Chris Moors
ST09001976
Sports Biomechanics
University of Wales, Institute Cardiff
The Effect of ‘Ball in Hand’ Transfer on Sprint Speed
and the Underlying Mechanisms of Sprint Technique in
Rugby Union Players
Contents Page
Acknowledgements.................................................................................................................................. i
Abstract .................................................................................................................................................. iii
CHAPTER ONE: Review of Literature....................................................................................................... 1
1. Introduction .................................................................................................................................... 1
2.1 Track Sprint Running ..................................................................................................................... 3
2.2 Kinematics ..................................................................................................................................... 4
2.2.1 Step Length & Step Frequency ............................................................................................... 4
2.2.2 Upper Extremities in Sprint Running ..................................................................................... 7
2.3 Sports Science Research ............................................................................................................... 7
2.4 Sprint Coaching ............................................................................................................................. 8
2.5 Sprint Running in Rugby Union ..................................................................................................... 9
2.6 Review Summary ........................................................................................................................ 11
CHAPTER TWO: Method ....................................................................................................................... 12
2.1 Participants ................................................................................................................................. 12
2.2 Data Collection ............................................................................................................................ 12
2.2.1 Experimental Setup Design .................................................................................................. 13
2.2.2 CODA Analysis Window ....................................................................................................... 14
2.2.3 Recovery Period ................................................................................................................... 14
2.3 Data Analysis ............................................................................................................................... 14
2.3.1 Upper Extremity ................................................................................................................... 15
2.3.2 Lower Extremity ................................................................................................................... 15
2.4 Statistical Analysis ....................................................................................................................... 16
CHAPTER THREE: Results ...................................................................................................................... 17
CHAPTER FOUR: Discussion .................................................................................................................. 23
4.1 Limitations................................................................................................................................... 27
4.2 Delimitations ............................................................................................................................... 28
4.3 Future Research .......................................................................................................................... 28
CHAPTER FIVE: Conclusion .................................................................................................................... 29
References ............................................................................................................................................ 30
Appendices............................................................................................................................................ 37
List of Tables
Table 1 : IRB Recorded time of ball in play, & the recorded number of scrums per
game for each of the previous five RWC Tournaments – Page 1
Table 2 : Shows the four separate data sets collected – Page 16
Table 3 : Direct performance descriptors for each condition, means & standards
deviations are shown – Page 17
Table 4 : RMSD values for direct performance indicators between the
two conditions – Page 18
Table 5 : Upper & lower body kinematics, means and standard deviations are show
– Page 19
Table 6 : RMSD values for kinematic variables between the two conditions – Page
20
List of Figures
Figure 1: Schematic representation of experimental design used – Page 13
Figure 2 : Upper Body Kinematics definitions – Page 15
Figure 3 : Lower Body Kinematics definitions – Page 16
Figure 4 : Effects of varying should joint angular displacement/range of motion upon
1)horizontal velocity 2)Step Length 3)Step frequency 4)Maximum hip flexion – Page
Acknowledgements
Firstly I wish to thank my Dissertation Supervisor, Dr. Ian Bezodis, for his extensive
support and honest advice throughout the entire research process. I would also like
to thank my family and close friends for their constant support and guidance through
my University Career.
i
Abstract
ii
Abstract
The ability to repeatedly reach high sprint velocities is a vital quality in field sports;
this proficiency particularly over short distances can determine sporting success in
Rugby Union. In modern day Rugby Union all players to some degree must now
possess the capability to repeatedly carry the ball whilst running at these high
speeds. The purpose of this study was to accurately assess how ‘ball in hand
transfer’ i.e. transferring the ball from one hand into two, impacted upon maximal
sprint velocity and the underlying mechanisms of sprint technique among Rugby
Union players. Altogether, six male rugby union players (height: 1.82 ± 0.05 m, body
mass: 83.28 ± 81 kg, age: 20.6 ± 0.74 years) were recruited. Each player performed
three 40m sprints under two separate conditions: without a ball in hand (control in
the study), and with the ball in hand accompanied with the transfer of the ball at a set
distance (21-24 m) of the run. The experimental design permitted the measurement
of all kinematic variables in two separate analysis windows; this enabled both pre
and post-ball-transfer movement patterns of each trial to be quantified. The present
study found that in comparison to sprinting without the ball, sprints with ball in hand
displayed a significant decrease (p<0.01) in the total angular displacement of the
arm at the shoulder joint. A similar decrease in range of motion was also found
between pre and post-ball transfer conditions. In this study it was clear that running
without the ball in hand resulted in the greatest horizontal running velocities (7.76 ±
0.15 ms-1 & 8.27 ± 0.19 ms-1). In contrast, running with ball in hand caused a
reduction in horizontal velocity (p>0.05). Post-ball-transfer results revealed an
increase in running velocity; however whether this increase was directly caused by
the transfer of the ball was undetermined. Ball carrying method and the transfer of
the ball itself appeared to have minimal effect up players step length, despite
showing significant differences (p<0.05) between conditions. Step frequency
although showing no significant differences between the two ball conditions (p>0.05),
proved to have a detrimental effect upon running velocity. Again, it was unclear as to
whether the reduction in step frequency was due to the transfer of the ball. Overall
the kinematic effects of ball in hand transfer remains unclear and undetermined.
Further work in this area is required before any serious practical implications can be
extracted and applied to the real world. Future work examining these effects within
the acceleration phase of sprint running may find stronger relations and implications.
iii
Chapter One
Review of Literature
CHAPTER ONE: Review of Literature
1. Introduction
Despite the large importance and vast interest in aerobic running in rugby union (Scott,
Roe, Coats & Piepoli, 2003; Hene, Basset & Andrews, 2011), the ability and contribution
of the anaerobic systems are rapidly becoming more pivotal. Recent law changes aimed
at increasing the appeal and participation in Rugby Union have resulted in the ball in play
time being increased significantly, with more sprints and fewer scrums (Eaton & George
2006). Supporting match statistics (Table 1) reveal that since the RWC 1995 ball in play
time has increased by 33%, as well as displaying a decrease from 27 to 17 scrummages
per game (International Rugby Board, 2011).
Table 1: Shows the IRB recorded time of ball in play, as well as number of scrums per game for each of the
five previous consecutive Rugby World Cup Tournaments
RWC Year
Total
1995
1999
2003
2007
2011
27
24
21
19
17
-37%
26mins 45secs
30mins 43secs
33mins 35secs
35mins12secs
35mins 25secs
33%
%Change
Average
Scrums
per
Game
Ball
Time
in
Play
Traditionally backline players exhibit superior sprinting ability in comparison with
forwards and spend more time in intense running (Doherty, Wegner & Near, 1988;
Duthie, Pyne & Hopper, 2003). Time-motion analysis research has previously shown
that backline players complete 14 ± 5 full sprints over distances of 15.2 ± 3.7 m
within a game, and that sprint running represents 25% of total game movements for
backs in contrast to the 4% of movement performed by forwards (Duthie et al., 2005;
Eaton & George, 2006; Jarvis et al., 2011). In addition to sprint ability backline
players also require the possession of specific attributes and skill sets, such as quick
change of direction at pace, adept handling skills and quick decision making ability.
