws. / 32
6
Trial results for subject six Solid vertical Line indicates the point of imagery
protocol introduction, dotted horizontal lines indicate pre and post
intervention means. Each data point represents a summed score of ten h e
throws. Breaks in the data line indicate practices missed. 133
7
Trial results for subject one. Solid vertical line indicates the point of
imagery protocol introduction, dotted horizontal Liws indicate pre and post
intervention means. Each data point represents a summed swre of ten Eee
throws. / 34
Graph displaying replication effects across subjects using a multiple-baseline
across individuals. Solid lines indicate staggered introduction of visual
imagery protocol.
Dotted lines indicate pre and post-intervention
paformance means for each individual. 1 37
Results for subject one using regression to indicate trends in
pre-intenmtion and post-intervention perfiormatlce. Solid vertical line
shows the point of imagery intwention Trend lines are also indicated for
each phase of data coUectiotl, / 38
Results for subject two using regression to indicate trends in
pre-intervention and post-intenention performance. Solid vertical line
shows the point of imagery intervention. Trend lines are also indicated for
each phase of data collection / 40
Results for subject three using regression to indicate trends in
pre-intenrention and post-Wention performance. Solid vertical line
shows the point of imagery intervention Trend lines are dso indicated for
each phase of data coUection. 141
Results for subject four using regression to indicate trends in
pre-intervention and post-intesvention performance. Solid vertical line
shows the point of imagery intemention. Trend lines are also indicated for
each phase of data coUectioa / 42
Results for subject five using regression to indicate trends in
pre-intervention and post-intervention performance. Solid vertical line
shows the point of imagery intervention. Trend lines are also indicated for
each phase of data collectioa 143
Results for subject six using regression to indicate trends in pre-intervention
and post-intervention perfonnaace. Solid vertical he shows the point of
imagery intervention. Trend lines are also indicated for each phase of data
collection. / 44
Results for subject seven using regression to indicate trends in
pre-intervention and post-intenrention performaace. SOU vertical line
shows the point of imagery intervention. Trend lines are also indicated for
each phase of data collection. 1 45
Introduction
As the field of applied sport psychology grows and more practitioners begin to
work with athletes in an effort to improve athletic performance, it becomes increasingly
important to evaluate the e f f i e n e s s of various mental skills interventions (Brewer &
Shillinglaw, 1992; Shambrook & Bull, 1996). Although sport psychology professionals,
coaches and athletes recognize the importance of mental skills training (Ravina, 1988),
some reviews have indicated the effectiveness of accepted techniques to be over-estimated
or exaggerated (FeItz & Landers, 1983; Greenspa. & Feltz, 1989; Kirschenbaum &
Wittrock, 1990).
In order for sport psychology professionals to provide effective
interventions to their athletic clients, it is important to determine which iutewentions are
effective for which athletes, given individual sets of restrictions and circumstances.
Greeuspan and Feltz (1989) suggest the use of cognitive restructuring strategies for
enhancing the performance of athletes in competitive situations. In their review of mental
training literature Greenspan and Feltz found cognitive restructuring intewentions to be
generally superior to either relaxation or behavioural interventions with regards to
performance enhancement e f f i s for athletes in competitive situations. The mental skill
of imagery, or visualization, has gained some empirical support (Keams & Cros1992; Shambrook & Bull, 1996) and represents a cognitive restructuring, behavioural
intervention which may provide performance enhancement benefits for novice and elite
subjects. Imagery is the use of all senses to create or recreate an experience in the mind.
It may be used to correct flaws in s l d execution, mentally create s u c c e s pdonnance
~
outcomes or practice without apparent physical exertion (Vealey & Walter, 1993).
Images are not simply passive reproductions of situations and events, they are active,
dynamic and subject to manipulation Despite the wealth of research on the mental image
there is still more to be lmown about the power ofthe mind's eye. There is a need to
determine the best way to guide the creation of mental images so that applied sports
psychology practitioners may take fidl advantage of what is presumed to be a powerfbl
too[,
Literature Review
A Brief W o r g of Imagery Thcoy
The mental imagery literature has generated two major schools of thought on why
mental imagery may benefit performance: psychoneuromuscular theory and symbolic
learuing theory (Murphy, 1994; V d e y & Walter, 1993).
A brief review of the
fundamental concepts of each theory is important in order to understand the integrative
framework which makes up the foundation of the present paper, that is, Lang's (1979)
bio-informational theory, which suggests that components of both theories serve to
explain the mechanisms behind imagery as a tool for performance enhancement.
Psychoneuromudar theory (Carpenter, 1894; Jacobson, 1931) suggests that
during the mental imagery process muscle groups involved in the imaginal material
become slightly activated. This activation is not sufficient to contract the muscle in any
visually meanin@ way, however, it does provide kinaesthetic feedback which may be
used to make adjustments to skill in fbture physical trials (Murphy & Jowdy, 1992). It is
unclear in the research whether the activation of musculature is completely localized and
specific to the muscles used in the imagery program (Mwphy & Jowdy, 1992). There is
some suggestion that increased activation is simply an indication of generalized arousal
and is not indicative of imagioal movement (Murphy & Jowdy, 1992). For the time being,
the results of studies which examine electromyographic data during mental imagery
routines are ecpivocaI, with no meaningsll Liak between signals in the premotor cortex,
activation of the peripheral musculature and the later execution of physical skins (Murphy,
1994; Murphy & Jowdy, 1992)
The symbolic learning theory (Sackett, 1934) suggests that mental imagery allows
physical skill execution to be improved because it allows individuals to prepare for and
plan performance (Murphy& Jowdy, 1992; Vealey & Walter, 1993). Individuals have,
within their central nervous system, a code or blueprint for the execution of physical skills
which can be reduced to essential symbolic componests. Mental imagery serves to
familiarize and integrate these symbolic components into the skill execution plan of the
performer. The more fimih the components are to an individual, the more automatic
their execution becomes. The symbolic learning theory suggests that imagery may help to
shape skills which are not readily executable by a performer because of the ability to
transform symbolic components. It is importanf to note that the symbolic learning
hypothesis does not imply any activation of peripheral musculature (Murphy & Jowdy,
1992).
Psychophysiology provides us with evidence that imaginal activities are
accompanied by efferent outflow. In his integrative bio-informational theory of imagery,
Lang (1979) proposes that visual images are finite, organized, propositional structures
which include a motor prognun. Further, he asserts that visual images are prototypes of
"overt behavioural expressiont' (p. 495) which are stored in long term memory. When
individuals engage in mental imagery, they activate stimulus and response propositions.
The stimulus proposition, equivalent to the blueprint ofthe symbolic learning hypothesis,
describes the content of the image to an individual while the response proposition
describes responses to given stimuli in the h a g i d situation The bio-informational
theory of imagery suggests that the focus during imagery is the modification of response
propostions to represent perfect control and execution of the skill. In order to eff&eIy
modify response propositions, it is important that any imagery protocol includes
behavioural, psychological and physiological responses to the imaginal situation, as well as
the physical wnditions of the situation itself(Vealey & Walter, 1993).
During motor skill imaging, efferent flow triggers neuromuscular responses which
are similar, ifnot identical, to the pattern of the skill. The exception here is the magnitude
of the neuromuscular activity.
Although there is an increase in muscular rigidity
accompanying visualization of a strength-intensive motor task, the actid increase in
neuromuscular firing is substantially less than that observed for actual physical
performance of the task It is important, however, to recognize that neuromuscular
activity does increase during imaginaI activity, therefore, there is a pattern of activation
which may mimic physical performance aud allows the athlete to practice a given skill
without apparent physical effort (Lang, 1979).
An investigation by Hecker and Kaczor (1988) demonstrated the relationship
between fbiliar stimuli (i.e. those situations for which subjects presumably possessed a
cognitive prototype for overt response) and increases
in physiological response, as
measured by increases in mean heart rate, during imagery. Subjects were presented with
scenes designed to elicit cardiac response based on their intensity and M a r i t y to the
subject. Those images which were spe&c to an individual's elicited sisnificmt increases
in heart rate while an UIlfamiliar scene, associated with fear, did not. These results suggest
that the use of fiuniliar images, in particular response information, will increase the
physiological response of the body during imaging- This increase in physiological arousal
may make the imagery protocol more effective for experts, rather than novices, for whom
familiar response propositions may not be readily available. Iowdy and Harris (1990)
suggest that experience, rather than increased physiotogical arousal itsex may be critical
when examining imagery intervention efiicacy. High and low skilled college jugglers
showed significant increases in muscular activity while imaging, however, there were no
sisnificant differences in muscular activity between the two groups. The lack of significant
differences in physiological activation between the groups may lead to the conclusion that
prototypes for overt behaviod responses may help mediate the effectiveness of imaginal
activity by allowing the body to interpret increases in arousal within the parameters of the
prototype. Efferent flow must not simply exist, it must be spec& to the action targeted
for improvement. It is important to note that no measwes of performance were taken for
either group in this study, therefore, it is difficult to substantiate this conclusion as one is
unsure whether the imagery protocol employed would have had a performance enhancing
effect on either or both groups, and what the magaitude of that dfea might be.
