Journal of Strength and Conditioning Research, 2006, 20(3), 682–688
! 2006 National Strength & Conditioning Association
ROLE OF ENERGY SYSTEMS IN TWO INTERMITTENT
FIELD TESTS IN WOMEN FIELD HOCKEY PLAYERS
KOEN A.P.M. LEMMINK
AND
SUSAN H. VISSCHER
Center for Human Movement Sciences, University Medical Center Groningen, University of Groningen,
The Netherlands.
ABSTRACT. Lemmink, K.A.P.M., and S.H. Visscher. Role of energy systems in two intermittent field tests in women field hockey players. J. Strength Cond. Res. 20(3):682–688. 2006.—The energetics of 2 field tests that reflect physical performance in intermittent sports (i.e., the Interval Shuttle Sprint Test [ISST]
and the Interval Shuttle Run Test [ISRT]) were examined in 21
women field hockey players. The ISST required the players to
perform 10 shuttle sprints starting every 20 seconds. During the
ISRT, players alternately ran 20-m shuttles for 30 seconds and
walked for 15 seconds with increasing speed. Anaerobic and aerobic power tests included Wingate cycle sprints and a V̇O2max
cycle test, respectively. Based on correlation and regression
analyses, it was concluded that for the ISST, anaerobic energetic
pathways contribute mainly to energy supply for peak sprint
time, while aerobic energetic pathways also contribute to energy
supply for total sprint time. Energy during the ISRT is supplied
mainly by the aerobic energy system. Depending on the aspect
of physical performance a coach wants to determine, the ISST
or ISRT can be used.
KEY WORDS. Interval Shuttle Sprint Test, Interval Shuttle Run
Test, maximal oxygen uptake, Wingate test, intermittent sport
physiology
INTRODUCTION
I
ntermittent sports, such as field hockey, require a high degree of physical fitness (23).
Time-motion analysis indicates that in women’s
field hockey, about 20% of the game is spent in
high-intensity activity, such as running and
sprinting (18). These high-intensity activities of short duration (5 seconds, on average) are alternated with lowintensity activities such as walking and jogging (18 seconds, on average). The skill requirements and postural
stress (semicrouched posture) are superimposed on the
work rate demanded by the game and its pattern of play
(23). It is therefore appropriate to view a field hockey
game as aerobically demanding, with frequent, though
brief, anaerobic efforts superimposed (21). High-intensity
efforts rely predominantly on the immediate (adenosine
triphosphate phosphocreatine) and short-term (anaerobic
glycolysis) anaerobic energy systems. The aerobic energy
system is important during prolonged intermittent exercise. Evidently, the energetics of field hockey require an
interaction of all 3 energy systems, with each system
playing a significant yet specific role in energy supply
during the game (7, 21, 31).
A number of intermittent field tests have been developed to evaluate physical performance of players in invasion games such as field hockey and soccer (1–3, 5, 8,
12, 19, 28). In this line, we developed 2 field tests: the
Interval Shuttle Sprint Test (ISST) and the Interval
Shuttle Run Test (ISRT) (14–17). The ISST comprises 10
682
shuttle sprints, each shuttle sprint consisting of 2 ! 6 m
and 2 ! 10 m of sprinting back and forth, starting every
20 seconds. The peak sprint time, the total sprint time,
and the drop-off index express the performance. The
ISRT consists of 30-second shuttle runs over 20 m, interspersed with 15-second walking periods at progressively
increasing speeds until exhaustion. Intermittent field
tests should challenge the energy systems in a manner
that closely replicates the game situation. Therefore, it is
important to investigate the relationship between anaerobic and aerobic energy systems and intermittent field
test performances.
The relationship between intermittent sprint field
tests (i.e., tests of repeated sprint ability) and measures
of anaerobic and aerobic energy systems has been well
documented, but study results show contradictory outcomes (1, 2, 5, 8, 28). Several reasons may be offered to
explain these varying results. First, there is a diversity
in repeated sprint test protocols (i.e., differences in sprint
distances [20–40 m], number of repetitions [6–18], and
recovery periods [15–25 seconds]). Second, there are a variety of laboratory tests to measure anaerobic power and
capacity, such as all-out cycle ergometer sprints of 10, 30,
and 90 seconds; all-out treadmill sprints; an intermittent
cycle ergometer and treadmill test; and laboratory tests
to measure aerobic capacity, such as maximal cycle ergometer and treadmill tests. Third, differences in homogeneity and performance levels of players may account for
different study outcomes. Intermittent endurance field
tests, such as the Intermittent Endurance Test (3) and,
more recently, the Yo-Yo Intermittent Recovery Test (12),
have been related to aerobic energy system measures. Results indicate moderate correlations between intermittent
endurance field tests and V̇ O2max.