There are however, further requirements in the modern game; additional power and
1
strength is now fundamental to ensure the security of possession at breakdown
situations (Jarvis et al., 2009). Forwards once known for their ability for short
duration high intensity competition in contact situations must now incorporate sprint
running with the ball, coupled with development of more adept handling and agility
skills (Scott et al., 2003).
Understandably the game is ever becoming faster with the considerable amounts of
sprinting and changes in direction; this entails the acceleration and deceleration of
the player’s body mass. The ability to repeatedly reach high sprint velocities coupled
with the ability to change direction whilst sprinting are vital qualities in field sports,
this proficiency particularly over shorter distances can determine sporting success in
rugby union (Baker & Nance, 1999; Docherty et al., 1988; Sayers, 2000). It is clear
that the demands of rugby are gradually evolving and that all players to some degree
must now possess the capability to repeatedly carry the ball whilst running at high
intense speeds.
Despite the growth in the game itself the development of the academic study in the
sport has been relatively slow compared with that in other sports such as soccer, golf
and cricket (Mellalieu et al., 2008). As such scientific research into the kinetics and
kinematics of maximal sprint running technique within the sport of rugby union is
limited; however previous research studies are evident within straight track running.
Sprints in the 30-50 m range have shown to be a good indicator for running speed
and predictors of on-field performance, as players rarely run at high speeds for more
than 30 m (Sayers, 2000). The relevance of straight track running is questioned
among coaches within field sports such as Rugby Union, as field running requires
rapid changes of direction in response to various stimuli e.g. another player’s
movement, movement of play or the ball (Sheppard & Young, 2006). Moreover, field
running generally includes repeated sprints over considerably shorter distances (<9
m) and on-field performance is rarely about maintaining horizontal velocity; as such
straight track running and field running can be seen as two different skills entirely.
Reinforcing this point, authors have mentioned a greater need for specificity between
training for sprinting and training for speed in sports that require agility, in that it
should seem important to provide specific training that replicates on-field movement
patterns as straight sprint training has little or no influence upon the improvement of
sprinting that requires changes in direction (Sayers, 2000; Young, McDowell, &
2
Scarlett, 2001). Therefore, sprint training for rugby players should focus upon
developing acceleration qualities along with some exposure to maximum running
velocities (Jarvis et al., 2009). In spite of these views, biomechanical comparisons
and conclusions can be drawn from track running literature as the field running style
in Rugby Union possesses similar technical characteristics, the only significant
difference being the holding of a rugby ball.
2.1 Track Sprint Running
Historically the sprint event has been a recognised focal component of track and
field i.e. showcasing the world’s fastest athlete. Athletic performance in the sprint is
influenced by a multitude of factors, including step characteristics, physiological and
musculoskeletal demands, muscle composition and running biomechanics. The
width and depth of knowledge required to understand sprint performance as a whole
is reflected in the considerable body of previous scientific literature. Such literature
has investigated the mechanical and physiological aspects regarding incidence of
injury within sprinters as well as the mechanical factors impacting upon sprint
performance (Jonhagen et al., 1994; Sugiura et al., 2008). In modern day sport, the
combination of science and biomechanics contributes significantly to the knowledge
of technical aspects of sprint training and performance from both a coaching and
research point of view. The simplicity of the sprint race makes it ideal for studying
elements of sprint running as the technique involves pure linear motion, with no
presence centripetal forces.
Previously both quantitative and qualitative studies have focused investigation upon
two main areas within track sprint running, the first of which is the measurement of
direct performance descriptors (Mann & Herman, 1985).
Motion analysis of
mechanical kinematic variables such as step length/step frequency and horizontal
velocity, among just a few, provide insight into determining the level and nature of
work and also allows a direct description of the overall performance to be obtained.
The study of upper and lower body mechanics is the second area of great interest.
This examination of body kinematics can provoke further insight regarding specific
movement patterns that bring about direct performance descriptors.
3
The greatest factor dictating success in sprinting is the maximum horizontal velocity
that an individual is able to achieve and consequently the performance is limited by
the athlete’s ability to maintain such horizontal velocity (Mann & Hermann, 1985).
Horizontal velocity is solely a function of two parameters; they are stride length and
stride frequency, a stride referring to two consecutive steps, a step consisting of one
foot contact to the next contact of the contralateral foot (Salo et al., 2011). The
relationship between these two parameters is fundamental when determining sprint
success. For the purpose of this study these parameters shall be referred to as ‘step’
length and ‘step’ frequency or rate.
2.2 Kinematics
Kinematics refers to the description of movement patterns found within a specific skill
or technique, and does not consider the contribution of forces. When analysing
kinematic variables of sprint technique, it is deemed essential to consider and
assess the underlying relationships found between parameters. For instance, an
individual’s body height greatly influences step length and step frequency; step
length also being effected by leg length, maximum flexion at the hip, flight time and
contact time, with a large flight time being associated with a faster sprint time (Geyer
et al., 2006; Novacheck, 1998). Therefore it follows that when examining step length
and step frequency, it is important to assess in detail the causative mechanisms i.e.
lower leg kinematics such as angular displacement of the knee and hip joint, and the
affect these parameters have upon the overall performance of the task.
2.2.1 Step Length & Step Frequency
The interaction between step length and step frequency is one that has been widely
examined and remains disputed and undetermined. Ideally an athlete should
possess a high step rate coupled with a large step length (Mann et al., 1984).
Although sounding straight forward, the relationship between step length and step
frequency is quite complex and potentially provides difficulty within a coaching
context. The two variables share a ‘negative interaction’ i.e. they are by nature
inversely proportional to one another; therefore an increase in one parameter often
leads to the reduction in the other (Gajer et al., 1999; Kuitunen et al., 2002; Salo et
al., 2011). Thus, in a coaching context it is important to find an optimal balance or
4
ratio between step length and step frequency, and these parameters should not be
considered as independent variables.
Initially, Hoffman (1971) used a rather traditional approach to examine the two
parameters step length and step frequency and how they are influenced by the
individual’s stature. Findings showed that there lies a close relationship between
standing height and average step length, in that the average step length was 1.14
times the athlete’s height or 2.11 times the leg length of the subject. It was also
found that step frequency decreased as the height and leg length of the athlete
increased. Importantly, in a later study Hoffman (1972) added to previous research
by finding that the best female sprinters, when compared to male sprinters in the
same class (equal body height, leg and step length) that female sprinters ran one
second slower due to a markedly lower step frequency. This puts forward the notion
that step frequency is an important parameter to consider, and if improved upon may
lead to an increase in sprint performance. Moreover, findings also imply a gender
specific distinction regarding the kinematic interaction between both parameters and
ultimately sprint performance. Such a distinction has been examined from a
multidisciplinary view (combination of biomechanics and exercise physiology)
particularly among the more contemporary research (Abe et al., 1998; Cheuvront et
al., 2005).
