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Abstract

https://www.tandfonline.com/doi/full/10.1080/02640414.2014.924055 This study aimed to investigate the contributions of kinetic and kinematic parameters to inter-individual variation in countermovement jump (CMJ) performance. Two-dimensional kinematic data and ground reaction forces during a CMJ were recorded for 18 males of varying jumping experience. Ten kinetic and eight kinematic parameters were determined for each performance, describing peak lower-limb joint torques and powers, concentric knee extension rate of torque development and CMJ technique. Participants also completed a series of isometric knee extensions to measure the rate of torque development and peak torque. CMJ height ranged from 0.38 to 0.73 m (mean 0.55 ± 0.09 m). CMJ peak knee power, peak ankle power and take-off shoulder angle explained 74% of this observed variation. CMJ kinematic (58%) and CMJ kinetic (57%) parameters explained a much larger proportion of the jump height variation than the isometric parameters (18%), suggesting that coachable technique factors and the joint kinetics during the jump are important determinants of CMJ performance. Technique, specifically greater ankle plantar-flexion and shoulder flexion at take-off (together explaining 58% of the CMJ height variation), likely influences the extent to which maximal muscle capabilities can be utilised during the jump.
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Journal of Sports Sciences 32, 1805-1812, 2014
Determinants of countermovement jump performance: a kinetic and kinematic
analysis
1Stuart McErlain-Naylor, 1Mark King, 1Matthew T G Pain
1School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, LE11 3TU, UK
ABSTRACT
This study aimed to investigate the contributions of kinetic and kinematic parameters to
inter-individual variation in countermovement jump (CMJ) performance. Two-dimensional
kinematic data and ground reaction forces during a CMJ were recorded for 18 males of
varying jumping experience. Ten kinetic and eight kinematic parameters were
determined for each performance, describing peak lower-limb joint torques and powers,
concentric knee extension rate of torque development, and CMJ technique. Participants
also completed a series of isometric knee extensions to measure rate of torque
development and peak torque. CMJ height ranged from 0.38 0.73 m (mean 0.55 ± 0.09
m). CMJ peak knee power, peak ankle power, and take-off shoulder angle explained
74% of this observed variation. CMJ kinematic (58%) and CMJ kinetic (57%) parameters
explained a much larger proportion of the jump height variation than the isometric
parameters (18%), suggesting that coachable technique factors and the joint kinetics
during the jump are important determinants of CMJ performance. Technique, specifically
greater ankle plantar-flexion and shoulder flexion at take-off (together explaining 58% of
the CMJ height variation), likely influences the extent to which maximal muscle
capabilities can be utilised during the jump.
Keywords: countermovement jump, kinetics, kinematics, technique, rate of torque development
INTRODUCTION
The countermovement jump (CMJ) is a key performance requirement in many
sports. Research has shown positive relationships between lower-limb strength and
power measures and CMJ performance (Ashley & Weiss, 1994; Nuzzo, McBride,
Cormie, & McCaulley, 2008; Sheppard et al., 2008; Wisløff, Castagna, Helgerud,
Jones, & Hoff, 2004). However, further research is needed to explain quantitatively
the relative contributions of kinetic and kinematic variables to this movement. Of the
kinetic determinants, greater rate of force or torque development has frequently been
associated with increased CMJ performance (De Ruiter, van Leeuwen, Heijblom,
Bobbert, & De Haan, 2006; Marcora & Miller, 2000; McLellan, Lovell, & Gass, 2011;
Thompson et al., 2013). Both rate of force development and rate of torque
development measure the capabilities of skeletal muscle to rapidly generate muscle
forces and for the purposes of the present study will be referred to as rate of torque
development. Furthermore, it seems that the maximum force-dependent, post-50
ms, rate of torque development is more strongly related to CMJ height than the
earlier, neurally-mediated rate of torque development (Tillin, Pain, & Folland, 2013).
