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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor

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Purpose: The purpose of this study was to assess the utility of an inertial sensor for assessing recovery in professional soccer players. Methods: In a randomized, crossover design, 11 professional soccer players wore shorts fitted with phase change material (PCM) cooling packs or uncooled packs (control) for 3 h after a 90 minute match. Countermovement jump (CMJ) performance was assessed simultaneously with an inertial sensor and an optoelectric system, pre match, and 12, 36 and 60 h post match. Inertial sensor metrics were flight height, jump height, low force, countermovement distance, force at low point, rate of eccentric force development, peak propulsive force, maximum power, and peak landing force. The only optoelectric metric was flight height. CMJ decrements, and effect of PCM cooling were assessed with repeated measures ANOVA. Jump heights were also compared between devices. Results: For the inertial sensor data there were decrements in CMJ height on the days after matches (88±10% of baseline at 36 h P=0.012, effect size 1.2, for control condition) and accelerated recovery with PCM cooling (105±15% of baseline at 36 h, P=0.018 vs. control, effect size 1.1). Flight heights were strongly correlated between devices (r=0.905, P<0.001) but inertial sensor values were 1.8±1.8 cm lower (P=0.008). Low force during countermovement was increased (P=0.031) and landing force was decreased (P=0.043) after matches, but neither were affected by the PCM cooling intervention. Other CMJ metrics were unchanged after matches. Conclusions: This small portable inertial sensor provides a practical means of assessing recovery in soccer players.
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
Note. This article will be published in a forthcoming issue of the
International Journal of Sports Physiology and Performance. The article
appears here in its accepted, peer-reviewed form, as it was provided by
the submitting author. It has not been copyedited, proofread, or formatted
by the publisher.
Section: Original Investigation
Article Title: Countermovement Jump Recovery in Professional Soccer Players Using an
Inertial Sensor
Authors: Malachy P. McHugh1,5, Tom Clifford2,5, Will Abbott3,4, Susan Y. Kwiecien1,5, Ian J.
Kremenic1, Joseph J. DeVita1, and Glyn Howatson5,6
Affiliations: 1Nicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital,
New York, NY; 2School of Biomedical Sciences, Newcastle University, United Kingdom; 3School
of Sport and Service Management, Brighton University, UK; 4Brighton and Hove Albion F.C,
American Express Elite Performance Centre, Lancing, UK; 5Department of Sport, Exercise and
Rehabilitation, Northumbria University, Newcastle, United Kingdom; 6Water Research Group,
School of Environmental Sciences and Development, Northwest University, Potchefstroom, South
Africa.
Journal: International Journal of Sports Physiology and Performance
Acceptance Date: May 14, 2018
©2018 Human Kinetics, Inc.
DOI: https://doi.org/10.1123/ijspp.2018-0131
Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
Title: Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor
Submission Style: Original Investigation
Authors: Malachy P. McHugh1,5, Tom Clifford2,5, Will Abbott3,4, Susan Y. Kwiecien1,5, Ian J.
Kremenic1, Joseph J. DeVita1, Glyn Howatson5,6
1Nicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital, New York,
NY; 2School of Biomedical Sciences, Newcastle University, United Kingdom;
3School of Sport and Service Management, Brighton University, UK;
4Brighton and Hove Albion F.C, American Express Elite Performance Centre, Lancing, UK;
5Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle, United
Kingdom;
6Water Research Group, School of Environmental Sciences and Development, Northwest
University, Potchefstroom, South Africa.
Corresponding Author:
Malachy P McHugh Nicholas Institute of Sports Medicine and Athletic Trauma, Manhattan Eye
Ear and Throat Hospital, 210 East 64 Street, New York, NY 10065, USA
PH: +1 212 434 2714, email: mchugh@nismat.org
Running head: Inertial sensor jump testing
Abstract word count: 249
Manuscript word count: 3987
Figures: 2
Tables: 2
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
ABSTRACT
Purpose: The purpose of this study was to assess the utility of an inertial sensor for assessing
recovery in professional soccer players. Methods: In a randomized, crossover design, 11
professional soccer players wore shorts fitted with phase change material (PCM) cooling packs or
uncooled packs (control) for 3 h after a 90 minute match. Countermovement jump (CMJ)
performance was assessed simultaneously with an inertial sensor and an optoelectric system, pre
match, and 12, 36 and 60 h post match. Inertial sensor metrics were flight height, jump height, low
force, countermovement distance, force at low point, rate of eccentric force development, peak
propulsive force, maximum power, and peak landing force. The only optoelectric metric was flight
height. CMJ decrements, and effect of PCM cooling were assessed with repeated measures
ANOVA. Jump heights were also compared between devices. Results: For the inertial sensor data
there were decrements in CMJ height on the days after matches (88±10% of baseline at 36 h
P=0.012, effect size 1.2, for control condition) and accelerated recovery with PCM cooling
(105±15% of baseline at 36 h, P=0.018 vs. control, effect size 1.1). Flight heights were strongly
correlated between devices (r=0.905, P<0.001) but inertial sensor values were 1.8±1.8 cm lower
(P=0.008). Low force during countermovement was increased (P=0.031) and landing force was
decreased (P=0.043) after matches, but neither were affected by the PCM cooling intervention.
Other CMJ metrics were unchanged after matches. Conclusions: This small portable inertial
sensor provides a practical means of assessing recovery in soccer players.
Key Words: muscle function, accelerometer, cryotherapy, phase change material, power
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
INTRODUCTION
Counter movement jump (CMJ) tests are commonly used to assess recovery of muscle
function following strenuous exercise. Impairments in CMJ have been demonstrated on the days
following various forms of exercise including drop jump protocols,1-3 repeated sprint and
simulated field sport tests4-9 and soccer matches. 10-11 Traditionally, CMJ performance has been
measured using a vertical structure where athletes jump to touch incrementally separated pegs with
their out stretched arm.3,12 Since this test involves an asymmetric vertical reach with one arm,
alternative tests have been adopted to better isolate the actual jump performance, and eliminate the
reaching component. To this end, CMJ performance has been assessed using contact mats4,8,11,13,14
or optoelectric systems1,5-7,9,10 that can accurately measure flight time, and thereby calculate center
of mass vertical displacement. These tests assume that the subjects land with the same body
alignment with which they took off.