Further investigation focusing more directly upon the ‘negative interaction’ between
step length and step frequency identified that increases in running velocity were
accompanied by a combination of increases in step length and step rate, with step
rate becoming the more important factor at higher running velocities (Sinning &
Forsyth, 1970; Hoshikawa, Matsui & Miyashita, 1973). Such findings oppose the
previous results of Hoffman (1972) but maintain the view that step rate is an
important factor when producing horizontal velocity. However limitations within both
studies were apparent, subjects were tested using a motorized treadmill which
restricted the maximum running velocity to 6.6 ms-1and 8.33 ms-1, velocities that now
fail to reflect modern day sporting performance, particularly within field sports. With
this limitation considered, Luhtanen & Komi (1978) investigated the same variables
but with a maximum sprint effort of 9.3 ms-1 and found that step length actually
levelled off at high velocities, whereas step rate continued to increase, again
concurring with previous research findings.
5
Kunz & Kauffman (1981) analysed 12 biomechanical variables of a small group of
elite World Class sprinters (n=3) through the means of computer assisted
digitisation; a more recent and more accurate method of motion capture and analysis
as opposed to the early traditional research approaches of Hoffman (1971). It was
found that the elite sprinters demonstrated a combination of greater step length and
higher step rate when compared to a group of decathletes (n=16) when performing
at maximal sprint effort. On the other hand, the work of Armstrong et al (1984) using
a similar style of comparative research found that collegiate sprinters exhibited larger
step length than marathon runners and yet found no significant differences regarding
step rate between the two measurement groups. A further study conducted by Mann
et al (1984) also used computer digitisation to analyse chosen variables. Such
kinematic variables were selected based upon those indicators of sprint performance
identified in previous relevant literature (Armstrong et al., 1984; Kunz & Kauffman,
1981; Luhtanen & Komi, 1978; Sinning & Forsyth, 1970), post-investigation it was
suggested that a high step frequency is beneficial but only if the step length can be
maintained and vice versa.
More contemporary studies such as Paruzel-Dyja et al (2006) found that step length
not step frequency has the most dominant impact on the 100m sprint, contradicting
previous implications. Interestingly it was found to be the opposite for female sprint
athletes implying a possible distinction in gender specifics; this suggestion reinforces
the early traditional suggestions of Hoffman (1972).
Considering the aforementioned, it is clear the vast research into step length and
step frequency possess many controversial results and no single conclusion has
been agreed upon therefore leaving room for further study and controversy.
6
2.2.2 Upper Extremities in Sprint Running
Throughout the past there has been a lack of interest with regards to the input of the
upper extremities i.e. arm action throughout sprint running, and there is still a clear
disagreement among coaches and sport scientists regarding these effects. Within
the field of sports biomechanics research, the majority of studies suggest the use of
the arms play an almost ineffective role in maximizing horizontal velocity, however
they do contribute to the improvement and maintenance of balance (Mann, 1981;
Mann & Herman, 1985).
Conversely, Bhowmick & Bhattacharyya (1988)
acknowledged that a greater extension of the upper arm can cause greater
contributions of momentum from the upper body to occur that possibly would result
in a longer stride action, and thus, an increase in sprint speed. The relationship
between arm action and the reduction in energetic cost has also been investigated
(Kaneko, 1990; Arellano & Kram, 2011; Ortega, Fehlman & Farley, 2008), with the
objective to identify whether or not humans not only minimise energetic cost but also
optimise lateral balance when running.
2.3 Sports Science Research
Early research of Bunn (1972) briefly qualitatively discussed the role of the arms as
that of balancing the action of the hips, claiming that a vigorous backswing of the
arms cause the legs to stride further and help maintain velocity when the legs
fatigue. The use of the ‘vigorous arm swing’ movement was also considered a key
element of sprinting by Korchemny, (1992).
Dyson’s (1977) work in this field led to more specific findings, in that both forward
and backward arm movements are part of a clockwise and anti-clockwise upper
body twist, and that these movements work in sympathy not opposition. It was finally
concluded by Dyson (1977) that the primary function of the upper body is to “take up”
reaction to the eccentric leg drive, counter-balancing and following leg action, and
that in order to absorb such angular momentum the arms have to operate with
sufficient force primarily in the sagittal plane. Further to this Mann (1981) and Mann
& Herman (1985), in contrast to some coach’s belief, argued that the motion of the
arms are of little importance other than to aid the balance of the sprinter, nor can
they be attributed to reducing energetic cost or increasing horizontal velocity. Such
7
studies agreeing with Dyson’s (1977) work also stated that the arms should be
swung in the sagittal plane. This leaves room for interesting investigation within field
sports such as rugby, as carrying a rugby ball subsequently restricts arm motion and
causes the arms to travel through a different plane of motion. Despite previous
research, Mann’s (1981) particular research findings could be reason why this
specific area of study lacks in research and interest.
In contrast to Mann’s (1981) belief, later experimental studies such as Hinrichs
(1987) suggested that the specific mechanical motion of the arms counteract the
angular momentum produced by the legs about the vertical axis and also reduce the
side to side motion of the centre of mass (Hamner et al., 2010); thereby improving
balance and reducing energy cost. This was later reinforced by Egbuonu et al (1990)
whose findings showed a 4% increase in the energetic cost of running without arm
swing. Conversely, Pontzer et al (2009) concluded running without arm swing did not
affect lateral balance or energetic cost. Harrison’s (2010) contemporary model was
later devised to try and bridge the gap between sports scientists and coaches. This
brief model assumes that the arms play a subordinate, counterbalancing role to the
leg action whilst sprinting, and therefore little emphasis should be placed upon
correction of arm action within a coaching context.
2.4 Sprint Coaching
Despite scientific research aiming to provide the coaching world with accurate
practical implications both the research and coaching sectors still possess opposing
beliefs, in particular regarding the input of the upper extremities in sprint running.
Jones et al (2009) used semi-structured interviews to examine technical knowledge
regarding the role of the upper extremities of seven expert sprint coaches, each
possessing a minimum of 10 years’ coaching experience. Overall, all coaches were
in agreement in that arm action plays a vital technical role during maximum velocity
running, a view that is not shared by sport science researchers. The coaches
interviewed suggested that the arms are crucial in order to synchronise an optimum
movement pattern, and that the arms and knees have to be in total synchronisation
and work efficiently (Jones et al., 2009). Furthermore, the arms offer balance and
help stabilise the trunk, one view that is in agreement with sports biomechanists.
8
Importantly the coaches also argued that an increase in arm range of motion
(angular displacement of upper and lower arm) could improve lower leg mechanics;
including step length and knee lift (flexion of the hip and knee joints). This notion
remains unsubstantiated within existing literature, and presents opportunity for
further exploration into the kinematic responses of leg mechanics in conditions
whereby arm movement is limited.
2.5 Sprint Running in Rugby Union
This specific area of sprint running, as mentioned before, is heavily lacking in
published research. Study into this particular division of sprinting may provide
technical insight into the actual ‘running requirements’ that are demanded of Rugby
players.
Although not entirely within the field of Rugby Union, Ropret et al (1998) examined
the effects of loading the arms upon 24 active male student athletes. During the arm
loading conditions subjects held 0, 1, 2, or 3 short lead rods (0.22 kg each) in each
hand. Such loading increased the moment of inertia of the loaded limbs by up to
50% of their unloaded values, and placed the sprinters under a similar condition that
rugby union players may find themselves in when carrying a ball. IRB rugby laws
state (Law 2) that a rugby ball must weigh between 0.41 kg and 0.46 kg. Considering
the third procedure condition of Ropret et al (1998) i.e. arm loading of 0.44kg (2
rods) a loading within the weight boundaries of the modern day rugby ball law, step
frequency and step length appeared to have approximate values of 4.25 Hz and
1.90m, respectively, when running at the maximal velocity phase of the run.
