The Test-Retest Reliability of Bilateral and Unilateral Force Plate-Derived Parameters of the Countermovement Push-Up in Elite Boxers

Abstract

Context:
Maximal power describes the ability to immediately produce power with the maximal velocity at the point of release, impact, and/or take off-the greater an athlete's ability to produce maximal power, the greater the improvement of athletic performance. In reference to boxing performance, regular consistent production of high muscular power during punching is considered an essential prerequisite. Despite the importance of upper limb power to athletic performance, presently, there is no gold standard test for upper limb force development performance.

Objective:
To investigate the test-retest reliability of the force plate-derived measures of countermovement push-up in elite boxers.

Design:
Test-retest design.

Setting:
High Performance Olympic Training Center.

Participants:
Eighteen elite Olympic boxers (age = 23 [3] y; height = 1.68 [0.39] m; body mass = 70.0 [17] kg).

Intervention:
Participants performed 5 repetitions of countermovement push-up trials on FD4000 Forcedeck dual force platforms on 2 separate test occasions 7 days apart.

Main outcome measures:
Peak force, mean force, flight time, rate of force development, impulse, and vertical stiffness of the bilateral and unilateral limbs from the force-time curve.

Results:
No significant differences between the 2 trial occasions for any of the derived bilateral or unilateral performance measures. Intraclass correlation coefficients indicated moderate to high reliability for performance parameters (intraclass correlation coefficients = .68-.98) and low coefficient of variation (3%-10%) apart from vertical stiffness (coefficient of variation = 16.5%-25%). Mean force demonstrated the greatest reliability (coefficient of variation = 3%). In contrast, no significant differences (P < .001) were noted between left and right limbs (P = .005-.791), or between orthodox or southpaw boxing styles (P = .19-.95).

Conclusion:
Force platform-derived kinetic bilateral and unilateral parameters of countermovement push-up are reliable measures of upper limb power performance in elite-level boxers; results suggest unilateral differences within the bilateral condition are not the norm for an elite boxing cohort.