The study of mental imagery and its effect on physical performance is certainly not
a new one, however, the history of mental imagery research suggests that there are areas
which remain unexplored and undefined, particularly with respect to the elite level
performer (Hrycaiko & Martin, 1996). h order to proceed with any investigation of
mental skills efficacy, it is important to consider which doors have already been opead
and, by virtue of past research, have closed upon themselves.
Early investigations of the &cacy
of imagery protocols in enhancing physical
sport pefformance focused on imagery as an alternative to physical practice (Hail,
Schmidt, Durand, & Buckoh, 1994). Ryan and Simons (1982) assigned highway patrol
officers to one ofsix practice conditions in the learning of a novel balancing task Practice
conditions included physical practice, a variety of mental imagery conditions and a no
practice, control group.
The results of this study are typical of early imagery
investigations; physical practice was better than mental practice which, in
was better
than no practice at all in enhancing balancing task performance. This investigation also
indicated a difference in the strength of image and the subsequent performance effect;
those officers who reported strong visual imagery were superior pdorrners to those who
reported weak visual imagery. It is important to note that this investigation contains a
number of typical elements of early imagery research, which have been criticized by some
authors (Hrycaiko & Martin, 1996; WoUman, 1986); the use of novice subjects in a novel
task indicates little about the effect of imagery for expert performers, and physical practice
is considered separately fiom mental imagery despite indications that imagery may
facilitate learning aad performance.
Epstein (1980) considered the use of internal and external imaginal styles in a
dart-throwing task for male and f d e college undergraduates. She found no daference
in mean accuracy between the imaginal styles and a control group &a undergoing a
single session imagery intervention. Epstein does note, however, that variability of
improvement significantly dSered across conditions for females. This difference in
improvement Epstien attniutes to the effkcts of additional physical practice for the less
experienced female students. In this investigation, additional physical practice did not
benefit the more experienced males. Once again, the effbcts of physical practice have
obscured the results for novice perfioxmers despite the apparent minhhtion of physical
practice effects in the experimental design: the singIe session imagery intewention and
restriction of trials to a minimum The group design employed may also mask individual
performance effects ofthe imagery protocol.
An investigation conducted on male termis players (Noei, 1980) is significant in a
historical context because it distinguishes between skill levels when considering the
effectiveness of an imagery protocol.
Egh ability performers were able to achieve
marginally significant improvements in performance, as measured by first serve
percentage, after visuahtion training, whereas low ability performers declined in
performance.
Noel suggests that the protocol employed was more conducive to
experienced players as the imagery was patterned on an "advanced service motion" @.
225). Differences between skill levels may be a ~ i u t e d according
,
to Lang's (1979)
theory, to the lack of appropriate response propositions for novices which inhibits the
elicitation of appropriate efferent outflow.
Additionally, Noel uses imagery as a
supplement to, as opposed to a substitute for, physical practice, which may account for
some individual improvement. Weinberg, Seabourne and Jackson (1981) used imagery in
combination with physical practice to enhance sparring performance in collegiate
artists of varying levels.
Although sparring performance was significantly better for
subjects in the imagery group, the investigators indicate no significant differences between
the imagery group, a relaxation group and a control group in the paformaace of skill and
combinations. In this iavestigation, there was a focus on arousal and appropriate response
to external cues, therefore, the lack of Werences between groups on the skills and
combinations may be atlrriutab1e to the broad range of optimal arousal for simple skills. It
is conceivable that all subjects could have been performing within this broad range,
regardless of their use of mental skills.
Woolfolk, Murphy, Gottesfed and Aitken (1985) distinguish between positive aad
negative performance and outcome imagery in an investigation with male college students
on a putting task The results of this study indicate that negative performance imagery,
imagery which incorporates imperfect physical skill execution, and negative outcome
imagexy, imagery which includes failure to achieve the goal of the skill, have the potential
to degrade skill performance. Woolfolk et al. did not find an enhancement effect for the
positive performaace or outcome images, therefore, the importance of developing positive
imagery for atbIetic performance may derive fiom the image's ability to counteract
negative thinking, rather than its reintbrcement of appropriate response patterns. It is
important to remember that novices may not possess appropriate prototypes of physical
behaviour and are therefore unable to take advantage of neuromuscular stimulation
associated with imaging. This notion that novices do not possess appropriate prototypes
is further supported by Barr and Hall (1992) in their examination of the imagery
characteristics of rowers of various skill levels. They found that novice rowers saw
themselves performing incorrectly during imaging to a greater extent than elite rowers.
Elite rowers reported feeling more sensations associated with correct skill execution
including the movement of the blade, boat swing and m d a f movemeat than did the
novices. As well, this investigation distinguishes between the use of primarily internal
kinaesthetic imagery by experts md primarily external visual imagery by novices.
There has been some interest in the reduction of external stimuli with subjects
engaged in an imagery protocol to determine whether @ormarice enhancement effects of
imagery may be increased by providing the opportunity for a higher level of concentration
during imaginal activity. This reductionist approach is important because it may lead to
more effective methods of skill imaging for elite level athletes in the future. Lee and
Hewitt (1987) found an increase in gymnastic performance for forty-four novice and
intermediate females when imagery was performed in a flotation tank.'
Suedfeld and
Bruno (1990) reported a significant improvement in fiee throw performance when an
audiotaped, multi-sensory imagery protocol was combined with a restricted environmental
stimulus technique which involved a flotation tank and the absence of external light and
sound during imaging . It is important to note that relatively novice subjects were used in
these studies, as a result there is much more room for improvement in a physical skill than
there would be for experienced performers. An investigation of the efficacy of restricted
environmental stimulus techniques, particularly flotation tank, with experienced subjects
1
The flotation tank allows efFortless majntenance of a supine psition in a controlled environment
by increasingthe density of water through bromine salt satmatiom The water, air and skin temperatures
are kept at 93.5 degrees Farenheit to m i n h b sensations associated with temperature change. As well,
the flotation taak apparatus is generally equipped with a stereo system in order to provide an audio
presentation of the imagery protocol (L,ee & Rewitt. 1987)-
may be warranted to determine the performance enhancement possiiilities of &.is
technique as a possible mediator ofimagery quality and effkctiveness.
In examiniag the body of research, one finds that there are some general
characteristics which are associated with success£bl mental imagery intmentions. Hall et
al. (1994) identify the following hctors as being related to successll mental practice: (a)
the cognitive demands of the skill are relatively low, (b) imagey instructions are clear and
multi-sensory; (c) skilled performers are more likely to benefit &om imagery especially
when used for strategy development; and (d) imagery which is positive in nature may have
a greater effkct than negative imagery.
The Creation of an Imagery Protocol
In order for a mental imagery intervention to have a potential performance
enhancing e f f i the sport psychology researcher must fobw a number of guidelines in
the creation of the imagery script (Albinson & Bull, 1988; Bull, 1991; Bull, AIbinson, &
Shambrook 1996; Orlick, 1990; Vealey & Walter, 1993). The imagery script should
include a period of progressive relaxation which wiU help the athlete to focus on the
creation of the image and mediate the arousal level experienced while imaging (Orlick,
1990). This period of relaxation will also help the atblete to concentrate on the skill of
imaging (Orlick, 1990). It is important for the imagery script to include descriptors which
will elicit appropriate sensory experience across the range of m
s pertinent to both
learning style and skiU execution There should be linkeages between visual, auditory and
kinaesthetic images within the context of the skill which will help to reinforce the
mind-muscle co~ectionsrequired to correctly execute physical skills (Albinson & Bull,
1988; Bull, A l b b n , & Shambrook. 1996). If necessary, the athlete may move individual
body parts in order to reinforce or refiesh the kinaesthetic sense within their bodies
(Orlick, 1990). From Lags (1979) bio-informational perspective, the scipt must include
stimulus and response propostions; the stitndus propositions are designed to activate It
is generally desireable during imagay routines which focus on skill performaace for the
athlete to view the performance through their own eyes (i-e- internal perspective imagery)
therefore imagery scripts should be created which encourage internal perspective imaging
through an emphasis on what is being seen, heard and felt during skill execution (Albinson
&
Bull, 1988). At the conclusion of the imagery routine there should be a period of
returning to an alert, yet relaxed, state (Alb'mn & Bull, 1988). For an example of an
imagery script for the basketball &ee throw please refa to Appendk A
The Single-Subject Design
Traditionally, wduations of the effectiveness of mental skills intementious have
followed the medical model of research (Hrycaiko & Martia, 1996). In this research
paradigm there is a random assignation of subjects to one of three conditions: i) a physical
practice condition, ii) an imagery condition which may or may not be combined with
physical practice and iii) a control condition. The foundations of the medical model are:
that subjects are selected at random from a population and that the dependent variable is
nomaily distn'buted throughout the population mys, 1994). While these conditions may
be met in a study of the effects of a mental skills intervention on a novice population, the
applied sport psychology researcher tends to draw fiom an inherently non-random subject
pool, that of experienced athletes, often with similar needs (Hrycaiko & Martin, 1996).
As well, the use of intercollegiate athletes fiom the academic institution of the researcher
further decreases the degree to which subjects are randody selected. If the researcher is
to make determinations about the efficacy of a given psychological intervention, it is
important that test subjects come f?om the pod for whom the intervention is intended.
