Content uploaded by Stuart A. McErlain-Naylor
Author content
All content in this area was uploaded by Stuart A. McErlain-Naylor on Oct 28, 2021
Content may be subject to copyright.
1
This is an Accepted Manuscript of an article published in Sports Biomechanics, accepted on 12
August 2020, available online: https://doi.org/10.1080/14763141.2020.1810750
Version: Accepted for publication
Publisher: © Taylor & Francis
Rights: This work is made available according to the conditions of the Creative Commons
Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full
details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/
Please cite the published version.
2
Sports Biomechanics
Post flywheel squat vs. flywheel deadlift potentiation of lower limb
isokinetic peak torques in male athletes
1 M. Beato, 1 K.L. de Keijzer, 1 A. Fleming, 1 A. Coates, 2 O. La Spina, 2 G. Coratella,
and 1 S.A. McErlain-Naylor.
1 School of Health and Sports Sciences, University of Suffolk, Ipswich, IP4 1QJ, UK
2 Department of Biomedical Sciences for Health, University of Milan, Italy
ABSTRACT
The present study investigated the post-activation performance enhancement (PAPE) of
isokinetic quadriceps and hamstrings torque after flywheel (FW)-squat vs. FW-deadlift in
comparison to a control condition. Fifteen male athletes were enrolled in this randomised,
crossover study. Each protocol consisted of 3 sets of 6 repetitions, with an inertial load of
0.029 kg.m2. Isokinetic quadriceps (knee extension) and hamstrings (knee flexion)
concentric peak torque (60º/s) and hamstring eccentric peak torque (-60º/s) were
measured 5 min after experimental or control conditions. A significant condition (PAPE)
effect was reported (f = 4.067, p = 0.008) for isokinetic hamstrings eccentric peak torque
following FW-squat and FW-deadlift, but no significant differences were found for
quadriceps and hamstrings concentric peak torques. The significant difference averaged
14 Nm between FW-squat vs. control (95% CI: 2, 28; d = 0.75, moderate; p = 0.033), and
13 Nm between FW-deadlift vs. control (95% CI: 1, 25; d = 0.68, moderate; p = 0.038). This
study reported that both FW-squat and FW-deadlift exercises are equivalently capable of
generating PAPE of isokinetic hamstrings eccentric torque. Practitioners may use these
findings to inform strength and power development during complex training sessions
consisting of flywheel-based exercises prior to a sport-specific task.
Keywords: iso-inertial; eccentric overload; post-activation potentiation; hamstrings; PAPE
INTRODUCTION
Post activation performance enhancement (PAPE) is a physiological
phenomenon associated with an acute improvement in neuromuscular and sport-
specific capabilities (Blazevich & Babault, 2019; Boullosa, Del Rosso, Behm, & Foster,
2018). The exact physiological mechanisms of this phenomenon are not yet clear and
differing theories exist (Blazevich & Babault, 2019; Boullosa et al., 2018). Very
recently, Boullosa et al. have reported further insights into the taxonomy of post-
activation and its application in sport (Boullosa et al., 2020). The most frequently
accredited mechanism relates to myosin regulatory light chain phosphorylation and an
increased sensitivity to calcium (Ca2+) (Tillin & Bishop, 2009). Such changes increase
the number of cross-bridges formed in myofilaments, increasing the rate and
magnitude of force generated (Beato, McErlain-Naylor, Halperin, & Dello Iacono, 2020;
Bishop, 2003). However, it is not clear to what extent the time frame of these responses
relate to the time frame of observed PAPE (Blazevich & Babault, 2019). PAPE-based
warm up protocols have been shown to acutely enhance sporting performance in a
variety of populations (Beato et al., 2020). The performance enhancement is generally
reported 3 min after the pre-load activity and persists for up to 9-12 minutes after the
initial conditioning activity (Beato, Stiff, & Coratella, 2019; Robbins, 2005; Tillin &
Bishop, 2009).
High-intensity traditional resistance exercises have achieved PAPE - proving
attractive for a variety of physical preparation objectives (Dello Iacono & Seitz, 2018;
3
Doma, Leicht, Boullosa, & Woods, 2020; Seitz & Haff, 2016). However, PAPE activities
using traditional barbell methodologies may not always be practical for field-based
sports. Application of these traditional methods may be limited by equipment access,
training locations, or the use of high-intensity load (e.g., 90% repetition maximum) prior
to training (Bauer et al., 2019; Doma et al., 2020). Recent research has supported the
use of flywheel-based exercises as alternative PAPE protocols (Beato et al., 2020; de
Keijzer, McErlain-Naylor, Dello Iacono, & Beato, 2020). Currently, it appears that both
methodologies – flywheel and traditional resistance exercises – can similarly enhance
acute strength and jump performance (Beato, Bigby, et al., 2019; Seitz & Haff, 2016).