Maximum running velocity was also found to be approximately 8 ms -1 under this
condition. Ropret et al (1998) concluded that the reduction in speed resulted from a
decrease in step rate as opposed to step length, and that loading one arm whilst
sprinting led to a decrease in maximal sprint running of magnitude 0-1.0 %.
It was
also identified that as the range of arm motion (angular displacement) became
smaller, step length shortened and step rate reduced.
In the context of Rugby
Union, the range of arm motion possible is predominantly dependent upon the ball
carrying technique used by players; and will vary as different methods are used, For
example when carrying the ball in two hands as opposed to under one arm, the
range of motion possible will be greatly reduced. The leads to the suggestion that the
9
lower leg mechanics and efficiency of the body whilst sprint running, are potentially
heavily influenced by the method of ball carry, and possibly even the transfer of the
ball from one hand to two. To date no study has quantified the range of motion
experienced by the upper extremity during different ball carrying techniques, within
the game of Rugby Union.
Such findings present large implications for sprint performance within Rugby Union,
and provide scope again for further study in this area. Sayers (2000) disagreed with
these findings when examining running techniques within field sports, conversely
suggesting that carrying a ball under one arm will result in an increase in pelvic
rotation and a reduced step length and therefore a reduction in speed.
The original and unique study of Grant et al (2003) examined three different methods
of ball carrying in Rugby Union and the effects each method had upon sprint speed,
using the athletes’ track sprint times i.e. without a ball, as the baseline for each
sprint. Of the three carrying techniques (under the left or right arm and in two hands)
it was concluded that carrying the ball in two hands proved to have the largest
negative effect upon sprint speed, followed by carrying the ball under one arm;
however no significant difference was found between carrying the ball under the left
and the right arm.
This study however failed to analyse the sprint technique of athletes whilst running
with the ball and does not investigate the effect of kinematic variables impacting
upon sprint velocity; it only describes the overall performance of each athlete’s sprint
performance with respect to time. The analysis of these variables would help inform
sport specific training, as within modern day rugby the two handed method is
emphasised by coaches as the preferred method of carrying a ball (Johnson, 1997).
Using this technique is the safest mode of carry, not only does it make it difficult for
the defender to knock/steal the ball but also it provides the player with more tactical
options i.e. pass left/right. Grant et al (2003) failed to incorporate any situational
specific or environmental conditions that reflect the game of rugby union, as when
running with the ball it is extremely common to transfer the ball from one hand, into
two hands and vice versa i.e. as to fend an oncoming defender or two, prepare for a
pass. This movement pattern is yet to be considered in sprint running among
academic studies.
10
2.6 Review Summary
From the review it is evident there is sufficient scope for further investigation into the
specific kinematic variables that impact upon maximal horizontal velocity within
Rugby Union. The analysis of sprint mechanics in this sport has the potential to
further knowledge regarding the role of the upper extremities and the effect they
have upon body kinematics i.e. effect of arm action upon sprint velocity and lower leg
mechanics, a topic already under scrutiny from both sport scientists and sports
coaches.
Further analysis would allow factors such as step length and step frequency to be
accurately analysed and assessed, in the hope that the understanding into the
relationship between these two parameters within field sports such as Rugby Union
can be developed. It may also provide novel evidence supporting the need for further
discrepancy between athletic sprint training and ‘sport specific’ sprint training that
focuses entirely upon the biomechanical requirements of rugby union i.e. findings
may help inform coaches regarding specific sprint training.
The purpose of the present study was to determine how ‘ball in hand transfer’ i.e.
transferring the ball from one hand into two, impacted upon maximal sprint velocity
and the underlying mechanisms of sprint technique among Rugby Union players.
Based upon previous literature, it is hypothesised that as the range of motion of the
arm at the shoulder joint decreases, this will cause a decrease in horizontal velocity
i.e. as the ball is transferred from one hand into two, sprint speed shall reduce. It is
also predicted that knee lift (hip flexion) as well as step length may be affected by the
ball
carrying
method,
however,
to
11
what
cause
is
uncertain.
Chapter Two
Methodology
CHAPTER TWO: Method
2.1 Participants
In this investigation six healthy male rugby union players (height: 1.82 ± 0.05 m,
body mass: 83.28 ± 81 kg, age: 20.6 ± 0.74 years) each possessing at least six
years of rugby experience as well as having representative honours at County level
were selected. Players were also recruited upon the grounds that they, at the time of
the study, were partaking in weekly training sessions and competition. All subjects
prior to data collection provided informed consent and the study was approved by
the University Research Ethics Committee.
2.2 Data Collection
Before data was collected anthropometrical measures of the subjects were obtained.
To assess the kinematics of the upper and lower extremities the Cartesian
Optoelectronic Dynamic Anthropometer (CODA 6.30B-CX1) motion analysis
software at a sampling frequency of 200Hz was used. Active markers were
unilaterally placed on eight body landmarks of each subject, the approximate centre
of the metatarsophalangeal (MTP), ankle, knee, hip, shoulder, and elbow and wrist
joints. One marker was also positioned medial to the first metatarsophalangeal joint
of the opposing foot as to gather data regarding step characteristics for each trial.
For the study, each subject was required to perform three trials under two separate
conditions (six sprints in total); repeated measurements were taken to ensure an
adequate level of reliability within the study. The first condition involved a straight,
forward, maximal 40 m sprint without a ball; this acted as the control in the study.
The second condition consisted of a 40 m sprint with the subject initially carrying a
rugby ball in the right arm (using subject’s preferred method of carry) followed by a
transfer of the ball from the one hand into two at a set distance of the run, the subject
finished the run with the ball in two hands. During the warm-up subjects were given a
brief opportunity to practice this specific transfer to encourage correct performance
behaviour throughout every trial. All data collection took place on a synthetic, indoor
track provided by Cardiff Metropolitan University, School of Sport.
12
2.2.1 Experimental Setup Design
The particular set up used in this research study was a modification of the simplistic
schematic design that was initially used in the work of Grant et al (2003).
S
T
A
R
T
(a)
T
R
A
N
S
F
E
R
CODA Analysis
Window 1
0m
10m
5m
(b)
1
15
m 2
20m
F
I
N
I
S
H
CODA Analysis
Window 2
25
m 3
30m
35m
40m
4
Figure 1. Schematic representation of the experimental design used, (a) CODA analysis windows either
side of the ‘transfer’ point highlighted in green (b) no. 1-4 represents the four CODA scanner units and
their relative positioning
1
Each trial was carried out using the set up as shown in Figure 1; four motion scanner
units were positioned perpendicular to the sagittal plane of motion at approximately 3
m from the centre of the running lane. In doing so, two separate analysis windows
were created at different distances of the run. This allowed upper and lower body
kinematics to be captured during both the pre and post-ball-transfer phase for each
trial i.e. two sets of kinematic data per trial (one data set per analysis window). Trials
requiring no ball in hand used the same experimental design (two sets of data were
also collected).