There is a need to know more than a simple relationsbip between mental imagery and
performance, we need to know for which individuals, under which conditions does mental
imagery improve performance (Kkschenbaum & Wittrock, 1990; Wollmaa, 1986)?
One
method of rectifyiDg the non-random selectioa of subjects in applied sport psychology
research is to employ a single-subject design (Bryan, 1987; Hrycaiko & Martin, 1996;
Wollmaq 1986).
The single-subject design typically utilizes three to five subjects to
determine whether the implementation of an intervention strategy leads to observable
changes in the dependent variable over time (Janosky, Al-Shbod, & PeIlitieri, 1995). This
design eliminates the need to draw a random sample &om the population because the
researcher describes only what is occurring for a given group of individuals and
circumstances. "Singlesubject methodology may...be better suited than group designs in
working with skilled athietes...who will not improve much fiom pretraining level"
(Wohnan, 1986, p. 136).
Hrycaiko and Mamn (1996) cite several additional reasons for the use of
single-subject designs in applied sport psychology research. First of all, single subject
designs involve repeated measures of athletic behaviour for the same subject across
several competitions or practices, therefore, they provide information on individual
response to intervention strategies over a given timehe.
They also suggest that
single-subject designs are more effective for studying expert athletic popuIations where
few potential subjects exist since these designs typically include three to five subjects with
similar psychological needs. All subjects in the single-subject design eventuaUy receive the
intervention, "an applied researcher is not fkced with the resistance of coaches and athletes
to participation in a no-treatment control group" @. 184). F ' d y , there is an emphasis on
social validation in singfeesubject designs not present in traditional, positivistic, research
paradigms. This assessment of how subjects feel about the methods used to influence
performance may provide valuable information from an appIied sport psychology
perspective.
A typical single-subjest design is the multipie-baseline across subjects approach.
"In the multiple baseline design, evidence that a particular intenentiom has produced a
change in behaviour is obtained by demonstrating that behaviour change occurs if; and
only
it: intervention is applied" (Bryan, 1987, p. 286). The multiple-baseline
across
subjects design is used in applied sport psychology research to examine the efficacy of
mental skills training in various subjects. The intervention is applied to each subject at a
different point on the study timeline. This allows the researcher to account for changes in
the dependent variable specifically related to the intervention, H there is an immediate
-
effect - generally accepted to be within two data points of the implementation on the
dependent variable after the introduction of an intmreation and this effect is obsewed
across subjects then there is support for a cause and && relationship between
intervention and performance.
The requiremerit ofthe multiple baseline approach is an independence of subjects,
settings or behaviours. In other words, an intervention with one behaviouq in one setting,
with one subject will not produce changes in untreated behaviours or subjects. One of the
challenges to the researcher is controhg contamination across subjects, partidarty if
subjects come &om the same team. There is a need for an agreement between the
researcher and subject for silence, in order to prevent the alteration of routine on the part
of subjects not yet exposed to the intewention
The popularity of muitipte baseline designs in general psychological research has
increased as a a c t i o n of their utility for examining special populations where a paucity of
subjects limits the amount of statistical power possessed by the researcher. It has been
suggested that behavioural and phannaco10gical treatments for phobics, particularly
children, should be studied using singIe subject, multiplebaseliw approach (OUendick,
1995; Ollendics Hagopian, & Huntzinger, 1991). This protocol is effective given the
generally small population fiom which subjects may be drawn As we& all individuals for
whom the therapy is designed will receive it.
This avoids the ethical conflict of
withholding behavioual therapy fiom individuals who may benefit from it.
Multiple basehe designs have also been employed to study cognitive interventions
in sport. Again the scarcity of subjects, in this case elite level competitors, makes the
multiple baseline design ideal for the examination of internention efficacy. Performance
increases which may have been masked by group effects or declared statistically
insignificant under the scrutiny of parametric testing7 have become evident through the
multiple baseline approach in figure skating (Hume7 Martin, Gonzalez, Cracklen, &
Genthon, 1985), gymnastics (Wolko, Hiycaiko, & Mirth, 1993) and soccer (Ziegler,
1994). It is important here to make mention of the diftkrences between practical and
significant differences in improvement in upper-level competitive sport. Although unlikeiy
to prove statistically significant, a difference of a single percentage point may distinguish
champion tkom competitor.
The single case, multipIebaseline across subjects design bas previously been used
to examine fiee throw and field goal shooting in basketball after the introduction of
imagery training (Kearns & Crossman, 1992; Lemer, Ostrow, Yura, & Etzel, 1996;
Shambrook & Bull, 1996; Templin & Vernacchia, 1999, cognitive-behaviod training
(Hamilton & Fremouw, 1985), and in a mental skills package which included mental
rehearsal, relaxation and seKtalk (Kendall, Hiycaiko, MaRin & KmdaU, 1990). Templin
and Vernacchia (1995) utilized the multiple-basehe across subjects design to evaluate the
impact of a music and video-enhanced imagery program on field goal proficiency for five
male intercollegiate basketball players.
Although they reported no significant
improvements, it is important to recognize that the use of a single subject design allows
the researcher to examine individual changes in performance. Despite the lack of
statistically significant differences, there was ewidence that subjects' field goal
performances increased to some d e p . From an applied perspective, any change which
may be attributed to an intervention may prove usefbl regardless of statistical significance.
Shambrook and Bull (1996) reported similar findings for an imagery intervention
designed to iduence fiee throw shooting performance in four female intercollegiate
basketball players.
In this study, only one individual demonstrated consistent
improvement, however if the traditional expeximental paradim had been used to examine
the efficacy of this imagery intervention, it is likely the improvement of one
individual
would have been lost during group analysis. Again, the importance of the single subject
design is demonstrated &om an applied sport psychology perspective-
Lemer et al. (1996) report eqybocaf findings for the effect of an imagery
intewention on the h e throw shooting perfbrmance of f d e intercollegiate basketball
players.
The imagery protocol alone produced a decline in performance during a
post-inteweution period for four players. In combination with a goal-setting protocol, one
athlete demonstrated post-intervention improvement. It is important to note that this
study emptoyed an A-B-A design and during the second baseline phase, perfonnance
means were higher for alI four athletes in the imagery only group suggesting a period of
latency prior to a improvement in performance. In this case, the athletes were only able to
use the recorded imagery protocol prior to he-throw shooting sessions. As well, the
imagery protocol was performance-centered, as opposed to, outwme-centered, therefore,
subjects may have attended to the physical requirements of skill execution in the
intervention phase, where they had not done so in the initid baseline phase. In this case
the athletes may have interfered with ingrained patterns of fie-throw execution,
essentially "out-tbiakingl' themselves.
Keam aad Crossman (1992) report moderate improvements in fiee throw
performance for three male varsity basketball players. In this investigation, the players
"exhibited neither...abnormally high or low fke throw shooting ability" (p. 1245) prior to
the introduction ofthe mental imagery protocol. One of the strengths of this study is its
exceptionally long baseline phase which provided relatively stable data for comparison
with post-intewention results. The study relies on visual inspection to determine the
efficacy of the imagery intenention, which may be effective given the length of the
baseline phase, however, strict reliance on visual inspection may have prevented the
discovery of pre and post-intervention trends with some predictive value. At issue in this
study, as well, are the pre-intenention perfbnnance levels ofthe subjects involved. None
of the subjects met the investigators' criteria b r highly skilled performance, an eighty
percent or better success rate, prior to intervention therefore there is some question
whether or not these subjects can be considered expert or simply experienced basketball
players.
Kendall, et al. (1990) demonstrated the effecfiveness of a mental skills intervention
package, including imagery reheard, relaxation and &-talk,
on defensive skill
performance in basketball. Videotapes of competitive performance were analysed for
correct or incorrect execution of the defensive skill on the part of four female
intercollegiate basketball players.
While the combination of interventions makes it
impossible to attribute impmvement to mental rehearsal alone, this study encourages the
use of single-case designs to evaluate the effectiveness of m e n d skills interventions.
Finally, Hamilton and Fremouw (1985) used a multiple-baseline across subjects
design to examine the effect of cognitive-behaviowal training on game f?ee throw
pefonnance. Although the authors indicated large increases in free throw percentage
post-intervention, they admitted their study was Iimited by the use of retrospective
seKreport data to evaluate cognitive restructuring in their subjects. As well, there are
I a ~ feluctuations m pre-intervention data, which may be expected when considering game
performance, these fluctuations make interpreting post-intewention data difficult because
of the instability of the baseheOther B u k e t b d Related Finding
Research by Hall and Edheyer (1983) suggests that visuo-motor behaviour
rehearsal, a technique which combines an initial period of relaxation and modelled visual
imagery of performance under s t n s s l l conditions, is more effective than visual imagery
alone. Female intercollegiate basketball players reported kinaesthetic sensations during
the execution of a mental imagery routine designed to improve free throw performance.
This report lends support to the need to elicit efferent outflow via response propositions,
as suggested by Lang (1979), as the two athletes with the greatest pediormance increases
reported muscular movement every time they engaged in the mental imagery protocol.
