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(1) Background: The aim of the study was to determine the post-activation performance enhancement (PAPE) of vertical and horizontal ground reaction force parameters during jumps and change of direction following flywheel squat exercise using two different flywheel inertias. (2) Methods: Eleven male athletes performed a countermovement jump (CMJ), standing broad jump (SBJ), and “modified 505” change of direction (COD) in a control condition and 6 minutes following three sets of six repetitions of flywheel half squats at one of two inertias (0.029 kg·m2 and 0.061 kg·m2). Peak directional ground reaction force, power, and rate of force development were calculated for each test. (3) Results: Higher inertia flywheel squats were able to acutely enhance CMJ peak vertical force (Bayes Factor (BF10) = 33.5, very strong; δ = 1.66; CI: 0.67, 2.70), whereas lower inertia flywheel squats were able to acutely enhance CMJ peak vertical power (BF10 = 3.65, moderate; δ = 0.93; CI: 0.11, 1.88). The vertical squat exercise induced no PAPE effect on resultant SBJ or horizontal COD ground reaction force parameters, nor were any differences observed between the inertias. (4) Conclusions: Researchers and practitioners should consider the kinetic and kinematic correspondence of a pre-load stimulus to the subsequent sport-specific activity (i.e., flywheel squat to CMJ).
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sports
Article
Post Flywheel Squat Potentiation of Vertical and Horizontal
Ground Reaction Force Parameters during Jumps and Changes
of Direction
Stuart A. McErlain-Naylor * and Marco Beato


Citation: McErlain-Naylor, S.A.;
Beato, M. Post Flywheel Squat
Potentiation of Vertical and Horizontal
Ground Reaction Force Parameters
during Jumps and Changes of Direction.
Sports 2021,9, 5. https://doi.org/
10.3390/sports9010005
Received: 25 November 2020
Accepted: 31 December 2020
Published: 5 January 2021
Publisher’s Note: MDPI stays neu-
tral with regard to jurisdictional clai-
ms in published maps and institutio-
nal affiliations.
Copyright: © 2021 by the authors. Li-
censee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and con-
ditions of the Creative Commons At-
tribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
School of Health and Sports Sciences, University of Suffolk, Ipswich IP4 1QJ, UK; M.Beato@uos.ac.uk
*Correspondence: s.mcerlain-naylor@uos.ac.uk
Abstract:
(1) Background: The aim of the study was to determine the post-activation performance
enhancement (PAPE) of vertical and horizontal ground reaction force parameters during jumps
and change of direction following flywheel squat exercise using two different flywheel inertias. (2)
Methods: Eleven male athletes performed a countermovement jump (CMJ), standing broad jump
(SBJ), and “modified 505” change of direction (COD) in a control condition and 6 minutes following
three sets of six repetitions of flywheel half squats at one of two inertias (0.029 kg
·
m
2
and 0.061 kg
·
m
2
).
Peak directional ground reaction force, power, and rate of force development were calculated for
each test. (3) Results: Higher inertia flywheel squats were able to acutely enhance CMJ peak vertical
force (Bayes Factor (BF
10
) = 33.5, very strong;
δ
= 1.66; CI: 0.67, 2.70), whereas lower inertia flywheel
squats were able to acutely enhance CMJ peak vertical power (BF
10
= 3.65, moderate;
δ
= 0.93; CI: 0.11,
1.88). The vertical squat exercise induced no PAPE effect on resultant SBJ or horizontal COD ground
reaction force parameters, nor were any differences observed between the inertias. (4) Conclusions:
Researchers and practitioners should consider the kinetic and kinematic correspondence of a pre-load
stimulus to the subsequent sport-specific activity (i.e., flywheel squat to CMJ).