However, flywheel-based protocols present some technological advantages. For
instance, an overload is generally obtained during the eccentric phase due to the active
deceleration of the disc angular momentum generated during the previous concentric
phase (Beato, Bigby, et al., 2019; Carroll et al., 2019). The ability to achieve high
intensities in the eccentric phase is a clear advantage of flywheel technology in
comparison to traditional resistance exercise (Beato, Bigby, et al., 2019; Maroto-
Izquierdo et al., 2019; Norrbrand, Pozzo, & Tesch, 2010). However, the current body
of research investigating flywheel-based PAPE protocols is very limited and further
studies are needed (Beato et al., 2020; de Keijzer et al., 2020). Current
recommendations have focused on protocols involving flywheel squats (FW-squat),
suggesting to utilise inertial loads ranging from 0.029 - 0.110 kg·m2 for 2 - 3 sets to
acutely enhance jumping performance (Beato et al., 2020; de Keijzer et al., 2020).
Isokinetic testing may shed further light on changes in lower-limb joint torques and offer
additional information regarding the acute response of specific muscles groups, such
as the quadriceps and hamstrings, in both concentric and eccentric modality (Beato,
Stiff, et al., 2019; Morin et al., 2015). Considering the importance of quadriceps and
hamstring strength in many sporting activities, it may be beneficial for practitioners to
understand how specific conditioning activities can help acutely enhance these
capabilities (Beato, Stiff, et al., 2019; Coratella, Beato, Cè, Scurati, & Milanese, 2019).
Furthermore, the necessary time window (e.g., 3 - 9 minutes) for recovery post-
conditioning activity has also been highlighted as important for ensuring a successful
PAPE response with FW-squat-based protocols (Beato, Stiff, et al., 2019). A lot
remains unknown about other modulating factors, including the effects of different
conditioning exercises such as the flywheel deadlift (FW-deadlift).
Barbell deadlifts and squats differ biomechanically, with the deadlift
demonstrating a sequential rather than synergistic movement (Hales, Johnson, &
Johnson, 2009). Greater hamstrings and lesser quadriceps activity has been reported
during traditional deadlift compared to squat exercise (Ebben et al., 2009). This may
influence the hamstrings vs. quadriceps-specific PAPE responses to such exercises
(Scott, Ditroilo, & Marshall, 2017). Previous research reported that near-maximal
concentric-only deadlifts acutely enhanced jumping performance within rugby league
players (Scott et al., 2017). Contrary to this, Gahreman et al. (2020) enrolled 15
resistance-trained youth wrestlers, who enhanced repeated jump performance after a
back squat protocol but not after a traditional deadlift protocol. Similarly, Till and Cooke
(2009) reported that a 5 repetition maximum traditional deadlift protocol did not acutely
enhance sprint or jump performance. These studies reported contrasting evidence
regarding the PAPE effect of traditional resistance deadlift exercises. However, no
research evaluating the PAPE effect of the deadlift exercise has utilised flywheel
devices to overload the eccentric phase of the exercise, nor have effects on the
hamstrings vs. quadriceps torque ratio (H:Q) been assessed. The conventional ratio
of concentric hamstrings to concentric quadriceps peak torques (Hconc:Qconc) and
functional ratio of eccentric hamstrings to concentric quadriceps peak torques
4
(Hecc:Qconc) offer insights about the strength balance, which have relevance for sport
performance and injuries (Beato et al., 2019; Coratella et al., 2015). For example, a
greater Hecc:Qconc ratio may indicate a greater capacity of the hamstring muscles to
provide dynamic knee joint stability (Aagaard, Simonsen, Magnusson, Larsson, &
Dyhre-Poulsen, 1998) during activities such as the final swing phase of sprinting where
eccentric hamstring strength must be sufficient to decelerate the knee extension
generated by the quadriceps muscle (Yeung, Suen, & Yeung, 2009). An overload in
the eccentric phase of the conditioning exercise may be an important strategy for those
individuals who have a deficit in eccentric strength or possible muscle imbalances.
Knowledge about the PAPE effects on these parameters could offer further insights
into the utility of flywheel-based PAPE protocols to prepare the lower limbs for the
demands of sport such as sprinting (Beato & Dello Iacono, 2020), accelerations (Morin
et al., 2015), and changes of direction (Beato, De Keijzer, et al., 2019).
The growth in application of flywheel resistance training due to its unique
characteristics (e.g. greater eccentric load than traditional resistance exercises) has
necessitated an investigation into acute PAPE responses following such novel
protocols. The available early studies into flywheel PAPE protocols have focused
primarily on squat protocols, showing positive results. However, no research has
investigated these effects following flywheel deadlifts and so a comparison is useful
and informative. Therefore, the aims of this study were: firstly, to investigate PAPE on
lower limb joint torques after FW-squat and FW-deadlift compared to a control
condition; and secondly, to compare the effectiveness of these two flywheel-based
protocols at stimulating PAPE effects on lower limb joint torques. It was hypothesised
that both protocols would generate a PAPE effect on concentric and eccentric
isokinetic hamstrings and quadriceps torques, but no a priori hypothesis was made
about the difference in effectiveness between FW-squat and FW-deadlift protocols.
METHODS
Participants
An a priori power analysis using G*power (Düsseldorf, Germany) indicated that
a sample of 15 participants was required to detect a moderate effect (f = 0.35) with
80% power and an alpha of 0.05. Fifteen male amateur university athletes (mean ±
SD: age 22 ± 3 years; body mass 79.4 ± 9.5 kg; height 1.84 ± 0.06 m) participated in
this study. The participants regularly engaged in either soccer training or resistance
training. Inclusion criteria were: the absence of any injury or illness; regular
participation in training activities (a minimum of 2 training sessions per week); and at
least 6 months of resistance training experience. All participants were informed about
the potential risks and benefits associated with the procedures of this study before
giving written consent. The Ethics Committee of the School of Health and Sports
Sciences at the University of Suffolk (UK) approved this study (SREC013/RT). All
procedures were conducted according to the Declaration of Helsinki for studies
involving human participants.