Up until now, most research on the relationship between intermittent field tests and energy-producing systems has been limited to a comparison with only one of
the energy systems as a criterion measure (1–4, 12). However, research should focus on the contribution of all energy systems at the same time, because the energetics of
intermittent field tests are complex, with anaerobic and
aerobic energy systems interacting and playing a specific
role in energy supply during test performance. Therefore,
the purpose of the present study was to evaluate the role
of anaerobic and aerobic energy systems with regard to
energy supply for 2 intermittent field tests (i.e., the ISST
and the ISRT) by relating these field tests with laboratory
tests for measuring anaerobic and aerobic performance.
We hypothesized that anaerobic as well as aerobic performance would be related to the ISST and the ISRT.
However, we expected the anaerobic and aerobic perfor-
ENERGETICS
OF INTERMITTENT
FIELD TESTS 683
TABLE 1. Physical characteristics (mean " SD) of the women
field hockey players (n # 21).
Age (y)
Height (cm)
Body weight (kg)
Body fat (%)
21.5
171.4
67.4
27.7
"
"
"
"
1.3 (19.0–24.0)
5.5 (162–180)
8.0 (52.6–83.0)
5.9 (13.6–36.6)
mance to be most strongly related to the ISST and the
ISRT, respectively.
METHODS
Experimental Approach to the Problem
Two intermittent field tests (i.e., the ISST and ISRT) and
2 laboratory tests for measuring anaerobic and aerobic
performance (i.e., the Wingate test and the V̇O2max test)
were conducted on separate days in a random order within a period of 2–4 weeks. Subjects were required to keep
their training and eating and drinking habits constant
during the test period (March and April) and to avoid
heavy meals 3 hours prior to the tests. During the day
preceding each test, the subjects refrained from high-intensity exercise.
The ISST and ISRT were administered on 2 separate
occasions during normal training hours on the same synthetic field hockey playing surface with subjects wearing
the same playing footwear both times. The environmental
conditions during both tests were comparable (i.e., dry
field, no high winds based on subjective observations,
temperatures between $2 and $1% C, and humidity between 81 and 89%). Subjects performed a 15-minute
warm-up consisting of jogging and stretching. The ISST
was carried out individually, while the ISRT was conducted in a group with a maximum of 8 subjects. The
other subjects performed field hockey exercises of low to
moderate intensity.
The Wingate test and the V̇O2max test, as measures
of the anaerobic and aerobic energy systems, respectively,
were administered on 2 different occasions at our laboratory under the supervision of a sports physician. The
subjects were only given feedback on their performance
after completing all tests.
Subjects
Twenty-one women field hockey players of the second
highest skill level in The Netherlands participated in the
study. Before testing, all subjects provided written informed consent and completed a medical questionnaire.
The procedures were conducted in accordance with the
ethical standards of the Medical Faculty of the University
of Groningen. During the study the teams maintained
their regular sports regimen (i.e., field hockey training
twice a week for 150 minutes and 1 match per week). The
subjects received no additional strength or conditioning
training. Prior to the first test, height, weight, and body
fat were determined. Body fat was predicted by means of
leg-to-leg bioelectric impedance analysis (Valhalla, San
Diego, CA) (20). This method proved to be reliable to measure body fat percentage, and results correlated with body
fat percentages, as measured with underwater weighing
and dual-energy x-ray absorptiometry in healthy adults.
The physical characteristics of the subjects are presented
in Table 1.
FIGURE 1.
Layout of the Interval Shuttle Sprint Test.
Physiological Measurements
Blood samples were taken from the ear lobe directly after
completion of the tests (Minilet Lancets; Bayer, Mishawaka, IN) and were analyzed (YSI 2300 lactate analyzer;
Yellow Springs, OH). Heart rate was recorded during all
tests at 5-second intervals (Polar, Kempele, Finland). The
highest rate for any 5-second interval was taken as the
maximum test heart rate.
ISST
The ISST consisted of 10 maximal sprints of 32 m while
the subject was carrying a hockey stick. Each 32-m sprint
included a 6-m and a 10-m shuttle sprint. Timing procedures (timing gates) meant that the initial and final meter of the sprint was not timed, so data are based on 30m distances (Figure 1).
