Gender Bias in the Effect of Dropping Height on Jumping Performance in Volleyball Players

Abstract

The goal of the present study is to investigate in skilled volleyball players (a) the effect of dropping height on women's and men's performance and (b) the drop jump technique with regard to gender. Nine male and 9 female skilled volleyball players were instructed to jump as high as they could, using a drop jump, from a box of 30 cm or from 2 boxes (60 cm). Kinematic and kinetic data were collected using 6 cameras and a force plate. The human body was summarized by using a 4-segment model (foot, shank, thigh, head-arms-trunk). Males performed higher jumps than females (46.6 +/- 7.5 cm vs. 36 +/- 5.4 cm; p < 0.05). This could be explained by higher mean power (56.9 +/- 26 W/kg vs. 42.4 +/- 19 W/kg; p < 0.05) and shorter eccentric time (-46.3%), both of which allowed a better stretch-shortening cycle. This study shows that women and men have different jump techniques when they drop from a higher position but without increasing the vertical performance. Women increase the values of force and stiffness (respectively +21.4% and +17.9%) without changing the temporal structure of the jump. Men reduce the eccentric time of the jump (41% vs. 31.8%) and keep the force parameters constant. The study findings indicate that it is necessary to find an optimal height for plyometric training for each athlete, allowing enhancement.

Full text

GENDER BIAS IN THE EFFECT OF DROPPING HEIGHT
ON JUMPING PERFORMANCE IN VOLLEYBALL PLAYERS
GUILLAUME LAFFAYE AND MOHAMED A. CHOUKOU
Laboratoire Contro
ˆle Moteur et Perception, University of Paris, Paris, France
ABSTRACT
Laffaye, G and Choukou, MA. Gender bias in the effect of
dropping height on jumping performence in volleyball players.
J Strength Cond Res 23(x): 000–000, 2009—The goal of
the present study is to investigate in skilled volleyball players (a)
the effect of dropping height on women’s and men’s per-
formance and (b) the drop jump technique with regard to
gender. Nine male and 9 female skilled volleyball players were
instructed to jump as high as they could, using a drop jump,
from a box of 30 cm or from 2 boxes (60 cm). Kinematic and
kinetic data were collected using 6 cameras and a force plate.
The human body was summarized by using a 4-segment model
(foot, shank, thigh, head-arms-trunk). Males performed higher
jumps than females (46.6 67.5 cm vs. 36 65.4 cm; p,0.05).
This could be explained by higher mean power (56.9 626 W/
kg vs. 42.4 619 W/kg; p,0.05) and shorter eccentric time
(246.3%), both of which allowed a better stretch-shortening
cycle. This study shows that women and men have different
jump techniques when they drop from a higher position but
without increasing the vertical performance. Women increase
the values of force and stiffness (respectively +21.4% and
+17.9%) without changing the temporal structure of the jump.
Men reduce the eccentric time of the jump (41% vs. 31.8%)
and keep the force parameters constant. The study findings
indicate that it is necessary to find an optimal height for
plyometric training for each athlete, allowing enhancement.
KEY WORDS hopping, spring-mass modelAU1 , vertical perfor-
mance, biomechanics
INTRODUCTION
Drop jumps increase performance in comparison
to countermovement jumps (12,18). It has been
shown that this gain is results from the elastic
energy stored in the muscle-tendon complex,
the activation-loading dynamics, the action of biarticular
muscles, and the level of prestretch loading (10,11,18). The
dropping phase increases downward kinetic energy, which
during breaking action (eccentric phase) is transferred into
elastic energy. The elastic energy is a part of the mechanical
output of the muscles. The height of the drop sometimes
increases performance among experts. In a 2006 study, it
was found (14) that volleyball players jump higher from a 60-cm
height than a 30-cm height (+8.5%) when performing a drop
jump, whereas novices performed lower jumps (26%) in these
conditions. Such an improvement of vertical jump performance
has not been found with skilled basketball players (13) and with
decathletes (9) with the same dropping conditions (21).