Keywords: PAPE; countermovement jump; standing broad jump; change of direction; PAP; isoiner-
tial; eccentric overload; kinetic; power; rate of force development
1. Introduction
Post-activation potentiation is an acute improvement in muscular contractile perfor-
mance following a pre-load stimulus such as a resistance exercise protocol of maximal
or submaximal loads [
1
,
2
]. Several explanatory mechanisms have been proposed, in-
cluding neuromuscular and mechanical, as well as biochemical and physiological acute
responses [
3
,
4
]. Currently, the most accredited theory reports that post-activation po-
tentiation may relate to the phosphorylation of myosin regulatory light chains during
a muscle contraction, leading to a greater rate of cross-bridge attachment [
2
]. The role
of post-activation potentiation on sports performance has been recently debated due to
uncertainties around the extent to which the time frames of myosin light chain phosphory-
lation and voluntary force enhancement overlap [
5
]. An alternative term, post-activation
performance enhancement (PAPE), has been proposed to incorporate changes in factors
such as the temperature, water content, and activation of muscle [5,6].
Previous research investigating PAPE reported acute improvements in lower limb
performance following resistance exercise [
4
,
7
,
8
], while other studies have failed to confirm
this [
2
,
9
]. These inconsistent results could relate to differences in pre-load protocol. Exercise
characteristics such as volume, intensity, muscle action, and recovery between pre-load
exercise and the following test are key variables known to determine the magnitude of
PAPE response [
3
,
10
]. The majority of studies evaluating the acute effects of pre-load
exercise have used traditional weightlifting protocols [
7
,
11
], while evidence about PAPE
following flywheel resistance exercise remains limited and superficial [4,12].
Sports 2021,9, 5. https://doi.org/10.3390/sports9010005 https://www.mdpi.com/journal/sports
Sports 2021,9, 5 2 of 9
The utility of flywheel devices for inducing PAPE is only recently beginning to be
understood [
10
]. Such devices are commonly utilized to facilitate eccentric overload proto-
cols in which the generated eccentric muscular force may exceed the maximal concentric
force [
13
,
14
]. The user rotationally accelerates the flywheel (resistance due to the flywheel
moment of inertia) during the concentric phase of the movement, resulting in flywheel
kinetic energy and inertial torque that imparts high linear resistance during the subsequent
eccentric phase of the movement [
15
,
16
]. Despite the observed acute improvements in
whole-body dynamic performance, a thorough analysis of the PAPE response in specific
directional kinetic parameters following flywheel exercise has not been conducted. The
impulse-momentum relationship necessitates that an improvement in jump distances or
change of direction (COD) time must be associated with an increase in ground reaction
force impulse in the appropriate direction. What remains less clear is the PAPE effect on
peak force, peak power, and/or peak rate of force development during specific vertically
and/or horizontally dominant activities [4].
In the only investigations of such parameters to date, flywheel squat exercise induced
increases in countermovement jump (CMJ) peak force and peak power [
4
]. Similarly, fly-
wheel squats acutely enhanced peak isokinetic eccentric knee flexion torque [
17
]. Evidence
of an effect on peak concentric knee flexion and extension torques has been inconsis-
tent [
4
,
17
]. No previous studies have reported the effect of flywheel PAPE protocols on
CMJ peak rate of force development. Moreover, the flywheel-induced PAPE effects on
such ground reaction force measures as peak force, peak power, and peak rate of force
development are yet to be investigated in horizontally dominant activities such as the
COD or activities requiring concurrent horizontal and vertical force application such as
the standing broad jump (SBJ). A recent investigation comparing protocols with different
flywheel squat inertias reported PAPE effects on CMJ, SBJ, and COD performance out-
comes, but no difference in the magnitude of responses between inertias [
18
]. It is currently
unknown whether the PAPE effects with each inertia were achieved through the same or
different kinetic mechanisms. For example, there may be a specificity of transfer from the
force–velocity region occupied during the pre-load exercise (due to exercise inertia) to the
subsequent kinetic PAPE response (e.g., peak force, peak power, and/or peak rate of force
development) [1922].
The aim of the present study was to determine the PAPE effects of flywheel half squat
exercise with two different flywheel inertias on vertical and horizontal ground reaction
force parameters during jumps and changes of direction. It was hypothesized that flywheel
half squat exercise would induce a PAPE effect on peak force and peak rate of force
development during CMJ, SBJ, and COD, as well as on peak power during CMJ and SBJ.