Performance during CMJ tests has also been assessed using inertial devices that measure
vertical acceleration.15-18 In addition to providing a measure of jump height, these devices can
derive other biomechanical metrics describing the jump performance, such as force, power,
velocity and center of mass position. Force data derived from inertial sensors has been shown to
agree well with simultaneously recorded force plate data.16 However, while jump heights derived
from inertial sensors correlate strongly with heights calculated from force plates, inertial devices
were shown to slightly underestimate jump height compared to force plate data.18 Furthermore,
inertial sensor derived CMJ heights were well correlated with optoelectric measurements but
provided slightly higher jump heights.18 Thus, practitioners are advised against using these systems
interchangeably.
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
Tests of CMJ performance have been used to assess recovery in numerous studies
examining interventions to accelerate exercise recovery; several studies used contact mats,4,8,13
while other studies used an optoelectric system,1 force plates,2 or an inertial sensor.15 In the one
study using an inertial sensor, Bieuzen et al15 examined recovery in professional soccer players in
response to an exercise protocol involving a combination of countermovement jumps and rowing
exercise. However, CMJ performance had recovered within one hour of the exercise intervention
so it was not possible to assess the ability of the inertial sensor to detect differences in recovery
over time or between intervention and control.
Standardized performance tests are important for monitoring athletes over the course of a
season to assess training adaptations and recovery. To this end CMJ performance has become a
common recovery metric in soccer across a range of playing abilities, including professional,14,15
semi-professional,4,9,10 college6,12,19 and youth players.11,18 The use of inertial sensors to assess
CMJ recovery in soccer players offers several advantages over other methods; inertial sensors are
small, portable, wearable devices that can provide metrics for different components of the CMJ in
addition to jump height. Therefore, the purpose of this study was to assess the utility of an inertial
sensor for examining recovery in professional soccer players. This dataset is part of a larger study
examining the effectiveness of a cryotherapy intervention on recovery in soccer players.20 The full
data set has been published previously but the data from the inertial sensor was not included
because the software for analysis was still under development. The specific goals of the present
study were to determine: (1) if the inertial sensor was sufficiently sensitive to detect decrements
in jump height on the days following a professional soccer match, (2) if the inertial sensor data
agreed with the optoelectric data, (3) if the inertial sensor was able to detect accelerated recovery
of jump height with the cryotherapy intervention, and (4) if the additional force, power, velocity,
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
and position metrics from the inertial sensor provided useful information on the biomechanics of
CMJ impairment and recovery. It was hypothesized that the inertial sensor would show impaired
CMJ metrics following the soccer match, accelerated recovery with the cryotherapy intervention,
and good agreement with the optoelectric measurements.
METHODS
Study Participants
The study participants were 11 professional soccer players (age 19±1 yrs, height 1.80±0.57
m, mass 75.9±7.2 kg, body fat 7.9±1.3%) from the under-23 squad of a team playing in the second
tier of the English league. All participants gave written informed consent and the study was
approved by institution review board.
Study Design
The full experimental protocol has been described in detail in the larger study20 and is
summarized here. This was a randomized crossover design examining the effectiveness of a novel
cryotherapy intervention on recovery on the days after a soccer match. For the cryotherapy
intervention, players wore shorts fitted with phase change material (PCM) cooling packs over the
quadriceps muscles. The PCM cooling packs maintained a temperature of 15°C during a 3 h
treatment. The control condition was room temperature PCM packs worn inside the same shorts.
Each player was randomized to wear the PCM cooling packs or the room temperature packs after
a match and received the opposite treatment after a subsequent match. Matches were selected
where the team had longer than a 3 h coach ride back to their team facility after the match. Thus,
compliance with the intervention could be confirmed by study personnel. The following tests were
administrated on the days prior to the study matches and on each of the following three mornings
after the matches: muscle soreness assessment, CMJ, maximal isometric voluntary contraction,
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
and an adapted Brief Assessment of Mood (BAM+) questionnaire. The details of the CMJ test are
described here. All other test results have been reported previously.20
CMJ Test
The CMJ performance was measured using two different instruments; an optoelectric
system (Optojump system, Bolzano, Italy) and an inertial sensor (BTS G-Sensor 2, Brooklyn, NY).
As described previously, participants started the movement standing upright with hands on their
hips and after a verbal cue, descended into a squat (countermovement) prior to performing a
maximal effort vertical jump. Participants performed three maximal efforts, separated by
approximately 60 s of standing recovery; the mean of the 3 jumps was used for analysis. During
testing the inertial sensor was placed in a pouch attached to a waistband strapped tightly to the
participants. The inertial sensor was aligned with the middle of the lumbar spine. The 70x40x18
mm inertial sensor weighed 37 g and contained a triaxial accelerometer, gyroscope and
magnetometer. The signals were collected at 100 Hz via Bluetooth® connection.
The metrics derived from the inertial sensor are described according to the phase in which
they occurred, countermovement, propulsive, or landing phase (Fig. 1).
Countermovement Phase: The countermovement phase started with the initiation of the
countermovement to the lowest point of the countermovement, with both points identified from
the derived position data. The countermovement metrics that were examined were: (1) low point
(lowest position of center of mass during countermovement); (2) low force (lowest force during
initiation of countermovement; (3) force at low point (the force at the lowest point of the
countermovement); (4) rate of eccentric force development (the difference between low force and
force at low point, divided by the time interval).
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
Propulsive Phase: The propulsive phase started from the point of initiation of the upward
movement from low point, to the maximum height of the jump, with both points identified from
the derived position data. The propulsive metrics that were examined were: (1) flight height
(calculated from time in air based on the acceleration data); (2) jump height (flight height plus
difference between standing height and takeoff height); (3) peak propulsive force (the peak force
during the propulsive phase occurring prior to take off); (4) maximum power (calculated from the
product of the force and velocity data).
Landing Phase: Only one metric from the landing phase was examined; peak landing force,
defined as the peak force occurring after ground contact when landing from the jump. All inertial
sensor data were processed using G-Studio software (BTS Bioengineering, Brooklyn NY).
Statistical Analyses
A single factor (time) repeated measures analysis of variance (ANOVA) was used to assess
if the inertial sensor was sufficiently sensitive to detect impairments in jump height and other jump
metrics on the days following the matches (baseline, 12 h, 36 h, and 60 h post match). Only the
control data were included and analyses were performed on absolute numbers and on values
expressed as a percentage of baseline. Low force during the countermovement was expressed as a
percentage of body weight. Changes in low force were not assessed as a percentage of baseline
since some baseline values were very low, creating a non-normal distribution for percent change.