During the vertical jump, gender differences have been
studied with regard to the vertical performance. Walsh et al.
(19) have recorded a significant difference of the flying time
on a 30.5-cm drop jump, showing a better performance for
men. During vertical jump, Abian et al. (1) have found a
difference of 10 cm between men and women. The difference
of performance could be explained by the difference of
the force parameters (8). Indeed, vertical jump performance
depends on the vertical velocity at the takeoff, which is
correlated to the power output (2). A great average force is
required to be applied to the ground during the contact phase
to accelerate the body at the takeoff (20). Several studies have
shown better values of force production for men than for
women during jumps (1,7,17). However, women seem to
have a better use of the transfer of energy by using a larger
percentage of the energy stored during the prestretching
phase of jumps (11). Some studies have shown kinematic and
kinetic differences between men and women (6,7,16,19,20),
but, to our knowledge, the effect of the height of the drop on
the gender has not been studied in skilled jumpers.
Considering this theoretical background, we tested 3
hypotheses in this study: (a) Men jump higher than women
by using better values of the mechanical parameters, (b) the
increase from the dropping height is greater for females than
for males, and c) females and males demonstrate a different
dropping jump technique.
METHODS
Experimental Approach to the Problem
A randomized, repeated-measures experimental design was
used to determine the effect of dropping height on gender
with regard to performance and biomechanical parameters.
Address correspondence to Guillaume Laffaye, guillaume.laffaye@
u-psud.fr.
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The dependent performance variable was the maximum drop
jump’s height. The dependent biomechanical variables were
the vertical ground reaction force, the maximum rate of force
development, the mechanical power, the leg stiffness, the leg
shortening, the time to peak force, and the impulse time. The
independent variable was the height of the drop. This variable
was randomly assigned during the experimental session.
Subjects
Nine female and 9 male athletes participated in this study.
Their characteristics are summarized in
T1 Table 1. They were
all expert volleyball players. Expert players were included
in this study if they had a minimum of 5 years of experience
in competition in the third French division and currently
a minimum of 2 training sessions per week.
Each volunteer signed a written informed consent statement
prior to the investigation after receiving oral and written descrip-
tion of the procedures in accordance with guidelines established
by the University Human Subject Review Board. They were
informed of the risks and benefits of participation in this study.
Procedures
After a 5-minute warm-up, subjects were instructed to go on
the box and keep their hands on their hips. The subjects then
were instructed to ‘‘Jump as high as you can.’’ No instruction
was given on the technique to be used during the drop jump.
Participants were asked to perform 5 jumps in 2 conditions
in a randomized order and counterbalanced across subjects to
avoid order effects. In the first condition, subjects dropped
from a box of 30 cm (DJ30) and in the second one from a
box of 60 cm (DJ60). The experimental session lasted about
15 minutes, including a 2-minute rest after the first 5 trials.
Because subjects were asked to level on a force plate, they
were initially asked to place the box so that they would be
comfortable when performing the jumps. To verify the
stability of the data for the dependent variables, we calculated
the population-specific intraclass correlation coefficient
(ICC). The ICCs of the height of the DJ30 and the DJ60
were 98% and 99%, respectively.
Data Analysis
The human body was represented by using a 4-segment, 2-
dimensional human body model (5): Foot, shank, thigh,
head-arms-trunk. The modelization was made with the 3D
VISION software (Vicon, United Kingdom) allowing the
construction of the center of mass of each segment of the
model and the general center of mass ( F1Figure 1). The vertical
ground reaction force was measured using a force platform
(AMTI OR 6–5), with a sampling frequency of 1 kHz.
Simultaneously, kinematic data were recorded by using
6 infrared cameras (VICON V8i) at a frequency of 500 Hz.