The subject began standing with both feet behind line
A (2 markers 2 m apart). On an auditory signal after a
5-second countdown (test CD), the subject sprinted 6 m
to line B, crossed the line with both feet and then returned to line A, again crossing the line with 2 feet. The
subject then sprinted 10 m to line C, crossed the line with
2 feet and then returned to finish over line A. The subject
then tapered down, turned, and walked back to line A,
waiting for the 5-second countdown to start the second
sprint. The second sprint started exactly 20 seconds after
the start of the first sprint.
Times were measured by photocell gates (Eraton,
Weert, The Netherlands) placed at 1.05 m above the
ground (approximately at hip height) and at 1 m behind
line A. The photocells were linked to an electronic timer
with a precision of 0.01 second. The following variables
were recorded: peak sprint time # fastest sprint time
(seconds), total sprint time # total sprint time of the 10
sprints (seconds), and drop-off index # decrement of the
sum of the ideal total sprint time (#peak sprint time multiplied by 10) to the actual total sprint time (%) (8). Research has shown that the test-retest reliability of the
test is satisfactory with intraclass correlation coefficients
of 0.81, 0.80, and 0.79 for peak sprint time, total sprint
time, and drop-off index, respectively, and no differences
in mean time scores between test sessions (14).
684
LEMMINK
AND
VISSCHER
attained during the sprint, and MPO refers to the mean
power output during the test period. Test values are expressed in absolute (W) and relative (to body weight)
terms (27).
Wingate 30-Second Test
FIGURE 2. Layout of the Interval Shuttle Run Test (" # 20
m–line pylons; # # 3 m–line pylons).
ISRT
Subjects were required to run back and forth on a 20-m
course while carrying a hockey stick with markers set 3
m before the turning lines (Figure 2). The frequency of
the sound signals on a prerecorded CD increased in such
a way that running speed was increased by 1 km·h$1 every 90 seconds from a starting speed of 10 km·h$1 and by
0.5 km·h$1 every 90 seconds starting from 13 km·h$1.
Each 90-second period was divided into two 45-second periods in which subjects ran for 30 seconds and walked for
15 seconds. Running and walking periods were announced on the CD. During the rest periods subjects just
had to walk back and forth to the 8-m line. The test
stopped when the subject was unable to follow the pace
(i.e., more than 3 m before the 20-m lines at 2 consecutive
audio signals, or when the subject felt that she could not
complete the run). The number of completed 20-m runs
was recorded. Earlier studies have shown that the ISRT
was reliable for repeated measurements with intraclass
correlation coefficients of 0.91 and 0.94 in men and women, respectively, and with no systematic bias between test
sessions (17). Furthermore, the ISRT discriminated for
playing level of soccer players (15).
Wingate 10-Second Test
The Wingate 10-second ergocycle test relies entirely on
the a-lactic anaerobic pathways (7, 25). A 5-minute warmup was completed to elicit heart rate increases to 150
b·min$1. The subjects then rested for 5 minutes to eliminate any fatigue associated with the warming-up process.
At the end of the resting period a 10-second countdown
was given to warn the subjects that the test phase would
follow immediately. The test phase started with full application of the predetermined workload (0.075 kp·kg$1).
The subject was asked to cycle the entire 10 seconds at
maximum effort, was not allowed to pedal in advance to
allow overcoming the inertial frictional resistance of the
flywheel, and was allowed to stand on the pedals during
the first few seconds. Verbal encouragement was given
throughout the test. The test was followed by a 3-minute
active recovery on the cycle ergometer (50 W) to lower the
heart rate. The protocol was executed by a computer, interfaced with the cycle ergometer (Lode Excalibur Sport,
Groningen, The Netherlands). Peak power output (PPO)
and mean power output (MPO) expressed test performance. PPO refers to the highest 1-second value of power
The performance on the Wingate 30-second ergocycle test
depends primarily (70%) on the lactic energy contribution
(7, 25). The 30-second test was administered after the 10second test. The active recovery period of the 10-second
test was followed by a 5-minute resting period to eliminate any fatigue associated with the test. The subject was
warned that the 30-second test phase followed this resting period immediately. The test phase started with full
application of the predetermined workload (0.075
kp·kg$1). Standing on the pedals during the first seconds
was allowed. Verbal encouragement was given throughout the test. After the 30 seconds, an active recovery period of 3 minutes was administered. As for the 10-second
cycle test, absolute and relative PPO and MPO were recorded.