Bonferroni corrections were used for planned pairwise comparisons (baseline versus 12 h, 36 h
and 60 h).
Pearson product-moment correlations were used to assess relative reliability between
inertial sensor and optoelectric measurements with paired t-tests used to assess bias. These
assessments were made on baseline flight height averaged between the PCM cooling and control
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
conditions. Differences between devices in ability to detect decrements in CMJ flight height were
assessed using 2x3 repeated measures ANOVA (device: inertial sensor vs. optoelectric
measurement; time: 12 h, 36 h and 60 h post match). The primary statistic of interest was the effect
of device comparing percent decrement in flight height between devices.
Treatment (PCM cooling vs. control) by time repeated measures ANOVA were used to
assess if the inertial sensor was able to detect accelerated recovery of CMJ height, and other jump
metrics, with the cryotherapy intervention. The treatment by time analysis of CMJ height from the
optoelectric system has been reported previously and is also provided here for comparison to
inertial sensor results. Bonferroni corrections were used for planned pairwise between treatment
comparisons at each of the time intervals (baseline, 12 h, 36 h and 60 h for absolute values, and
12 h, 36 h and 60 h for values expressed as a percentage of baseline).
All variables were tested for normality of distribution using the Shapiro-Wilk test.
Variables with non-normal distribution were analyzed with the Friedman test for time effects and
the Wilcoxon signed ranks test for pairwise comparisons. Additionally, within ANOVAs,
Greenhouse-Geisser corrections were applied for violations of sphericity. Effect sizes for time or
treatment effects were computed using Cohen’s dZ statistic21 with the magnitude of effects
considered either small (0.200.49), medium (0.500.79) or large (>0.80). Statistical analyses
were performed using SPSS (v21 IBM, Armonk, NY).
RESULTS
Match Details
There were no significant differences in playing demands between PCM cooling matches
and control matches. Average playing time was 81±18 min for the matches after which players
received PCM versus 83±11 min for control matches. Other match demand metrics did not differ
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
between treatments (PCM vs.control: total distance ran 9414±2142 m vs. 9742±1365 m; sprint
distance 330±129 m vs. 339±85 m).
Inertial Sensor CMJ Flight Height and Jump Height
Flight height (time effect P=0.018) and jump height (time effect P=0.007) were decreased
on the days after the matches (Table 1). Similar effects were evident when heights were expressed
as a percentage of baseline (Time effects: flight height P=0.028, jump height P=0.006, Table 1).
Greatest decrements were evident 36 h post match for flight height (88% of baseline, P=0.012 for
post hoc pairwise comparison) and 12 h post match for jump height (90% of baseline, P=0.006 for
post hoc pairwise comparison).
Comparison Between Inertial Sensor and Optoelectric System
Inertial sensor and optoelectric CMJ flight heights were strongly positively correlated
(r=0.905, P<0.001), but there was significant bias, with inertial sensor values 1.8±1.8 cm lower
than optoelectric values (P=0.008).
Optoelectric measurement of CMJ flight height was decreased on the days after the match
(time effect P=0.035 for absolute and relative values). Flight height was 93±8% of baseline at 36
h (P=0.027 for post hoc pairwise comparison, effect size 1.0). Decrements in CMJ flight height
were greater with the inertial sensor compared with the optoelectric system (inertial sensor
averaged 90±3% of baseline across measurements at 12, 36, and 60 h versus 95±2% for the
optoelectric device, effect of device P=0.047, device by time P=0.22). This effect was most
pronounced at 60 h (91±12% vs. 99±11%, P=0.045 for post hoc pairwise comparison).
Effect of PCM Cooling Intervention on CMJ Height
The inertial sensor showed accelerated recovery of absolute jump heights with PCM
cooling versus control (treatment by time P=0.027, Fig. 2A) but there were no significant effects
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
for absolute flight heights (treatment effect P=0.072, treatment by time P=0.054). When expressed
as a percentage of baseline, flight heights and jump heights were both better for PCM cooling
versus control (flight height: treatment effect P=0.007, treatment by time P=0.061, Table 2; jump
height: treatment effect P=0.035, treatment by time P=0.013, Fig. 2B). With the optoelectric
system the effect of PCM cooling on flight height was similar to that observed with the inertial
sensor (absolute flight height: treatment effect P=0.037, treatment by time P=0.103; relative flight
height: treatment effect P=0.064, treatment by time P=0.095, Table 2).
Countermovement, Propulsive and Landing Phase Metrics
Countermovement Phase: Low point (time effect P=0.427) and force at low point (time
effect P=0.497) did not differ from baseline on the days after the match. However, low force was
elevated on the days after the match (time effect P=0.031); at baseline, low force was 18% of body
weight compared with 30% at 12 h (P=0.393 for post hoc pairwise comparison, effect size 0.5),
39% at 36 h (P=0.051 for post hoc pairwise comparison, effect size 0.9) and 32% (P=0.096 for
post hoc pairwise comparison, effect size 0.8) at 60 h post match. Additionally, low force was
negatively correlated with flight height at baseline (r=-0.81, P=0.003), 12 h (r=-0.96, P<0.001), 36
h (r=-0.64, P=0.04) and 60 h (r=-0.62, P=0.04) indicating that the magnitude of unweighting during
the initiation of the countermovement improved jump height. Eccentric rate of force development
was not normally distributed and there was no significant effect of time using the Friedman test
(P=0.263).
Propulsive Phase: Peak propulsive force (time effect P=0.98) and maximum power (time
effect P=0.199) were not different from baseline on the days after the match.
Landing Phase: Peak landing force was decreased on the days after the match (time effects:
P=0.040 for absolute values, P=0.043 for values relative to baseline). Landing force was 99% of
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
baseline at 12 h (P=0.999 for post hoc pairwise comparison), 89% of baseline at 36 h (P=0.039 for
post hoc pairwise comparison) and 98% of baseline at 60 h (P=0.126 for post hoc pairwise
comparison).