The calibrated volume was 2 m wide 31 m deep 32.80 m
high, using the standard procedure recommended by the
constructor of the video cameras: A static and dynamic
calibration of the data acquisition region. The average mean
error associated with absolute point reconstruction was ,1
mm (SD: 0.1 mm) along axis X, Y, Z. Retroreflective markers
were placed on several locations: The tip of the first toe, fifth
metatarsophalangeal joint, lateral malleolus, lateral epicon-
dyle of the femur, greater trochanter, and the acromio
scapulae. Force platform and kinematic data were synchro-
nized by using an external electronic timer.
The maximum rate of force development (RFDMAX) was
obtained by first calculating the first-time derivative of the
vertical ground reaction force and then by keeping the higher
value. The mechanical power was obtained by multiplying
the vertical ground reaction force by the vertical velocity
of the center of mass of the jumper during the ground contact
time. The jump performance was calculated by subtracting
the position of the center of mass at the standing position
(measured during the static calibration) to the position of the
center of mass at the apex of the flight. Leg stiffness was
defined as the ratio of the maximal ground reaction force
Fmax during the active peak to the leg shortening Dr at the
time of maximum leg shortening (3):
kleg ¼Fmax=Drmax:
The leg stiffness values in the present study represent the
combined stiffness of the 2 legs in contact with the ground.
The peak vertical ground reaction force (Figure 1) occurs
at the same time as maximum leg shortening (5). The ICCs
of the force, RFDMAX, power, and leg stiffness measures for
DJ30 and DJ60 were 0.96–0.98, 0.76–0.83, 0.89–0.94, and
0.95–0.98, respectively. The duration of the downward
moment, called time to peak force (TTP), was defined as
the time between the instant of the landing and the moment
the center of mass reached its lowest position. The duration
of the pushoff phase was defined as the time between the
moment the center of mass reached its lowest position and
the instant of takeoff. The impulse time was defined as the
instant of the landing to the instant of the takeoff. The ICC
for leg shortening, impulse time, and TTP for DJ30 and DJ60
was 0.79–0.83, 0.88–0.92, and 0.91–0.97, respectively.
Statistical Analyses
A232 (gender 3jumping condition) mixed-model analysis
of variance (ANOVA) with repeated measures on the second
variable was performed to determine if use of a drop jump
from 30 cm or 60 cm affected jump performance and
TABLE 1. Anthropometrics and general statistics of
subjects.
Males (n= 9) Females (n=9)
Age (years) 21.8 63 22.6 63.6
Height (cm) 184.5 64.9 171.3 65.3
Body mass (kg) 73.2 66.7 63.4 68.6
Lean mass (%) 87.7 61.9 79.2 61.1
Body fat (%) 12.3 61.9 20.8 61.1
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biomechanical parameters differently in men and women. The
gender variable (men vs. women) is a between-subject factor,
and the jumping condition is a within-subject factor (DJ30 vs.
DJ60). Considering that all the data of the dependent variables
are stable (all ICC significant), we have averaged the values of
the 5 jumps for each subject. The level of significance chosen
for the statistical analysis was p#0.05.
RESULTS
Performance
There was a significant main effect for gender [F(1,16) =
10.12; p,0.05] but not for jumping condition [F(1,16) =
1.18; p= 0.58.]. The mean value for males was 46.6 cm
(SD = 7.5) and 36.0 cm (SD = 5.4) for females. The inter-
action was not significant [F(1,16) = 1.81; p= 0.54].
Leg Stiffness
The ANOVA did not reveal a gender effect [F(1,16) = 1.28;
p= 0.27] or a jumping condition effect [F(1,16) = 2.97; p=
0.10], with mean values of 10.84 N/m (SD = 6.6) in DJ30
and 10.88 kN/m (SD = 5.6) in DJ60. The interaction was
not significant [F(1,16) ,1].
Vertical Ground Reaction Force
The ANOVA did not reveal gender effect [F(1,16) ,1;
p= 0.43] but a main effect of the jumping condition
[F(1,16) = 4.4; p,0.05], with mean values of 3.5 body
weight (BW) (SD = 0.86) in DJ30 and 4 BW (SD = 0.9) in
DJ60. The interaction was not significant [F(1,16) = 2.32;
p= 0.14].