V̇o2max Cycle Ergometer Test
V̇O2max was assessed on a cycle ergometer (Lode Excalibur Sport) during a stepwise incremental protocol. Metabolic measurements were made using an online respiratory gas analysis system (Jaeger Oxycon Delta, Hoechberg, Germany). This system was calibrated with O2 and
CO2 gases. During the test the subjects breathed room air
through a rubber mouthpiece and wore a nose clip. All
players were familiarized with the test procedures.
The subjects were told to pedal at 60–80 rpm throughout the test. After performing a 3-minute warm up at 50
W, the workload was increased by 50 W every 3 minutes
up to 200 W and by 25 W every 3 minutes thereafter.
Test performance was expressed as absolute (L·min$l)
and relative (ml·min$l·kg$1) V̇O2max. The individual’s
V̇O2max was determined as the highest V̇O2 in a 30-second
period when at least 2 of the following criteria were
achieved: (a) respiratory exchange ratio value of at least
1.1, (b) postexercise blood lactate concentration of at least
8.0 mmol·L$1, (c) having attained 95% of the individual
estimated maximal heart rate, and (d) exercising to volitional exhaustion (6).
Statistical Analyses
Descriptive data (mean, standard deviation, and range)
were computed for all variables. Pearson product-moment
correlation coefficients were used to determine the relationship between the various test performance indices. A
stepwise multiple regression analysis was conducted to
assess the contribution of the performance indicators of
anaerobic and aerobic energy system measures to the variance of the field test scores. The level of statistical significance was set at p ! 0.05.
RESULTS
Overall results for the ISST and ISRT field tests and the
Wingate and V̇O2max laboratory tests are presented in
Table 2. The peak sprint time ranged from 8.5 to 10.9
seconds, with a mean drop-off index of 9.5 " 2.7%. The
total sprint time ranged from 95.2 to 116.6 seconds. Mean
maximal heart rate and posttest blood lactate concentrations during the ISST were 190 " 7 b·min$1 and 9.0 "
ENERGETICS
TABLE 2. Descriptive data of Interval Shuttle Sprint Test
(ISST), Interval Shuttle Run Test (ISRT), Wingate 10-second
test, Wingate 30-second test, and the VO2max test. Values are
mean " SD (n # 21).
ISST
Fastest sprint time (s)
Total sprint time (s)
Drop-off index (%)
Maximum heart rate (b·min$1)
Posttest blood lactate (mmol·L$1)
ISRT
Number of 20-m runs
Maximum heart rate (b·min$1)
Posttest blood lactate (mmol·L$1)
9.3
102.8
9.5
190
9.0
"
"
"
"
"
0.5 (8.5–10.9)
4.6 (95.2–116.6)
2.7 (4.8–14.9)
7 (176–203)
2.0 (6.6–13.5)
65.0 " 11.9 (52–90)
197 " 7 (185–211)
10.1 " 2.1 (7.5–14.5)
Wingate 10-second test
Peak power output (W)
Peak power output (W·kg$1)
Mean power output (W)
Mean power output (W·kg$1)
779.9
11.62
596.7
8.87
"
"
"
"
97.9 (608–925)
1.24 (9.67–14.23)
103.7 (454–883)
1.29 (7.28–12.91)
Wingate 30-second test
Peak power output (W)
Peak power output (W·kg$1)
Mean power output (W)
Mean power output (W·kg$1)
Posttest blood lactate (mmol·L$1)
760.2
11.35
505.3
7.53
7.0
"
"
"
"
"
94.6 (591–924)
1.41 (9.26–13.61)
53.0 (407–590)
0.60 (6.18–8.69)
1.1 (5.1–9.0)
VO2max
VO2max (l·min$1)
VO2max (ml·min$1·kg$1)
Maximum heart rate (b·min$1)
Posttest blood lactate (mmol·L$1)
3.27
48.7
187
8.6
"
"
"
"
0.41 (2.69–4.18)
4.8 (41.8–56.5)
8 (169–203)
2.1 (5.8–13.4)
2.0 mmol·L$1, respectively. The mean number of 20-m
runs of the ISRT was 65 " 12, with a mean maximal
heart rate of 197 " 7 b·min$1 and a mean posttest blood
lactate concentration of 10.1 " 2.1 mmol·L$1.