Full text

The Test–Retest Reliability of Bilateral and Unilateral Force
Plate–Derived Parameters of the Countermovement Push-Up
in Elite Boxers
Gemma N. Parry, Lee C. Herrington, Ian G. Horsley, and Ian Gatt
Context:Maximal power describes the ability to immediately produce power with the maximal velocity at the point of release,
impact, and/or take off—the greater an athlete’s ability to produce maximal power, the greater the improvement of athletic
performance. In reference to boxing performance, regular consistent production of high muscular power during punching is
considered an essential prerequisite. Despite the importance of upper limb power to athletic performance, presently, there is no
gold standard test for upper limb force development performance. Objective:To investigate the test–retest reliability of the force
plate–derived measures of countermovement push-up in elite boxers. Design:Test–retest design. Setting:High Performance
Olympic Training Center. Participants:Eighteen elite Olympic boxers (age = 23 [3] y; height = 1.68 [0.39] m; body mass = 70.0
[17] kg). Intervention: Participants performed 5 repetitions of countermovement push-up trials on FD4000 Forcedeck dual force
platforms on 2 separate test occasions 7 days apart. Main Outcome Measures:Peak force, mean force, flight time, rate of force
development, impulse, and vertical stiffness of the bilateral and unilateral limbs from the force–time curve. Results:No
significant differences between the 2 trial occasions for any of the derived bilateral or unilateral performance measures. Intraclass
correlation coefficients indicated moderate to high reliability for performance parameters (intraclass correlation coefficients =
.68–.98) and low coefficient of variation (3%–10%) apart from vertical stiffness (coefficient of variation = 16.5%–25%). Mean
force demonstrated the greatest reliability (coefficient of variation = 3%). In contrast, no significant differences (P<.001) were
noted between left and right limbs (P= .005–.791), or between orthodox or southpaw boxing styles (P= .19–.95). Conclusion:
Force platform–derived kinetic bilateral and unilateral parameters of countermovement push-up are reliable measures of upper
limb power performance in elite-level boxers; results suggest unilateral differences within the bilateral condition are not the norm
for an elite boxing cohort.
Keywords:upper limb power, Forcedecks, boxing
Upper limb muscular performance has previously been evalu-
ated via medicine ball throws, bench press, and timed push-ups.
1–5
These methods tend to report power as a measurement of distance
thrown rather than as a rate or time quantity, which suggests these
tests are more representative of work output, not power produced.
These movements also require the incorporation of the whole body,
and as such, it is difficult to isolate the specific contribution by the
upper limb. With little consensus around what constitutes optimal
load and with loading parameters to maximize power output not
clearly defined, the mechanisms concerning adaptation following
ballistic exercise remains unknown.
6,7
Plyometric exercises are
performed with body mass and are not subjected to methodological
study design issues of load selection. Also ballistic in nature, these
exercises are distinguished by stretch shortening cycle (SSC)
muscle actions.
7
Athletes who require fast, explosive patterns, upper limb
plyometrics, such as the countermovement push-up (CMPU),
which optimize the SSC are considered elemental for inducing
adaptation, as well as an important component to end stage
rehabilitation.
1,8,9
The plyometric push-up negates the limitations
of the medicine ball throws and bench press throw (BPT), allowing
an athlete to explosively displace body mass through a vertical
plane ballistic in nature; explosive push-ups do not require the
application of a preselected load like BPT.
Similar to a shot-put throw, which when performed in sitting is
reported to provide isolated performance of the upper limb, better
understanding of upper limb performance is achievable during
CMPU due to around only 68% of body mass being on a force
plate. Punching is an immensely explosive, succinct, dynamic
action, which occurs during a small period of time
10
; it is proposed
that as coaches and clinicians use the CMPU as a training tool to
develop muscular power, it could be informative of upper limb
muscular power output of a boxer. Rate of force development
(RFD), power, and force components play a critical role in
plyometric muscular contractions.
8
Recently, the CMPU or plyo-
metric push up in relation to upper limb performance parameters
has been reliably assessed using force-plate- and force–time-
derived parameters.
2–4,11
Boxing is a nonsymmetrical sport that requires the develop-
ment of accuracy, strength, and power. Boxers choose to face their
opponent via one of 2 strategies—either via the “southpaw”or
“orthodox”stance. During either stance, the boxers will keep their
stronger hand at the back to keep the space needed to deliver power