No a priori hypothesis was made regarding the effect of flywheel inertia on these effects
due to the lack of prior evidence.
2. Materials and Methods
2.1. Participants
An a priori power analysis (G*Power version 3.1.9.7, Heinrich Heine University Düs-
seldorf, Germany) revealed that 10 participants would provide an 85% chance of achieving
α
= 0.05 in a frequentist 2
×
2 repeated measures analysis of variance, assuming an effect
size of 0.40 (from a previous PAPE effect on CMJ peak power 5 min after flywheel squat
exercise [
4
]) and a high correlation (r= 0.8) between repeated measures. Multiplication
by a Bayesian inflation factor of 1.084 resulted in the requirement for 11 participants [
23
].
Eleven male recreational team sports athletes (22
±
2 years; 82.6
±
12.5 kg) participated in
this investigation, each with more than 10 years of experience in their sport and currently
participating in at least one resistance training session per week. All participants trained
and competed at least twice per week and were free from injury or illness. Each was
familiar with the flywheel squat exercise and the CMJ, SBJ, and “modified 505” COD tests,
as recently suggested [
24
]. The study was approved by the ethical advisory committee
Sports 2021,9, 5 3 of 9
of the University of Suffolk. Participants were informed of the benefits and risks of the
investigation prior to signing informed consent.
2.2. Design
A within-participants randomized controlled crossover design was utilized. Each
participant attended the laboratory on 5 separate occasions, separated by at least 48 h
of recovery to avoid any possible transient fatigue due to repeated efforts. The 5 testing
sessions were randomly allocated to reduce learning effects. Participants maintained their
normal nutritional intake during the experimental period. Alcohol and caffeine were not
permitted prior to the experimental sessions but hydration was allowed during the sessions.
The 5 sessions were as follows in a randomized order: (1) control condition (no pre-load
exercise) followed by CMJ, SBJ, and COD; (2) lower inertia flywheel half squats followed
by jumps (CMJ and SBJ); (3) lower inertia followed by COD; (4) higher inertia flywheel
half squats followed by jumps; (5) higher inertia followed by COD.
2.3. Procedures
A standardized warm-up consisting of 5 min of cycling at a constant power on an
ergometer (Sport Excalibur lode, Groningen, The Netherlands) was performed at the
beginning of each testing session [
4
]. Mobilization was performed immediately after the
cycling for a duration of 3 min, consisting of dynamic movements mimicking the exercise
(e.g., half squat) and dynamic hip, knee, and ankle movements. In the control session,
a maximal CMJ, SBJ, and COD were performed in a randomized order following the
warm-up. The warm-up in each of the other sessions was followed by 3 sets of 6 flywheel
ergometer (D11 Full, Desmotec, Biella, Italy) half squat repetitions, with 2 minutes of
passive recovery between sets [
4
]. This multi-set exercise protocol has previously been
utilized to successfully induce PAPE in similar cohorts of participants [
4
,
25
]. The flywheel
half squats were followed after 6 min of passive recovery by maximal efforts of either
1 CMJ and 1 SBJ (order randomized), or 1 COD only, depending on the session. This timing
(6 min) after the pre-load exercise has previously been shown to characterize the optimal
PAPE response following such exercise [
18
]. Randomization of sessions, as well as tests
within a session, minimized potential confounding effects of training, learning, or fatigue.
2.4. Flywheel Exercise
Participants were instructed to perform the concentric phase of the flywheel half
squats with maximal velocity, and the eccentric phase to approximately 90
of knee flexion
as in previous similar successful acute interventions [
12
,
17
,
18
,
25
]. The combined load of the
ergometer plus flywheel was 1 “large” disc and 1 “medium” disc (mass = 3.0 kg; moment
of inertia = 0.029 kg
·
m
2
) during lower inertia exercise, and 1 “Pro” disc
(mass = 6.0 kg;
moment of inertia = 0.061 kg
·
m
2
) during higher inertia exercise. These moments of inertia
were used to generate PAPE effects on CMJ, SBJ, and COD performance outcomes in a
previous investigation [18].