The PPO ranged from 9.67 to 14.23 W·kg$1 for the 10second sprint and from 9.26 to 13.61 W·kg$1 for the 30second cycle sprint. The mean MPO for the 10-second and
the 30-second tests was 8.87 " 1.29 and 7.53 " 0.60
W·kg$1, respectively. Posttest blood lactate concentrations
ranged from 5.1 to 9.0 mmol·L1. Relative V̇O2max values
ranged from 41.8 to 56.5 ml·min$l·kg$1, maximal heart
ranged from 185 to 211 b·min$1, and mean posttest blood
lactate concentration was 8.6 " 2.1 mmol·L$1.
Table 3 shows the correlations between the perfor-
OF INTERMITTENT
FIELD TESTS 685
mance indices of the field tests and the laboratory tests.
Peak sprint times were correlated with relative PPO and
MPO of the 10-second cycle sprint (r # $0.43 and $0.44,
respectively; p ! 0.05), absolute and relative PPO and
MPO of the 30-second cycle sprint (r # $0.66 to $0.39; p
! 0.05), and relative V̇O2max (r # $0.39; p ! 0.05). Total
sprint times were correlated with both Wingate 10-second
and Wingate 30-second relative PPO (W·kg$1) (r # $0.44
and r # $0.62; p ! 0.05), relative MPO of the 30-second
cycle sprint (r # $0.57; p ! 0.05), and relative V̇O2max
(r # $0.64; p ! 0.05). Correlations were also observed
between the drop-off index and absolute PPO and MPO
of the 10-second and 30-second cycle sprints (r # 0.39–
0.57; p ! 0.05) and the relative MPO of the 30-second
cycle sprint (r # 0.39; p ! 0.05). The number of 20-m runs
of the ISRT was correlated to the relative 10-second PPO
(r # 0.37; p ! 0.05), the relative 30-second PPO and MPO
(r # 0.37 and 0.38, respectively; p ! 0.05), and the relative V̇O2max (r # 0.74; p ! 0.05). The power values for
the significant correlations (p ! 0.05) ranged from 50.3%
(r # 0.37) to 99.7% (r # 0.74).
The results of the stepwise multiple regression analyses for both interval shuttle tests, including the multiple
R, R2, standard error of prediction (SE), and p values, are
provided in Table 4. Relative MPO and absolute PPO of
the 30-second cycle sprint were the only significant predictors of the peak sprint time, explaining 55% of the
shared variance. Relative V̇O2max and relative PPO of the
30-second cycle sprint contributed significantly to the prediction of total sprint times, with a percentage of explained variance of 58%. Absolute MPO of the 30-second
cycle sprint was the only significant contributor to the
drop-off index, explaining 33% of the shared variance. Finally, only relative V̇O2max contributed significantly to
the number of 20-m runs of the ISRT, with a percentage
of shared variance of 54%.
DISCUSSION
The aim of this study was to provide an image of the
energetics of 2 intermittent field tests, the ISST and the
ISRT, in women field hockey players. Since field hockey
places a demand on both anaerobic and aerobic processes,
the present study focused on the energy continuum of anaerobic and aerobic energetic pathways.
For the ISST, results showed significant correlations
between relative PPO and MPO during 10-second and 30-
TABLE 3. Pearson correlation coefficients between the Interval Shuttle Sprint Test (ISST), Interval Shuttle Run Test (ISRT),
Wingate 10-second test (W10), Wingate 30-second test (W30), and the VO2max test of the women field hockey players (n # 21).*
W10 PPO (W)
W10 PPO (W·kg$1)
W10 MPO (W)
W10 MPO (W·kg$1)
W10 PPO (W)
W30 PPO (W·kg$1)
W30 MPO (W)
W30 MPO (W·kg$1)
VO2max (L·min$1)
VO2max (ml·min$1·kg$1)
ISST
Peak (s)
ISST
Total (s)
$0.27
$0.43†
$0.31
$0.44†
$0.50†
$0.59‡
$0.39†
$0.66‡
$0.21
$0.39†
$0.09
$0.44†
$0.09
$0.34
$0.33
$0.62‡
$0.12
$0.57‡
$0.23
$0.64‡
* PPO # peak power output; MPO # mean power output.
† Significant (p ! 0.05).
‡ Significant (p ! 0.01).