There are discrepancies among the results of the few studies investigating
ankle, knee and hip joint contributions during the CMJ. Hubley and Wells (1983)
found the greatest contributor to be the knee joint (49% of the total positive work),
whilst Fukashiro and Komi (1987) found it to be the hip joint (51%). More recently,
Vanezis and Lees (2005) obtained values (30% at the knee and 42% at the hip) that
were in closer agreement with Fukashiro and Komi (1987) than with Hubley and
Wells (1983). A novel finding by Vanezis and Lees (2005) was a negative
relationship between hip work and knee work, indicating a technique difference
between participants. The authors suggested that this difference could account for
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previous discrepancies in the literature, implying that technique determines the
relative contribution of different lower-limb joints. The inclusion of an arm swing
increased jump height by approximately 10 cm, supporting previous arm swing-
induced performance improvements (Feltner, Fraschetti, & Crisp, 1999; Shetty &
Etnyre, 1989). Likely contributors to this effect include the increase in work done at
the hip joint (Hara, Shibayama, Takeshita, & Fukashiro, 2006; Lees, Vanrenterghem,
& De Clercq, 2004) and maximised pre-takeoff mass centre displacement (Cheng,
Wang, Chen, Wu, & Chiu, 2008; Harman, Rosenstein, Frykman, & Rosenstein, 1990;
Payne, Slater, & Telford, 1968) in jumps with an arm swing. Simulation studies of
squat jumping show the augmented hip work to be due to a slowing of hip extension
enabling the musculature to work on a more favourable region of the force-velocity
curve (Blache & Monteil, 2013; Cheng et al., 2008; Domire & Challis, 2010).
Approximately one third of the arm swing related performance improvement results
from the work and energy induced at the shoulder joint (Domire & Challis, 2010).
Countermovement depth has also been linked to CMJ performance. Moran and
Wallace (2007) found that increasing the knee joint range of motion from 70° to 90°
resulted in a 17% improvement in CMJ height. Similarly, high ankle dorsi-flexion
range of motion has been shown to contribute to CMJ performance in men but not
women (Georgios, Fotis, Thomas, Vassilios, & Iraklis, 2007). Simulation studies
have shown an increase in squat depth to improve squat jump performance due to
an increase in time to develop joint torques (Bobbert, Casius, Sijpkens, & Jaspers,
2008; Domire & Challis, 2007). Proposed mechanisms for the benefit of the
countermovement phase in a CMJ include the development of active state prior to
concentric action (Bobbert, Gerritsen, Litjens, & van Soest, 1996; Bobbert & Casius,
2005), tendon elastic recoil (Alexander, 1995), and the enhancement of subsequent
force following muscle stretch (Edman, Elzinga & Noble, 1978).
Few researchers have compared kinetic and kinematic CMJ determinants.
Vanezis and Lees (2005) concluded that kinematic technique factors were less
important than muscle capabilities, although their technique analysis was limited to
the timing of the lowest vertical mass centre position and the use (or not) of an arm
swing. An increase in strength does not always result in a subsequent performance
improvement (Clutch, Wilton, McGown, & Bryce, 1983), perhaps due to the need to
adapt coordination following strength gains (Bobbert & van Soest, 1994). Supporting
the importance of appropriate technique utilisation, Luhtanen and Komi (1978)
reported that well-trained participants were able to utilise only 76% of the available
mechanical energy during a CMJ but that optimal coordination could increase this to
84%. It is evident that in order to gain a broad understanding of the determinants of
CMJ performance, it is necessary to study both kinetic and kinematic variables.
If the findings of this study are to be practically applicable when considering
progression from poor to good countermovement jumping ability then it is important
that variables contributing to the difference between good and poor jumpers are
identified. This necessitates the recruitment of a heterogeneous ability range to the
sample population so that the effects of variability in each of the kinetic and kinematic
variables can be observed. The purpose of the present study is therefore to quantify
the relative contributions of these factors in order to identify the most important
determinants of CMJ height.
METHODS
Eighteen physically active males (21.2 ± 2.2 years, 1.80 ± 0.08 m, 78.1 ± 9.2
kg, mean ± SD) participated in this investigation. Participants with large variation in
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jumping experience were selected so as not to distort the importance of individual
variables. The testing procedures were explained to each participant and informed
consent was obtained in accordance with the Loughborough University Ethical
Advisory Committee.
Participants attended two laboratory testing sessions: 1) isometric knee
extension measurement; 2) anthropometric and CMJ measurement. They were
required to refrain from strenuous physical activity for 36 hours prior to each session.
The knee extensor contractile properties of the dominant leg were tested using a
dynamometer (Con-Trex; CMV Aargau, Switzerland; hip angle 100°; frequency 512
Hz). Following dynamic stretching and submaximal warm up trials of incremental
intensity, isometric unilateral knee extension torque was measured at five angles
(15°, 30°, 45°, 60°, 75°; indicated a fully extended leg) in a randomised order.