Meyers and Schleser (1980) report significant increases in points scored per game,
shooting percentage and percentage of total team s c o ~ gfor an individual intercollegiate
basketball player in an uncontrolled case study. The player was directed through a
relaxation exercise and asked to imagine and report on a variety of game situations. There
is a decrease in free throw shooting performance indicated for this athlete, however, the
investigators indicate fiee throw performance was not a targeted behaviour for
improvement and suggest that cognitive interventions may not generalize across
behaviours. It is important, in Light of this conclusion, that the practitioner of mental skills
training considers only those skills tatgeted for enhancement when determining the
efficacy of a mental imagery intervention.
Replication
The present study exists, to a certain extent, as a reproduction of Sbambrook and
BuPs (1996) work It is important to recognize the need for applied sport psychology
researchers to replicate and extend published results in order to broaden the base of
knowledge with respect to the efficacy of accepted mentd skills techniques
~ s c h e n b a u m& Wittrock, 1990). While it is important to kmw that a given
intervention improves sport perfonname, we also want to know for which individuals is
the intervention effective and under what conditions?
Previous investigators have employed designs which examine performance outside
of the athletes' normal practice or game setting (Hall & Erffineyer, 1983; Shambrook &
Bull, 1996). It is suggested that this creates an artificial situation in which the focus shifts
from game-related skill demands to the skill of foul shooting itself Exclusive focus on
task demands pertaining to an investisation may lead to a performance decrement as the
task is taken away fiom the context of practice or competition. The Hawthorne effect
suggests that subjects who know they are part of an experiment may change patterns of
behaviour because they are singled out for treatment. As a result of this behaviomal
change, one is unable to attribute outcome to the specific intervention provided (Ness
Evans, 1992).
The present study rectifies this problem by studying flee throw
performance as a normal process within the course of structured practice.
.
There is a clear trend towards the use of f d e subjects in previous studies of
mental slrills training and free throw performance (Hall & E h e y e r , 1983; Kendall et al.,
1990; Lerner et al., 1996; Shambrook & Bull, 1996). As well, in Shambrook and B d t s
study, although the subjects were "four [British] female team basketball players...varsity
level with at least five years playing acperiencen (1996, p. 30), they did not possess
pre-intetvention foul shooting skill levels which would suggest an expert population; initial
proficiency levels for three of the four subjects were less than fifty-fie per cent. A low
initial performance level for these subjects forces the present investigator to label these
subjects novices. Despite their lwels of previous playing experience these athletes would
seem more likely to benefit from additional physical practice, rather than cognitive
intervention. From this study we can learn little about the effect of mental imagery on the
foul shooting performance of basketball players who have reached apparent performance
ceilings at performance levels of seventy-five per cent or better. If there is indeed a need
to discriminate the efficacy of mental skills training for Merent populations, it is
important that we consider differences in culture, experience and gender when applying
sport psychology techniques.
Bull (1991) suggests that subjects who develop individualized mental skills training
programs are more likely to adhere to the mental skills regimen than subjects following a
generalized routine. There is evidence of individuahtio~~
in the music and video highlight
choices made by subjects in Templin and Vernacchids (1995) study of basketball field goal
shooting performance, however, there remeins a lack of research into the forms which
individuaIized programs may take (Wollmaa, 1986). While these packages are designed to
address specific individual issues, it would be interesting to determine whether patterns
emerge in imagery rehearsal routines depending on the sport demands of each subject.
For example, are starters more likely to include competitive state imagery (Le. imagery
which includes components of the competitive situation as opposed to the practice
situation)in their mental h a g a y routines than non-starters?
The present study is designed to examine the &ectiveness of an imagery rehearsal
intervention on basketball fiee throw shooting performance with experienced performers.
The single-case research design was employed to d o w the researcher to evaluate the
impact of the imagery rehearsal htwention on each subject's performance &om an
objective and subjective point of view.
Method
Sim@e 0 t d EkperirnenfaIDesign
Subjects were seven2male team basketball players, (mean age = 20.7 years,
=
LO), partkipatins at the varsity level in the Ontario University Athletic Association. All
subjects had at least six years of previous playing experience (mean playing experience =
10 years,
= 2.2).
Only one subject had received previous, formal, mental
skills
traininsS The present investigation exceeded the recommended number of subjects for a
multiple baseline design for two reasons; it would have been unethical to offer a
potentially performaace enhancing intenrention to an entire team aad subsequently deny
some members ofrhe team access; as well, subjects could be paired to examine the effkcts,
if any, of daferrntial adherence to the imagery program. Subjects underwent a minimum
of ten weeks of physical practice prior to the introduction of the mental imagery protocol.
The large amount of previous physical practice, years of experience and high
pre-intervention performance lwel demonstrated by these subjects suggested that the
investigator could reasonably attniute changes in performance to intervention rather than
physical practice effects.
During the seven week investigation period n o d team activity took place. In
this case, normal team activity involved an average of three-and-a-half practices and two
games per week. In order to eliminate artificiality and, to some degree, the Hawthorne
effect, from the investigation, free throws attempted during the regular course of practice
were used to evaluate individual proficiency. Specifically, the first ten fkee throws
-
2
-
-
Eleven indisicluals initially indicated itrterest in the present study. One potential subject mas
removed h
r
n the -ty
team for disciplinary reasons. Three other team members failed to achieve the
criteria for a baseline at any time during the investigation period.
attempted by each team member were scored on a &point s d e . The mivdmum score an
-
individual codd receive for each shot was five and the minimum zero (clean basket 5,
-
-
-
-
rim and in 4, backboard and in 3, rim and out 2, backboard and out 1, complete miss
-0
This scoring system is consistent with previous fiee throw proficiency investisations
(Hardy & Partin, 1991; Shambrook & Bull, 1996). In order to evaluate several athletes at
one time, two video cameras were used to record the fiee throw shooting component of
practice. Individuals whose performances were recorded on videotape had proficiency
scores determined by the investigator post-practice. The fke throw was selected as the
skill for intervention based on previous literature and its closed, sespaced nature.
In order to establish when the athletes were performing at a consistent level, a
baseline was considered to exist when performance outcome fell within a three point range
in five consecutive trials. This protocol is similar to that employed by Lerner et al. (1996)
with female intercollegiate players. Subjects one and two achieved the basehe criteria
after five trials; subjects three, four and five began the intervention after eight trials;
subjects six aad swen began the intervention after thirteen trials. There were a minimum
of two subjests per introduction in order to study adherence effects.
The intervention procedure consisted of a standardized thirty minute codtation
with the author
- who
had previous mental skills traiaiag experience with athletes in
football and track and field. The consultation consisted of an imagery session, completion
of a questionnaire to assess the athlete's initial mental rehearsal skill level and the
presentation of an audio tape containing the imagery dialogue, and a diary in which to
record any imagery sessions. At this time, subjects were also encouraged to clarify any
concerns they may have had with the imagery protocol. In accordance with Sbambrook
and Bull (1996) and Bull (1991) the athletes were encouraged to spend at least five
minutes per day practising and i n d i v i d u ~ s the mental rehearsal routine.
Individrlalization of the routine was to occur gradually as the athletes became more
familiar with the mental rehearsal process.
Bull (1991) recommends that a w e s
individllalize imagery training routines in order to promote adherence to mental skins
trainingflt~numentufion
An imagery rehearsal dialogue was created for the skill of basketball free throw
shooting (Appendix A). It was originally hoped that the dialogue used in the Shambrook
and Bull (1996) study could be utilized, however, this script was unavailabte. The imagery
rehearsal dialogue consisted of a short period of relaxation followed by a set of stimulus
and response propositious consistent with Lang's Bio-informational Theory (1979); a
technique suggested by the results of research by Hecker and Kaczor (1988).
It was
important that each subject feel emotionally and personally involved in the imagery
process to elicit appropriate efferent outflow and thereby increase the probability that
correct motor program selection will occur when executing the free throw shot.
To encourage adherence to the imagery rehearsal routine, the subjects were asked
to seKmonitor and record practice sessions in a provided imagery diary. When each
subject completed the study, they were interviewed to determine whether the subject felt
the imagery routine was effective in improving their f?ee throw shooting consistency and
whether they would use the iuqery routine in the future or in different settings. An
25
interview was also conducted with the basketball coach to determine his impressions of
each subject's fkee throw shooting proficiency over the course ofthe study.
Treatment of Data
Individual shot proficiency scores were summed each session in order to give each
athlete a total session score out of fXky. The scores for each individual were plotted
against time to allow for visual detembtion of trends in performance fouowiag the
intervention.
Mean performance was calculated for the pre-intervention and
post-intervention phase to allow for a numeric comparison between phases. The criteria
for v i d inspection of multiple baseline data suggested by Hrycaiko and Mamn (1996)
was used to determine whether an &kt occurred as the result of intervention. These
criteria include: the immediacy of the effect following the introduction ofthe intervention,
the number of overlapping data points and data points below the pre-intervention mean,
the size ofthe effect and the number oftimes the effect was observed across subjects. As
well, a comparison of mean performance outcomes pre- and post-intenation was done to
eliminate the reliance on proficiency increases, as measured on the previously mentioned
five point scale, for determining intervention effectiveness.
Shambrook and Bull (1996) employ the split-midde technique to aid in the
determination of intervention efficacy.
The splitmiddle analysis involves the
determination of regression lines for the pre and post-intervention data sets.