ISST
Drop-off (%)
0.39†
0.16
0.45†
0.33
0.45†
0.19
0.57‡
0.39†
0.05
$0.23
ISRT
20-m runs
$0.09
0.37†
$0.19
0.10
$0.04
0.37†
$0.15
0.38†
0.19
0.74‡
686
LEMMINK
AND
VISSCHER
TABLE 4. Multiple regression analyses (stepwise) for the Internal Shuttle Sprint Test (ISST) and the Interval Shuttle Run Test
(ISRT).*
Criteria tests
ISST
Peak (s)
Total (s)
Drop-off (%)
ISRT
20-m runs
Beta
R
R2
SE
p
W30 MPO (W·kg$1)
W30 PPO (W)
VO2max (ml·min$1·kg$1)
W30 PPO (W·kg$1)
W30 MPO (W)
$0.57
$0.36
$0.48
$0.45
0.57
0.66
0.74
0.64
0.76
0.57
0.43
0.55
0.41
0.58
0.33
0.41
0.37
3.61
3.11
2.23
0.00
0.04
0.01
0.01
0.01
VO2max (ml·min$1·kg$1)
0.74
0.74
0.54
8.28
0.00
* Beta # standardized beta weights; R # multiple-correlation coefficient; R # shared variance; SE # standard error of prediction;
W30 # Wingate 30-second test; MPO # mean power output; PPO # peak power output.
2
second cycle sprints and the peak sprint time of the ISST
(r # $0.66 to $0.39; p ! 0.05). Although not significant,
Baker et al. (2) reported a correlation of $0.58 between
the absolute PPO on a 30-second cycle sprint and the
peak sprint time (8 ! 40 m with 20-second recoveries).
Multiple regression analysis showed that relative MPO
and absolute PPO of the 30-second cycle sprint were significant predictors of the peak sprint time, explaining
55% of the shared variance. In contrast to our expectations, correlations between the 30-second cycle sprint and
the peak sprint time were slightly higher than for the 10second cycle sprint. Since mean peak sprint time (9.3 seconds) was comparable with the time period of the 10-second Wingate test, we expected higher correlations with
the 10-second test than with the 30-second test. Perhaps
as a result of a pacing strategy, individual fastest sprint
times were not always the sprint times on the first sprint.
When peak sprint time was reached in a latter sprint,
then the lactic anaerobic energy system and the aerobic
energy system was more important for energy supply, resulting in a higher correlation with 30-second cycle test
outcome values and a significant correlation with relative
V̇O2max (r # $0.39; p ! 0.05). Conversely, no correlation
was found between V̇O2max and peak sprint time in the
Aziz et al. (1) study (8 ! 40 m with 30-second rest). As a
result of the longer rest periods, their sprint protocol is
less sensitive for a pacing strategy. The design of the
ISST, which includes slowing down, turning, and accelerating at 6-, 12-, and 22-m points, may have weakened
the relationship with 10-second and 30-second cycle
sprints.
Significant correlations (p ! 0.05) existed between, on
the one hand, relative PPO of the 10-second cycle sprint
(r # $0.44), PPO and MPO of the 30-second cycle sprint
(r # $0.62 and $0.57), and the relative V̇O2max (r #
$0.64) and, on the other hand, the total sprint time of
the ISST (10 ! 30 m). In addition, results of the multiple
regression analysis showed that relative V̇O2max and relative PPO of the 30-second cycle sprint contributed to the
prediction of total sprint times (p ! 0.05), explaining 58%
of the shared variance. This illustrates that all energy
systems are important for repeated sprint performance.
The correlations between relative V̇O2max and total
sprint time in our study (r # $0.64; p ! 0.05) are higher
than those found in other studies. Aziz et al. (1) reported
a correlation of $0.32 (p ! 0.05) between relative V̇O2max
and total sprint time (8 ! 40 m with 30-second rest periods) in men field hockey and soccer players, whereas
Dawson et al. (7) showed a correlation of $0.49 (p ! 0.05)
between relative V̇O2max and total sprint time (6 ! 40 m,
departing every 30 seconds) in competitive team and racquet sport players. In contrast, Wadley and Rossignol (28)
found no correlation between relative V̇O2max and total
sprint time (12 ! 20 m, departing every 20 seconds) in
football players. The differences in number of sprints,
sprint distance, and work–rest ratio may have influenced
the strength of the relationship with V̇O2max. The short
recovery periods in our protocol (approximately 10 seconds) compared to the other protocols (approximately 15–
30 seconds) may have increased the lactic anaerobic and
aerobic energy contribution in adenosine triphosphate resynthesis during the ISST, since replenishment of the
phosphate stores and breakdown and removal of lactate
during recovery was limited. The contribution of the lactic
anaerobic energy system is supported by the high posttest
blood lactate concentrations (9.0 " 2.0 mmol·L$1).