Experimental design
The acute effects induced by FW-squat and FW-deadlift (experimental
conditions) on isokinetic hamstrings and quadriceps peak torques compared to a
control condition were investigated in the present randomised, crossover study. Each
participant attended the laboratory on 4 separate occasions (Figure 1). All sessions
5
were performed two to four days apart and at least 48 hours after the last competition
or training session to avoid the effects of accumulated fatigue on performance.
Figure 1 - Experimental procedure.
During the first (familiarisation) visit, participants’ body mass and height were
recorded through a stadiometer (Seca 286dp; Seca, Hamburg, Germany). The
participants were familiarised with the same flywheel exercise and isokinetic testing
protocols used during the experimental protocol. Full self-selected recovery was
provided between familiarisation of isokinetic testing, flywheel squats and flywheel
deadlifts. Isokinetic tests were familiarised first to enable comparison with the control
condition for inter-session reliability analysis. Within the remaining visits, the
participants performed one of the 3 test protocols in a randomised order after a
standardised warm-up: FW-squat; FW-deadlift; or control (no exercise between the
standardised warm-up and standardised isokinetic testing) condition. The sessions
were randomised to reduce any learning effect on the isokinetic tests. The use of a
control (no pre-load exercise) condition enabled investigation of the PAPE effect
without the increased likelihood of fatigue that would be associated with performing
two sets of isokinetic tests and maximal pre-load exercise within a single session.
Between the protocol and subsequent isokinetic test, 5 min of passive standing
recovery were required to limit transient effects of fatigue on the following isokinetic
task. PAPE can be obtained after 3 - 9 min of recovery (Beato, Stiff, et al., 2019), and
so 5 min represents a compromise between any remaining fatigue (e.g. at 3 min) and
possible reduced PAPE magnitude (e.g. at 9 min).
Standardised warm-up
During each session, participants performed a standardised warm-up of 10 min
cycling at a constant power (1 W/kg body mass) on an ergometer (Sport Excalibur
lode, Groningen, Netherlands) followed by dynamic mobilisation exercises
(bodyweight squats, lunges, and deadlifts). Each participant performed all testing
sessions at the same time of day to reduce the effect of circadian rhythms on
performance. Participants were instructed to avoid stimulants or depressant
substances 24 hours prior to each testing session and to rehydrate ad libitum.
Isokinetic tests
An isokinetic dynamometer (Bide Medical Systems, Shirley, NY, USA) was used
to measure quadriceps and hamstrings peak torque. The device was calibrated
according to the manufacturer’s guidelines and the centre of rotation was aligned with
6
the tested knee (dominant leg: the preferred limb used to kick a ball). Participants were
seated on the dynamometer chair, with a hip angle of 95 degrees. The quadriceps
(knee extension) peak torque was measured in the concentric phase, and the
hamstrings (knee flexion) peak torque was measured in concentric and eccentric
phases (all 60º/s). Each testing modality consisted of 5 consecutive maximal
repetitions. Peak torques (from single greatest repetition) were extracted for further
analysis. Strong standardised verbal encouragements were provided to the
participants to maximise performance. The conventional ratio (Hconc:Qconc) and
functional ratio (Hecc:Qconc) were also calculated.
Flywheel half squat and deadlift
FW-squat and FW-deadlift were performed using a standardised ergometer (D11
Full, Desmotec, Biella, Italy). The protocols each consisted of 3 sets of 6 repetitions (2
initial submaximal repetitions were performed to attain the initial momentum) at
maximal concentric velocity, interspersed by 2 min of passive recovery (de Keijzer et
al., 2020). The following combined load was used for each participant during both FW-
squat and FW-deadlift exercises: 1 large disc (diameter = 0.285 m; mass = 1.9 kg;
moment of inertia = 0.02 kg·m2) and 1 medium disk (diameter = 0.240 m; mass = 1.1
kg; moment of inertia = 0.008 kg·m2). The moment of inertia of the ergometer was
estimated as 0.0011 kg.m2, therefore the total moment of inertia was 0.029 kg.m2. This
inertial load was selected based on power outputs and inertial loads previously used
to enhance performance following flywheel squat exercises (Beato, De Keijzer, et al.,
2019). Power outputs for both concentric and eccentric phases were collected for each
repetition using an integrated rotatory position transducer. The participants were
instructed, in both FW-squat and FW-deadlift exercises, to perform the concentric
phase with maximal velocity and to achieve approximately 90° of knee flexion during
the eccentric phase. Each movement was evaluated qualitatively by an investigator,
offering kinematic feedback to the athletes as well as strong standardised
encouragements to maximally perform each repetition.
Statistical Analyses
All statistical analyses were performed using JASP software (version 0.9.2;
JASP, Amsterdam, The Netherlands). The Shapiro-Wilk test was used to determine
normality of distributions. Data were presented as mean ± standard deviation (SD).