There was no effect of PCM treatment on these countermovement, propulsive or landing
phase metrics (treatment by time effects: low point P=0.518; force at low point P=0.293; low force
P=0.254; eccentric force development P=0.220; peak propulsive force P=0.781; maximum power
P=0.388; peak landing force P=0.965).
DISCUSSION
With respect to the specific goals of the study: (1) the inertial sensor was sufficiently
sensitive to detect decrements in jump height on the days following a professional soccer match;
(2) the inertial sensor data correlated strongly with the optoelectric data but recorded significantly
lower flight heights; (3) the inertial sensor was able to detect accelerated recovery of jump height
with the cryotherapy intervention; and (4) the additional force, power, velocity, and position
metrics from the inertial sensor provided limited information on the biomechanics of CMJ
impairment and recovery. Each of these goals is discussed in detail in the following four sections.
Inertial Sensor Detection of Impairments in CMJ on the Days After a Soccer Match
Marked impairments in both flight height and jump height were apparent on the days after
the soccer match. However, lowest flight height was apparent at 36 h (88% of baseline) but the
lowest jump height occurred earlier (90% of baseline at 12 h). Additionally, by 60 h post game
jump height had fully recovered (102% of baseline) while flight height was still impaired (91% of
baseline). To put these results in context it is important to understand the difference between flight
height and jump height. Flight height is the maximum vertical displacement of center of mass
while the body is off the ground. Jump height is flight height plus the difference between standing
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
height and take-off height. Differentiating the two using inertial sensor data is non-trivial.
Biomechanically the difference between flight height and jump height represents the sequential
thrust of hip extension, knee extension and plantarflexion prior to take off. The actual differences
between flight height and jump height were 11.9±1.6 cm at baseline, 9.6±1.6 cm at 12 h, 12.9±1.0
cm at 36 h, and 16.1±1.5 cm at 60 h (time effect P=0.005). It is not clear whether these numbers
represent actual changes in jump mechanics or are systematic errors in accelerometer data
processing. Regardless, from a practical perspective the flight height data seems to be more
sensitive than jump height for measuring performance impairment.
Inertial Sensor Versus Optoelectric System
Flight heights measured by inertial sensor were shown to be strongly correlated with
opetoelectric values, but the inertial sensor heights were on average 1.8 cm lower. This represents
a 5% underestimate of flight height compared with optoelectric values. Using a different inertial
sensor than that used here, Lesinski et al18 also showed that inertial sensor heights were strongly
correlated with optoelectric values in measurements made on youth female soccer players.
However, they found that the inertial sensor flight heights were on average 0.55 cm higher than
optoelectric values. Importantly, CMJ height calculated from force plate data, was 1.21 cm higher
than optoelectric values and 0.66 cm higher than inertial sensor values. Differences in hardware
and software between inertial sensor devices likely means that absolute values cannot be compared
directly. Furthermore, comparisons between CMJ heights derived from different technologies is
not advised.
Both devices showed significant decrements in CMJ after the soccer matches, with
similarly large effect sizes at 36 h (optoelectric 93±12%, effect size 1.0 vs. inertial sensor
88%±10%, effect size 1.1). However, overall, greater decrements were evident with the initial
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
sensor versus the optoelectric system. Based on the effect sizes reported in Table 1 for the inertial
sensor a 6-8% decline in flight or jump height represents a moderate effect and an impairment of
more than 8% represents a large effect. The decrements in post-match optoelectric flight height
(96% at 12 h, 93% at 36 h, 99% at 60 h) are comparable to other studies using the same optoelectric
system; 96% at 24 h, 98% at 48 h, 100% at 72 h after a soccer match,10 and 95% at 24 h, 95% at
48 h, 96% at 72 h after a simulated soccer match.9 Higher values for post-match decrements in
CMJ height were reported for elite under-21 soccer players when CMJ was assessed using contact
mats (88% at 24 h, 95% at 48 h, 97% at 72 h).11 Together these data indicate that the optoelectric
system might be less sensitive to detecting decrements in CMJ compared with other techniques.
However, these four studies differed in standard of play (professional current study, semi-
professional,9,10 elite youth11) and may have differed in match intensity. Thus, it is not possible to
definitively attribute differences in CMJ decrements to the different technologies used in the
respective studies.
Effect of PCM Cooling Intervention of CMJ Recovery
We have previously reported that the PCM cooling intervention accelerated recovery of
strength and soreness, but recovery of optoelectric CMJ height was not significantly accelerated.21
The relative changes in optoelectric CMJ height that were reported in that study are also included
here for the purposes of comparison to inertial sensor data (Table 2). The absolute changes in
optoelectric CMJ height were not previously reported.
The benefits of PCM cooling on CMJ recovery were more apparent with the inertial sensor
data than the optoelectric data (Table 2). The inertial sensor data showed a marked benefit of PCM
cooling for relative flight height, with large effect sizes at 36 h and 60 h. A benefit of PCM cooling
was demonstrated for both relative and absolute jump heights (Fig. 2). By comparison, the benefits
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
of PCM cooling on CMJ recovery were less clear with the optoelectric data (Table 2). Since PCM
cooling is a novel recovery intervention it is not possible to compare CMJ recovery metrics to
other PCM cooling studies. The best comparison to PCM cooling would be cold water immersion.
Two systematic reviews22,23 concluded that, from limited data, cold water immersion may be
beneficial in accelerating CMJ recovery. The current PCM cooling data are consistent with that
conclusion.
Inertial Sensor Additional Biomechanical Metrics
In general, the additional CMJ biomechanical metrics generated from the inertial sensor
did not show obvious changes on the days following the soccer matches, nor were there changes
in recovery associated with the PCM cooling intervention. While one would assume that
decrements in power, force, or rate of force development would be apparent when CMJ height is
impaired, such studies have not been performed in soccer players during recovery from a match.
It is noteworthy that low force and landing force differed from baseline on the days after the soccer
matches.
The increase in low force on the days after the match indicates that the players did not
unweight themselves as much during the initiation of the countermovement. In Figure 1 the nadir
in acceleration at approximately 0.3 s shows this subject unweighting himself at the initiation of
the countermovement. For this subject, the low force amounted to 11% of his body weight (force
data not shown). The average low force for baseline jumps in the control condition was 18%,
increasing to 30-39% on subsequent days. Importantly, low force was negatively correlated with
flight height, indicating that the more a player unweighted himself at the initiation of the jump the
better his vertical jump was. Thus, the higher values for low force on the days after the soccer
matches may represent increased leg stiffness due to muscle damage. However, since there was no
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
indication of improvement in low force with the PCM cooling intervention, it is unclear the extent
to which this metric may have been a mechanism for the impaired performance.