Mean Power
The ANOVA revealed gender effect on the scaled mean power
[F(1,16) = 4.06; p,0.05] but did not reveal effect of the
jumping condition [F(1,16) = 1.14; p= 0.30], with mean
values of 47.9 W/kg (SD = 26.4) in DJ30 and 51.5 W/kg
(SD = 18.1) in DJ60. The interaction was not significant
[F(2,32) = 2.3].
Leg Shortening
The ANOVA did not reveal gender effect on the leg short-
ening [F(1,16) ,1] and on the types of jump [F(1,16) = 3.42;
p= 0.08], with mean values of 27.4 cm (SD = 8.3) in DJ30
and 30 cm (SD = 8.4) in DJ60. The interaction was not
significant [F(1,16) ,1].
Figure 1. Modelization of the human body in a 4-segment, 2-dimensional model (foot, shank, thigh, head-arms-trunk) and corresponding phase of the ground
reaction force. The circle represents the position of the center of mass.
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Impulse Time
The ANOVA did not reveal gender effect for impulse time
[F(1,16) ,1] and for the types of jump [F(1,16) ,1], with
mean values of 405 ms (SD = 122) in DJ30 and 405 ms (SD =
119) in DJ60. The interaction was not significant [F(1,16) ,1].
Time to Peak Force
The ANOVA revealed gender effect for TTP [F(1,16) = 4.92;
p,0.05] and a main effect on the types of jump [F(1,16) =
8.51; p,0.05], with mean values 182 ms (SD = 53) in DJ30
and 116 ms (SD = 57) in DJ60. The interaction was not
significant [F(1,16) = 2.41; p= 0.14].
Maximum Rate of Force Development
The ANOVA did not reveal gender effect on RFDMAX
[F(1,16) ,1] but a main effect of the jumping condition
[F(1,16) = 27; p,0.05], with
mean values of 110.9 kN/s
(SD = 59.2) in DJ30 and 194.5
kN/s (SD = 89) in DJ60. The
interaction was significant
[F(1,16) = 6.06; p,0.05],
revealing a stronger increase
of RFDMAX with the height
of the dropping box by females
than by males.
DISCUSSION
The first hypothesis, men jump
higher than women by using
better values of the mechanical
parameters, is validated. In fact,
males jump 22.7% higher than
females (46.6 67.5 cm vs. 36 6
5.4 cm; p,0.05, + 10.6 cm). The mean value (41.2 66.1 cm)
was approximately the same as that found in 4 precedent
studies (4,10,14,23)—about 39 cm on skilled men jumpers.
This difference of performance between men and women
could be first explained by better values of biomechanical
output. Indeed, we found higher values of the relative mean
power for males (56.9 625 W/kg) against 42.4 619 W/kg
for females, representing a difference of 25.5%. Considering
that the power is the most predictive parameter of the
vertical jump performance (2), this is the main reason for the
performance’s difference. Moreover, men produced a shorter
eccentric time (-46.3%) than women. This short eccentric
time allows the increase of the stretch-shortening cycle
and contributes to enhance power and thus performance
(11). The value of leg stiffness is slightly greater for men
Figure 2. Average duration of eccentric phase and pushoff phase during drop jump of 30 cm (DJ30) and drop jump
of 60 cm (DJ60) for male and female skilled volleyball players.
TABLE 2. Values of the studied variables (mean and SD) for expert volleyball players (males and females) for the jumping
conditions: drop jump of 30 cm (DJ30) and drop jump of 60 cm (DJ60).