Two trials were recorded at each angle, separated by 2 min rest: a 5 s maximal
voluntary contraction; then a measure of rate of torque development, with the
participant instructed to increase their knee extension torque as fast as possible
(Sahaly, Vandewalle, Driss, & Monod, 2001). The participants rested for 3 min
between each knee angle. The peak isometric knee extension torque was identified
as the highest of the angle-specific peak torques. The rate of torque development
trial at the angle corresponding to peak isometric torque was used to obtain the rate
of change of joint torque in 50 ms intervals (RTD0-50, RTD50-100, RTD100-150) from 0-
150 ms after the onset of contraction (identified manually; Tillin, Jimenez-Reyes,
Pain, & Folland, 2010). This enabled the investigation of the earlier agonist neural
drive dominated and later maximal voluntary torque dominated rate of torque
development (Andersen & Aagaard, 2006; Tillin, Pain, & Folland, 2012). All isometric
parameters were normalised to body mass.
For the CMJ measurement, thirty-eight 14 mm retro-reflective markers were
attached to each participant, positioned over bony landmarks. The metatarso-
phalangeal, ankle, knee, shoulder, elbow and wrist joint centres were calculated from
a pair of markers placed across the joint so that their mid-point coincided with the
joint centre, similarly to Ranson, King, Burnett, Worthington, and Shine (2009). The
centre of the neck was defined as the midpoint between two parkers positioned over
the sternoclavicular notch and the C7 vertebra. The centre of the head was defined
as the average position of four markers and the hip joint centres were calculated from
four markers placed over the left and right anterior and posterior superior iliac spine
(Davis, Õunpuu, Tyburski, & Gage, 1991). Participants were given the chance to
perform a self-selected warm-up and to practice before performing three maximal
CMJs using a natural technique of their selection, including arm swing. They were
permitted to rest between trials for as long as they felt necessary, with a minimum
rest period of 15 s imposed (Read & Cisar, 2001). Trials were recorded using a 17
camera (M2 MCam) Vicon Motion Analysis System (OMG Plc, Oxford, UK) operating
at 480 Hz. Ground reaction forces were measured using an AMTI force platform
(600 x 400 mm, 960 Hz).
The CMJs were manually labelled and processed and all data were
synchronised in Vicon’s software. Two-dimensional position data were used, with the
assumption of negligible movement in the medio-lateral plane. All joint centre
trajectories were filtered using a recursive fourth-order low-pass Butterworth filter
with a cut-off frequency of 6 Hz determined based on a residual analysis and
qualitative evaluation of the data (Winter, 1990). Unilateral joint centre positions
were assumed to represent the bilateral location and the errors in jump height and
peak joint torques caused by this assumption were calculated for one participant.
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These were found to be less than 1%, with the error in mass centre displacement
and joint torques remaining small throughout the movement.
Subject-specific segmental inertia parameters were computed from
anthropometric measurements using Yeadon’s (1990) geometric inertia model of the
human body. The average centre of mass height during the approximately 2 s period
of stationary standing prior to the jump was defined as zero displacement and thus
the CMJ height was determined as the maximum vertical mass centre displacement,
with the highest jump for each participant used for further analysis. Inverse dynamics
was used to obtain body mass normalised peak ankle, knee and hip net joint torques
and powers, with extension torques presented as positive. In order to provide
methodological consistency with the isometric rate of torque development and
facilitate the investigation of different time periods during knee extension, CMJ rate of
torque development was computed from 0-200 ms of knee extension in 50 ms
intervals (CMJ RTD0-50, CMJ RTD50-100, CMJ RTD100-150, and CMJ RTD150-200). Eight
kinematic parameters were also defined: minimum absolute joint angles and those at
take-off for the ankle, knee, hip, and shoulder. Shoulder extension beyond the line of
the greater trochanter to glenohumeral joint was defined as negative, with flexion
forwards from this line positive.
All statistical analyses were performed within SPSS v.20 (SPSS Corporation,
USA). To address the aim of the study and identify which of the isometric, CMJ
kinematic, and CMJ kinetic (independent) variables best explained the variation in
CMJ height (dependent variable), forwards stepwise linear regressions were used.