In contrast to the increase in low force, landing force was decreased on the days after the
soccer match. This could reflect decreased eccentric strength. It is noteworthy that peak changes
in low force, landing force and flight height occurred at the same time, 36 h post match. However,
the PCM cooling intervention did not impact landing force or low force, despite improving CMJ
height. The acute effects of fatigue on jump landing forces have been examined in several studies
but there is no consensus on whether muscle fatigue increases or decreases landing forces.24 The
effects of prior exercise, such as a soccer game on landing forces on subsequent days has not been
examined previously.
PRACTICAL APPLICATIONS, LIMITATIONS AND FUTURE DIRECTIONS
Testing professional athletes during the rigors of a long competitive season may not be the
best environment in which to assess the utility of a new CMJ testing device. A field study using
professional athletes provides less control than one would have in a laboratory-based study using
less high demand participants. This potential sacrifice of experimental control is offset by the
greater ecological validity of the findings for practitioners working in high demand elite sports.
Future studies should test CMJ metrics derived from this inertial sensor against kinetic and
kinematic data from high speed cameras and force plates. Additionally, future studies should
establish the day-to-day variability in jump metrics with this inertial sensor, in a controlled setting
without an exercise intervention that systematically affects jump performance. Finally, since
inertial sensor measurements of impairments in jump performance differed between flight height
and jump height, future work, using high speed motion capture with ground reaction forces, is
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
needed to examine whether this was due to a change in jumping mechanics or an error in inertial
sensor data processing.
CONCLUSIONS
The inertial sensor was sensitive to detecting impairments in CMJ and in demonstrating
accelerated recovery in CMJ in professional soccer players. This small portable device can provide
a practical means of collecting objective recovery data in repeated sprint sports, like soccer.
Finally, improvements in inertial sensor recorded CMJ performance with PCM cooling reaffirms
the accelerated recovery provided by this novel cryotherapy intervention.
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
REFERENCES
1. Clifford T, Bell O, West DJ, Howatson G, Stevenson EJ. The effects of beetroot juice
supplementation on indices of muscle damage following eccentric exercise. Eur J Appl
Physiol. 2016 Feb;116(2):353-62.
2. Hill J, Howatson G, van Someren K, Gaze D, Legg H, Lineham J, Pedlar C. The Effects
of Compression-Garment Pressure on Recovery After Strenuous Exercise. Int J Sports
Physiol Perform. 2017 Sep;12(8):1078-1084.
3. Howatson G, Hoad M, Goodall S, Tallent J, Bell PG, French DN. Exercise-induced
muscle damage is reduced in resistance-trained males by branched chain amino acids: a
randomized, double-blind, placebo controlled study. J Int Soc Sports Nutr. 2012 Jul
12;9:20.
4. Bell PG, Stevenson E, Davison GW, Howatson G. The Effects of Montmorency Tart
Cherry Concentrate Supplementation on Recovery Following Prolonged, Intermittent
Exercise. Nutrients. 2016 Jul 22;8(7).
5. Brown MA, Howatson G, Keane KM, Stevenson EJ. Adaptation to Damaging Dance and
Repeated-Sprint Activity in Women. J Strength Cond Res. 2016 Sep;30(9):2574-81.
6. Harper LD, Hunter R, Parker P, Goodall S, Thomas K, Howatson G, West DJ, Stevenson
E, Russell M. Test-Retest Reliability of Physiological and Performance Responses to 120
Minutes of Simulated Soccer Match Play. J Strength Cond Res. 2016 Nov;30(11):3178-
3186.
7. Keane KM, Salicki R, Goodall S, Thomas K, Howatson G. Muscle Damage Response in
Female Collegiate Athletes After Repeated Sprint Activity. J Strength Cond Res. 2015
Oct;29(10):2802-7.
8. Leeder JD, van Someren KA, Bell PG, Spence JR, Jewell AP, Gaze D, Howatson G.
Effects of seated and standing cold water immersion on recovery from repeated sprinting.
J Sports Sci. 2015;33(15):1544-52.
9. Thomas K, Dent J, Howatson G, Goodall S. Etiology and Recovery of Neuromuscular
Fatigue after Simulated Soccer Match Play. Med Sci Sports Exerc. 2017 May;49(5):955-
964.
10. Brownstein CG, Dent JP, Parker P, Hicks KM, Howatson G, Goodall S, Thomas K.
Etiology and Recovery of Neuromuscular Fatigue following Competitive Soccer Match-
Play. Front Physiol. 2017 Oct 25;8:831.
11. Fatouros IG, Chatzinikolaou A, Douroudos II, Nikolaidis MG, Kyparos A, Margonis K,
Michailidis Y, Vantarakis A, Taxildaris K, Katrabasas I, Mandalidis D, Kouretas D,
Jamurtas AZ. Time-course of changes in oxidative stress and antioxidant status responses
following a soccer game. J Strength Cond Res. 2010 Dec;24(12):3278-86.
Downloaded by mchugh@nismat.org on 05/31/18, Volume ${article.issue.volume}, Article Number ${article.issue.issue}
Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
12. Rupp KA, Selkow NM, Parente WR, Ingersoll CD, Weltman AL, Saliba SA. The effect
of cold water immersion on 48-hour performance testing in collegiate soccer players. J
Strength Cond Res. 2012 Aug;26(8):2043-50.
13. Howatson G, Hough P, Pattison J, Hill JA, Blagrove R, Glaister M, Thompson KG.
Trekking poles reduce exercise-induced muscle injury during mountain walking. Med Sci
Sports Exerc. 2011 Jan;43(1):140-5.
14. Meister S, Faude O, Ammann T, Schnittker R, Meyer T. Indicators for high physical
strain and overload in elite football players. Scand J Med Sci Sports. 2013
Mar;23(2):156-63.
15. Bieuzen F, Pournot H, Roulland R, Hausswirth C. Recovery after high-intensity
intermittent exercise in elite soccer players using VEINOPLUS sport technology for
blood-flow stimulation. J Athl Train. 2012 Sep-Oct;47(5):498-506.