punches and the weaker hand at the front for the closer, quicker
jabs.
10
Investigation into lower limb (LL) asymmetry during single-
leg jumps indicates that vertical jump performance is better in
Parry and Gatt are with GB Boxing, English Institute of Sport, Sheffield, United
Kingdom. Parry and Herrington are with the Human Performance Laboratory, Sport,
Exercise and Physiotherapy, University of Salford, Greater Manchester, United
Kingdom. Herrington and Horsley are with the Physiotherapy Department, English
Institute of Sport, Manchester, United Kingdom. Parry (g.parry1@edu.salford.ac.
uk) is corresponding author.
1
Journal of Sport Rehabilitation, (Ahead of Print)
https://doi.org/10.1123/jsr.2020-0340
© 2021 Human Kinetics, Inc. TECHNICAL REPORT
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dominant legs compared with nondominant legs. During a CMPU,
it would be expected that both arms would add equally to kinematic
parameters; however, if side-to-side differences existed, it might
be an indicator of physiological adaptation, injury, or deficit in
sporting performance by the more utilized side. Following injury,
within the clinical environment, injured sides of the body are
frequently compared with the noninjured side to assess perfor-
mance parameters. This is frequently seen with the LL, where the
unilateral single-leg hop is compared with the bilateral counter-
movement jump (CMJ).
Previous studies
2–4,11
demonstrated good reliability of
CMPU–derived parameters; its value as a screening test and
evaluator of rehabilitation and condition programs is presently
limited. All studies utilized bilateral arm data; no authors presented
data on unilateral differences or analyzed differences in CMPU
upper limb kinematics in relation to symmetry. If asymmetry is
expected when considering dominance, research documenting the
relationship between upper limb force platforms–derived parame-
ters and between limbs, asymmetry could provide insight into
injury risk, rehabilitation protocols, and areas of power perfor-
mance development. The aims of this study were two-fold—first to
establish if CMPU-derived parameters are reliable for double limb
and single limb and second, to establish if unilateral differences
occur during bilateral CMPU to inform clinicians how to monitor
and assess upper limb performance in relation to athlete monitor-
ing, training program effects, and guide injury rehabilitation. It
was hypothesized that CMPU kinetic data will demonstrate good
reliability and that asymmetries will exist during CMPU, with
data reflecting dominant and nondominant differences in boxing
styles.
Methods
Experimental Approach to the Problem
Single-group repeated measures design were 5 repetitions of
maximal effort CMPU on 2 separate testing sessions 7 days apart.
Testing occurred over 21 days, prior to the start of a 6-week power-
based phase, leading towards a major competition.
Participants
A total of 22 elite male boxers (age = 23 [3] y; height = 1.68
[0.39] m; body mass = 70.0 [17] kg) comprising of 2 flyweights,
2 bantamweights, 6 lightweights, 1 welterweight, 2 middleweights,
1 light heavyweight, 2 heavyweight, and 2 super heavyweights
participated in this study. Two athletes withdrew due to injury not
associated with the upper limb, and 2 withdrew due to attending
tournaments. The University of Salford review board approved the
investigation, and testing was completed within the spirit of the
Declaration of Helsinki, proceeding to test all subjects provided
written informed consent.
Procedures
Five repetitions maximal effort CMPU trials, with 1-minute rest,
were completed on 2 separate occasions at the same time of day,
in line with previously published protocol.
11
Each trial was inter-
spersed by a 60-second rest to allow for relocation of the athlete’s
hands and to eliminate fatigue.
8
Trials were completed on 2
portable force platforms (FD4000 Forcedeck dual force platforms;
VALD Performance, Sydney, Australia) and neuromuscular
performance techniques Forcedeck Software (version 1) at a
sampling frequency of 1000 Hz. Raw data were analyzed via
custom-designed Microsoft Excel Software (Redmond, WA) and
filtered of high-frequency noise using a Butterworth low pass filter
at 10 Hz. Force plates were zeroed: with weight evenly distributed
between both hands, participants adopted a self-selected hand
width, shoulder to 90°, torso, legs, and elbows extended, malleolus
and feet together. Bodyweight was established from the push-up
position.
11
Following a 3-second countdown, participants immediately
lowered their torso rapidly toward the force plate, then immediately
pressed vertically as high as possible, aiming for maximal height and
trunk elevation, elbows extended hands clearing the force plates,
landing back on the force plates with both hands at the same time.
Peak force (PF), mean force (MF), RFD, flight time (FT), vertical
stiffness (VS), movement time, and impulse were taken from the
force–time curve (Figure 1). The methodological recommendations
of Maffiuletti et al
8