Predictor variables included in these three regression models were put forward as
‘candidate’ variables to an overall regression model. Scatterplot and Pearson
Product Moment Correlation analyses revealed a significant (r = 0.68, P < 0.01)
quadratic relationship between CMJ RTD0-50 and CMJ height and thus an
exponentiation transformation was performed on CMJ RTD0-50, raising each value to
the power of two prior to its inclusion in the linear regression analyses. The
requirement for the inclusion of a parameter in the regression equations was P <
0.05. Similarly, regression models were rejected if coefficient 95% confidence
intervals included zero or if correlations, tolerance statistics, or variance inflation
factors showed any evidence of multicollinearity (Bowerman & O’Connell, 1990;
Draper & Smith, 1998; Field, 2013; Menard, 1995; Myers, 1990). To confirm the
normality of the standardised residuals in the regression models Shapiro-Wilk tests
for normality were performed. The P-values ranged from 0.22 to 0.88 indicating no
evidence against the assumption of normality of the residuals. The percentage of
variance in the dependent variable (CMJ height) explained by the independent
variable(s) in a regression was determined by Wherry’s (1931) adjusted R squared
value. This represents an attempt to estimate the proportion of variance that would
be explained by the model had it been derived from the population (young physically
active males) from which the sample was taken. To overcome the potential limitation
of stepwise regressions relying on a single best model, the explained variance for all
possible regressions with the same number of predictor variables as the stepwise
solution were determined for comparison. Pearson Product Moment correlation was
used to establish relationships, with a P-value < 0.05 indicating statistical
significance.
RESULTS
The eighteen males participating in this study achieved CMJ heights of 0.38 -
0.73 m (mean 0.55 ± 0.09 m). There was substantial variation in the isometric
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parameters (Table I) with a mean peak isometric knee extension torque of 3.62 ±
0.68 N∙m∙kg-1. Of the CMJ kinematic parameters (Table I), the shoulder showed the
largest variation, indicating a technique difference at this joint. Mean peak powers at
the ankle, knee, and hip were 18.00 ± 4.20 W∙kg-1, 22.02 ± 4.94 W∙kg-1, and 9.83 ±
3.54 W∙kg-1 respectively (Table I). The mean concentric CMJ rate of torque
development was negative for all four 50 ms intervals.
Table I. Summary of parameters
isometric
parameters
mean ±
SD
CMJ kinetic
parameter
mean ± SD
CMJ kinematic
parameter
mean ±
SD
peak torque
(N∙m∙kg-1)
3.62 ±
0.68
PT ankle (N∙m∙kg-1)
2.79 ± 0.40
minimum ankle angle
(°)
84 ± 9
RTD0-50
(N∙m∙kg-1∙s-1)
11.67 ±
8.12
PT knee (N∙m∙kg-1)
3.31 ± 0.62
minimum knee angle
(°)
81 ± 16
RTD50-100
(N∙m∙kg-1∙s-1)
18.96 ±
7.92
PT hip (N∙m∙kg-1)
2.20 ± 0.44
minimum hip angle (°)
75 ± 15
RTD100-150
(N∙m∙kg-1∙s-1)
10.84 ±
5.07
PP ankle (W∙kg-1)
18.00 ± 4.20
minimum shoulder
angle (°)
-67 ± 26
PP knee (W∙kg-1)
22.02 ± 4.94
TO ankle angle (°)
137 ± 12
PP hip (W∙kg-1)
9.83 ± 3.54
TO knee angle (°)
174 ± 14
CMJ RTD0-50
(N∙m∙kg-1∙s-1)
-0.93 ± 6.07
TO hip angle (°)
172 ± 5
CMJ RTD50-100
(N∙m∙kg-1∙s-1)
-4.75 ± 8.12
TO shoulder angle (°)
103 ± 37
CMJ RTD100-150
(N∙m∙kg-1∙s-1)
-1.18 ± 8.15
CMJ RTD150-200
(N∙m∙kg-1∙s-1)
-0.66 ± 7.14
Note: CMJ: countermovement jump; RTD0-50, RTD50-100, RTD100-150, RTD150-200: rate of torque development from
0-50, 50-100, 100-150, 150-200 ms (of concentric knee extension for the CMJ RTD); PT: peak torque; PP:
peak power; TO: take-off.
Figure 1. Predicted countermovement jump (CMJ) height against actual CMJ height for the overall
three parameter stepwise solution (Table II). 74% of the variation in CMJ height explained
by: CMJ peak knee power; take-off shoulder angle; CMJ peak ankle power. With a higher
percentage of the variation in CMJ height explained the closer the data points lie to the
dashed line y = x (predicted height = actual height).