2.5. Physical Tests
Ground reaction force parameters during the CMJ, SBJ, and COD were assessed
using a force platform (Kistler, Winterthur, Switzerland; 900
×
600 mm; 1000 Hz). CMJs
were performed for maximum height from an upright stationary starting position with
a self-selected depth, and hands on hips to avoid influence of arm swing [
26
]. Bilateral
SBJs for maximum anterior distance were performed from an upright stationary starting
position with a self-selected depth and arm swing. COD (aiming for minimum completion
time) was tested via a dominant leg unilateral 180
turn separating 2
×
5 m sprints [
27
],
commonly referred to as a “modified 505”. COD trials started on the “Go” command from
a standing position, with the front foot up to the measured starting mark [28].
Sports 2021,9, 5 4 of 9
2.6. Dependent Variables
All kinetic parameters were calculated in MATLAB (Version R2020a, The MathWorks
Inc., Natick, MA, USA) from ground reaction force data in the primary direction of perfor-
mance determination. For CMJ, peak vertical force, power, and rate of force development
were calculated. For SBJ, peak resultant (of anterior–posterior and vertical) force, power,
and rate of force development were calculated. For COD, peak anterior-posterior force and
rate of force development were calculated. Thus, eight kinetic parameters were determined
for each of control, following lower inertia, and following higher inertia. Peak force was
determined as the maximum positive (vertical or anterior) ground reaction force at any
time point during ground contact prior to take-off. Peak power was determined as the
maximum dot product of force and velocity (velocity calculated via the impulse method) at
any time point during ground contact prior to take-off. Peak rate of force development was
determined as the maximum positive rate of ground reaction force development at any
time point during ground contact prior to take-off (which was calculated as the average rate
of development over a 50 ms period using a rolling mean method) [
29
]. Ground contact
was identified using a 10 N vertical ground reaction force threshold.
2.7. Statistical Analyses
All statistical analyses were performed within JASP (University of Amsterdam,
The Netherlands) software version 0.9.2.0. Data were presented as mean
±
SD. A fully
Bayesian inferential statistical approach was used to provide probabilistic statements
(see [
30
] for an introduction). Each analysis was conducted with the JASP-default
“noninformative” prior (Cauchy distribution, 0.707) due to the lack of strong a priori
evidence [
31
]. Bayesian repeated measures ANOVA was used to evaluate the effects
of time (within: control vs. 6 min) and inertia (between: lower vs. higher inertia) on
the 8 kinetic parameters describing CMJ, SBJ, and COD performance. Bayes factor
(BF
10
) was reported to indicate the strength of the evidence and interpreted as follows:
1/3 < anecdotal
3; 3 < moderate
10; 10 < strong
30; 30 < very strong
100;
extreme > 100 [
32
]. Evidence for the alternative hypothesis (H
1
) was set as BF
10
> 3,
and evidence for the null hypothesis (H
0
) was set as BF
10
< 1/3. Estimates of median
standardized effect size (
δ
) and 95% credible interval (CI) were calculated [
32
]. Markov
Chain Monte Carlo with Gibbs sampling was used to make inferences (10,000 samples).
δ
was interpreted by Cohen as follows: trivial < 0.2; 0.2
small < 0.6; 0.6
moderate < 1.2;
1.2 large < 2.0; very large 2.0 [33].
3. Results
Meaningful PAPE (within: 6 min vs. control) effects were reported for CMJ peak
force (BF
10
= 294; extreme), CMJ peak power (BF
10
= 7.12; moderate), and CMJ peak rate
of force development (BF
10
= 4.35; moderate). No meaningful PAPE effects were reported
for any SBJ or COD parameters (within: 0.247
BF
10
0.712; Table 1). No meaningful
differences between exercise inertias (between: 0.223
BF
10
0.569) or interactions
between time and inertia (0.100
BF
10
0.883) were reported
(Table 1).