Inter-session reliability (two-way mixed model) was assessed via comparison to the
control condition using an intraclass correlation coefficient (ICC) and interpreted as
follows: excellent ≥ 0.9; 0.9 > good ≥ 0.8; 0.8 > acceptable ≥ 0.7; 0.7 > questionable ≥
0.6; 0.6 > poor ≥ 0.5; unacceptable < 0.5 (Atkinson & Nevill, 1998). Smallest worthwhile
change (SWC) was calculated as 0.2 × the between-participant SD. One-way repeated
measures analysis of variance (ANOVA) reporting f values was used to detect possible
between-condition effects. Post-hoc analysis was performed using Holm’s corrections
(applied to the alpha value). Delta difference with 95% confidence intervals (CI) were
also reported (Harrison et al., 2020). Significance was set at p < 0.05 and reported to
indicate the strength of the evidence. The effect size based on the Cohen’s d principle
was calculated and interpreted as follows: trivial < 0.2; 0.2 ≤ small < 0.6; 0.6 ≤ moderate
< 1.2; 1.2 ≤ large < 2.0; very large > 2.0 (Hopkins, Marshall, Batterham, & Hanin, 2009).
7
RESULTS
The following test-retest reliability (ICC) and SWC were reported: isokinetic
quadriceps concentric peak torque ICC = 0.88, good, SWC = 8 Nm; hamstring
concentric peak torque ICC = 0.89, good, SWC = 4 Nm; and hamstring eccentric peak
torque ICC = 0.93, excellent, SWC = 7 Nm; FW-Squat concentric power output ICC =
0.98, excellent, SWC = 58W; FW-squat eccentric power output ICC = 0.97, excellent,
SWC = 59 W; FW-deadlift concentric power output ICC = 0.96, excellent, SWC = 62
W; and FW-deadlift eccentric power output ICC = 0.96, excellent, SWC = 58 W.
FW-squat concentric and eccentric power outputs were 1132 ± 289 W and 1040
± 292 W, respectively. FW-deadlift concentric and eccentric power outputs were 1026
± 311 W and 992 ± 288 W, respectively. A significant difference of Δ 106 W (95% CI
34, 178; p = 0.007, d = 0.81, moderate) in concentric power output was reported
between FW-squat and FW-deadlift. No significant difference (Δ 48 W; 95% CI -31,
127; p = 0.216, d = 0.33, small) in eccentric power output was reported between FW-
squat and FW-deadlift.
No significant condition (PAPE) effect was reported (f = 1.538, p = 0.233) for
isokinetic quadriceps concentric peak torque following FW-squat and FW-deadlift
(Figure 2). Standardised differences (effect size) between FW-squat vs. control (p =
0.528, d = 0.31, small) and FW-deadlift vs. control (p = 0.518, d = 0.37, small) were
reported. Comparison between FW-squat vs. FW-deadlift did not report any significant
difference (p = 0.552, d = 0.157, trivial).
Figure 2 - Quadriceps concentric peak torque following flywheel squat (FW-squat) and flywheel deadlift
(FW-deadlift) post-activation performance enhancement (PAPE) conditions compared to control
condition. Error bars represent 95% confidence intervals. *: p < 0.05 compared with Control.
No significant condition (PAPE) effect was reported (f = 2.456, p = 0.104) for
isokinetic hamstrings concentric peak torque following FW-squat and FW-deadlift
(Figure 3). Standardised differences (effect size) between FW-squat vs. control (p =
0.101, d = 0.61, moderate) and FW-deadlift vs. control (p = 0.585, d = 0.27, small)
were reported. Comparison between FW-squat vs. FW-deadlift did not report any
significant difference (p = 0.587, d = 0.282, small).
8
Figure 3 - Hamstrings concentric peak torque following flywheel squat (FW-squat) and flywheel deadlift
(FW-deadlift) post-activation performance enhancement (PAPE) conditions compared to control
condition. Error bars represent 95% confidence intervals. *: p < 0.05 compared with Control.
A significant condition (PAPE) effect was reported (f = 4.067, p = 0.008) on
isokinetic hamstrings eccentric peak torque following FW-squat and FW-deadlift
(Figure 4). The significant difference (Δ) was 14 Nm between FW-squat vs. control was
(95% CI: 2, 28; d = 0.75, moderate; p = 0.033), and 13 Nm between FW-deadlift vs.
control (95% CI: 1, 25; d = 0.68, moderate; p = 0.038). Comparison between FW-squat
vs. FW-deadlift did not reported any significant difference (p = 0.688, d = 0.106, trivial).
Figure 4 - Hamstrings eccentric peak torque following flywheel squat (FW-squat) and flywheel deadlift
(FW-deadlift) post-activation performance enhancement (PAPE) conditions compared to control
condition. Error bars represent 95% confidence intervals. *: p < 0.05 compared with Control.
No significant condition (PAPE) effect was reported (f = 0.639, p = 0.535) for
isokinetic conventional Hconc:Qconc ratio following FW-squat and FW-deadlift (Figure
5). Standardised differences (effect size) between FW-squat vs. control (p = 0.101, d
= 0.18, trivial) and FW-deadlift vs. control (p = 0.587, d = 0.08, trivial) were reported.
Comparison between FW-Squat vs. FW-Deadlift did not reported any significant
difference (p = 0.536, d = 0.36, small).