The
regression equation allows for a visual plot of data which indicates performance trend over
a given period of time. The trend for the baseline phase is extended through the point of
intervention and a binomial test is performed on the post-intervention data to determine
whether data points above the pre-intervention trend could have occurred as the result of
chance rather than as an effect of the intervention In this stage of intervention evaluation,
the data is tested to determine whether the "number of data points above the projected
performance slope...is sdiciently low to reject the null hypothesis that there is no change
in performance across the phases" (pp. 33-34). The split-middle results are also discussed
in realtion to sweral aspects of change: (a) change in slope of the performance trend
across phases, caldated by dividing the larger trend by the smaller trend (b) change in
level of performance, relative to performance trend f?omthe end ofthe pre-intervention to
the beginning of the post-intervention phase, and (c) the aforementioned binomid test.
Results
Vislral inspection rmu&sis.
Interpretation of the data followed the visual inspection
criteria recommended by Hrycaiko and Martin (1996). Each subject is considered
individually with respect to the visual criteria and the results of the seven subjects are
pooled to determine whether a replication of effects across subjects has occurred. As
well, subjects are evaluated in tenas o f ~ o m c outcome
e
as a measure of the practical
significance of the imagery intervention
Subject One (Figure 1.)
Size of eflect. For subject one there appears to be a mall increase in performaace f?om
pre-intervention to post-intervention phase. The performance mean increases fkom 42.8
(SJ
= 4.1) to 44.6 (S9 = 2.6). fkom pre-intervention
score of 1.8 (4%).
to post-intervention an increase in
Fmre I. Trial resuIts for subject one, Solid vertid line indicates the point of imagery
protocol introduction, dotted horizonhl hes indicate pre and post intervention meam Each
data point represents a summed score of ten h e t-r
B m b in the data Line indicate
practices missed
Imrneakcy of eflect There appears to be an immediate reaction to imagery training for
this subject which is sustained throughout the duration of the study.
Overkpprirg data points. -Although fourteen of eighteen (78%). post-internention data
points overlap with data points pre-intervention, only three (17%) drop below the
pre-int ervention mean.
Per$onnance outcome effects. In addition to a proficiency increase, subject one displayed
an increase in fkee throws successfully executed. His mean performance outcome score
improved fiorn 8.4
= 1.2) to 8.7
(m= 1.0) an increase of 0.3 (4%)
successM free
throws per ten attempts.
Szm~tlmy. There appears to be a small, but discernible, increase in performance for
subject one. There is a sustained effect of the intervention which is demonstrated by the
small number of data points below the pre-intervention mean. The decrease in standard
deviation post-intervention indicates an improvement in perfomance consistency.
Subject Two (Figure 2.)
Finre 2. Trial mdts for subject two. Solid vertiai lime indicates the point of imagery
protocol introduction, dotted horizontal lines indicate pre and post interrention means- Each
data point represents a summed score of ten free throws. Break in the data line indicate
practices missed
Sire of efect-
For subject two there is a modest decrease in performance from
pre-intervention to post-intervention phase. The performance mean falls &om 43.6 ISD =
2.3) to 40.2
= 3.9),
a decrease in score of 3.4 (8%) from pre-intervention to
post-intervention.
Immediacy of effect. Although there is an immediate decrease in performance at the
introduction of the intervention, this decrease does not become sustained until the sixth
trail po st-intervention.
&erkrppbg dhtcz points.
Seventeen of eighteen (94%) post-intervention data points
overlap with pre-intervention scores. As well meen post-intervention scores (83%) fall
below the mean of the pre-intervention performances.
Peg50nnmce outcome eflectr. Subject two displayed a substantial decrease in fkee throws
successllly executed. His performance outcome mean dropped 6om 8.6 (SI!= LO) to
7.2(SD = 1.2) a decrease of 1.4 (1 6%) successful free throws per ten attempts.
Summary. The evidence presented suggests that the intenention may have had a negative
impact on consistency and proficiency of performaace for subject two.
Subject Three (Figure 3 .)
F i r e 3. Trial results for subject three. Solid vertical line indicates the point of imagery
protocol introduction, dotted horizontal lines indicate pre and post internention means. Each
data point represents a summed score of ten free throws. Breaks in the data line indicate
p mctices missed,
Size of effect.
For subject three there is a modest decrease in performance fkom
pre-intervention to post-intervention phase. The perfkornance mean f d s fkom 42.4
=
2.2) to 39.9 (SD = 3.9), fkom pre-intervention to post-intervention, a decrease in score of
2.5 (6%).
Immediacy of e m .
There is an immediate performance decrement foUowing the
intervention which fluctuates considerably throughout the post-intervention phase. There
is some question about the motivation of subject three post-intervention as he was
involved in a disciplinary action on the part of the head coach immediately preceding the
intervention.
UverIapping dato points. Twelve of fifteen (80%) post-intervention data points overlap
with pre-intervention scores. As well, eleven post intenrention scores (73%) fall below
the mean of the pre-interventiondata
Perfrnzmce outcome effects Subject three displayed a substantial decrease in free throws
successllly executed. In this case, performance outcome mean dropped fiom 8.4 (SD =
0.5) to 7.4
= 1.4) a decrease of 1.0 (12%) successfirl f k e throw per ten attempts.
Szmmury. The evidence suggests that the intervention may have had a negative impact on
the consistency a . proficiency of performance for subject three. There is a n immediate
decline in performance following the introduction of imagery which suggests an
interference of free throw execution by the v i s u ~ t i o protocol.
n
Subject Four (Figure 4.)
1
l
l
l
J
I
l
l
~
l
f
t
~
l
Trial Number
Fipure 4- Trial mults for subject four. Solid vertical tine indicates the point o f imagery
protocoi introduction, dotted horizontal liner indicate pre and post intervention means. Each
data point represents a summed score of ten free thrown The data line ends abruptly because
of n seasonsnding injury to subject four.
r
l
Size of effect. Subject four demonstrated a substantial increase in proficiency from 40.1
= 3.2)
to 44.4 (SB = 3.1) from pre-intewention to post-intervention phase. This
represents an improvement in mean score of4.3 (11%).
Immedacy of eflect.
There is an immediate increase in performance following the
introduction of the imagery protocol. This response appears to be sustained wen into the
post-intervention period.
Overlapping &a points- Subject four had comparatively few overlapping data points.
Only three (30%) of the data points post-intewention overlap with pre-intervention dataAs we& ody one post-intervention data point (10%) fell below the mean of the
pre-intervention data.
Perfnnance outcome eflects. Subject four displayed a substantial increase in fiee throws
successfbily executed. In this case, perfonmince outcome mean rose from 7.4 @Q = 1.1)
to 8.6 (SJ
= 1.0) an increase of 1.2 (16%) successrl f?ee throws per ten attempts.
Stmmary. Subject four demonstrated a consistent and sustained increase in performance
immediately following the introduction of the intervention. This suggests that imasery
training had a positive effect on this individual's free throw performance. The dramatic
decrease in performance at the end of the intervention set may have been caused by a
late-diagnosed injury to subject four's thumb.
Subject Five (Figure 5.)
Figure 5. Trial results for subject five. Solid vertical line indicates the point of h a g e q
protocol introduction, dotted horizontal lines indicate pre and post intervention me=. Each
data point rep resents a summed score of ten free throws.
Size of effect. Subject f i e demonstrated a moderate increase in performance, with
proficiency increasing fiom 40.5
= 1.9) to 43 -3
=3.9,
a change in mean of 2.8
(7%).
Immedacy of effect. There is an immediate increase in perfonnance following the
introduction of the imagery protocol. The second and third proficiency scores following
the introduction of the intervention are considerably higher that the last data point in the
pre-intervention period.
Overlapping &a pofi~ts-Subject five had overlappins of nine (56%) post-inten-ention
data points. Five (3 1%) post-intervention points fell below the pre-intervention mean.
Perfmmce olrtcome effects. Subject five displayed a moderate increase in free throws
successfUUy executed. Subject five's performance outcome mean rose eom 7.6 ISD= 0.7)
to 8.4 (SD = 1.5)
an increase of 0.8 (10%) successfbl fiee throws per ten attempts.
Stmmary. Subject f i e demonstrated an immediate and positive, though inconsistent,
improvement in free throw proficiency &er the introduction of imagery training. This
suggests that the imagery protocol may have had a positive effect on the performance of
subject five.
Subject Six (Figure 6.)
I
TriaI Number
I
Fimtre 6. Trial results for subject sit Solid verticat line indicates the point of imager?protocol introduction, dotted horizontal lines indicate pre and post intervention meaas. Each
data point represents a sumrued score of ten f n e throws. Breaks in the line indicate practices
missed
Sile of efect.
Subject six displays no discernible change in performance £?om
pre-intervention to post-intervention. There is a mild decrease in mean &om 42.0 ISD =
3.4) to 41.8
= 2.4) a change of 0.2(<I%).
Immediacy of effect. There appears to be no effective immediate difference between the
pre-intervention and post-intervention scores.
Overlapping data points. AU data points post-intervention overlap with pre-intenrention
proficiency scores.
AU pre-intervention data points are greater than the lowest
post-intervention data point. Four of eleven (36%) post-internention data points f
d
below the pre-intervention mean.
Performance arrcome e f f e c ~ .Subject six's performance outcome means are consistent
with his proficiency means, there is a slight decrease in successllly executed ftee throws
from 8.0 (SD = 1.2) to 7.8
= 0.8).