Bayesian post
hoc comparisons of the PAPE effect (control vs. 6 min; Table 2) reported meaningful
differences in CMJ peak force following higher inertia (BF
10
= 33.5; very strong;
δ= 1.656;
CI: 0.666, 2.695) and CMJ peak power following lower inertia
(BF10 = 3.65;
moderate;
δ= 0.932;
CI: 0.110, 1.877). No other post hoc comparisons reported meaningful differ-
ences (0.689 BF10 2.738).
Sports 2021,9, 5 5 of 9
Table 1.
Within (time: post-activation performance enhancement (PAPE)) and between (inertia) effects on directional
kinetic parameters describing countermovement jump (CMJ), standing broad jump (SBJ), and change of direction (COD)
performance 6 min following flywheel half squat exercise with lower (0.029 kg
·
m
2
) and higher (0.061 kg
·
m
2
) inertia (n= 11).
Variable Inertia
(kg·m2)Control 6 min BF10 within
(Time) Assessment BF10 between
(Inertia) Assessment
CMJ PF
(BW)
0.029 2.27 ±0.19 2.40 ±0.23 293.8 extreme H10.392 anecdotal
0.061 2.44 ±0.24
CMJ PP
(W·kg1)
0.029 49.94 ±4.50 52.73 ±6.07 7.122 moderate H10.417 anecdotal
0.061 51.40 ±5.37
CMJ PRFD
(BW·s1)
0.029 10.06 ±2.59 11.42 ±4.39 4.354 moderate H10.569 anecdotal
0.061 12.91 ±4.92
SBJ PF
(BW)
0.029 2.55 ±0.26 2.52 ±0.30 0.257 moderate H00.242 moderate H0
0.061 2.54 ±0.25
SBJ PP
(W·kg1)
0.029 44.40 ±4.85 43.37 ±4.50 0.263 moderate H00.275 moderate H0
0.061 44.14 ±5.54
SBJ PRFD
(BW·s1)
0.029 11.70 ±3.82 12.47 ±3.39 0.247 moderate H00.269 moderate H0
0.061 11.64 ±4.62
COD PF
(BW)
0.029 1.21 ±0.24 1.18 ±0.23 0.324 moderate H00.223 moderate H0
0.061 1.17 ±0.18
COD PRFD
(BW·s1)
0.029 19.98 ±7.02 18.58 ±4.03 0.712 anecdotal 0.283 moderate H0
0.061 17.37 ±4.76
PF: peak force; PP: peak power; PRFD: peak rate of force development; H
0
: evidence for the null hypothesis; H
1
: evidence for the alternative
hypothesis. All kinetic parameters are vertical ground reaction force for CMJ, resultant (vertical and anterior–posterior) for SBJ, and
anterior–posterior for COD.
Table 2.
Bayesian post hoc comparisons (PAPE effect) of directional kinetic parameters describing countermovement jump
(CMJ) performance between control and 6 min following lower (0.029 kg
·
m
2
) and higher (0.061 kg
·
m
2
) inertia flywheel half
squat exercise (n= 11).
Variable Inertia
(kg·m2)Control 6 min BF10 Assessment δδ95% Credible
Interval Assessment
CMJ PF
(BW)
0.029 2.27 ±0.19 2.40 ±0.23 2.738 anecdotal 0.854 0.037, 1.770 moderate
0.061 2.44 ±0.24 33.549 very strong 1.656 0.666, 2.695 large
CMJ PP
(W·kg1)
0.029 49.94 ±4.50 52.73 ±6.07 3.650 moderate 0.932 0.110, 1.877 moderate
0.061 51.40 ±5.37 0.689 anecdotal 0.446 0.251, 1.279 small
CMJ PRFD
(BW·s1)
0.029 10.06 ±2.59 11.42 ±4.39 0.725 anecdotal 0.462 0.255, 1.293 small
0.061 12.91 ±4.92 1.904 anecdotal 0.741 0.046, 1.655 moderate
PF: peak force; PP: peak power; PRFD: peak rate of force development;
δ
: median standardized effect size. All CMJ kinetic parameters are
vertical ground reaction force.