9
Figure 5 - Conventional (a) and functional (b) hamstrings:quadriceps peak torque ratio following flywheel
squat (FW-squat) and flywheel deadlift (FW-deadlift) post-activation performance enhancement (PAPE)
conditions compared to control condition. Error bars represent 95% confidence intervals. *: p < 0.05
compared with Control.
No significant condition (PAPE) effect was reported (f = 1.895, p = 0.169) for
isokinetic functional Hecc:Qconc ratio following FW-squat and FW-deadlift (Figure 5).
Standardised differences (effect size) between FW-squat vs. control (p = 0.309, d =
0.44, small) and FW-deadlift vs. control (p = 0.602, d = 0.27, small) were reported.
Comparison between FW-squat vs. FW-deadlift did not report any significant difference
(p = 0.605, d = 0.25, small).
DISCUSSION AND IMPLICATIONS
The present study investigated the PAPE of hamstrings and quadriceps isokinetic
torque after FW-squat and FW-deadlift compared to a control condition. For both
protocols, the capacity to generate PAPE has been confirmed in isokinetic hamstring
eccentric peak torque only. Additionally, conventional Hconc:Qconc ratio reported trivial
changes in both FW-squat and FW-deadlift, whereas functional Hecc:Qconc ratio
reported small positive (however non-significant) increments. The second aim was to
compare PAPE responses between FW-squat and FW-deadlift protocols, and this study
found them equivalently capable of enhancing hamstring eccentric performance.
Practitioners may use the present findings to optimise strength and power development
during complex training sessions using flywheel-based PAPE protocols.
The rationale for using a flywheel device to obtain a PAPE response was
associated with the eccentric overload that can be generated, and which is not
achievable using traditional resistance exercises (Beato, Bigby, et al., 2019; Norrbrand
et al., 2010). During the eccentric phase of the flywheel exercise, the athlete actively
decelerate the disc angular momentum generated during the concentric phase (Beato,
Bigby, et al., 2019; Beato et al., 2020). This results in greater force and power generation
which can contribute to the acute enhancement of the subsequent performance (Beato
et al., 2020; Norrbrand et al., 2010). The physiological and mechanical advantages of
the eccentric contraction (and overload) have been largely reported in the literature
(Maroto-Izquierdo et al., 2017), presenting characteristics such as greater forces, lower
energy requirement, selective recruitment of higher-order motor units, preferential
recruitment of predominantly fast-twitch synergists, and a greater cortical excitability but
a lower motor unit discharge compared to concentric contraction (Beato et al., 2020;
Douglas, Pearson, Ross, & McGuigan, 2017).
10
In the current study, both FW-squat and FW-deadlift PAPE responses reported a
moderate effect on isokinetic hamstring eccentric, but not quadriceps concentric or
hamstring concentric, peak torque. It should also be noted that the mean difference in
hamstring eccentric peak torques in both conditions (14 Nm for FW-squat and 13 Nm
for FW-deadlift) are greater than the SWC (7 Nm) for these parameters, which represent
meaningful changes in performance. The present findings are supported by a previous
small significant change in hamstring eccentric and trivial change in concentric
quadriceps peak torques following FW-squat exercise, but are partially in contrast with
the previous significant small change in hamstring concentric peak torques (Beato, Stiff,
et al., 2019). These results in combination imply that the hamstrings (particularly during
eccentric contractions) may be more susceptible to flywheel-PAPE protocols than the
quadriceps. This could be related to different recruitment strategies during the FW-squat
eccentric hamstring activity such as preferential recruitment of fast-twitch and higher-
order motor units or the higher percentage of fast-twitch fibres of the hamstring
compared to the quadriceps (Coratella, Bellin, Beato, & Schena, 2015; Douglas et al.,
2017). These factors may make the hamstrings more responsive to particularly eccentric
PAPE protocols. However, an exhaustive explanation of these differences cannot be
reported. The limited PAPE effect on isokinetic quadriceps peak torque may relate to
differing fibre composition between the muscle groups and to kinematic differences
between the pre-load exercise and the following test. Previous research reported that a
FW-squat protocol can stimulate PAPE in rapid closed-kinetic chains movements such
as long and vertical jumps (Beato, De Keijzer, et al., 2019; Beato et al., 2020), whereas
transfer to open-kinetic chain exercises (such as isokinetic tests) may be more limited.
This is the first study comparing PAPE between FW-squat and FW-deadlift
protocols, observing that the FW-squat protocol enhanced quadriceps and hamstrings
peak torque to a similar extent to FW-deadlift. Significantly and moderately greater
concentric power was achieved during the FW-squat than the FW-deadlift, while no
difference was observed during the eccentric phase. These findings underline that
similar eccentric power production between exercises may explain the similar PAPE
responses reported in this study. It is not clear why the difference in concentric power
outputs did not favour the generation of a larger PAPE following the FW-squat protocol.