were observed by taking the average of the 3 best
efforts for further data analysis to ensure that all variables, notably
peak, mean force, and RFD were optimally maximized.
Statistical Analysis
Reliability of the performance measures between sessions (first
aim), paired-sample ttests were performed to deduce any signifi-
cant changes between trials, intraclass correlation coefficients
(ICCs), and within-subject coefficient of variation (CV%) were
calculated with 95% confidence intervals to determine relation-
ships between test–retest. Boxing style correlational differences
were tested by applying the Mann–Whitney Utest for side-to-side
differences (the second aim). All standard error of the mean and
smallest detectable difference were also included to represent
and identify the smallest clinically worthwhile change that is
statistically significant using SD (pooled) ×p1−ICC for stan-
dard error of the mean and 1.96 ×p2×standard error of the mean
for smallest detectable difference.
12
Statistical analysis was com-
pleted using SPSS (version 23; IBM, Armonk, NY). Data are
presented as mean (SD).
Results
Reliability statistics are presented for each derived parameter in
Table 1. Paired sample ttests indicated no significant differences
between the 2 trial occasions for all parameters apart from vertical
stiffness. The ICCs and within-subject CV% calculations indicated
substantial to high reliability (ICC = .76–.98; CV% = 3%–8%).
The smallest detectable difference was large for all parameters
Figure 1 —Example of force–time countermovement push-up curve.
(Ahead of Print)
2Parry et al
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(8.3%–58.9%). There were no significant differences between right
and left limbs for all derived parameters (z= 0.116–0.791, P=
.001), and differences were trivial (Table 2).
Southpaw style boxers scored higher on FT (mean rank
R = 19.13; mean rank L = 21.31), RFD (mean rank R = 20.19;
mean rank L = 20.38) and VS (mean rank R = 18.81; mean rank
L = 19.56) than orthodox boxing styles (FT: mean rank R = 18.00;
mean rank L = 16.25; RFD: mean rank R = 17.25; mean rank
L = 17.00; VS: mean rank R = 18.25; mean rank L = 17.65). Ortho-
dox boxing style demonstrated higher scores of PF (mean rank
R = 19.00; mean rank L = 19.05), MF (mean rank R = 20.55; mean
rank L = 19.43) and impulse (mean rank R = 18.60; mean rank
L = 20.43) than southpaw boxing styles (PF: mean rank R = 17.88,
mean rank L = 17.81; MF: mean rank R = 15.94; mean rank
L = 17.34; Impulse: mean rank R = 18.38; mean rank L = 16.09).
No statistical differences observed between boxing style groups
(Table 3). Effect sizes between parameters and boxing styles were
too small for all data (Table 2).
Discussion
The prime focus of this study was to investigate the test–retest
reliability of force–time-derived parameters of the CMPU in both
double and single limb in elite boxers. No significant differences
(P>.05) were observed between test sessions for all derived
parameters apart from vertical stiffness (P= .01). As hypothesized,
CMPU reliability was good to excellent (ICC >.77–.98) for bilat-
eral and unilateral evaluation of right (ICC >.67–.93) and left
(ICC >.79–.98) limbs; however, there was no statistical difference
between right and left limb or for dominant and nondominant
differences in boxing styles. The findings of this study indicate that
CMPU bilateral and unilateral force plate–derived parameters are
reliable indicators of performance in elite-level boxers.
High reliability (CV% = 2.3–11) of force–time plyometric
push-up is evident within a rugby league population with mean
force demonstrating the best reliability (CV% = 4.8). Moderate to
high test–retest reliability (ICC = .80–.98 and .84–.98) respectively
for RFD, impulse, and peak average force has also been noted
2,3
Moreover, 4 variations of plyometric push-ups performed by
recreationally active subjects, and active duty marines have also
recorded
4
as having moderate to high test–retest reliability for RFD
(ICC = .90–.96) and peak force (ICC = .85–.97). These authors,
2–4
along with research on collegiate athletes,
11
noted that RFD did not
demonstrate the same reliability (CV% = 11–14.9). In contrast, this
Table 1 Mean (SD) Values of Reliability for CMPU-Derived Parameters Bilateral and Unilateral Limb (n = 18)
Derived parameters Trial 1 Trial 2 SEM CV% ICC (95% CI) SDD SDD%
Bilateral condition
Flight time, ms 0.7 (0.1) 0.7 (0.2) 0.1 6.9 .765 (.481–.650) 0.2 29.5
Peak force, N 1012 (213) 1009 (97) 53.6 4 .929 (.821–.902) 148.5 14.7
Mean force, N 496 (113) 495 (97) 14.9 3 .978 (.892–.943) 41.2 8.3
Rate force development, N·s
−1
2022 (544) 1990 (534) 239.1 8 .799 (.539–.920) 662.6 33
Impulse, N·s 85 (34) 83 (34) 8.2 8 .94 (.849–.977) 22.6 26.9
Vertical stiffness, kN·m
−1
3.02 (1)* 2.82 (0.9)* 0.6 16.5 .563* (.151–.262) 1.7 58.9
Right limb
Flight time, ms 0.4 (0.1) 0.3 (0.1) 0 8 .665 (.307–.859) 0.1 35.1
Peak force, N 510 (109) 503 (104) 28.7 4 .925 (.813–.971) 79.6 15.7
Mean force, N 252 (56) 249 (45) 16.9 4 .88 (.711–.953) 45.9 18.3
Rate force development, N·s