4. Discussion
This study investigated the PAPE effects on specific directional ground reaction force
parameters following flywheel half squat exercise and compared such effects between
different flywheel inertias. The present study reported a meaningful PAPE effect on CMJ
peak vertical force following higher inertia (very strong likelihood) but not lower inertia
flywheel squats. Contrastingly, a meaningful PAPE effect on CMJ peak power was reported
following lower inertia (moderate) but not higher inertia flywheel squats. A meaningful
(moderate) overall PAPE effect on CMJ peak rate of force development was reported. No
meaningful differences between inertias were reported. Thus, this study reports for the
first time that higher and lower inertia flywheel squats can differentially enhance CMJ peak
force and peak power, respectively.
The observation of PAPE in all vertical kinetic parameters measured during the CMJ
supports the present study’s hypothesis that flywheel half squat exercise can induce a
PAPE effect on peak force, peak power, and peak rate of force development during a
CMJ. This further supports the findings of previous studies reporting flywheel-induced
Sports 2021,9, 5 6 of 9
PAPE effects on CMJ performance (e.g., jump height) and associated kinetic (e.g., peak
vertical force and power) measures [
4
,
12
]. However, the lack of a PAPE effect on horizontal
kinetic parameters during the COD or resultant kinetic parameters during the SBJ suggests
that the kinetic response to a flywheel pre-load exercise relates to its specific directional
loading nature (e.g., vertical loading relative to the participant during a squat exercise
and a CMJ) [
34
]. The fact that acute performance enhancements have previously been
observed in SBJ and COD following flywheel squats [
12
,
18
] suggests that further research
is needed to verify the hypothesis of an association between specific pre-load directional
loading nature and subsequent task performance or ground reaction force application. It
may be supposed that any such effect relates more to dynamic correspondence (e.g., the
corresponding regions of muscle force-length and force-velocity curves occupied during
the activities) than a simple dichotomy of vertical or horizontal exercises relative to the
participant.
A previous study investigating overall performance in the same tasks as the current
study reported no meaningful effect of flywheel inertia on magnitude of PAPE response [
18
].
The present study investigated this effect in more detail, reporting on specific kinetic pa-
rameters, and again found no overall meaningful difference between flywheel inertias. Post
hoc analysis of specific effects revealed contrasting meaningful PAPE effects on CMJ peak
vertical force following higher but not lower inertia exercise, and on CMJ peak vertical
power following lower but not higher inertia exercise. These initial results indicate the
possibility of a relationship between flywheel exercise intensity and the mechanism of
subsequent acute performance enhancement. The results suggest that practitioners can use
three sets of six flywheel squats 6 min prior to countermovement jumps within training
interventions to acutely enhance specific kinetic parameters within the jump. A recent
study reported that increases in flywheel inertia are associated with decreases in peak and
mean velocities during the concentric and eccentric phases of the flywheel squat but had
no significant effect on peak concentric or eccentric power [
22
]. The study recommended
the use of velocity-based flywheel resistance training [
35
], using peak concentric veloc-
ity to individualize exercise prescription. The present study suggests there may exist a
specificity of transfer from the force–velocity region occupied during the pre-load exercise
(due to flywheel inertia) to the subsequent kinetic PAPE response (e.g., peak force, peak
power, and/or peak rate of force development). For example, the likely greater forces
generated at higher inertias (prescribed via lower target velocities) may transfer more to
acute improvements in countermovement jump peak force, whilst the greater velocities
at lower inertias may transfer more to acute improvements in countermovement jump
peak power [
22
,
36
]. Further research is needed to assess the efficacy of such individual-
ized longitudinal interventions (e.g., in response to individual athlete force or velocity
deficiencies) [37,38].
Whilst this study supports previous knowledge that PAPE is observed following a
recovery period (e.g., 6 min) [
2
], it does not attempt to determine whether a shorter or
longer passive recovery (e.g., 3 or 10 min) may be more effective to enhance kinetic PAPE
response during sport-specific tasks. Future studies using different recovery times may be
useful to clarify whether different intensities could be more effective at inducing quicker
or slower PAPE response onsets. If this were the case then time windows may be altered
for the specific pre-load strategy adopted [
39
]. Moreover, the interpretation of the current
findings could imply that protocols using horizontally loaded pre-load exercises relative
to the participant may exhibit the opposite direction-specificity of PAPE response (e.g.,
greater transfer to horizontal kinetic parameters). Further research is needed to confirm or
deny this rationale, as well as to similarly investigate the effect of squat depth on observed
responses [
40
]. The use of electromyography, beyond the scope of the current study, would
enable relationships between pre-load exercise and subsequent muscle activation to be
established. This may provide insight into the underlying neurophysiological mechanisms.