From the pilot study it was found that placing the four scanners at distances of 9.2
m-17.5 m (Window 1) and 24 m-32.3 m (Window 2) created two separate
overlapping fields providing a sagittal view of the athlete over 8.3 m of track in each
window (16.6 m in total). From this sufficient kinematic data was acquired. The
‘transfer’ point refers to the specific distance at which the subjects were required to
transfer the ball from the right hand into two hands. From the pilot study it was
13
concluded that a gate ranging from 21 m-24 m (3 m gate) provided optimum time for
a successful transfer. This transfer point was a set distance and remained controlled.
2.2.2 CODA Analysis Window
It was deemed essential that the positioning of the motion scanners allowed the
collection of the kinematic data throughout the mid-acceleration phase of the sprint
Delecluse et al (1995). This phase involves the continuation of acceleration up to the
attainment of maximal running velocity (10-36 m) (Johnson & Buckley, 2001) i.e.
subjects would reach maximum horizontal velocity. Despite Sayers (2000) describing
the initial 30 m of the run as the acceleration phase, it follows that the above protocol
and experimental design was viewed adequate for the measurement of the kinematic
variables during maximal horizontal velocity running.
2.2.3 Recovery Period
During data collection subjects carried out the protocol in pairs. Between trials
subjects were allocated a period of rest. During maximal sprinting, phosphocreatine
is the predominant source of energy used for the re-synthesis of ATP (adenosine triphosphate); therefore a sufficient period of rest is needed to allow the replenishment
of these stores. Harris et al (1976), Fleck and Kramer (1987) and Holmyard et al
(1994) have reported that a recovery of 3 minutes and 50 seconds is adequate to
prevent fatigue and any decrement in sprint performance. Therefore in this study
subjects were allowed a recovery period of 4 minutes.
2.3 Data Analysis
As movements predominantly occurred in the sagittal plane with proportions of the
upper body moving in the coronal plane, a three-dimensional protocol was
considered satisfactory for this study. Assuming bilateral symmetry the 3D motion
data from the eight markers were used to define a six-segment biomechanical
model. Based on residual analysis (Winter, 1990) all raw kinematic data was
smoothed using a low pass digital filter at a cut off frequency of 12 Hz. The kinematic
parameters impacting upon sprint performance identified from prior research were
quantified (Mann & Herman, 1985; Ropret el al., 1998). Data regarding the upper
14
and lower extremities for each trial under each condition were extrapolated and
analysed using the CODA software.
2.3.1 Upper Extremity
The minimum and maximum angles of the shoulder and elbow joint reached
throughout each stride sequence in each condition was quantified; from this the total
angular displacement for both joints was calculated.
Maximum flexion at the
shoulder joint was associated with negative displacement and positive values
showed maximum extension of the joint. Figure 2 demonstrates the joint angle
definitions used to quantify the motion of the upper extremities.
(c)
(a)
(d)
(b)
Figure 2. Upper Body Kinematics as defined by Mann & Herman (1985): a) minimum angle at shoulder
joint b) maximum angle at shoulder joint c) minimum angle at elbow joint d) maximum angle at elbow
joint
2.3.2 Lower Extremity
Maximum flexion of the hip joint (Figure 3) during the recovery stage of each stride
was calculated for all trials. In order to determine the stride characteristics of each
subject it was vital to accurately define the instant of touchdown of the foot in relation
to the ground; this was achieved using a method outlined by Bezodis et al (2007).
Using the peak vertical (z-axis) acceleration of both MTP active markers (the right
and left foot) it was possible to locate the instant of touch down (in terms of time and
distance of the run) for each step; step length and step frequency was calculated
from this.
15
(a)
Figure 3. Lower Body Kinematics as defined by Mann & Herman (1985): a) the maximum flexion at the
hip during the recovery phase of the running cycle.
2.4 Statistical Analysis
An average value for each kinematic variable across the four sets of data (see Table
2) was calculated for each of the six players. The root mean squared differences
(RMSD) between each variable across the four groups of data were also calculated.
A general linear model (repeated measures ANOVA) statistical test was used to
determine the significance of the differences in the means of the variables across the
four conditions (sets of data). Significant values or p-values were obtained as a
measure difference, a value of p<0.05 indicates a significant difference, p<0.01
indicates a strong significant difference.
Table 2. Presents the four separate data sets collected (two sets for each condition).
Condition
Data Set
Without Ball
1
Analysis Window 1
Carry
2
Analysis Window 2
With Ball
3
Ball in Right Hand - Analysis Window 1 (Pre-transfer)
Carry/Transfer
4
Ball in Two Hands – Analysis Window 2 (Post-transfer)
16
Chapter Three
Results
CHAPTER THREE: Results
The results for direct performance descriptors for each of the three separate running
conditions are presented in Table 3. All the results are averaged over the maximum
number of steps available for each trial. Table 4 presents the RMSD (Root Mean
Squared Difference) values for each performance descriptors across each condition.
Step length showed to be quite varied between conditions despite showing low
difference values (0.03, 0.06 m), values ranged from 1.79 m to 1.98 m; results show
step length whilst sprinting without a ball in hand (1.87 ± 0.1 m, 1.97 ± 0.2) was
greater than whilst running with the ball under one arm (1.79 ± 0.1 m). When
comparing the two transfer conditions, step length increased once the ball had been
transferred from one hand (1.79 ± 0.1 m) into two hands (1.98 ± 0.2 m); a RMSD
value of 0.18 m between the two conditions imitated such an increase. Step length
post-transfer showed to be greatest over all three running conditions.
Table 3. Direct Performance Descriptors for each condition and data set (shown in brackets), means
and standard deviations are shown for each variable.
Condition
Variable
Without Ball (1)
Without Ball (2)
Pre-Transfer (3)
Post-Transfer(4)
7.76 ± 0.1
8.27 ± 0.2
7.59 ± 0.2
8.06 ± 0.3
Step Length (m)
1.78 ± 0.1
1.97 ± 0.2
1.79 ± 0.1
1.98 ± 0.2
Step Frequency (Hz)
4.35 ± 0.3
4.21 ± 0.3
4.24 ± 0.4
4.12 ± 0.4
Horizontal Velocity
(ms-1)
Across all subjects step frequency ranged between 4.12 and 4.28 Hz across the two
conditions. Sprinting without a ball in hand evidently allowed a higher step frequency
to be generated (4.35 ± 0.2 Hz & 4.21 ± 0.3 Hz) in contrast to both transfer
conditions. Results display a reduction in step frequency once the ball is transferred
from one to two hands; with the pre-transfer frequency (4.24 ± 0.4 Hz) decreasing to
a post-transfer step frequency of 4.12 ± 0.4 Hz. Such a reduction in step frequency is
17
mirrored in the difference value of 0.17 Hz. The results reveal that a similar
horizontal velocity was reached when running without a ball in hand (8.27 ± 0.2 ms -1)
to when running with the ball in two hands (8.06 ± 0.3 ms -1), as reflected with a
difference value of 0.25 ms-1. The slowest velocity attained was whist carrying the
ball in one hand (7.59 ± 0.2 ms-1) i.e. pre-transfer of rugby ball.