Based on the current results, it might be argued that the difference in concentric power
output is not a discriminant to obtain acute performance enchantments using flywheel
exercises (Beato, Bigby, et al., 2019). Moreover, based on previous research, PAPE
response may depend on the biomechanical or muscle activation pattern similarities
between pre-load and subsequent tasks. Deadlift and squat exercises differ
biomechanically from one another (Hales et al., 2009), and particularly greater
hamstrings vs. quadriceps activity was reported during traditional deadlift compared to
the squat (Ebben et al., 2009). This may influence the lower limb musculature PAPE
responses (Scott et al., 2017). Instead, in this study there were no significant differences
in PAPE response between the two flywheel protocols. These findings are supported by
another recent study which found no differences in PAPE response on change of
direction tasks between flywheel exercises with fundamental biomechanical differences
such as flywheel leg extension, squat, and cross-cutting step exercises (Beato,
Madruga-Parera, Piqueras-Sanchiz, Moreno-Pérez, & Romero-Rodriguez, 2019).
These findings suggest that PAPE response may not be strongly associated with the
biomechanical similarity between pre-load and subsequent exercises.
The conventional Hconc:Qconc ratio reported only trivial changes following both
FW-squat and FW-deadlift, whereas the functional Hecc:Qconc ratio reported small
positive (however non-significant) increments. Previous research similarly reported a
trivial variation in conventional Hconc:Qconc ratio following a FW-squat protocol but a
11
significant small enhancement in functional Hecc:Qconc ratio (Beato, Stiff, et al., 2019).
The cumulative evidence of these two studies suggest that the greater effect on the
functional compared with conventional ratio is likely due to the acute enhancement of
eccentric hamstring peak torque. An explanation for the apparent greater sensitivity of
the hamstring than the quadriceps to flywheel-based PAPE protocols may be related to
greater muscle activity in the hamstring in comparison to the quadriceps during the
eccentric phase of a squat (Yoo, 2016). This greater hamstring activation during the
eccentric phase of the squat or deadlift can be accentuated during flywheel exercise
(Beato et al., 2020; Maroto-Izquierdo et al., 2019). This greater sensitivity of the
hamstring to flywheel-based PAPE protocols may be beneficial for transfer to sporting
performance, making it an attractive method to prepare the hamstrings for the demands
of sport – including sprinting accelerations (Morin et al., 2015), changes of direction
(Beato, De Keijzer, et al., 2019) and possible injury risk reduction (Coratella et al., 2015).
This is particularly true in sports where lack of hamstrings eccentric force to decelerate
the knee extension may be a predisposing factor to hamstring strains (e.g. on the final
swing phase during sprinting). Although thresholds of 0.6 and 0.8 have been previously
used for the conventional (Zvijac, Toriscelli, Merrick, & Kiebzak, 2013) and functional
(Croisier, Ganteaume, Binet, Genty, & Ferret, 2008) ratios, respectively, any increase in
eccentric hamstrings strength will likely be beneficial in this regard. Although eccentric
quadriceps peak torque is not utilised in the calculation of either H:Q ratio, future
investigation into the acute effect of flywheel squats and deadlifts on this parameter is
of interest. This is particularly true given the possibility for eccentric overload during
flywheel pre-load exercise and the present study’s significant PAPE effect on eccentric
hamstring peak torque.
The current study presents some limitations. First, it involved male amateur
athletes only. Therefore, generalisation to other sport-specific populations such as
professional athletes may be limited. Future studies may replicate the protocols reported
in this study within different populations. Second, this study utilised a moment of inertia
of 0.029 kg.m2, which may have been sub-optimal to generate optimal PAPE responses,
even though this load was previously used with success to acutely enhance
performance (Beato, De Keijzer, et al., 2019). Future studies using different inertial loads
are necessary to provide more specific recommendations regarding PAPE effects of
both FW-squat and FW-deadlift on isokinetic lower limb torque parameters.
CONCLUSION
Both FW-squat and FW-deadlift exercises can significantly enhance acute
isokinetic hamstring eccentric performance in male athletes. Small to moderate but non-
significant effects on concentric quadriceps and hamstring peak torques were also
reported. This study did not report any significant difference between FW-squat and FW-
deadlift exercises in PAPE on isokinetic lower limb parameters and as such these
exercises should be considered equivalently capable for the specific purpose of
generating PAPE. Practitioners may use these findings to inform strength and power
development during complex training sessions consisting of flywheel-based exercises
prior to a sport-specific task.
REFERENCES
Aagaard, P., Simonsen, E. B., Magnusson, S. P., Larsson, B., & Dyhre-Poulsen, P.
(1998). A new concept for isokinetic hamstring: quadriceps muscle strength ratio.
The American Journal of Sports Medicine, 26(2), 231–237.
https://doi.org/10.1177/03635465980260021201
12
Atkinson, G., & Nevill, A. M. (1998). Statistical methods for assessing measurement
error (reliability) in variables relevant to sports medicine. Sports Medicine, 26(4),
217–238. https://doi.org/10.2165/00007256-199826040-00002
Bauer, P., Sansone, P., Mitter, B., Makivic, B., Seitz, L. B., & Tschan, H. (2019). Acute
effects of back squats on countermovement jump performance across multiple sets
of a contrast training protocol in resistance-trained men. Journal of Strength and
Conditioning Research, 33(4), 995–1000.
https://doi.org/10.1519/JSC.0000000000002422
Beato, M., Bigby, A. E. J., De Keijzer, K. L., Nakamura, F. Y., Coratella, G., & McErlain-
Naylor, S. A. (2019). Post-activation potentiation effect of eccentric overload and
traditional weightlifting exercise on jumping and sprinting performance in male
athletes. PLOS ONE, 14(9), e0222466.