Finally, this research enrolled male team sports athletes and thus wider generalization to
alternative samples (e.g., females, professional athletes, resistance training experts) cannot
Sports 2021,9, 5 7 of 9
be inferred. Such groups may exhibit different PAPE response characteristics, especially
given relationships between muscular capabilities and PAPE magnitude
[39,41,42].
Porta-
bility, access, and adherence to flywheel protocols should be considered by strength and
conditioning practitioners before implementing flywheel-based training interventions.
5. Conclusions
The vertically dominant flywheel squat pre-load exercise induced increases in peak
vertical force, power, and rate of force development during CMJ, but no such increases in
resultant or horizontal kinetic parameters during the SBJ or COD. As such, practitioners
should consider the directional nature and kinetic characteristics of the required acute
kinetic response in order to optimize the programming of PAPE-based training or compe-
tition interventions. Meaningful PAPE effects were reported on CMJ peak vertical force
following higher inertia but not lower inertia flywheel squats, and on CMJ peak vertical
power following lower inertia but not higher inertia flywheel squats. Therefore, higher
inertia flywheel exercise may be more effective at enhancing peak force, and lower inertias
may be more effective at enhancing peak power, during subsequent CMJ. Since this is the
first study to have analyzed such effects, future research is needed before drawing final
conclusions.
Author Contributions:
Both authors were involved in all stages of the research process. All authors
have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement:
The study was conducted according to the guidelines of the
Declaration of Helsinki, and approved by the ethical advisory committee of the University of Suffolk
(STE_REC 18010; January 2019).
Informed Consent Statement:
Informed consent was obtained from all participants involved in the
study.
Data Availability Statement:
The data presented in this study are available on reasonable request
from the corresponding author.
Conflicts of Interest: The authors declare no conflict of interest.
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... Over the last decade, flywheel training has widely shown its usefulness to promote muscular hypertrophy and strength gains (Maroto-Izquierdo et al., 2017b;Nuñez and Sáez de Villarreal, 2017), alongside improvements in actions related to sports performance such as sprinting, jumping and changes of direction (Beato et al., 2019a;McErlain-Naylor and Beato, 2021a;Raya-González et al., 2021c). In addition, flywheel training has shown promising results for both rehabilitation (Romero-Rodriguez et al., 2011) and injury prevention purposes (Askling et al., 2003;de Hoyo et al., 2015;Beato et al., 2021). ...
... For such a reason, the first mechanical gravity independent device was developed to overcome these limitations, allowing crews to train in microgravity situations and limiting the deleterious effects of space flights (Berg and Tesch, 1994). After the first pioneering studies, sport scientists and later on, practitioners, understood the advantages offered by flywheel technology and they started to use it for training purposes such as performance development, injury prevention, and clinical rehabilitation (Askling et al., 2003;Tous-Fajardo et al., 2006;Tesch et al., 2017;Allen et al., 2021;Mcerlain-Naylor and Beato, 2021). ...