Positive correlations between absolute power output
values of the Wingate tests and the drop-off index of the
ISST (r # 0.39–0.57; p ! 0.05) indicate that the higher
the power output, the higher the decrement in sprint
times during the 10 consecutive sprints. Baker et al. (2)
reported slightly higher correlations between PPO and
MPO during a 30-second cycle sprint and the fatigue index (i.e., the difference between the mean of the fastest 2
and the slowest 2 sprints expressed as percentage of the
fastest 2 sprints). Only absolute MPO of the 30-second
cycle sprint in our study was a significant predictor of the
drop-off index, with 33% explained variance (p ! 0.05).
In agreement with the study of Baker et al. (2), there was
a significant correlation between the peak sprint time and
the drop-off index (r # $0.61; p ! 0.05). This indicates
that those subjects with the fastest sprint times and highest PPO and MPO during the cycle sprints also exhibited
the greatest fatigue, perhaps as a result of a high proportion of fast-twitch fibers. In accordance with our findings, Wadley and Rossignol (28) reported no significant
correlation between V̇O2max and percentage decrement
for their repeated sprint ability test. In contrast, 2 other
studies (1, 7) reported significant but modest correlations
between absolute V̇O2max values and the percentage decrement in sprint times. Several explanations have been
offered for these results, such as the relation of the dropoff index to the ability of the muscles to return to homeostasis quickly from the preceding sprints, or a greater
proportion of slow-twitch fibers that lead to greater capillarization of the muscle fibers and a superior ability to
utilize lactate aerobically (13). Since the reported significant correlations are low to moderate and are only for
ENERGETICS
absolute V̇O2max, further research is needed to clarify
this relationship.
For the ISRT, relative V̇O2max was significantly correlated with the number of 20-m runs during the ISRT (r
# 0.74; p ! 0.05) and contributed significantly to the prediction (explained variance 54%; p ! 0.05). This finding
duplicates earlier data showing that the correlation between treadmill V̇O2max values and the ISRT performance was 0.77 (p ! 0.05) in Dutch soccer players (16).
Recently, nearly the same correlation was reported by
Krustrup et al. (12) between relative V̇O2max and the distance covered in the Yo-Yo Intermittent Recovery Test (r
# 0.71; p ! 0.05). Despite the differences in test protocol
(i.e., 30 seconds of 20-m shuttle runs interspersed with
15 seconds of walking during the ISRT, compared to one
20-m shuttle run interspersed with 10 seconds of jogging
during the Yo-Yo Intermittent Recovery Test), the aerobic
energy contribution seems comparable. Bangsbo and
Lindquist (3) reported a lower correlation coefficient between V̇O2max and their Intermittent Field Test score
(i.e., the total distance during 10 minutes of high-intensity running, in 14 professional soccer players; r # 0.47;
p ! 0.05). The duration of their test was 16.5 minutes,
while the players alternated between high- and low-intensity exercise for 15 and 10 seconds, respectively. As a
result of the differences in duration of high- and low-intensity exercise periods (15 and 10 seconds instead of 30
and 15 seconds), high-low intensity ratio (3 to 2 instead
of 2 to 1), and type of activity in the low-intensity exercise
periods (jogging instead of walking), the contribution of
the aerobic energy production is probably lower than for
the ISRT.
The significant correlations between the relative PPO
of the 10-second and relative PPO and MPO of the 30second cycle sprints and the number of 20-m runs indicate that a-lactic and lactic anaerobic energy systems contribute to ISRT performance. As a result of the intermittent character of the ISRT, phosphate stores can be partly
replenished during the 15-second rest periods, increasing
the role of the a-lactic energy system in the energy supply. To cover the energy needs of the muscles for the 30second running periods, especially during the higher running speeds, the energy delivered by the aerobic energetic
pathways is insufficient. Thus, the lactic anaerobic energy system makes an essential contribution to the energy supply of the muscles. This contribution is supported
by the high posttest blood lactate concentrations (10.1 "
2.1 mmol·L$1).