16. Setuain I, Martinikorena J, Gonzalez-Izal M, Martinez-Ramirez A, Gómez M, Alfaro-
Adrián J, Izquierdo M. Vertical jumping biomechanical evaluation through the use of an
inertial sensor-based technology. J Sports Sci. 2016;34(9):843-51.
17. Setuain I, Millor N, González-Izal M, Gorostiaga EM, Gómez M, Alfaro-Adrián J,
Maffiuletti NA, Izquierdo M. Biomechanical jumping differences among elite female
handball players with and without previous anterior cruciate ligament reconstruction: a
novel inertial sensor unit study. Sports Biomech. 2015 Sep;14(3):323-39.
18. Lesinski M, Muehlbauer T, Granacher U. Concurrent validity of the Gyko inertial sensor
system for the assessment of vertical jump height in female sub-elite youth soccer
players. BMC Sports Sci Med Rehabil. 2016 Nov 11;8:35.
19. Cone JR, Berry NT, Goldfarb AH, Henson RA, Schmitz RJ, Wideman L, Shultz SJ.
Effects of an individualized soccer match simulation on vertical stiffness and impedance.
J Strength Cond Res. 2012 Aug;26(8):2027-36.
20. Clifford T, Abbott W, Kwiecien SY, Howatson G, McHugh MP. Cryotherapy Re-
Invented: Application of Phase Change Material for Recovery in Elite Soccer. Int J
Sports Physiol Perform. 2017 Sep 5:1-21.
21. Lakens D. Calculating and reporting effect sizes to facilitate cumulative science: a
practical primer for t-tests and ANOVAs. Front Psychol. 2013 Nov 26;4:863.
22. Bleakley CM, McDonough S, Gardner E, Baxter GD, Hopkins JT, Davison GW. Cold-
water immersion (cryotherapy) for preventing and treating muscle soreness after exercise.
Cochrane Database Syst. 2012;15;(2):CD008262.
23. Leeder J, Gissane C, van Someren KA, Gregson W, Howatson G. Cold water immersion
and recovery from strenuous exercise: A meta-analysis. Br J Sports Med.
2012;46(4):233-240.
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
24. Zadpoor AA, Nikooyan AA. The effects of lower extremity muscle fatigue on the vertical
ground reaction force: a meta-analysis. Proc Inst Mech Eng H. 2012 Aug 226(8):579-88.
Downloaded by mchugh@nismat.org on 05/31/18, Volume ${article.issue.volume}, Article Number ${article.issue.issue}
Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
Figure 1: Position, velocity and acceleration recording during a baseline CMJ from a sample
player. The inertial sensor measured acceleration, from which position and velocity were derived.
The shaded area to the left indicates the countermovement phase, starting at the initiation of the
countermovement and ending at the lowest position. The shaded area to the right indicates the
landing phase, starting from the highest position (jump height) and ending when the subject returns
to standing upright position. On the position graph, jump height is indicated by the horizontal line
from the apex in position. Flight height is jump height minus position when the subject left the
ground, indicated by the lower horizontal dashed line on the position graph. Acceleration equals 0
at peak velocity and equals -9.81 m.s-2 at the point of take-off. Baseline force (N) is body mass x
9.81 and thereafter was the product of acceleration. Power was the product of force and velocity
force and power not shown in this figure).
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
Figure 2: Effect of PCM cooling intervention on absolute (A) and relative (B) changes in jump
height. Absolute jump height: treatment effect P=0.020, treatment by time P=0.027. Relative jump
height: treatment effect P=0.035, treatment by time P=0.013. * higher jump height with PCM
cooling treatment versus control P<0.05. Mean±SE displayed.
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Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor” by McHugh MP et al.
International Journal of Sports Physiology and Performance
© 2018 Human Kinetics, Inc.
Table 1: Inertial sensor CMJ flight height and jump height before and after soccer match in control
condition.
Flight Height
Jump Height
cm
% baseline
Effect Size
vs. baseline
cm
% baseline
Effect Size
vs. baseline
35.1±5.0
100%
47.0±6.6
100%
32.4±6.7
92±13%
0.6
41.9±6.0*
90±9%*
1.1
30.7±3.7*
88±10%*
1.1
43.6±4.5
94±10%
0.7
31.5±4.2
91±12%
0.8
47.6±6.8
102±15%
0.1
P=0.018
P=0.028
P=0.007
P=0.006
Effect of time is P value for ANOVA; *P<0.05 different from baseline; effect size is Cohen’s dZ calculated from
differences in absolute height from baseline. Mean±SD reported.
Table 2: Effects of PCM cooling on recovery of flight height for inertial sensor and optoelectric
measurements.
Inertial Sensor
Optoelectric System
PCM
Control
Effect
Size
PCM
Control
Effect
Size
Baseline
100%
100%
100%
100%
12 h
102±13%
92±13%
0.4
99±5%
96±7%
0.3
36 h
105±15%*
88±10%
1.1
102±7%
93±8%
0.8
60 h
103±10%*
91±12%
0.9
107±14%
99±11%
0.4
Treatment Effect
P=0.007
P=0.064
Treatment x Time
P=0.061
P=0.095
*P<0.05 different from control; effect size is Cohen’s dZ calculated from differences in relative height between
treatments. Mean±SD reported.
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... The purpose of the eccentric phase of a jump is to store elastic energy in the muscle tendon units of the prime movers to augment COM propulsion. [23][24][25][26] Elastic energy is best utilized by a rapid transition from the eccentric countermovement to the concentric propulsion. 12 A rapid transition from countermovement to propulsion would equate to maximal acceleration occurring during this phase and would be evident in peak force occurring at low position. ...
... Consistent with this observation, unweighting has been shown to be impaired on the days after a professional soccer game, while countermovement depth was not. 26 The majority of CMJs were bimodal (78%). This differs somewhat from a sample of 33 professional rugby players in which only 52% of jumps were bimodal. ...
... The practical implications of these findings remain to be established and would be dependent on the purpose of the CMJ testing. For example, CMJ testing is used to monitor recovery in athletes 26 and it is possible that biomechanical efficiency is impaired when athletes are not fully recovered. Examining the occurrence of peak force relative to low position might be an important practical metric. ...