https://doi.org/10.1371/journal.pone.0222466
Beato, M., De Keijzer, K. L., Leskauskas, Z., Allen, W. J., Dello Iacono, A., & McErlain-
Naylor, S. A. (2019). Effect of post-activation potentiation after medium vs. high
inertia eccentric overload exercise on standing long jump, countermovement jump
and change of direction performance. The Journal of Strength and Conditioning
Research. https://doi.org/10.1519/JSC.0000000000003214
Beato, M., & Dello Iacono, A. (2020). Implementing flywheel (isoinertial) exercise in
strength training: current evidence, practical recommendations, and future
directions. Frontiers in Physiology, 11, 569.
https://doi.org/10.3389/fphys.2020.00569
Beato, M., Madruga-Parera, M., Piqueras-Sanchiz, F., Moreno-Pérez, V., & Romero-
Rodriguez, D. (2019). Acute effect of eccentric overload exercises on change of
direction performance and lower-limb muscle contractile function. Journal of
Strength and Conditioning Research.
https://doi.org/10.1519/JSC.0000000000003359
Beato, M., McErlain-Naylor, S. A., Halperin, I., & Dello Iacono, A. (2020). Current
evidence and practical applications of flywheel eccentric overload exercises as
postactivation potentiation protocols: A brief review. International Journal of Sports
Physiology and Performance, 15(2), 154–161. https://doi.org/10.1123/ijspp.2019-
0476
Beato, M., Stiff, A., & Coratella, G. (2019). Effects of postactivation potentiation after
an eccentric overload bout on countermovement jump and lower-limb muscle
strength. Journal of Strength and Conditioning Research.
https://doi.org/10.1519/JSC.0000000000003005
Bishop, D. (2003). Warm up II: performance changes following active warm up and
how to structure the warm up. Sports Medicine, 33(7), 483–498.
https://doi.org/10.2165/00007256-200333070-00002
Blazevich, A. J., & Babault, N. (2019). Post-activation potentiation versus post-
activation performance enhancement in humans: historical perspective, underlying
mechanisms, and current issues. Frontiers in Physiology, 10, 1359.
https://doi.org/10.3389/fphys.2019.01359
Boullosa, D., Beato, M., Dello Iacono, A., Cuenca-Fernandez, F., Doma, K.,
Schumann, M., Zagatto, A., Loturco, I., & Behm, D. (2020). A new taxonomy for
post-activation potentiation in sport. International Journal of Sports Physiology and
Performance.
13
Boullosa, D., Del Rosso, S., Behm, D. G., & Foster, C. (2018). Post-activation
potentiation (PAP) in endurance sports: A review. European Journal of Sport
Science, 18(5), 595–610. https://doi.org/10.1080/17461391.2018.1438519
Carroll, K.M., Wagle, J.P., Sato, K., Taber, C.B., Yoshida, N., Bingham, G.E., & Stone,
M.H. (2019). Characterising overload in inertial flywheel devices for use in exercise
training. Sports Biomechanics, 18(4), 390-401.
https://doi.org/10.1080/14763141.2018.1433715
Coratella, A. G., Beato, M., Cè, E., Scurati, R., & Milanese, C. (2019). Effects of in-
season enhanced negative work-based vs traditional weight training on change of
direction and hamstrings-to-quadriceps ratio in soccer players. Biology of Sport,
36(3), 241–248. https://doi.org/10.5114%2Fbiolsport.2019.87045
Coratella, G., Bellin, G., Beato, M., & Schena, F. (2015). Fatigue affects peak joint
torque angle in hamstrings but not in quadriceps. Journal of Sports Sciences,
33(12), 1276–1282. https://doi.org/10.1080/02640414.2014.986185
Croisier, J.-L., Ganteaume, S., Binet, J., Genty, M., & Ferret, J.-M. (2008). Strength
imbalances and prevention of hamstring injury in professional soccer players. The
American Journal of Sports Medicine, 36(8), 1469–1475.
https://doi.org/10.1177/0363546508316764
de Keijzer, K. L., McErlain-Naylor, S. A., Dello Iacono, A., & Beato, M. (2020). Effect
of volume on eccentric overload-induced postactivation potentiation of jumps.
International Journal of Sports Physiology and Performance, 15(7), 976–981.
https://doi.org/10.1123/ijspp.2019-0411
Dello Iacono, A., & Seitz, L. B. (2018). Hip thrust-based PAP effects on sprint
performance of soccer players: heavy-loaded versus optimum-power development
protocols. Journal of Sports Sciences, 36(20), 2375–2382.
https://doi.org/10.1080/02640414.2018.1458400
Doma, K., Leicht, A. S., Boullosa, D., & Woods, C. T. (2020). Lunge exercises with
blood-flow restriction induces post-activation potentiation and improves vertical
jump performance. European Journal of Applied Physiology, 120(3), 687–695.
https://doi.org/10.1007/s00421-020-04308-6
Douglas, J., Pearson, S., Ross, A., & McGuigan, M. (2017). Eccentric exercise:
physiological characteristics and acute responses. Sports Medicine, 47(4), 663–
675. https://doi.org/10.1007/s40279-016-0624-8
Ebben, W. P., Feldmann, C. R., Dayne, A., Mitsche, D., Alexander, P., & Knetzger, K.