Heart rate at the end ("95% of the predicted maximal
heart rate [220 minus age in years]) and postexercise
blood lactate concentration ("8 mmol·L$1) are often used
to confirm the maximal nature of a performance test (1,
29). Given the values for the maximal heart rate of the
V̇O2max cycle test (187 " 7.9 b·min$1, 94.2% of predicted
maximal heart rate) and the ISRT (197 " 7.2 b·min$1,
99.2% of predicted maximal heart rate) and the mean
posttest blood lactate concentrations of the maximal cycle
ergometer test (8.6 mmol·L$1) and the ISRT (10.1
mmol·L$1), we consider that both tests were conducted
under maximal conditions. In addition, maximal heart
rates at the end of the ISRT in our study are comparable
with maximal heart rates during the ISRT and shuttle
run tests in earlier studies (14, 15, 26, 30). Despite the
fact that maximal heart rate and postexercise blood lactate concentration may not be the best indicators of max-
OF INTERMITTENT
FIELD TESTS 687
imal performance on anaerobic tests, such as the ISST
and Wingate tests, their values demonstrate that the effort of the subjects was considerable and comparable to
that expended in the other tests.
The difference in exercise mode between the laboratory and field tests may have negatively influenced the
magnitude of the correlations. The anaerobic energy system indices were measured using Wingate tests, since reliable and valid treadmill running protocols to measure
anaerobic energy system performances of sport players
were not available. Wingate tests have been used extensively in the evaluation of anaerobic characteristics of
athletes (7, 8, 10, 11, 25). The women field hockey players
in our study obtained an absolute PPO of approximately
780 W during the 10-second cycle ergometer sprint and
760 W during the 30-second cycle sprint. These maximal
values are in line with the results in other team-sports
athletes (2, 10). Baker et al. (2) showed that the correlations between 40-m peak sprint time and PPO and MPO
values of 30-second treadmill sprints and 30-second cycle
sprints were comparable, indicating little influence of the
exercise mode of anaerobic laboratory tests. In order to
maintain consistency between our laboratory measurements, the V̇O2max was assessed during an incremental
cycle ergometer test. The V̇O2max values ranged from
41.8 to 56.5 ml·min$1·kg$1, with a mean V̇O2max of 48.7
ml·min$1·kg$1. These findings show a resemblance to values observed in elite women hockey squads, ranging from
45 to 59 ml·min$1·kg$1 (22, 24). In general, V̇O2max values
assessed during cycling are somewhat lower than those
obtained during running (9). However, since the pattern
of V̇O2max values in a group of subjects will be more or
less similar between cycling and running, the magnitude
of the correlation will not be substantially affected.
In conclusion, results of the correlation and regression
analyses indicate that anaerobic as well as aerobic energy
systems contribute to the energy supply during the ISST.
Anaerobic energetic pathways contribute mainly to energy supply for the peak sprint time, while aerobic energetic pathways also contribute to the energy supply for
repeated sprint performance (i.e., total sprint time). The
a-lactic and lactic anaerobic energy systems were positively related to the drop-off index, and there was no relationship between the aerobic energy system and the
drop-off index. The energy during the ISRT is supplied
mainly by the aerobic energy system. However, as a result of the interval character, anaerobic energy production also contributes to total energy requirement.
PRACTICAL APPLICATIONS
Coaches and trainers of intermittent sports, such as field
hockey and soccer, can use the ISST and ISRT, as these
tests reflect the intermittent character of field hockey
games and the interaction of anaerobic and aerobic energy systems. In addition, both tests can be administered
easily within a short period of time and using limited test
equipment. The ISRT and the ISST can be used to assess
young athletic talent, to differentiate between players of
different playing positions, and to monitor changes over
time. If a coach wants to determine repeated sprint capacity of forwards or defenders, he or she can use the
total sprint time during the ISST as a performance indicator. If a coach wants to determine midfielders’ interval
endurance capacity (i.e., the capacity to perform moderate- to high-intensity activities frequently during a pro-
688
LEMMINK
AND
VISSCHER
longed period of time), he or she can use the number of
20-m runs during the ISRT as a performance indicator.
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Acknowledgments
The authors would like to express their sincere appreciation to
the trainers and players of field hockey club, G.C.H.C.
Groningen, and to Chris Visscher, Marije Elferink-Gemser,
Robert Lamberts, Frans van der Heide, and Gerrit Mook for
their contribution to the study.
Address correspondence to Dr. Koen A.P.M. Lemmink,
[email protected].