... The purpose of the eccentric phase of a jump is to store elastic energy in the muscle tendon units of the prime movers to augment COM propulsion. [23][24][25][26] Elastic energy is best utilized by a rapid transition from the eccentric countermovement to the concentric propulsion. 12 A rapid transition from countermovement to propulsion would equate to maximal acceleration occurring during this phase and would be evident in peak force occurring at low position. ...
... Consistent with this observation, unweighting has been shown to be impaired on the days after a professional soccer game, while countermovement depth was not. 26 The majority of CMJs were bimodal (78%). This differs somewhat from a sample of 33 professional rugby players in which only 52% of jumps were bimodal. ...
... The practical implications of these findings remain to be established and would be dependent on the purpose of the CMJ testing. For example, CMJ testing is used to monitor recovery in athletes 26 and it is possible that biomechanical efficiency is impaired when athletes are not fully recovered. Examining the occurrence of peak force relative to low position might be an important practical metric. ...
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The purpose of this study was to determine whether countermovement jump (CMJ) metrics differed based on whether or not peak vertical ground reaction force (GRF) occurred at the lowest point of the countermovement (low position). CMJs from 100 athletes were categorized based on whether or not the peak force occurred at low position and whether they had unimodal or bimodal GRF profiles. CMJ metrics were compared between jump categories and between athletes with above average, average, and below average jump heights. Peak force occurred at low position in 52% of jumps. The majority of jumps were bimodal (78%) and in 73% of bimodal jumps the first peak was higher than the second peak. Both performance metrics (5% higher jump, 25% greater reactive strength index) and most braking phase metrics were superior for jumps in which peak force coincided with low position (P < .01). Peak force occurred at low position in 76% of above average jumps, 50% of average jumps, and 37% of below average jumps (P = .019). The optimal profile for CMJ performance is one in which peak force occurs at low position, regardless of whether it is unimodal or bimodal. This provides a qualitative means of identifying biomechanically efficient jumps.
... While the precise underlying mechanisms remain to be elucidated, cryotherapy is purported to reduce muscle temperature and attenuate inflammation and oxidative stress (White and Wells, 2013). A recently implemented form of cryotherapy that has produced encouraging results as a recovery aid is phase change material; PCM Kwiecien et al., 2018;McHugh et al., 2018). Phase change material is a substance with a high heat fusion, which melts and solidifies at certain temperatures. ...
... Despite the promising results of recent studies Kwiecien et al., 2018;McHugh et al., 2018), more evidence is required to substantiate the efficacy of PCM as a recovery intervention and to gain mechanistic insight into the potential benefits of PCM on recovery. Accordingly, the aim of the present study was to examine the effect of wearing cold PCM garments on recovery of neuromuscular function, as well as physical and perceptual measures following soccer matchplay. ...
... Veritably, studies have neither been consistent nor produced compelling evidence to support the role of cryotherapy in reducing inflammation and improving aspects of recovery (Leeder et al., 2012), and it has been suggested that many of the previously reported benefits of cryotherapy could simply be due to a placebo effect, rather than any physiological effect (Broatch et al., 2014). Despite the promising findings from recent studies using cold PCM as a recovery aid McHugh et al., 2018), and that applying these garments has been shown to reduce muscle temperature , there is no evidence to suggest that cold PCM reduces inflammation. As such, it is possible that PCM cold had no effect on the inflammatory processes suggested to interfere with contractile and CNS function. ...
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Aim: Cryotherapy is commonly implemented following soccer match-play in an attempt to accelerate the natural time-course of recovery, but the effect of this intervention on neuromuscular function is unknown. The aim of the present study was to examine the effect of donning lower-body garments fitted with cooled phase change material (PCM) on recovery of neuromuscular function following competitive soccer match-play. Methods: Using a randomized, crossover design, 11 male semi-professional soccer players wore PCM cooled to 15∘C (PCMcold) or left at ambient temperature (PCMamb; sham control) for 3 h following soccer match-play. Pre-, and 24, 48, and 72 h post-match, participants completed a battery of neuromuscular, physical, and perceptual tests. Maximal voluntary contraction force (MVC) and twitch responses to electrical (femoral nerve) and magnetic (motor cortex) stimulation (TMS) during isometric knee-extension and at rest were measured to assess central nervous system (CNS) (voluntary activation, VA) and muscle contractile (quadriceps potentiated twitch force, Qtw,pot) function. Fatigue and perceptions of muscle soreness were assessed via visual analog scales, and physical function was assessed through measures of jump [countermovement jump (CMJ) height and reactive strength index (RSI)] performance. A belief questionnaire was completed pre- and post-intervention to determine the perceived effectiveness of each garment. Results: Competitive soccer match-play elicited persistent decrements in MVC, VA measured with femoral nerve stimulation, Qtw,pot, as well as reactive strength, fatigue and muscle soreness (P < 0.05). Both MVC and VA were higher at 48 h post-match after wearing PCMcold compared with PCMamb (P < 0.05). However, there was no effect of PCM on the magnitude or time-course of recovery for any other neuromuscular, physical function, or perceptual indices studied (P > 0.05). The belief questionnaire revealed that players perceived that both PCMcold and PCMamb were moderately effective in improving recovery, with no difference between the two interventions (P = 0.56). Conclusion: Although wearing cooled PCM garments improved MVC and VA 48 h following match-play, the lack of effect on measures of physical function or perceptual responses to match-play suggest that PCM offers a limited benefit to the recovery process. The lack of effect could have been due to the relatively small magnitude of change in most of the outcome measures studied.
... [1][2][3][4] Previous studies utilizing this technique often report peak braking (eccentric) and peak propulsive (concentric) force, among several other metrics across the phases of the CMJ. [5][6][7][8][9] In these types of analyses, the low position of the center of mass (bottom of the countermovement) represents the end of the braking phase and start of the propulsive phase. However, McHugh et al 4 recently suggested this may not accurately reflect the GRFs obtained during the different phases of the CMJ. ...
... Several studies 4,8,10,15,[33][34][35][36][37] have suggested that greater unweighting may lead to more efficient braking phase, propulsive phase, and performance metrics during CMJs. Recently, in NCAA Division I athletes, McHugh et al 4 reported that subjects unweighted themselves to 19% of their body weight when peak force coincided with the low position of the countermovement compared to only 32% of body weight when peak force did not coincide with the low position of the countermovement. ...