Female
Mean
Male
MeanDJ30 DJ60 DJ30 DJ60 Difference
Performance (cm) 36.3 (5.3) 35.7 (5.5) 36.0 (5.4) 46.7 (7.2) 46.5 (7.8) 46.6 (7.5) +22.7%*
Leg stiffness (kN/m) 8.7 (4.8) 10.6 (5) 9.6 (4.9) 12.9 (7.5) 11.1 (6.2) 12.5 (6.2) +19.6%
VGRF (BW) 3.3 (0.8) 4.2 (1)†3.75 (0.9) 3.7 (0.8) 3.9 (0.8) †3.8 (0.8) +1.3%
Mean power (W/kg) 41.7 (23) 43.1 (15) 42.4 (19) 54.1 (29) 59.8 (21) 56.9 (26) +25.5% *
Leg shortening (cm) 28.7 (8.3) 30.1 (9.9) 29.4 (8.7) 26.1 (8.3) 29.8 (6.9) 28 (7.4) 25.2%
Impulse
AU3 time (ms) 445 (122) 432 (144) 438 (136) 365 (122) 380 (94) 372 (108) 217.7%
Time to peak (ms) 205 (58) 196 (76)†200 (65) 158 (47) 116 (38)†137 (42) 246.3%*
Time to peak (%) 44.1 (8) 40.3 (10.6) 42.2 (9) 41 (10) 31.8 (16) 36.4 (13) 215.9% *
RFDMAX (kN/s) 99.8 (5.5) 216.5 (98)‡158.1 (74) 122.1 (62) 172.6(79.6)‡147.3 (70) 27.3%
VGRF: vertical ground reaction force; RFDMAX: maximum rate of force development.
*Significant gender effect p,0.05.
†Significant drop effect p,0.05.
‡Significant gender 3drop effect p,0.05.
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(12.5 66.2 kN/m) than for women (9.6 64.9 kN/m) but
without significant effect. As shown by Granata et al. (8), the
higher value of leg stiffness for men could be only explained
to compensate their heavier weight. The mean value of leg
stiffness (11.6 65.3 kN/m) is close to those found in the
literature in different styles of jump—11.5 kN/m in the
running 1-leg jump (12); 14 kN/m during long jump (15);
and 15.4 kN/m in the drop jump (14)—confirming that
a minimum value of leg stiffness is necessary to jump high.
The normalized maximum vertical ground reaction force
shows no difference between women and men, with values of
3.75 60.9 times BW and 3.8 60.8 times BW, respectively.
Considering that the power is the product of the vertical force
by the velocity, and that there is no gender difference in the
force production, we can conclude that, during the pushoff
phase, the men are more able to accelerate their body than
women. These values are close to those found in the studies
on drop jumping, in which no technical advice was given
to the subject (14), but they are lower than those found with
a bouncing technique (2,4) . It is interesting to note that
a same value of vertical ground reaction force obtained for
both sexes is in disagreement with the results of previous
studies (1,6,17). This seems to be the result of a different
adaptation of the constraints of the task for men and women
when the dropping height increases. This difference will be
discussed later.
The second hypothesis, the increase from the dropping
height will be greater for female than for male, is not validated.
Indeed, we have failed to show an increase of performance
with dropping height for women (36.3 65.3 cm in DJ30 vs.
35.7 65.5 cm in DJ60) and for men (46.7 67.2 cm in DJ30 vs.
46.5 67.5 cm in DJ60). These results are in accordance with
some studies (9,21) that did not find an increase of the
performance with the height of the drop jump among skilled
jumpers, but they are in disagreement with other studies
(13,18) that showed a slight increase of performance with the
drop height. This hypothesis was supported by the results
obtained by Komi and Bosco (11), who have shown a better
use of the transfer of energy by women, using a larger
percentage of the energy stored during the prestretching
phase of jumps. In their study, they have found an increase of
performance with dropping height from 26 cm to 62 cm for
men and from 20 cm to 50 cm for women. Two reasons could
explain why in our study volleyball players did not increase
the performance by using a higher drop jump position. First,
the level of training (2 training sessions per week) is maybe
not enough to increase plyometric qualities. Second, the
laboratory conditions are perhaps too restrictive (armless
condition) to increase performance. This explanation is
confirmed by a recent study (14) on skilled volleyball players
that has shown a decrease of the vertical performance
with dropping height by using a restricted arm movement
(24.2 cm).