Table 4. RMSD (Root Mean Squared Difference) values for direct performance descriptors between the two
conditions (four data sets, shown in brackets).
Without Ball (1)
Without Ball (1) /Post-
Without Ball (2)/ Post-
Pre-transfer (3) / Post-
/Without Ball (2)
transfer (3)
transfer (4)
transfer (4)
Step Length (m)
0.21
0.03
0.06
0.18
Step Frequency (Hz)
0.21
0.16
0.25
0.17
0.63
0.20
0.39
0.49
Variable
Horizontal Velocity
(ms-1)
Results regarding the upper and lower extremity joint kinematics for each condition
are depicted in Table 5, as well as the RMSDs for each variable in Table 6. All the
results are averaged over the maximum number of strides available for each trial.
Sprint runs whereby no ball was carried resulted in greater amounts of flexion (-66° ±
9°) at the shoulder joint (minimum joint angle) compared to both pre and posttransfer phases. After the ball was transferred from one hand (-58° ± 6°) into two (48° ± 10°) i.e. post-transfer, again a decrease in amount of flexion was evident.
Shoulder extension throughout each stride also showed a decrease from sprints
without a ball (45° ± 5°) to those whilst carrying the ball in two hands (37° ± 6°),
although, it was apparent that shoulder extension was greatest during the pretransfer phase (52° ± 9°).
18
Table 5. Upper and Lower Body Joint Kinematics for each condition, means and standard deviations are
shown for each variable.
Condition
Variable
Without Ball (1)
Without Ball (2)
Pre-Transfer (3)
Post-Transfer(4)
minimum
-66 ± 9
-66 ± 8
-58 ± 6
-48 ± 10
maximum
45 ± 5
44 ± 6
52 ± 9
37 ± 6
111 ± 11
110 ± 10
110 ± 12
86 ± 10
minimum
65 ± 15
64 ± 15
80 ± 11
67 ± 10
maximum
152 ± 4
151 ± 10
99 ± 23
92 ± 6
88 ± 8
87 ± 14
20 ± 13
29 ± 4
123 ± 3
132 ± 3
123 ± 5
136 ± 6
Shoulder Joint
Angle (°)
total angular
displacement
Elbow Joint Angle
(°)
total angular
velocity
Maximum Hip Flexion during
Recovery Phase (°)
Total angular displacement of the shoulder joint was similar (RMSD value of 5°) for
running without a ball, 110° ± 10° and 111° ± 11°, and whilst under one arm (pretransfer), 110° ± 12°. A large decrease in angular displacement at the shoulder was
clearly evident post-transfer (86° ± 10°), with a difference (RMS) of 26° clear
between conditions.
Flexion at the elbow proved greatest whilst in pre-transfer phase (80° ± 11°),
throughout post-transfer phase and running without a ball elbow flexion was shown
to be alike, 65° ± 15° and 67° ± 10°, respectively. A maximum joint angle (extension)
of 152° ± 4° at the elbow was found whilst sprinting without a ball in hand, results
clearly portray a large decline in elbow extension once subjects were required to
carry a ball. Pre and post-transfer angles regarding elbow extension range from 92°
± 6° (Post-transfer) to 99° ± 23° (Pre-transfer).
Sprints without a ball in hand
exhibited the greatest amount of angular displacement at the elbow joint (88°± 8°)
throughout each stride sequence, results indicate a large reduction in this angular
19
motion during both conditions whereby carrying a ball is involved. Angular
displacement during pre-transfer condition decreased to value of 20° ± 13° (RMSD
value of 72° between running without a ball); results suggest that the angular
displacement at the elbow increased once ball transfer is complete (29° ± 4°),
although, in contrast to sprinting without a ball the decrease in the range of motion
experienced by the elbow joint is still unmistakeably large (RMSD of 65°).
Further results regarding maximum hip flexion during the recovery phase of each run
indicate that whilst sprinting with the ball in two hands (223° ± 5°), the flexion
occurring at the hip is lesser than prior to ball transfer (237° ± 5°); a difference (RMS)
value of 13° emulates this decrease in hip flexion. Results also show that hip flexion
is greatest whilst running with the ball in one hand (pre-transfer), such a degree of
flexion differed to running when no ball carrying is required (232° ± 5°).
Table 6. RMSD (Root Mean Squared Difference) values for kinematic variables between the two conditions
(four data sets, shown in brackets)
Variable
Angular Displacement at
Shoulder (°)
Angular Displacement at
Elbow (°)
Maximum Hip Flexion (°)
Without Ball
Without Ball (1)/Pre-
Without Ball (2)/
Pre-transfer (3)/
(1)/Without Ball (2)
transfer (3)
Post-transfer (4)
Post-transfer (4)
5
8
27
26
6
72
65
15
10
4
5
13
20
(a)
Figure
MAXIMUM HIP FLEXION (°)
138
4.
Effects
of
varying
shoulder
joint
angular
135.5
displacements/range of motion (ROM) upon (a) maximum hip
133
flexion during recovery phase (b) horizontal velocity (c) step
130.5
frequency (d) step length. Error bars depict standard errors for
128
each data point. Data points filled in black indicate the two sets of
125.5
data whereby a ball was not held, those that are not filled
123
indicate data whereby subjects did carry a ball (in one and two
120.5
hands). Asterisks by data sets indicate significant differences
118
between each of the four conditions * P < 0.05, ** P<0.01. Beside
4.5
each asterisks is a Roman numeral, each numeral is part of a pair
4.45
and corresponds to another asterisks on the graph. Each pairing
4.4
indicates that there was a significant difference between these
STEP FREQUENCY (Hz)
(b)
4.35
two conditions.
*I
4.3
4.25
4.2
*I
4.15
4.1
4.05
4
2.1
(c)
2.05
STEP LENGTH (m)
2
*II
*III
1.95
1.9
1.85
*II
1.8
*III
1.75
1.7
8.6
HORIZONTAL VELOCITY (m/s)
(d)
8.4
**IV
8.2
**V
8
7.8
**IV
**V
7.6
7.4
7.2
Range of
Motion at
Shoulder Joint
(°)
Without
Ball (1)
Without
Ball (2)
111
110
Pre-transfer
(3)
110
Post-transfer
(4)
86
Figure 4. Change in Sprint Kinematics in relation to angular displacement/range of motion at the shoulder
joint. The joint angles in the table correlate to the four sets of data above each value.
21
Figure 4a illustrates a decrease in maximum flexion created at the hip as ROM at the
shoulder decreases from 110° (pre-transfer) to 86° (post-transfer). There is also a
decrease between the two data sets whereby a ball was not carried. However, none
of these differences were determined as significant (p>0.05). Part (b) shows a
significant difference in step frequency between the two conditions whereby a ball
was not held (p<0.05). No significant difference was found (p>0.05) between pre-and
post-ball-transfer. However it is clear that step rate decreases as the ROM of the
arm at the shoulder joint becomes less. Part (c) shows that step length did not
greatly differ between running with and running without a ball. However significant
differences (p<0.05) were found between each data set within the separate
conditions. No relation between step length and ROM at the shoulder joint is
apparent. Part (d) illustrates a significant difference (p<0.01) in horizontal velocity
between running with the ball in one hand (pre-transfer) and without a ball i.e.
velocity increases once the ball is in two hands. There is also a significant increase
(p<0.01) between the two conditions whereby a ball is not held.