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Table II. Regression equations predicting countermovement jump height from computed variables using stepwise
linear regression
95% confidence
intervals
parameter(s)
coefficient
lower
bound
upper
bound
P
percentage
explained
isometric regression
peak isometric knee
extension torque
0.064
0.002
0.127
0.045
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CMJ kinematic
regression
TO shoulder angle
TO ankle angle
0.0016
0.0007
0.0024
0.001
58
0.004
0.002
0.007
0.003
CMJ kinetic
regression 1
CMJ peak knee power
CMJ peak ankle power
0.011
0.005
0.017
0.002
57
0.008
0.001
0.016
0.032
CMJ kinetic
regression 2
CMJ peak knee torque
0.087
0.036
0.138
0.002
57
CMJ peak ankle power
0.009
0.002
0.017
0.018
overall regression
CMJ peak knee power
0.010
0.005
0.015
0.001
74
TO shoulder angle
0.001
0.0004
0.002
0.005
CMJ peak ankle power
0.008
0.002
0.014
0.010
Note: CMJ: countermovement jump; TO: take-off; CMJ kinetic regression 1: stepwise solution; CMJ kinetic
regression 2: alternative solution. P < 0.05 indicates a significant relationship.
The best individual predictor of CMJ height was peak power at the knee joint,
explaining 44% of the observed variation (P < 0.01). This increased to 74% with the
addition of one CMJ kinematic parameter (take-off shoulder angle) and a further CMJ
kinetic parameter (peak ankle power; Figure 1). Higher jumps were associated with
greater peak powers at the knee and ankle, and greater shoulder flexion at take-off.
The CMJ kinematic regression showed the shoulder angle at take-off to be the
greatest kinematic predictor of jump height (R2 = 0.26, P < 0.05). Greater shoulder
flexion and ankle plantar-flexion at take-off predicted greater jump heights (together
explaining 58% of the variation). Two CMJ kinetic parameters (peak knee power and
peak ankle power) explained 57% of the variation (Table II). Increases in these
parameters were associated with greater CMJ heights. Further analysis showed that
an alternative CMJ kinetic regression model including peak knee torque and peak
ankle power also explained 57% of the variation in jump height.
The peak isometric knee extension torque alone accounted for 18% of the jump
height variation (P < 0.05; Table II), with insufficient evidence to support the addition
of any further isometric parameters to the regression equation (i.e. P > 0.05). The
correlation between peak isometric knee extension torque and CMJ peak knee power
was non-significant (r = 0.267; P = 0.142), with only 7% of the variation in peak knee
power explained by peak isometric torque.
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DISCUSSION
The present study has identified the parameters that best explain CMJ height.
In particular, 74% of the performance variation can be explained using just three
parameters: CMJ peak knee power; take-off shoulder angle; and CMJ peak ankle
power. Two CMJ kinematic parameters (take-off shoulder angle; and take-off ankle
angle) explained 58% of the jump height variation, whilst two CMJ kinetic parameters
(peak knee power or peak knee torque; and peak ankle power) and one isometric
parameter (peak isometric knee extension torque) explained 57% and 18%
respectively.
The inclusion of peak power at the knee and ankle joints in the overall
regression model supports previous claims that CMJ performance is positively
associated with lower-limb power (Ashley & Weiss, 1994; Nuzzo et al., 2008;
Sheppard et al., 2008; Vanezis & Lees, 2005). The work-energy-power relationship
makes it inevitable that greater joint powers result in more positive work done and so
greater total body kinetic energy and mass centre vertical velocities at take-off. As
an indicator of maximal capabilities of the knee extensor musculature, a greater peak
isometric knee extension torque enables greater joint torques and powers to be
produced during the CMJ. However, whilst the inclusion of peak isometric torque in
the isometric regression furthers the existing evidence for a relationship between
strength and CMJ height (Ashley & Weiss, 1994; Sheppard et al., 2008; Wisløff et al.,
2004), CMJ peak knee power explained a much greater proportion of the
performance variation (44% versus 18%). Similarly, Young, Wilson, and Byrne
(1999) showed that CMJ height is more closely related to measures of speed-
strength qualities than maximum strength. Indeed the low R2 (0.07) and lack of
significant correlation between body mass normalised peak isometric torque and
CMJ peak knee power variables suggest it is not maximal muscle strength that
causes the strong relationships between CMJ kinetic variables and jump height.
Given that the isometric parameters explained only 18% of the variation and 58% can
be explained by CMJ kinematic parameters it seems likely that technique (kinematic
parameters) determines the extent to which the maximal muscle capabilities
(isometric parameters) can be utilised during the jump (to produce the CMJ kinetic
parameters). Indeed, Bobbert and van Soest (1994) showed that an increase in
muscle strength only improves CMJ performance if technique is adapted to the
specific muscle capabilities. Thus, both the technique used and the joint kinetics
during the jump are likely important determinants of CMJ height in the current sample
of participants, where jumping ability varied greatly (from 0.38 0.73 m).