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The purposes of this study were to determine whether countermovement jump (CMJ) force profiles differ for jumps in which peak force occurred at the low position of the countermovement (LP) compared to jumps in which peak force did not occur at the low position of the countermovement (NLP), and compare relationships among CMJ and isokinetic metrics between groups. Thirty‐nine male and female youth athletes between 9‐17‐years‐old participated. Participants completed CMJs and isokinetic knee extensions from 60‐300°·s‐1. Ground reaction forces were collected during CMJs to quantify unweighting, braking, propulsive, and performance metrics. Torque and power were quantified during all isokinetic knee extensions. Forty‐one percent of participants had LP force profiles, while 59% of participants had NLP force profiles. The LP group had more efficient unweighting and braking phase metrics than the NLP group, while the NLP group had greater isokinetic torque and power, and greater relationships between CMJ and isokinetic metrics, than the LP group. CMJs from the LP group represent more biomechanically efficient jumps than CMJs from the NLP group. Additionally, the NLP group may be more reliant on concentric force production during the CMJ, while the LP group may have more efficient storage and utilization of elastic energy.
... The ratio of flight time to contraction time (FT:CT) has shown greater associations to variability in match external load perhaps due to its reflection of outputs concerning concentric 'push-off' (FT) and 'countermovement' portions (CT) of the CMJ (Rowell et al. 2017(Rowell et al. , 2018. Nevertheless, there is inconsistency in the literature in relation to the sensitivity of the CMJ outputs to match and training demands (Thorpe et al. 2015;De Hoyo et al. 2016;Rowell et al. 2017Rowell et al. , 2018Mchugh et al. 2019). Further research is required to investigate whether alternative measures derived from CMJ testing are sensitive to changes in match and training load in elite football players. ...
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Purpose: Examine acute changes from 90-minutes of competitive match-play in countermovement jump (CMJ), creatine kinase (CK) and urine osmolality (Uosm) in elite senior football players over a season and their association to match external load. Methods: Eighteen professional football players participated over a full season to quantify changes in CMJ, CK and Uosm one day pre-match and two days post-match. Match performance data was examined using a semi-automated multi-camera recognition system (Prozone®). Results: Post-match CK concentrations increased by 49 % (ES: 0.66), while CMJ flight-time (FT), flight time: contraction time ratio (FT:CT), take-off velocity (TV) and average power (AP) all decreased by 2.4 to 7.4 % post-match (ES: 0.39 to 0.63). Reductions in CMJ height showed a small effect size change post-match by 4.2 % (ES: 0.35). Reductions in CMJ FT and AP showed associations with high intensity distance covered (HID), high intensity number (HIN), explosive sprints (EXS) and medium intensity accelerations (r = -0.395 to -0.496, P < 0.05). Changes in CMJ FT also displayed associations to total sprint distance (TSD), total sprint number (TSN) and medium intensity decelerations (r = -0.395 to -0.446, P < 0.05). Increases in CMJ CT were associated with HIN (r = 0.39), and CMJ AF with HIN, EXS and medium accelations/decelerations (r = -0.397 to 0.459) completed during the match. Conclusion: The data demonstrates that CMJ outputs from the push-off phase (FT, AP, TV, height) and the movement strategy variables from the countermovement phase (FT:CT) are sensitive to change in neuromuscular fatigue. Creatine kinase concentrations are sensitive to the overall demands of match-play resulting in a change 2-days post-match. This helps practitioners determine the readiness of individual players, and aid to design and adjust individual player’s recovery strategies
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Purpose: This study examined whether donning lower body garments fitted with cooled phase change material (PCM) would enhance recovery after a soccer match. Methods: In a randomized, crossover design, eleven elite-soccer players from the reserve squad of a team in the 2nd highest league in England wore PCM cooled to 15°C (PCMcold) or left at ambient temperature (PCMamb; sham control) for 3 h after a soccer match. To assess recovery, countermovement jump (CMJ) height, maximal isometric voluntary contraction (MIVC), muscle soreness (MS), and the adapted Brief Assessment of Mood Questionnaire (BAM+) were measured before, 12, 36 and 60 h after each match. Pre and post intervention, a belief questionnaire (BFQ) was completed to determine perceived effectiveness of each garment. Results: Results are comparisons between the two conditions at each time point post-match. MIVC at 36 h post was greater with PCMcold vs. PCMwarm (P =0.005; ES=1.59; 95% CI=3.9 to 17.1%). MIVC also tended to be higher at 60 h post (P =0.051; ES=0.85; 95% CI= -0.4 to 11.1%). MS was 26.5% lower in PCMcold vs. PCMwarm at 36 h (P =0.02; ES=1.7; 95% CI= -50.4 mm to -16.1 mm) and 24.3% lower at 60 h (P =0.039; ES=1.1; 95% CI= -26.9 mm to -0.874 mm). There were no between condition differences in post-match CMJ height or BAM+ (P >0.05). The BFQ revealed that players felt the PCMcold was more effective than the PCMamb after the intervention (P =0.004). Conclusions: PCM cooling garments provide a practical means of delivering prolonged post-exercise cooling and thereby accelerating recovery in elite soccer players.
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Purpose: To identify the effects of 2 different grades of compression garment on recovery indices after strenuous exercise. Methods: Forty-five recreationally active participants (n = 26 male and n = 19 female) completed an eccentric-exercise protocol consisting of 100 drop jumps, after which they were matched for body mass and randomly but equally assigned to a high-compression pressure (HI) group, a low-compression pressure (LOW) group, or a sham ultrasound group (SHAM). Participants in the HI and LOW groups wore the garments for 72 h postexercise; participants in the SHAM group received a single treatment of 10-min sham ultrasound. Measures of perceived muscle soreness, maximal voluntary contraction (MVC), countermovement-jump height (CMJ), creatine kinase (CK), C-reactive protein (CRP), and myoglobin (Mb) were assessed before the exercise protocol and again at 1, 24, 48, and 72 h postexercise. Data were analyzed using a repeated-measures ANOVA. Results: Recovery of MVC and CMJ was significantly improved with the HI compression garment (P < .05). A significant time-by-treatment interaction was also observed for jump height at 24 h postexercise (P < .05). No significant differences were observed for parameters of soreness and plasma CK, CRP, and Mb. Conclusions: The pressures exerted by a compression garment affect recovery after exercise-induced muscle damage, with higher pressure improving recovery of muscle function.
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