The totd difference between pre and post
intervention means is 0.2 (3%) successll fiee throws per ten attempts, a change which is
probably not the result ofthe imagery intervention
Szmmmy. It is unlikely that the imagery protocol had any effect, positive or negative, on
the Eee throw shooting performance of subject six. There is au apparent increase in
consistency post-intervention, however it is diffidt to attribute small changes to the
application of the imagery protocol.
Subject Seven (F@pre 7-)
Trial Number
Fimn 7. Trial results for subject seven. Solid vertical h e indicates the point of imager).
protocol introduction, dotted horizontal lines indicate pre and post inteweationmeans. Each
data point represents a summed score o f ten free throxs.
Size of eflect. Subject seven displayed the largest increase in free throw proficiency, with
performance increasing fiom 40.2
= 5.1) to 45.6 (Sr!= 2.3), a change in mean of 5.4
(14%).
Immedi~cyof effect.
There is an immediate and reIatively sustained increase in
performance following the introduction of the imagery protowL The &st three data
points of the post-intervention period are all higher than the last two points in the basehe.
Overf'qping&a pin&. Although all post-intervention data points overIapped with the
highest pre-intervention performance, only five (38%) pre-intewention points were equal
to or greater than the lowest post-intemention performance.
As well, none of the
post-intervention data points fell below the pre-intexvention mean.
Perjionnmce mdcome eflects. Subject seven's performance outcome mean rose fiom 7.5
(SD = 1.6) to 9.2 (SD = 0.8) an increase of 1.7 (23%) successll fiee throws per ten
attempts.
S m m q . The evidence presented suggests that imagery training had a positive e f f i on
fkee throw proficiency. The increase in performance between the phases is immediate and
sustained.
Replicat-ionof eflect across subjects. Figure 8 indicates the secpential introduction of the
imagery intervention across subjects. Combining the graphical representation of this data
with previously discussed results indicates a fivourable response to internention by
subjects one, four, five and seven. Subjects two, three and six do not provide evidence for
the efficacy of the intervention The results, therefore, provide only partially support the
use of mental imagery for performance enhancement. It is important to note, in spite of
the drop in mean performance for subjects two and three, six of the seven subjects
experienced increases h performance within two trials of the introduction of the
intervention.
SUBJECT 1
SUBJECT 2
"
Is?rs.
SUBJECT 3
1
SUBJECT 4
SUBJECT 5
I
SUBJECT 6
Fimre 8.
Graph displaying replication effects across subjects using a
multiple-basetin~acmss-individuals. Solid lines indicate staggered introduction of visual
imagery protocol, Dotted lines indicate pre and post-[ntel'~entionperformance means for
each individual
Split-midine mo&sis. Although the visual inspection analysis protided some indication of
performance change as a result ofthe intervention, a split-middle analysis was carried out
to reduce variability in the pre-intervention data and determine whether improvements in
performance may have occurred as the result ofa trend in performance data as opposed to
the intervention itself,
Subject One (Figure 9.)
Trial Nuher
Fire 9. Results for subject one using regressiou to indicate trends in pre-intervention and
port-intervention peflormmer Solid vertical line shorn the poiat of imagery internution.
Trend lines are aIso indicated for each phase of data coIIectjou.
Change in slope. From the pre-intervention slope l e d of -1 -8 there was a change in the
level of the slope by a factor of -0.034, to 0.0613. A measure of the rate of change in
performance between consecutive trials, slope is caldated by dividing the larger of two
known values on a trend line by the smaller one and fbrther dividing this value by the
number of trials between the two points (Hays, 1994; Shambrook & Bull, 1996). In the
case of subject one, the change in slope represents a reversal of trend fiom rapidly
decreasing perfomce to stabilization or modest increase in performance fouowing
intervention,
Chmrge in leveL The pre-intervention perfomce slope produces a final level of 37.4.
The initial perfotmaflce score on the post-intenention trend line is 44.2, an increase of63
(1 8%) across the intentention.
C b g e in perfo~c~nceA Binomial test on this data indicates a significant (E< 0.0001)
increase in performance when comparing post-intervention data to projected performance
levels as suggested by an extension of the pre-intervention trend line through the
introduction of the intervention. At issue here is the stability of the pre-intervention
basetine which may have idheace the'initial dope. As a result, the efficacy of this line as
a comparative tool for the post-intervention slope is questionable.
Suntmaty.
This method of analysis suggests for subject one that there was an increase in
performance after the intemention, and that the intervention may have reversed a
downward trend in performance. The binomial test indicates that the performance
improvement was sisaificant in comparison to the trend established pre-intervention.
Subject Two (Figure 10.)
Change in dope. There was an increase in the level of performance slope across the
phases of the investigation,
Slope changed fkom -0.4 pre-intervention to 0.00722
post-intervention, an increase in slope by a fhctor of -0.018.
Change in &''el. Despite the increase in slope, &ere was a decrease in the level of
performance across the phases. The change fiom 42.4 at the end of the pre-intervention
40
phase to 40.1 at the beginning of the post-intervention phase represents a 5% decrease in
performance.
Fire 10. Results for subject two usiug regression to indicate trends in pre-intervention
and post-intervention performance. Solid v e t i d line shows the poiat of imagery
intervention. Trend h e s are also indicated for each phase of data coUetioa.
C ' g e in perjiommce. The Binomial test on this data indicates that post-internention
performance for subject two is si@cantIy
(e < 0.05) elevated from pre-intervention
levels predicted by the baseline performance stope.
Szmmary. The change in slope combined with the results of the Binomial test suggests
that subject two experienced improvement as the result of the intervention. Based on the
decrease in performance level across the phases, the improvement in performance appears
to take the form of an increase in consistency rathzr than raw proficiency.
Subject T h m (Figure 11.)
Chmge in slope. There was a change in the lwel of the slope 6om 0.8 pre-intervention to
0.0321 post-intervention. This decrease of a factor of 0.04 suggests a decrease in
proficiency between trails in addition to the overall fall in performance.
--
T Mk&er
F i r e 11. R d t s for subject three using regmsiaa to indicate trends in pre-interrentioa
and post-intervention performance. Solid vertical line shows the point of imagecintervention. Trend lines ore also iadicated for each phase of data collection.
Chmge in level. There was also a substantid decrease in level of performance &om the
eild of the pre-intervention phase, where performance level stands at 44.8, to the
beY@ming of the post-intervention phase. At the beginning of the post-intervention phase,
performance is 39.6,thus there is an overall decrease in performance across phases of 5.2
Chge
* perfotmance- The Binomial test for subject three indicates that performance
decreased sisnificantly @ < 0.0001) fiom the trend predicted by pre-intervention data.
Szmntary. The decrease in performance level and slope indicate that the intervention may
have had a negative impact on the tiee-throw shooting proficiency of this subject. A
performance decrease is funher supported by the results of the Binomid tsst for
post-intervention data It should be noted that there may be some basehe instability in
this case which may prevent the use of the trend Line as an effective tool of comparison for
post-intervention data.
Subject Four (Figure 12.)
,
30o
.
5
I
t
.
30
.
15
I
20
Triaf Nurrber
Firmre 12. Remlts for subject four using regression to indicate trends in pre-intervention
and post-latecvention pertormana, Solid vertfcol line shows the point of imagery
internention. Trend lines are dso indicated for each phase of data colIection.
Chrmge in slope. Subject four displays a reversal in performance trend across phases.
Slope changes fiom 0.702 in the pre-intervention phase to -0.691 post-intervention, a
changt by a factor -0.984.
Change in level. Despite the apparent downward trend in performance post-intervention,
there is a considerable increase in Ievel fbrn 42.6 at the end of the pre-intervention phase
to 18.2 at the beginning of the post-intervention phase, a difference of 5.6 (13%).
Chmzge in per$ormmce.
si-&cant
The results of the Binomial test for subject foru indicate no
increase (e > -35 ) in performance between phases.
Szmnary. The reversal in performance trend fiom pre- to post-intervention and the
results of the Binomial test suggest that, from a statistical perspective, there is Little
support for the efficacy of the intervention for this subject, despite the large increase in
performance level across the phases.
Subject Five
13.)
F i r e 13. Results for subject fme using regression to indicate treads in pre-inten-entioa
and post-interrention pertomancc Solid vertical h e shows the point of imagery*
internation. Trend lines are also indicated for each phase of data colIection.
Change in slope. Subject five displays a reversal in performance trend across phases.
Slope changes fiom -0.071in the pre-intervention phase to 0.071 post-intewention, a
change by a faaor -0.99
Change in Ieve1. In addition to the change in slope, there is an increase in performance
across phases from 40.3 at the end of the pre-interventionphase to 42.5 at the start of the
post-intewentioa phase. Tbis difference (2.2) represents a 5% increase in performance.
Change in perfmance. The Binomial test for subject five indicates a significant (E <
0.005) elevation in performance in the post-intervention phase.
Brmmary. The reversal in trend, increase in performance level and the results of the
Binomial test support the efficacy of the imagery intervention for subject five.
Subject Sir @@re 14.)
Trial Nurrber
Fimre 14. Rerufb for subject sir ruing regression to indicate trends in pre-internention
and post-iatemeation performance. Solid vertical lime shows the point of imagery
internention. Trend lines are aha indicated for each phase of data couection.