22
Chapter Four
Discussion
CHAPTER FOUR: Discussion
This study was designed to improve understanding of sprint running within Rugby
Union, with the more specific aim to expand knowledge regarding the kinematic
effects of ‘ball in hand transfer’ upon running velocity and sprint technique. The main
findings of this investigation revealed that running without a ball in hand resulted in
the greatest horizontal running velocities, 7.76 ± 0.15 ms-1 (window 1) and 8.27 ±
0.19 ms-1 (window 2), see Table 3. This supports previous work of Grant et al (2003)
who found quicker sprint times (2.57+0.155 s) were achieved whilst sprinting without
a ball in hand. This outcome was expected as in the absence of a rugby ball arm
motion predominantly occurs within the sagittal plane, subsequently allowing the
effective counteraction towards rotating pelvic movements that may potentially
compromise balance (Dyson, 1977; Mann, 1981) and reduce speed (Sayers, 2000).
In contrast to running without a ball, horizontal velocity was found to slower in
conditions whereby a ball was held (7.59 ± 0.20 ms -1 and 8.06 ± 0.29 ms-1), this
difference in velocity proved insignificant (p>0.05). Holding the ball in the one hand
caused a reduction of 0.97% in running velocity, a reduction replicating similar
results of Ropret et al (1998). These findings also support the work of Ropret et al
(1998) who reported approximate running velocities of 8 ms -1 whilst running with a
similar load to that of a rugby ball
When transferring the ball from one hand into two, horizontal velocity increased by
6.2% (p<0.01). Interestingly, this data alone suggests that the transfer of the ball
enhances sprint performance. This particular effect seemed irregular, as according
to the work of Grant et al (2003) the effect of carrying a ball in two hands should lead
to a reduction in sprint speed. However a similar increase of 6.5% (p<0.01) was also
true between data sets one and two (without a ball condition), therefore when
equating both conditions together it becomes unclear as to whether an increase in
velocity can actually be associated with the transfer of the ball.
The irregularity of these results could be explained by the idea that subject
had not made the transition from the acceleration phase into the attainment of
maximal velocity, commonly known as the ‘drive phase’ (Harrison, 2010) i.e. players
were still accelerating as and when the transfer took place. Running velocities within
both conditions certainly support the theory that maximal velocity within the run was
not attained, as a clear increase in velocity is apparent within each condition,
23
Reinforcing this, Sayers (2000) acknowledged that players rarely reach full speed
over 30m, as an acceleration phase is an major component of the 30m distance.
Sayers (1999) also suggested that the two handed method may actually be quicker
than one handed methods; as both arms can still drive to counteract pelvic
movements. Importantly, Sayers (2000) acknowledged that carrying the ball in two
hands is difficult to do well, as it requires excellent pelvic control to maintain balance
and efficient lower legs mechanics. Such ability may be prominent at the elite end of
the game; however in terms of this study it is unlikely that this level of skill can be
exhibited by players at County level. Nevertheless in the present study the effect of
the ball transfer appears to have a positive effect upon running velocity. Whether this
increase in velocity was directly caused by the transfer of the ball was undetermined.
This study, unlike any previous research in Rugby Union, quantified the varying
degrees of constraint placed on the arms during different ball carrying techniques. To
date, the role of the arms within sprint running is debated among both sport
scientists and sport coaches. Practitioners such as Mann and Herman (1985)
maintain the view that the arms simply play a balancing role in running, whilst some
sports coaches (Jones et al., 2009), suggest that an increase in arm range of motion
could improve lower leg mechanics; including step length and knee lift.
In comparison to sprinting without a ball, sprints with ball in hand displayed a
significant decrease (p<0.01) in the total angular displacement at the elbow joint. It
was not surprising that the decrease in angular displacement from 87° and 88°
(without a ball in hand) to 20° and 29° (with ball in hand) emerged. Observably when
carrying a rugby ball the range of motion at the elbow considerably reduces, as the
ball inhibits the ability to fully flex and extend (Table 5) the joint during both ball
carrying techniques. When running without a ball extension at the elbow ranged from
151° – 152°, dissimilarly, extension at the elbow ranged from 92° - 100° when a ball
was held.
Results highlighted show no significant difference (p>0.05) in the total
angular displacement at the shoulder joint when running without a ball (111° ± 12°) in
comparison to when running with the ball in the right hand (110° ± 11°). Observably
minimal constraint is placed upon the arms whilst carrying the ball in one hand, and
the overall movement of the arm throughout each stride sequence did not
significantly alter. A core finding of the study was that angular displacement at the
24
shoulder joint (86° ± 10°) for each subject decreased significantly (p<0.01) after the
ball was transferred into the two handed method; the range of motion at the shoulder
joint during this condition undoubtedly experienced the most constraint.
This
decrease (of 24°) in angular displacement was due to both arms being forced to
travel laterally across the body through the coronal plane, consequently reducing the
joint’s ability to extend the arm forward through in the sagittal plane. Extension at
the shoulder pre-transfer (-58° ± 6°) decreased to -48° ± 10° once the ball had been
transferred to two hands, this coupled with a reduction in joint flexion (of 10°)
evidently placed a large restriction over the range of motion possible at the shoulder
joint. Despite both arms still being able to contribute to upper body drive the shoulder
joint can no longer attain its full range of movement, resulting in a limited counter to
body rotation and adversely affecting the maintenance of balance. All results
regarding the upper extremity confirm speculation by Grant et al (2003), that different
ball carrying methods bears varying constraints upon the range of motion possible at
the shoulder and elbow joints.
Previous studies have generally identified that as the range of motion of the
arms becomes smaller, the step length should shorten (Sayers, 2000) and the step
rate should become slower (Ropret et al., 1998). Bunn (1972) mentioned that a
vigorous backswing of the arms (flexion of the shoulder joint) can cause the legs to
stride further. It has also been reported by Bhowmick & Bhattacharyya (1988) that a
greater extension of the upper arm can cause greater contributions of momentum
from the upper body to occur, that could result in a longer stride action. The present
study found that step length did not significantly change (p>0.05) when running with
the ball in hand compared to running without, nor did the transfer of the ball appear
to have a significant effect upon the players’ step length. This implies that the
restrictions placed on the arms during the different ball carrying methods, have no
significant impact upon the step length generated by the players. Such findings
oppose previous suggestions of Sayers (1999), Bunn (1972) and Bhowmick &
Bhattacharyya (1988), and also conflict with suggestions made by sports coaches.
Step frequency, was shown to decrease within both test conditions. Compared to
running without a ball, players’ step rate decreased when running with a ball in hand.
Step frequency also decreased once the ball was transferred from one hand (4.24 ±
0.31 Hz) into two hands (4.12 ± 0.35 Hz). However, this difference was not classed
25
as significant as a similar decrease was evident across the two data sets whereby a
ball was not held. So yet again it becomes unlikely that the specific transfer of the
ball can be attributed to the decrease in step rate.