The last hypothesis was that females and males would
demonstrate a different dropping jump technique. First, the
temporal parameters show a large effect of gender. During
drop jumps, males jump more quickly than females, with
mean values of 438 6136 ms for contact time (200 665 ms
for TTP) for women vs. 372 6108 ms (137 642 ms for TTP)
for men. The jump’s temporal aspect shows a shorter
eccentric time for males with 41 610% against 44.1 68%
for females with DJ30 and 31.8 616% against 40.3 610.6%
for females with the DJ60.
Last, women and men change their jump technique
differently when they drop from a higher position. Indeed,
women increase the values of relative vertical ground reaction
force (from 3.3 60.8 BW with DJ30 to 4.2 61 BW with
DJ60, + 21.4 %), leg stiffness (from 8.7 64.8 kN/m with
DJ30 to 10.6 65 kN/m with DJ60, +17.9%), and maximum
rate of force development (from 99,8 65.5 kN/s to 216 698
kN/s) without changing the temporal structure of the jump
(about 440 ms for impulse time and about 200 ms for the
eccentric time).
Men reduce the eccentric time of the jump (41 610% vs.
31.8 616 %), whereas the force parameters remain constants
or decrease. Indeed, the value of the time to peak decreases
from 158 647 ms to 116 638 ms. The relative vertical
ground reaction force shows a slightly and nonsignificant
increase (3.7 60.8 BW with DJ30 and 3.9 60.8 BW with
DJ60), whereas the leg stiffness decreases (12.9 67. 5 k N /m
with DJ30 and 11.1 66.2 kN/m with DJ60).
These values of contact time are close to these found in
volleyball players (14), with mean values of 396 ms with
DJ30 (416 ms with DJ60), but smaller than impulse times
of decathletes, with 576 ms with DJ30 and 577 with DJ60 (9).
Naturally, these values are larger than those found in studies
in which subjects were advised to use a bouncing technique.
Our study confirms that skilled volleyball players use
a countermovement technique with large contact time, small
power output, and leg stiffness. This typical behavior could
be explained as follows. First, this long contact time may be
used to find a better balance and to reduce the passive peak at
touchdown (14), allowing takeoff with an optimal orientation
of the body. Second, large contact time is possibly a result of
the specific task of volleyball, which consists in taking off at
the best moment so as to touch the ball at the higher position
or to block the opponent attack. So, the impulse should be
modulated with respect to the opponent behavior.
To conclude, this study shows that males perform better
jumps than females (+22.7%), by higher mean power
(+25.5%) and shorter eccentric time (-46.3%), both param-
eters allowing a better stretch-shortening cycle. Indeed,
several theories have been proposed to explain that rapid
muscle’s stretch before contraction affords an enhancement
of the power and so of the vertical performance (11).
Moreover, this study shows that women and men have
different jump techniques when they drop from a higher
position but without increasing the vertical performance.
Women increase the values of force and stiffness (respectively
+21.4% and +17.9%) without changing the temporal
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structure of the jump. Men reduce the eccentric time of the
jump (41% vs. 31.8%), whereas the force parameters remain
constants.
PRACTICAL APPLICATIONS
The first study finding indicates that to jump from a 60-cm
box or a 30-cm box does not change the vertical performance.
The optimal dropping height to enhance performance is
probably between 30 cm and 60 cm, but a drop from a 60-cm
box seems to be too high for these subjects. That implies that
it is necessary to find for each athlete the optimal level for
plyometric training, allowing enhancement.
The second study finding indicates that women and men
use a different way to adapt their technique to the high
constraints of the task of drop jumping. Indeed, women
increase the values of force and rate of force development
with dropping height. These values are higher by women
than by men with the DJ60. That implies that coaches should
differentiate their training approach and technical advice for
both sexes.
ACKNOWLEDGMENTS
The research reported in this article was supported by the
University of Paris XI. We would like to thank Mrs. Isabelle
Siegler for her help in writing the English version of the
manuscript.