Change in slope. There is a decrease in slope fiom the pre-intervention phase to the
post-intervention phase by a factor of -0.73. Slope of the pre-intervention data is 0.112;
slope of the post-intervention data is -0.082.
Change f i z leveL There is a very slight decrease in performance level across the phases.
The end of the pre-intervention trend line has a value of 42.7, the start of the
post-intervention trend line has a value of 42.4, this difference of 0.3 represents a 1%
decrease in performance. This is consistent with the visual inspection for subject six which
suggested that the intervention had no effect on fkee throw shooting proficiency.
Change in perfonnume. The results of the Binomial test show no significant @ > 0.5)
increase in performance level in the post-internention phase in relation to levels predicted
by pre-intervention data.
45
Srmmary. The reversal in trend, slight decrease m perfbrmance IeveI and results of the
Binomial test indicate little support for the value of the intervention for subject six.
Subject Seven (Fi-me 15.)
30
0
t
5
10
15
20
25
30
TrhI Nuher
Firmre 15. Results for subject seven using rqpssion to iodide trends in pre-intervention
and post-interventioa performance Solid vertical Kne shows the point of imagery
intervention. Trend lines are also indicated for each phase of data collection.
Chrmge in slope. There is a decrease in slope across phases for subject seven The
pre-intervention slope value is 0.456, the post-intervention slope value is 0.264, a
reduction in slope from pre-intervention values by a factor of 0.57. This reduction in
slope suggests that the intervention may have had a detrimental effe& on a trend toward
perforinance improvement.
C h g e in level. There is a slight increase in the level of performance across phases. The
end of the pre-intervention trend line has a value of 43.9. The value of the start of the
post-intervention trend line is 44.2. The difference of 0.3 represents a 1% increase in
performance with the introduction ofthe intervention
Change in pefonnance.
Results of the Binomial test for subject seven indicate no
significant (e > 0.5) increase in performance level post-intervention fiom that predicted by
pre-intervention data
Stmmary. The slight decrease in slope in the post-intervention phase appears to be
enough to o f k t the performance increase experienced as a result of intenention The
Binomial test confirms that W e support is found for the edlicacy of the intervention in the
case of subject seven
Summary of the sgli-miiaWe m&sis.
The split-middle analysis confirms the results of
visual inspection for subjects one, three, f i e and six. There is no statistically sigd3cant
diflierence between the baseline established trend and the performance results
post-intervention for subjects four and seven which is less convincing evidence of the
efficacy of imagw training for these subjects tban was the visual inspection Subject two
shows a reversal in performance trend &om baseline to post-intervention phase which
represents a sisnificaot difference in performance as the result of the intervention Like
the visual inspection, the split-middle d y s i s shows equivocal results for the effectiveness
of the imagery protocol for the group as a whole.
Results of post-inveMgtfon interviews. In post-investigationintemiews, six of the seven
subjects indicated that they used the imagexy intenreation throughout the duration of the
study and believed it to have either a positive or non-significant impact on their
performance. The seventh subject, subject three, indicated that he stopped using the
imagery protocol one week aAer being introduced to it claiming that the intervention had a
negative impact on his free throw performance. This discontinuation of the imagery
protocol on the part of subject three allows the investigator to use subject three as a
control subject to whom other players may be compared in order to examine the effects of
adherence on the efficacy ofthe mental skills intervention
A post-season interview with the head basketball coach indicated that the
intervention was well received by the coaching staff. When asked if he felt the imagery
training program had a positive impact on team h e throw shooting performance, the
coach indicated he &It it helped a number of athletes become more productive and
consistent in their fiee throw shooting. Mental skills training was finther supported by the
head coach through his expressed desire to continue a mental training program into the
following season. It is important to conduct post-investigationinterviews ofthis nature in
order to socially validate the use of mental skills. In other words, it is important to
consider the perceptions of athletes and not simply the effects of interventions when
creating mental skills training programs (Hrycaiko & Martin, 1996).
Discussion
General Discussion
The present investigation replicated earlier singIe-subject, dtipie-baseline designs
in an effort to support the use of mental imagery with collegiate basketball players as a
performance enhancing tool. This investigation a h presented two analytic techniques for
data interpretatox visual inspection and the split-middle analysis. In three out of seven
cases, there was no agreement between the analytical techniques with regards to the
efficacy of the mental imagery intervention Despite the equivocal nature of the results,
the intwention appeared to be generally well received by the coach and players. The
team head coach indicated that the intmention seemed to have a positive impact on flee
throw performance in practice and game situations, although the playa for whom the
intervention appeared to have the greatest impact, fiom the coach's perspective, Wed to
achieve a consistent baseline and was not included in the investigatioa3
The advantage gained by using a single-subject, multiple-baseline design in this
investigation is the ability of the investigator to gauge the effects of an imagery
intervention on the individual. When using experienced samples, group pre-iatennntion
performance ceilings may prohibit large gains in proficiency, therefore it is important to
note changes in individual performance. These individual effects may be lost as group
members with different magnitudes and directions of performance change begin to cancel
each other out in parametric analysis. From an applied sport psychology penpective, this
method proves quite efficacious as it allows the investigator to examine individual
3
A post hoc regression analysis indicates that the player in question did have an upward tread in
performance over the cwrse of the investigation. This ptayer n-asnot among tam leadm in free throw
shooting and may have benefitted fiom changes in technique or physical practice efkcts alone.
datkences in imagery routine in order to understand why the routine had a positive or
negative effect on a given individual's perfionnance.
Re~ardessof the analytical technique employed to evaluate the data, the results of
this investigation are eqyivocal regarding the efficacy of the mental imagery intervention
The imagery protocol presented to the athletes in the study has allowed the researcher to
gain information regarding the use of such protocols with athletes at upper levels of
performance. Relatively large increases in mean performance outcome were observed for
some individuals despite the assumption that athletes with years of physical practice
behind them were likely to be at perfionnance ceilings. Shambrook and Bull (1996) make
use of spit-middle analysis, in part, to acwunt for the & i s of learning on fkee throw
performance. With novice performers additional units of physical practice are considered
to positively effect performance outcome therefore the split-middle technigue may be valid
for determining whether changes in learning trends occur as the result of intervention. In
other words, whether improvements in performance occur fiom the intervention, despite
the learning effects associated with additional physical practice.
Certainly at issue in this imrestigation is how to interpret the differences in results
between the two methods of examiniug singlasubject data. There are clear effects of the
imagery protocol for four of the subjects: two individuals demonstrated improvement, one
suffered a decline, and one experienced no apparent change in post-intenmtion
performance under the scrutiny of visual inspection @ the splitmiddle technique. The
question is how to interpret the results for the remaining three subjects, for whom the two
methods of analysis appear to indicate different eEkts. At the heart ofthis interpretation
is the difference between changes in performance which are statistically significant and
those which are practically significant-
The split-midde technique indicates no
improvement beyond chance levels for subjects four and seven, however, these athletes
experienced the greatest mean gaias in Bee throw proficiency and @onmince
outcome
following intemention- Subject two shows the opposite effect; although split-middle
d y s i s suggests a reversal ofperformatlce trend and increase in performance consistency
for this athlete, he also experiences a large decline in mean performance outcome. An
interpretation of the efficacy of the intervention lies somewhere between the statistical
methodology of the split-middle analysis and the practical evaluation of performance
provided by visual inspection This imrestigation suggests that the mean performance
outcome improvements for subjects four and seven outweigh the non-si@cant
findings
of the spB-middle anaiysis because, tiom a practical perspective, the large change in mean
sugges that these players are more likely to s u c c e s ~ yexecute the free throw shot,
post-intervention, than they were during the pre-intewention phase.
The increased
likelihood of successfid fiee throw execution is further confirmed by the decrease in
standard deviation of performance across phases, indicating a greater consistency in
performance for subjects four and w e n , and the small number of data points below the
pre-intervention performance mean in the post-intervention phase for both subjects. In the
case of the intercollegiate team as a whole, a difference of a few percentage points in
performance outcome at the foul line may havebeen the Merence between victory and
defeat in two regular-season league games.'
4
The basketball team in question did, in fact, lose two home games in overtime. During both of
these games, the team had lower successfirl ftee tEuow percentages than the performance outcome mean of
the group involved in the study (GIR=79.26/o,G2 FT=55.9?h,Participant Mean lT=8 1.4%).
The split-middle technique indicated a significant, positive change in performance
for subject two across phases which was not evident through visual iaspectioa While
subject two experienced overall decliws in mean proficiency and mean performance
outcome, split-middle analysis suggest that the intmention had a stabilin'ng effect on
performance. Although there is some question about the quality of the baseline, an
intenmition which stabilizes or reverses performance trend may prove valuable for
athletes in a downward performance spiral.