The decrease in step frequency across both conditions, as well as the general
decrease in sprint speed found in this study, could be heavily influenced by the type
of training each subject was exposed to. Although maximal running is a requirement
in Rugby Union, the necessity to attain and maintain maximal horizontal velocity is
limited. As open running space in a game is often restricted to shorter distances,
training tends to focus upon improving maximal acceleration and changes in
direction; both achieved through high force generation and maximal stride rates
(Brechue, 2011). Players exposed to this type of training may favour greater step
rates to facilitate the changes in direction, thus, the protocol design may not
accurately mirror the specific training or the requirements of Rugby Union.
Considering that step length remained unchanged it was determined that step
frequency in this particular study proved to have a detrimental effect upon horizontal
velocity. This was true within the case of Ropret et al (1998), whereby loading the
arm led to a decrease in sprint speed due to a decrease in step rate as opposed to
step length. This was predicted not to be the case, as stride rate is set within the
first two steps, and increasing stride length becomes the major determinant towards
attaining maximal velocity (Brechue, 2011). These results conflict previous
suggestions of Paruzel-Dyja et al (2006), but succeed in underlying the importance
of step frequency when producing horizontal velocity. An importance previously
emphasised by Hoffman (1971 & 1972).
Based upon the findings regarding the step characteristics exhibited in this
study, specific training implications could be suggested. For instance specific training
focusing upon improving players’ step frequency may bring about enhancement in
overall sprint speed. Improvement in this area could be beneficial, but only if step
length can be maintained (Mann et al., 1984).Swanson & Caldwell (2000) claimed
high intensity incline treadmill training is a useful method to elicit adaptations in step
frequency by increasing the activation and joint power of the lower extremity.
Moreover, higher step frequency requires cross bridges within the muscles fibres to
be formed at high rates, thus, there is a requirement for high rates of neural
activation. With this in mind training should be tailored to permit such neural
adaptations to be produced i.e. neural conditioning.
26
Finally it was found that post-ball-transfer the maximum angle at the hip joint (during
the recovery phase) throughout each stride sequence increased from 123° ± 5° to
136° ± 6°. This increase (of 13°) in hip angle suggests a reduction in hip flexion once
the ball has been transferred from the right hand into two hands i.e. lower knee lift
with ball in two hands. However, similar reductions in joint angles were also evident
between the data sets whereby no ball was held, thus, again there seemed to be no
apparent kinematic effect caused by the transfer of the ball. This particular finding
rejects the proposal made by sprint coaches within the study of Jones et al (2009),
whom suggested an increase in arm range of motion could improve some aspects of
lower leg mechanics, such as knee lift (flexion at the hip).
4.1 Limitations
There are a number of limitations surrounding the present study. Approximating joint
centre locations during marker set up, coupled with the movement of the markers
whilst running limited the accuracy of joint angle measurements. This inaccuracy
may have influenced the results and calculations that were derived from these
measurements. In addition, all sprint runs were performed on an indoor synthetic
track, although this environment provided good running conditions for the athletes,
performing the experiment on grass would be more ecologically valid.
A
homogenous group of six rugby players were recruited for this study; more
participants would improve the statistical power and validity of the findings.
In
addition these findings may not necessarily apply to female athletes or athletes of a
higher ability i.e. elite athletes. This said, there is still room for investigation regarding
sprint mechanics within different sporting populations.
Another limitation of this study was that the ‘transfer point’ was a set distance,
therefore subjects knew at what distance to make the transfer. The experimental
design fails to incorporate any unanticipated reactions that players are faced with
whilst in a game context. The addition of an external stimulus to act as a cue for the
transfer may reflect the conditions of a rugby game more accurately. Playing position
of players was not accounted for in this study, Players such as wingers or fullbacks
who spend more time at higher running velocities during a game may exhibit
different sprint mechanics to that of forward players.
27
4.2 Delimitations
All the kinematic data collected was backed up onto an external hard drive as to
avoid any chance of data loss. In addition repeated trials of each condition were
required as to increase the reliability and validity of the measurements taken.
Moreover, relative positioning of the CODA equipment was accurately altered and
improved during the pilot study; this permitted the two analysis windows to
successfully record the whole movement pattern within each run,
4.3 Future Research
Future research designs may incorporate a larger analysis window post-transfer as
to allow adequate time for potential changes in velocity and technique to occur. Also
placing the ‘transfer point’ at a further distance in the run may ensure subjects reach
maximal velocity before the ball transfer takes place. However, by increasing the
distance of the transfer of the run it is arguable that the design would then not
accurately reflect the conditions of a game of rugby.
As it is strongly suggested that the arms play an important role in maintaining
balance, it would be interesting to investigate the varying methods of ball carry within
an agility run whereby balance is a contributing factor to successful performance i.e.
zig-zagged pattern tailored around the specific requirements of Rugby union. This
would better simulate the type of space and running that rugby union players often
find themselves in. Equally replicating a similar experimental design examining the
effects of ball carrying method and transfer during the acceleration phase of the run
may prove intriguing; as rugby players predominantly run for distances between 1020 m during a game.
Finally as only kinematic variables during the run were measured, kinetic variables
may exhibit stronger relationships and be better predictors of sprint performance.
This is particularly relevant when looking at the acceleration phase of the run as
force development and rate of force development are crucial in generating high step
frequencies
during
the
initial
28
sprint
phase.
Chapter Five
Conclusion
CHAPTER FIVE: Conclusion
From the present study, it has come to light that carrying the ball whilst sprint running
unmistakably places large constraint over the range of movement possible at the
shoulder and elbow joints; a view previously acknowledged by sports coaches but
never before quantified within Rugby Union. The actual transfer of the ball from the
right hand into two hands appeared to have almost no effect upon sprint velocity.
Although horizontal velocity was clearly affected by the decrease in step frequency,
whether this reduction in step frequency was caused by the transfer itself was
undetermined. Further work into this area is required before any serious practical
implications can be drawn. It was also concluded that step length as well as
maximum flexion at the hip was not significantly affected by the levels of restriction
placed on the upper extremity during varying methods of ball carrying. Core findings
of this study suggest that the use of arm action play an almost ineffective role in
maximising sprint velocity, a view held by Mann (1981) alongside Mann & Herman
(1985). However, based on the inconclusiveness surrounding this topic there still
appears to be room for further investigation regarding the effects of different ball
carrying/transfer techniques upon running technique. Research examining such
effects within the acceleration phase of sprint running could lead to interesting
findings.
29
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36
Appendices
(a)
Significance Values (p Values)
Without (1)/ Without (2)
Without (1)/ Pre-Transfer
Without (2)/ Post-Transfer
Pre-Transfer (3)/ Post-Transfer (4)
Horizontal Velocity
0.003
0.079
0.113
0.001
Step Length
0.001
0.100
0.598
0.003
Step Frequency
0.056
0.042
0.472
0.122
Ang.Disp.Shoulder
0.816
0.737
0.000
0.001
Ang.Disp.Elbow
0.464
0.002
0.000
0.443
Flexion at Hip
0.000
0.928
0.115
0.000