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Purpose: To summarize the evidence on postactivation potentiation (PAP) protocols using flywheel eccentric overload (EOL) exercises. Methods: Studies were searched using the electronic databases PubMed, Scopus, and Institute for Scientific Information Web of Knowledge. Results: In total, 7 eligible studies were identified based on the following results: First, practitioners can use different inertia intensities (eg, 0.03-0.88 kg·m2), based on the exercise selected, to enhance sport-specific performance. Second, the PAP time window following EOL exercise seems to be consistent with traditional PAP literature, where acute fatigue is dominant in the early part of the recovery period (eg, 30 s), and PAP is dominant in the second part (eg, 3 and 6 min). Third, as EOL exercises require large force and power outputs, a volume of 3 sets with the conditioning activity (eg, half-squat or lunge) seems to be a sensible approach. This could reduce the transitory muscle fatigue and thereby allow for a stronger potentiation effect compared with larger exercise volumes. Fourth, athletes should gain experience by performing EOL exercises before using the tool as part of a PAP protocol (3 or 4 sessions of familiarization). Finally, the dimensions of common flywheel devices offer useful and practical solutions to induce PAP effects outside of normal training environments and prior to competitions. Conclusions: EOL exercise can be used to stimulate PAP responses to obtain performance advantages in various sports. However, future research is needed to determine which EOL exercise modalities among intensity, volume, and rest intervals optimally induce the PAP phenomenon and facilitate transfer effects on athletic performances.
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Worcester, KS, Baker, PA, and Bollinger, LM. Effects of inertial load on sagittal plane kinematics of the lower extremity during flywheel-based squats. J Strength Cond Res XX(X): 000-000, 2020-Increasing load increases flexion of lower extremity joints during weighted squats; however, the effects of inertial load on lower extremity kinematics during flywheel-based resistance training (FRT) squats remain unclear. The purpose of this study was to evaluate sagittal plane kinematics of lower extremity joints during FRT squats at various inertial loads. Nine recreationally resistance-trained subjects (3M, 6F) completed a bout of FRT squats with inertial loads of 0.050, 0.075, and 0.100 kg·m. Two-dimensional sagittal plane kinematics were monitored with retroreflective markers at a rate of 60 Hz. Joint angles and angular velocities of the knee, trunk + hip, trunk inclination, and ankle were quantified throughout concentric and eccentric actions. Effects of inertial load were determined by repeated-measures analysis of variance with α = 0.05. Average power and average vertical velocity decreased with increasing inertial load, whereas average force increased. Minimal and maximal sagittal plane joint angles of the knee, trunk + hip, trunk inclination, and ankle were not significantly different among inertial loads. However, peak joint angular velocities of the knee and trunk + hip tended to decrease with increasing inertial load. Conversely trunk inclination and ankle dorsiflexion velocities were not significantly different among inertial loads. Increasing inertial load from 0.050 to 0.100 kg·m significantly reduces average power during FRT squats primarily by decreasing movement velocity, which seems to be specific to the knee and hip joints. It is possible that lower concentric energy input at high inertial loads prevents increased joint flexion during FRT squats.
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Purpose: To compare the effects of 2 postactivation potentiation (PAP) protocols using traditional-set or cluster-set configurations on countermovement jump performance. Methods: Twenty-six male basketball players completed 3 testing sessions separated by 72 hours. On the first session, subjects performed barbell jump squats with progressively heavier loads to determine their individual optimum power load. On the second and third sessions, subjects completed 2 PAP protocols in a randomized order: 3 sets of 6 repetitions of jump squats using optimum power load performed with either a traditional-set (no interrepetition rest) or a cluster-set (20-s rest every 2 repetitions) configuration. After a warm-up, countermovement jump height was measured using a force platform before, 30 seconds, 4 minutes, and 8 minutes after completing the PAP protocols. The following kinetic variables were also analyzed and compared: relative impulse, ground reaction force, eccentric displacement, and vertical leg-spring stiffness. Results: Across both conditions, subjects jumped lower at post 30 seconds by 1.21 cm, and higher in post 4 minutes by 2.21 cm, and in post 8 minutes by 2.60 cm compared with baseline. However, subjects jumped higher in the cluster condition by 0.71 cm (95% confidence interval, 0.37 to 1.05 cm) in post 30 seconds, 1.33 cm (95% confidence interval, 1.02 to 1.65 cm) in post 4 minute, and 1.64 cm (95% confidence interval, 1.41 to 1.88 cm) in post 8 minutes. The superior countermovement jump performance was associated with enhanced kinetic data. Conclusions: Both protocols induced PAP responses in vertical jump performance using jump squats at optimum power load. However, the cluster-set configuration led to superior performance across all time points, likely due to reduced muscular fatigue.