Experienced jumpers would be expected to use similar, close to optimal, techniques
and thus muscle capabilities may distinguish between their performances, as
reported by Vanezis and Lees (2005).
The lack of significant finding relating to the initial, neutrally-mediated isometric
RTD0-50 is in agreement with Tillin et al. (2013) but not De Ruiter et al. (2006). It
seems likely that the countermovement phase of the jump diminishes the importance
of fast neural activation by enabling the development of an active state prior to the
onset of concentric muscle contraction and thus increasing the time available to
activate the musculature and to generate extension joint torques (Bobbert et al.,
1996; Bobbert & Casius, 2005). In the very early stages of knee extension, whilst the
total length of the knee extensor musculo-tendon units decrease, the contractile
elements may still be being stretched as the tendon begins its elastic recoil and so
knee extension begins with large eccentric muscle forces (Alexander, 1995). All of
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these factors reduce the importance of fast initial rate of torque development during
CMJs.
The association between later (post-50 ms) rate of torque development and
CMJ height is dependent on absolute maximal force (Tillin et al., 2013) and so with
peak isometric knee extension torque already included in the stepwise regressions,
the inclusion of the later isometric rates of torque development did not significantly
improve the prediction of jump height. Previous studies have used correlation
coefficients rather than stepwise regressions to assess the rate of torque
development-jump height relationship and so were not affected by this issue (De
Ruiter et al., 2006; Marcora & Miller, 2000; McLellan et al., 2011; Thompson et al.,
2013; Tillin et al., 2013). These assertions are further supported by a significant
correlation between peak isometric torque and RTD100-150 (r = 0.546; P = 0.01) in the
present study.
The significant quadratic relationship between CMJ RTD0-50 and CMJ height (r =
0.68, P < 0.01) was explained by a significant (r = -0.48, P < 0.05) negative
correlation between CMJ RTD0-50 (variable x) and the knee extension torque at
concentric onset (variable y). This relationship takes the form x + ay constant (i.e.
there is a trade-off between the two variables), with (x2 + y2) positively correlating to
CMJ height (r = 0.69, adjusted R2 = 0.45, P < 0.01). This (x2 + y2) relationship means
that the higher jumpers either produced high eccentric knee extension torques
(greater y; resulting in an apparent benefit of negative rates of torque development
as torque subsequently decreased during knee extension) or were able to maintain
their knee extension torque during early concentric contraction (greater x), with those
participants in the mid-range for both variables (neither high x nor high y) achieving
the lowest jump heights.
Despite the discussed benefits of the countermovement phase, the minimum
knee and ankle angles were not included in the stepwise solutions. This is in
contrast with previous findings that increased knee and ankle joint ranges of motion
result in greater jump heights (Georgios et al., 2007; Moran and Wallace, 2007).
Further analysis of individual subject data in the present study showed that the
highest jumper was the participant with the greatest knee flexion. In theory there is
no limit to the relationship between increased squat depth and increased squat jump
height (Domire & Challis, 2007); however, jumps from a deep squat are rarely
optimally coordinated due to a lack of practice with this technique. This same issue
is likely present in inexperienced countermovement jumpers and may explain why
the link between minimum knee angle and CMJ height was only observed in the best
performing participant.
Previous studies have simply compared jumps with and without an arm swing
(Feltner et al., 1999; Harman et al., 1990; Payne et al., 1968; Shetty & Etnyre, 1989;
Vanezis & Lees, 2005), whereas the present study investigated shoulder angles at
key points in the arm swing movement. Greater shoulder flexion at take-off was a
strong predictor of CMJ height, likely indicating greater use of the arm swing, and
thus a slowing of hip extension leading to greater work done at the hip as well as the
shoulder (Blache & Monteil, 2013; Cheng et al., 2008; Domire & Challis, 2010). Both
greater shoulder flexion and ankle plantar-flexion at take-off increase the ‘stretch
height’ and thus pre-takeoff displacement and both were included in the CMJ
kinematic regression. Because CMJ height was calculated relative to standing
position, pre-takeoff displacement was included and thus jump height may be
affected by anthropometric variables such as foot length. However, the degree to
which any anthropometric advantage is reflected in the stretch height is dependent
9
on technique such as shoulder flexion and ankle plantar-flexion. An analysis of
individual participant data suggests that the degree of ankle plantar-flexion and
shoulder flexion during the propulsion phase distinguishes the highest two jumpers
from the rest of the participants and explains the underestimation of their jump
heights by the CMJ kinetic and isometric parameter regression models. Exclusion of
these participants would increase the adjusted R2 for these two regressions to 0.66
and 0.40 respectively, illustrating the importance of recruiting a heterogeneous
sample so as not to overestimate the importance of individual factors in the
progression from poor to good countermovement jumping.