REFERENCES
1. Abian, J, Alegre, LM, Lara, AJ, Rubio, JA, and Aguado, X. Landing
difference between men and women in a maximal vertical jump
aptitude test. J Sport Med Phys Fitness 48: 305–310, 2008.
2. Aragon-Vargas, L and Gross, M. Kinesiological factors in vertical
jump performances: Differences within individuals. J Appl Biomech
13: 45–65, 1997.
3. Blickhan, R. The spring-mass model for running and hopping.
J Biomech 22: 1217–1227, 1989.
4. Bobbert, MF, MacKay, M, Schinkelshoek, D, Huijing, PA, and Van
Hingen Schenau, GJ. Biomechanical analysis of drop and counter-
movement jumps. Eur J Appl Physiol 54: 566–573, 1986.
5. Farley, CT and Gonzales, O. Leg stiffness and stride frequency in
human running. J Biomech 29: 181–186, 1996.
6. Ford, KR, Myer, GD, and Hewett, TE. Valgus knee motion during
landing in high school female and male basketball players. Med Sci
Sports Exerc 35(10): 1745–1750, 2003.
7. Ford, KR, Myer, GD, Smith, RL, Byrnes, RN, Dopirak, SE, and
Hewett, TE. Use of an overhead goal alters vertical jump
performance and biomechanics. J Strength Cond Res 19(2): 394–399,
2005.
8. Granata, KP, Padua, DA, and Wilson, SE. Gender differences in
active musculoskeletal stiffness. Part II. Quantification of leg stiffness
during functional hopping tasks. J Electromyogr Kinesiol 12: 127–135,
2002.
9. Hunter, JP and Marshall, RN. Effects of power and flexibility
training on vertical jump technique. Med Sci Sports Exerc 34: 478–486,
2002.
10. Komi, PV. Stretch shortening cycle: A powerful model to study
normal and fatigued muscle. J Biomech 33: 1197–1206, 2000.
11. Komi, PV and Bosco, C. Utilization of stored energy in leg
extensor muscles by men and women. Med Sci Sports Exerc 10: 261–
265, 1978.
12. Laffaye, G, Bardy, B, and Durey, A. Leg stiffness and expertise during
men jumping. Med Sci Sports Exerc 37: 536–543, 2005.
13. Laffaye, G, Taiar, R, and Bardy, B. The effect of instruction on leg
stiffness regulation in drop jump. Sci Sport 20: 136–143, 2005.
14. Laffaye, G, Bardy, B, and Taiar, R. Upper-limb motion and drop
jump: Effect of expertise. J Sports Med Phys Fitness 46(2): 536–543,
2006.
15. Seyfarth, A, Friedrichs, A, Wank, V, and Blickhan, R. Dynamics of
the long jump. J Biomech 32: 1259–1267, 1999.
16. McNair, PJ, Prapavessis, H, and Callender, K. Decreasing
landing forces: Effect of instruction. Br J Sports Med 34: 293–296,
2000.
17. Quatman, CE, Ford, KR, Myers, GD, and Hewett, TE.
Maturation leads to gender differences in landing force and
vertical jump performance. Am J Sports Med 34(5): 806–813, 2006.
18. Voight, M, Simonsen, EB, Dyhre-Poulsen, P, and Klausen, K.
Mechanical and muscular factors influencing the performance in
maximal vertical jumping after the different prestretch loads.
J Biomech 28: 293–307, 1995.
19. Walsh, MS, Walters, J, and Kersting, UG. Gender bias on the effect of
instruction on kinematic and kinetic jump parameters of high level
athletes. Res Sports Med 15: 283–295, 2007a.
20. Walsh, MS, Bohm, H, Butterfield, M, and Santhosam, J.
Gender bias in the effect of arms and countermovement
on jumping performance. J Strength Cond Res 21(2): 362–366,
2007b.
21. Young, W, Pryor, JF, and Wilson, GJ. Effects of instructions on
characteristics of countermovement and drop jump performance.
J Strength Cond Res 9: 232–236, 1995.
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Gender Bias in Drop Jumping