J. (2009). Muscle activation during lower body resistance training. International
Journal of Sports Medicine, 30(1), 1–8. https://doi.org/10.1055/s-2008-1038785
Gahreman, D., Moghadam, M., Hoseininejad, E., Dehnou, V., Connor, J., Doma, K., &
Stone, M. (2020). Postactivation potentiation effect of two lower body resistance
exercises on repeated jump performance measures. Biology of Sport, 37(2), 105–
112. https://doi.org/10.5114/biolsport.2020.93034
Hales, M. E., Johnson, B. F., & Johnson, J. T. (2009). Kinematic analysis of the
powerlifting style Squat and the conventional deadlift during competition: is there a
cross-over fffect between lifts? Journal of Strength and Conditioning Research,
23(9), 2574–2580. https://doi.org/10.1519/JSC.0b013e3181bc1d2a
Harrison, A. J., McErlain-Naylor, S. A., Bradshaw, E. J., Dai, B., Nunome, H., Hughes,
G. T. G., Kong, P. W., Vanwanseele, B., Vilas-Boas, J.P., & Fong, D. T. P. (2020).
Recommendations for statistical analysis involving null hypothesis significance
testing. Sports Biomechanics, 19(5), 561-568.
https://doi.org/10.1080/14763141.2020.1782555
14
Hopkins, W. G., Marshall, S. W., Batterham, A. M., & Hanin, J. (2009). Progressive
statistics for studies in sports medicine and exercise science. Medicine and Science
in Sports and Exercise, 41(1), 3–13.
https://doi.org/10.1249/MSS.0b013e31818cb278
Maroto-Izquierdo, S., Fernandez-Gonzalo, R., Magdi, H. R., Manzano-Rodriguez, S.,
González-Gallego, J., & De Paz, J. A. (2019). Comparison of the musculoskeletal
effects of different iso-inertial resistance training modalities: flywheel vs. electric-
motor. European Journal of Sport Science, 19(9), 1184–1194.
https://doi.org/10.1080/17461391.2019.1588920
Maroto-Izquierdo, S., García-López, D., Fernandez-Gonzalo, R., Moreira, O. C.,
González-Gallego, J., & de Paz, J. A. (2017). Skeletal muscle functional and
structural adaptations after eccentric overload flywheel resistance training: a
systematic review and meta-analysis. Journal of Science and Medicine in Sport,
20(10), 943–951. https://doi.org/10.1016/j.jsams.2017.03.004
Morin, J.-B., Gimenez, P., Edouard, P., Arnal, P., Jiménez-Reyes, P., Samozino, P.,
Brughelli, M., & Mendiguchia, J. (2015). Sprint acceleration mechanics: the major
role of hamstrings in horizontal force production. Frontiers in Physiology, 6, 404.
https://doi.org/10.3389/fphys.2015.00404
Norrbrand, L., Pozzo, M., & Tesch, P. A. (2010). Flywheel resistance training calls for
greater eccentric muscle activation than weight training. European Journal of
Applied Physiology, 110(5), 997–1005. https://doi.org/10.1007/s00421-010-1575-7
Robbins, D. W. (2005). Postactivation potentiation and its practical applicability: a brief
review. Journal of Strength and Conditioning Research, 19(2), 453–458.
https://doi.org/10.1519/R-14653.1
Scott, D. J., Ditroilo, M., & Marshall, P. A. (2017). Complex training: The effect of
exercise selection and training status on postactivation potentiation in Rugby
League players. Journal of Strength and Conditioning Research, 31(10), 2694–
2703. https://doi.org/10.1519/JSC.0000000000001722
Seitz, L. B., & Haff, G. G. (2016). Factors modulating post-activation potentiation of
jump, sprint, throw, and upperbody ballistic performances: a systematic review with
meta-analysis. Sports Medicine, 46(2), 231–240. https://doi.org/10.1007/s40279-
015-0415-7
Till, K. A., & Cooke, C. (2009). The effects of postactivation potentiation on sprint and
jump performance of male academy soccer players. Journal of Strength and
Conditioning Research, 23(7), 1960–1967.
https://doi.org/10.1519/JSC.0b013e3181b8666e
Tillin, N. A., & Bishop, D. (2009). Factors modulating post-activation potentiation and
its effect on performance of subsequent explosive activities. Sports Medicine, 39(2),
147–166. https://doi.org/10.2165/00007256-200939020-00004
Yeung, S. S., Suen, A. M. Y., & Yeung, E. W. (2009). A prospective cohort study of
hamstring injuries in competitive sprinters: preseason muscle imbalance as a
possible risk factor. British Journal of Sports Medicine, 43(8), 589–594.
https://doi.org/10.1136/bjsm.2008.056283
Yoo, W. (2016). Comparison of hamstring-to-quadriceps ratio between accelerating
and decelerating sections during squat exercise. Journal of Physical Therapy
Science, 28(9), 2468–2469. https://doi.org/10.1589/jpts.28.2468
Zvijac, J. E., Toriscelli, T. A., Merrick, S., & Kiebzak, G. M. (2013). Isokinetic concentric
quadriceps and hamstring strength variables from the NFL scouting combine are
not predictive of hamstring injury in first-year professional football players. The