One limitation of the present study is the introduction of errors by any
movement outside of the sagittal plane, although this is expected to have been
negligible. Furthermore, isometric knee extensions were measured at five discrete
joint angles and so the true peak isometric torque is likely at an intermediate angle.
In a review by Jakobi and Chilibeck (2001) 5 out of 8 studies showed no bilateral
deficit in isometric knee extension. The effect is present, however, in explosive
voluntary contractions such as the isometric rate of torque development trials in this
study (Buckthorpe, Pain, & Folland, 2013). The potential implications of this deficit in
the present study are minor, with the application of unilateral measures to the
investigation of a bilateral performance task unlikely to distort the observed
relationships. The 74% of CMJ height variation explained by the overall three
parameter regression suggests that the important aspects of performance have been
identified. In particular, those wishing to improve their CMJ height should seek to
maximise power at the knee and ankle joints and utilise greater ankle plantar-flexion
and shoulder flexion. These results are likely to provide a valuable framework upon
which to base coaching and conditioning as athletes progress from poor to good
countermovement jumping. Future studies should continue to explore the interaction
between kinetic and kinematic factors, including joint ranges of motion and the
timings of muscle activations, possibly using methods beyond the scale of the current
study such as simulation modelling or electromyography. It is also important to
address whether these results are independent of anthropometric differences and
whether the same results are observed in a female population.
In conclusion, the purpose of the study was to quantify the relative contributions
of kinetic and kinematic parameters in order to identify the most important
determinants of CMJ performance. The findings suggest that both kinetic and
kinematic factors during the jump are important determinants of CMJ performance,
with technique influencing the extent to which maximal muscle capabilities can be
utilised during the jump. The study has revealed the importance of lower-limb joint
powers and previously underestimated, coachable technique factors including
greater ankle plantar-flexion during the jump and shoulder flexion during the arm
swing. Both the kinetic and kinematic variables during the jump explained a large
proportion of the performance variation and further research is needed to fully
understand the interactions between these two sets of factors.
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... Isokinetic dynamometer can measure muscle strength parameters of single joint or joint chains under different motion modes and angular velocities, and provide a more detailed assessment of the torque generating capacity of the muscles involved in specific joint movements. The combination of the two can better reflect the muscle strength and power characteristics of athletes [6,8,9]. ...
... However, we failed to arrive at similar results, the parameters of CMJ have no difference in hikers and trapeze sailors, as well as high-level and low-level groups. Both kinetic and kinematic factors during the jump are important determinants of CMJ performance, on the one hand, the adaptation of neuromuscular tissue to strength and power training is improved, and on the other hand, technique influencing the extent to which maximal muscle capabilities can be utilized during the jump [8]. The CMJ transmits the reaction force of the ground to the longitudinal direction by extending the hips, knees and ankles. ...
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... However, Fukashiro [29] examined joint moment and mechanical power flow of the lower limb during the vertical jump and found that the greatest contributor was the hip joint. More recently, one study [30] suggested that the kinematic and dynamic parameters of the knee and ankle joints might explain CMJ performance variation. The magnitude of countermovement has also been associated with CMJ performance, with the knee flexion angle during the eccentric phase being an important variable that influences its outcome. ...
... Achieving maximum jump performance in volleyball spike jump (VSJ) is a frequent subject of sports analysis, whether kinetic (Slovák et al., 2021;Sarvestan et al., 2020a) or kinematic (Oliveira et al., 2020;Ikeda et al., 2018;Sarvestan et al., 2020b, Zahálka et al., 2017 because the height of the jump is seen as a key component, in having a higher success rate (Sarvestan et al., 2020b;Ziv & Lidor, 2010). Similar to a typical standing jump movement, such as a countermovement jump (CMJ) with arm swing, the VSJ is executed by both legs (McErlain-Naylor et al., 2014;Fuchs et al., 2019). Differing from standing vertical jumps, the VSJ movement is characterized by using arm swings during the last two or three counter-movement steps (Fuchs et al., 2021), while transferring the horizontal momentum of the body into the vertical acceleration before take-off (Wagner 2009). ...