From a practical perspective there are two possiik, positive, performance
outcomes which may occur with mental skills training increases in meaa performance and
increases in consistency of performance. Mhough both types of pediormance increase are
desirable, an increase in consistency is more useful to the coach as it allows for strategic
planning based on probable outcomes. In basketball,the players most likely to be fouled
are those who are assertive within the key: either as shooters or rebounders. Consistent
foul shooting perfofmsu~cefor athletes who play this role on a team will influence the
coach to utilize o f f d e strategies which encourage players to be more assertive when
they are near the basket or close contact with defenders. The near zero slopes of
post-intervention trend lines and decreases in the standard deviations of petforxnance
outcome and proficiency, indicate improvements in consisteucy for subjects one and six in
this investigation. This result suggests that the intervention had an effed on subject six
which is obscured through strict visual or split-middle analysis. In order to understand
changes in performance, we must consider the post-intwention mean performance and
the deviation around that performance.
The pr.esent investigation was able to replicate Shambrook and Bull's (1996)
results with respect to the efficacy of the intervention; both studies found the use of
imagery to be effective for some subjects. The present investigation considered a slightfy
greater breadth of desirable performance changes which dows the investigator to suggest
that; the imagery protocol had some positive &kt on six out of seven subjects involved in
the investigation (Appendix B).
Pdorrnance trends following the intervention were generally Merent fiom those
observed by Shambrook and Bull (1996). While the intwentioa may have decreased the
rate of performance increases for some subjects in the previous study, all subjects
continued to have an upward sloping trend in performance, indicating improvement over
the entire duration of the investigation. The majority of post-intervention performance
trends in the present investigation, possess slope values d e r than 0.1. Low slope
values indicate stabilization of performance in the post-intervention phase rather than
performance change. This stabilization can be attributed to the difference in expertise
between Shambrook and Buil's subjects and subjects involved in the present investigation.
It is unlikely that differences in performance are attributable to the use of males in the
present investigation and females in previous studies as the closed skill of fiee throw
shooting should not favour one gender or the other.
Limitatibns of the Present Iitvesfrgcrirbn
The conundrum ofthis investigation is which method of analysis provides the most
reliable results regarding the performance enbancement effects of an intervention? From
the applied point of view, it is important to consider both visual inspection and
split-middle analysis when determining the efficacy of an intervention By virtue of his or
her choice of analysis technique, the applied sport psychologist may end up subverting an
e f f d v e intervention or continuing an ineffective one. It is therefore paramount7 as
Shambrook and Bull (1996) suggest, that the researcher consider diffaent analytical
techniques as complementary rather than competing. The researcher who undertakes the
study of experienced or elite level pdotmers must ensure that regardless of the method of
analysis, a strong and stable baseline is established. The ideal baseline is one which
produces a regression slope of zero, that is, no change in performance across time. The
closer an investigator can come to the ideal, the more codidem he or she can be in
attniuting performance changes to the intervention
The present investigation was not designed to support performance outcome
imagery as superior to process imagery, however7subject three stopped using the mental
imagery technique two weeks after it was introduced to him. The rationale behind this
decision was that the imagery protocol caused him to f o ~ on
s fiee throw shooting more
than he had previous to the intervention and the image became one of process, rather than
performance. This is consistent with Lerwr et al. (1996) as it appears, to some extent,
that experienced pdormers who use process oriented imagery tend to think too much
about the actual movements made in shooting a fiee throw. Physical process imagery may
interfere with the attainment of a "proper attentional state necessary for skilful
performance" @. 393). One potential solution to the problem of athletes using process
oriented imagey would be increasing the number of consultation sessions that the athlete
has with the researcher. This would give the athkte an opportunity to clarify i m a g y
protocol iastnrctious and voice any concerns that the athlete has about their performance
as the result o f a mental training intervention. An increase in the number of consultations
an athlete has with the sport psychology researcher would also allow for a more accurate
examination of individuals' level of adherence and explain large deviations in performance.
Prior to his injury, subject four experiences three consecutive decreases in performance
which were not accounted for in a retrospective interview, although there is strong
possibility that this subject experienced a broken thumb during the final of these three
practices, prior to shooting his set of free throws. Wah no apparent diffierences in day to
day use of the imagery protocoi, the eqtanation for performance changes may be
attributable to Mestyle fictors which may become evident through Eequent
communications between athlete and investigator.
There were no general trends in adherence elicited by post-investigation
interviewing that would account for differences in imagery protocol efficacy between
subjects: with the exception of the disuse ofthe protocol by subject three. In general all
subjects reported continued use of the imagery protocol, however, the exent of the use of
the imagay program remains somewhat vague. In order to examine adherence effects in
the future, it is recommended that subjects submit to regular meetings with the
investigator to discuss issues of imagery use. Within the context of this investigation, the
withdrawl of subject three allow this individual to be used as a control against whom other
subjects can be compared. In light of the widespread performance decrement experienced
by subject three, the investigator may suggest that the mental imagery intervention may
have had some effect on the performance and proficiency of the other subjects for whom
decreased performances are not experienced under visual inspection and the split middle
dysis.
Although this investigation found equivocal results for the efficacy of an imagery
protocol for the fiee throw shot, there are a fw important g a k made as far as the
development of applied sport psychology intmentions is concerned. Unlike Lemer et al.
(1996), there was support for the imagery intenention with some individuals, regardless
of the analytic technique used. These performance enhancement effects may be related to
the structure of the imagery intervention itseff In this imrestigation, the construction of
the i m a p q script around performaace outcome, rather than physical process, may have
enhanced the value of the imagery intervention by reidorcing appropriate efferent
pathways. The removal of the d y t i c component of imagery prevented subjects &om
thinking too much, which can interfere with the attainment of an appropriate anentiod
state for skiEd performance (Feltz & Landers, 1983), thereby making skill execution less
automatic. The nature of expert pdormance is mechanistic skill execution., that is skill
execution without thought. If one assumes that appropriate motor pathways exist within
the central programming of the expert subject then one must assume that performance
outcome imagery will stimulate these pathways without interference. it is important to
consider the level of performer with whom one is working, and the cognitive demands of
the physical task when constructing an imagery routine.
Recommen~om
for F m e Research
Splitmiddle and visual inspection analysis are dective techniques for the
interpretation of data &om a dtipIe-baseline investigation Future investigators should
strive to consider both practical and statistical significance when evaluating the efficacy of
mental skills intenentiom.
[o
order to fUly appreciate the potential value of mental
imagery for the elite performer, it is recommended that a criteria for expertise, within the
closed skill of fiee throw shooting, be deve10ped. Athletes who meet such stringent
performance criteria should be investigated to determine whether mental imagery can have
an effect on pecfofma~~ce
for the highest-functioning members of an athletic population.
In order to increase the confidence with which one may say that an effct has occurred, it
is recommended that base& measures be taken over an extended period of time with the
hope that a regression analysis of baseline data produces a trend slope of zero. It is
important to consider mental training adherence issues in fimrre investigations as well.
There is a need to determine whether a single session of imagery is sufficient to produce a
performance effkct, or, whether athletes need multiple consultations with practitioners in
order to derive maximum performance enhancement.
Additionally, research which
considers the influence on performance effects of the amount of time spent imaging each
day, should be undertaken.
The present investigation represents a response to calls for single-subject designs
(Hrycaiko & Manin, 1996) and replication (Kirschenbaum & Wlttrock, 1990) in applied
sport psychology research. Through replication and exteasion of sound experimental
paradigms, the sport psychology researcher may learn more about mental training and its
effect at individual and group levels.
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Appendix A
Imagvg Script For The Basketball Free Throw
This exercise uses imagery as a means to mentalIy practice the fiee throw shot. To begin,
put yourself in a comfortabie position. Adjust your body until you are as comfortable as
possibIe. Feel your body supported by the surfkce below you. If at any time during this
exercise you need to adjust this position, do so.
* To begin, take a deep breath through
your mouth and nose. Hold it. Now exhale passively. Begin to breathe slowly and
deeply.
* Focus on the rhythm of your slow, deep, abdominal breathing.
Each time you
exhale, you become more relaxed Close your eyes and continue to focus on your
breathing.
** Picture yourself at the foul line. Scan your body for the physical sensations
of standing at the foul he, ready to receive the bail. Examine your surroundings: the gym
floor, the backboard and rim, other players.
*W
e this picture as detailed as possiile.
Now feel yourself receive the ball. Feel its smooth, pebbled, leather mfkce. Feel the
weight of the ball in your hands. * Go through your pre-shot routine. Scan your body for
the physical sensations of preparing to shoot. You are calm, confident and relaxed.
*
Now you shoot. Feel the baU release from your hands. See the ball travel through the air
into the heart of the basket. Hear the snap of the mesh as the ball travels through it.
Now step away fiom the line.
*
* Rehrm to the line and prepare to take a second shot. * At
your own pace make your second shot. Once again, see the ball travel through the heart
of the basket and hear the mesh snap as the ball travels through it.
** Continue to feel
* You should repeat this exercise several times. Each time
the exercise is pedormed, you will find the images more realistic. * When you are ready to
relaxed, calm and confidemt.
return to an alert state, count back fhm ten to one, bend and stretch your arms and legs,
move your head &om side to side and open your eyes. You feel awake, alert, calm and
confident.
Each * represents apauw of qprroxiateleiy ten s e c o d
Appendix B
PerCormanceEffccb Under Various Criteria for Each Subject
Subject
h c d Iacrrased Deed blrrscd Binomial NearZcro P w W e
of Pd.
d PC&
Test
Slope
PerC. Slope
JYYJ=
Y a
no
Prof. Mean Perf. Mean
1