−1
1043 (296) 994 (297) 169.3 10 .671 (.316–.862) 469.3 46.1
Impulse, N·s 42 (21) 44 (20) 7.8 18 .845 (.635–.939) 21.7 50.8
Vertical stiffness, kN·m
−1
1.49 (1)* 1.40 (1)* 0.4 24 .410* (.064–.731) 1.2 81.3
Left limb
Flight time, ms 0.4 (0.1) 0.4 (0.1) 0 7 .783 (.511–.913) 0.1 31
Peak force, N 502 (108) 507 (103) 28.6 4 .923 (.807–.970) 79.4 15.7
Mean force, N 243 (57) 245 (55) 7.4 3 .982 (.954 –.993) 20.5 8.4
Rate force development, N·s
−1
978 (268) 996 (265) 114.1 9 .813 (.567–.926) 316.4 32.1
Impulse, N·s 43 (15) 40 (18) 7.6 17 .801 (.553–.920) 20.9 50.6
Vertical stiffness, kN·m
−1
1.53 (1)* 1.42 (1)* 0.3 17 .688* (.349–.869) 0.8 55.1
Abbreviations: CI, confidence interval; CMPU, countermovement push-up; CV, coefficient of variation; ICC, intraclass correlation coefficient; SDD, smallest detectable
difference; SEM, standard error of the mean.
*Significant difference P≥.05.
Table 2 Wilcoxon Signed-Rank Test Results for the
Right Versus Left Limb
Derived parameter Pvalue rvalue
Flight time, ms .791 .10
Peak force, N .632 .06
Mean force, N .005 .35
Rate of force development, N.s
−1
.116 .20
Impulse, N.s .314 .12
Vertical stiffness, kN.m
−1
.676 .05
(Ahead of Print)
Bilateral and Unilateral Parameters CMPU in Boxers 3
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study demonstrated better RFD reliability (CV% = bilateral 8%,
right limb 10%, and left limb 9%) and less variability than
previously reported. This is an important finding, given the impor-
tance of RFD to fast, forceful muscle contraction, this study
demonstrates that by following a methodological protocol
8
of
sampling at 1000 Hz and averaging the 3 best trial efforts of 5,
RFD can be reliably used to interpret power output performance.
The lack of statistical difference observed between limbs (P<
.001) or boxing styles (P>.05) was unanticipated because of
punching impact force being a primal performance criterion within
elite boxing.
10
Despite southpaw boxing styles demonstrating
higher FT, RFD, and VS and orthodox styles demonstrating higher
PF, MF, and impulse scores, results refute the hypothesis that
boxing style dominance difference would associate with right and
left limb differences. Rejection of the unilateral difference hypoth-
esis may also be related to equipment used. Force decks are a linked
dual force platform device, with software that contains preset
performance parameters for common screening tests such as
CMJ and drop jump. While a gap observed left between force
plates to minimize cross-interference, high-frequency noise re-
mained on all output data. Prior to analysis, data were filtered
via a low-pass filter to remove high-frequency noise, as upper limb
(UL) forces are less than those observed within the LL due to
CMPU utilizing 3 quarters of body weight.
4,11
It is possible the
preset LL parameters and algorithms of the force plates were not
sensitive enough to discern the lesser UL forces and motion
equations required.
Power output between sides showed no statistical differences
for either orthodox or southpaw boxing styles. Differences
observed between the mean values of orthodox and southpaw
boxers, however, maybe attributed to specific sensorimotor var-
iances required for these contrasting styles. This suggests that used
as a bilateral test, both arms would add equally to the kinematic
parameters obtained in a CMPU. Despite conditioning practices
being bilateral in nature, boxing itself is a nonsymmetrical sport,
and differences in both force and power are observed within the
literature.
10
If using the CMPU to monitor training program effects
and to guide injury rehabilitation, in relation to physiological
adaptation side-to-side differences should not exist within any
program aiming to develop equal conditioning. It appears unilateral
differences within the bilateral condition are not the norm within
this cohort. Any observed unilateral differences in limb perfor-
mance could potentially indicate injury risk or signs of perfor-
mance deficit seen through a more reduced score within that side.
Practitioners therefore might wish to collect data throughout the
year to detect any changes in bilateral performance.
During boxing movements such as jabbing and power punch-
ing, the upper limb generates a small portion of the force delivered
by the boxer, with the full force occurring due to combined
concurrent effort in the upper and lower limbs.
13
Boxing punches
are initiated from the application of force to the ground, with the
upper limb segmental extension entirely dependent on the transition
of force from the ground through hip and trunk rotation.
13
While a
CMPU is useful for demonstrating upper limb power to further
establish asymmetrical differences in boxing styles, future research
should analyze additional power measurements such as through a
CMJ in addition to CMPU, providing further insight into the
generation of explosive power through the punching movement
pattern as a whole, and better discern the contribution and relation-
ship of the lower limb to the upper limb power performance within a