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... However, no significant correlation has been reported between the eccentric knee flexion force and jump height [11]. Knee torque and power during the CMJ contribute to the jump height [33], which is reasonable, given the importance of knee strength for jumping performance. This was also the case for squatting, which was related to the greater torque exerted by the knee during this movement [34]. ...
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... s; the moment from when the jumper's takeoff foot touches the ground to the moment when the takeoff foot leaves the ground is only 0.1~0.2 s [58], and many studies have also confirmed that having a better RFD could produce faster movements and greater explosive strength [61][62][63]. ...
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... Moreover, it is important when testing lower-limb power to utilize a 'best practice' in terms of equipment (i.e., best equipment available) and standardized protocol with the same technology equipment (66,117,118). Table 3 here, please*** It is generally accepted that force platforms are considered the gold standard for jump testing, as they provide force-time data which enables a more detailed interpretation of any mechanistic changes which may result in an increase or decrease in performance, i.e., jump height or power (93). That said, force platforms may not be accessible or feasible in all performance settings, therefore, field-based testing equipment (e.g., jump mat or optoelectronic devices) provide a realistic alternative and estimate jump height from flight time (36,114). ...
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Beato, M, Datson, N, Anderson, L, Brownlee, T, Coates, A, and Hulton, A. Rationale and practical recommendations for testing protocols in female soccer: A narrative review. J Strength Cond Res XX(X): 000-000, 2023-The aim of this narrative review is to evaluate the presented literature on tests (aerobic, speed, changes of direction [COD], strength, power, jump, and anthropometry) of the varied components of female soccer and to draw attention to the most suitable protocols to allow practitioners to accurately track players' fitness status. The 2 most common field tests used to assess aerobic fitness are the Yo-Yo intermittent test (level 1 and level 2) and the 30-15 intermittent fitness test because of an ability to measure multiple players at once with a soccer-specific intermittent profile. The sprinting performance can be assessed on distances of <30 m; however, longer distances (e.g., 40 m) allow for achieving peak speed (flying sprint test), which can be assessed using global navigation satellite system. Changes-of-direction capacity has been found to be an important component of players testing and training programs, although there is no "gold standard" to assess COD or repeated sprint ability performance in female players. Lower-limb power can be assessed using jump tests that can use force platforms, jump mats, and optoelectronic devices, while maintaining a good reliability. Several in-direct tests are currently available for assessing anthropometry parameters, such as skinfold thickness, hydrodensitometry, and ultrasound. However, dual-energy x-ray absorptiometry is the most valid and reliable method for assessing body composition in team sport athletes, with the addition of bone health that is a key measure in female athletes. In conclusion, the evidence reported in this review will be able to aid practitioners, coaches, and researchers to decide which tests meet the requirements of their environment.
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Background This study aimed to analyze knee ligament of load and joint moment to simulate the strengthening of the hip abductor and hamstring muscles using musculoskeletal modeling, thereby contributing to decrease of knee ligament load. Methods Forty participants (age: 21.85 ± 1.90 years; height: 1.76 ± 0.06 m; body mass: 68.5 ± 7.06 kg) were instructed to run at 4.5 ± 0.2 m/s from a 5 m distance posterior to the force plate, land their feet on the force plate, and perform the cutting maneuver on the left. In the musculoskeletal modeling, the hip abductor and hamstring muscles were targeted to construct a model with a 30% increase in the contraction force of the hip abductor, hamstring, and both 2 muscles. The variables were the ligament force and knee joint moment. One-way repeated measure ANOVA and Bonferroni test were used to compare the abductor/hamstring, abductor, hamstring and control models. Results There were significant differences in anterior bundle of the anterior cruciate ligament (ACL) (P = .001), inferior bundle of the superficial layer of the medial collateral ligament (MCL) (P = .016), and posterior bundle of the superficial layer of the MCL (P = .022) force. The post hoc showed that the hamstring model had lower anterior bundle of the ACL and inferior bundle of the superficial layer of the MCL than the abductor/hamstring and abductor models (P < .05) and lower posterior bundle of the superficial layer of the MCL than the abductor and control models (P < .05). There was a significant difference in the adduction (P = .028) and internal rotation moments (P = .014). The post hoc showed that both moments were lower in the hamstring model than in the other models (P < .05). Conclusions The hamstring strengthening may contribute significantly to preventing ACL or MCL injury by reducing knee ligament load.
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