boxing cohort. There are large interindividual differences in upper
limb power due to the range of anthropometrics and characteristics
between the different weight categories, which could have impacted
the variance of results. Traditionally, power is normalized to 100%
body mass (BM) to reduce bias within results with research
10
in
agreement that athletes of larger strength and size generate greater
power outputs. However, unlike the CMJ, which uses 100% BM,
CMPU only involves approximately 3-quarters BM,
4,9,11
as all
subjects’initial mass was averaged on the force plate prior to test
commencement, it is argued that all kinematic parameters should be
appropriate to each participant’s BM.
The results of this study highlight that UL power output in
elite-level boxers can be reliably assessed by practitioners using
force-plate- and force–time-derived parameters, and unilateral data
can be reliably extrapolated from the bilateral condition. When
using CMPU to monitor training program affects, no difference
between limbs should be noted. This will be useful if completed
prior to any injury, as CMPU can be used to better appraise and
guide injury rehabilitation until the athlete returns to the improved
performance levels. When sampling at 1000 Hz and averaging 3
best trial efforts of 5, this study’s methodology has shown that RFD
can be used to reliably interpret UL power output. Future research
design should consider similar methodologies to refine the inter-
pretation of RFD within research and practical settings, until then
RFD results should continue to be interpreted with caution.
References
1. McGuigan MR, Wright GA, Fleck SJ. Strength training for athletes:
does it really help sports performance? Int J Sports Physiol Perform.
2012;7(1):2–5. PubMed ID: 22461461 doi:10.1123/ijspp.7.1.2
Table 3 Mean (SD) Boxing Styles Comparison of Kinematic-Derived Parameters Between Limbs
Right limb Left limb
Derived parameters
Orthodox,
mean (SD)
Southpaw,
mean (SD)
P
value
r
value
Orthodox,
mean (SD)
Southpaw,
mean (SD)
P
value
r
value
Flight time, ms 0.4 (0.03) 0.4 (0.04) .75 .053 0.3 (0.03) 0.4 (0.03) .152 .025
Peak force, N 571 (21) 499 (21) .75 .053 511 (15) 496 (27) .726 .058
Mean force, N 288 (11) 268 (4) .191 .218 253 (5) 234 (7) .556 .098
Rate of force develop-
ment, N.s
−1
1100 (61) 1073 (162) .39 .145 948 (73) 1036 (105) .34 .159
Impulse, N.s 48 (5) 41 (7) .949 .158 45 (7) 36 (4) .22 .036
Vertical stiffness, kN.m
−1
1.6 (0.3) 1.5 (0.3) .873 .145 1.4 (0.2) 1.5 (0.3) .588 .098
Note: Significance set at P<.001.
(Ahead of Print)
4Parry et al
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2. Hogarth L, Deakin G, Sinclair W. Are plyometric push-ups a reliable
power assessment tool? J Aust Strength Cond. 2013;21:67–69.
3. Hrysomallis C, Kidgell D. Effect of heavy dynamic resistive exercise
on acute upper-body power. J Strength Cond Res. 2001;15(4):426–
430. PubMed ID: 11726252
4. Koch J, Riemann BL, Davies GJ. Ground reaction force patterns in
plyometric push-ups. J Strength Cond Res. 2012;26(8):2220–2227.
PubMed ID: 21986698 doi:10.1519/JSC.0b013e318239f867
5. Stockbrugger BA, Haennel RG. Validity and reliability of a medicine
ball explosive power test. J strength Cond Res. 2001;15(4):431–438.
PubMed ID: 11726253
6. Cormie P, McGuigan MR, Newton RU. Developing maximal neuromus-
cular power-part 1-biological basis of maximal power production. Sport
Med.2011;41(1):17–38. doi:10.2165/11537690-000000000-00000
7. Cormie P., McGuigan M., Newton R. Developing maximal neuro-
muscular power part 2 –training considerations for improving
maximal power production. Sport Med. 2011;41(2):125–146. doi:10.
2165/11538500-000000000-00000
8. Maffiuletti NA, Aagaard P, Blazevich AJ, Folland J, Tillin N, Duch-
ateau J. Rate of force development: physiological and methodological
considerations. Eur J Appl Physiol. 2016;116(6):1091–1116. PubMed
ID: 26941023 doi:10.1007/s00421-016-3346-6
9. Moore LH, Tankovich MJ, Riemann BL, Davies GJ. Kinematic
analysis of four plyometric push-up variations. Med Sci Sports
Exerc. 2011;43(suppl 1):832–843. doi:10.1249/01.MSS.0000402317.
48479.a7
10. Chaabène H, Tabben M, Mkaouer B, et al. Amateur boxing: physical
and physiological attributes. Sport Med. 2015;45(3):337–352. doi:10.
1007/s40279-014-0274-7
11. Parry GN, Herrington LC, Horsley IG. The test–retest reliability of
force plate–derived parameters of the countermovement push-up as a
power assessment tool. J Sport Rehabil. 2019:1–3. doi:10.1123/jsr.
2018-0419
12. Munro A, Herrington L, Carolan M. Reliability of 2-dimensional
video assessment of frontal-plane dynamic knee valgus during com-
mon athletic screening tasks. J Sport Rehabil. 2012;21(1):7–11.
PubMed ID: 22104115 doi:10.1123/jsr.21.1.7
13. Lindsay RS, Lenetsky SM. The contribution of expert coaches’
experiential knowledge in understanding punching performance in
boxers. J Emerging Sport Stud. 2020;3:1–15.
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Bilateral and Unilateral Parameters CMPU in Boxers 5
DCFEECCF:0458141IBFEBEEICBAC  2/5