Postactivation potentiation following different modes of exercise.
ABSTRACT The performance characteristics of skeletal muscle are transient in nature and have been shown to be significantly affected by its contractile history, where the phenomenon of acute enhancement is termed postactivation potentiation (PAP). Acute enhancement of dynamic activity has been observed when preceded by resistance exercises; however little information exists for plyometric activity as a conditioning stimulus. In addition, no study has examined PAP effects on more than one subsequent performance trial. The purpose of the present study was to determine whether countermovement jump (CMJ) performance could be enhanced if preceded by heavy-resistance exercise or by dynamic plyometric activity over 3 trials. Thirteen anaerobically trained male subjects (mean +/- SD: age, 22 +/- 3 years; height, 182.4 +/- 4.3 cm; body mass, 82.7 +/- 9.2 kg) performed in a counterbalanced order 3 half squats using a 3 repetition maximum loading (SQUAT), a set of 24 contacts of lower body plyometric exercises (PLYO), or a control of no activity (REST) 5 minutes before each CMJ. Three sets of each treatment and CMJ were performed in total and maximal displacement (dmax), peak power (Ppeak), and peak vertical force (Fpeak) were recorded, whereas rate of force development and relative force (F/body mass) were calculated for every trial. No significant differences were revealed for any of the other variables, but greater displacement was found for SQUAT compared to REST or PLYO, whereas no differences were revealed for any of the conditions for the repeated trials. Although heavy resistance-induced PAP seems to enhance jump height compared to REST or PLYO in repeated CMJ performance, it has no additional benefit on repeated trials.
- SourceAvailable from: Daniel A. Boullosa[Show abstract] [Hide abstract]
ABSTRACT: This study verified if a prior five repetition maximum (5RM) strength exercise would improve the cycling performance during a 20-km cycling time trial (TT20km). After determination of the 5RM leg press exercise load, eleven trained cyclists performed a TT20km in a control condition and 10-min after 4 sets of 5RM strength exercise bouts (potentiation condition). Oxygen uptake, blood lactate concentration, ratings of perceived exertion (RPE) and power output data were recorded during the TT20km. Cycling economy index was assessed before the TT20km and pacing strategy was analyzed assuming a "J-shaped" power output distribution profile. Results were a 6.1% reduction (p < 0.05) in the time to complete the TT20km, a greater cycling economy (p < 0.01) and power output in the first 10% of the TT20km (i.e. trend; p= 0.06) in the potentiation condition. However, no differences were observed in pacing strategy, physiological parameters and RPE between the conditions. These results suggest that 5RM strength exercise bouts improve the performance in a subsequent TT20km.The Journal of Strength and Conditioning Research 02/2014; 28(9):2513-2520. · 1.80 Impact Factor
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ABSTRACT: The purpose of this study was to compare the effects of two protocols of post-activation potentiation (PAP) on swim start performance (SS).Fourteen trained swimmers (10 men and 4 women) volunteered for this study. An intra-group design of randomised repetitive measurements was applied. A previous SS trial, performed after a standard warm up (SWU), served as a reference. Two methods of PAP, performed after one hour of rest, were randomly added to the SWU: i) three lunges at 85% of 1 repetition maximum (LWU), and ii) four repetitions on the flywheel device YoYo squat (YWU). Swimmers were tested in an SS eight minutes after the PAP warm-ups. Kinematic variables were collected using three underwater digital video cameras fixed poolside and operating at 25 Hz, and one high speed camera focused on the block and operating at 300Hz. Data obtained from the video analysis were processed using a repeated measures analysis of the variance.The mean horizontal velocity of the swimmer's flight improved after both PAP methods, with the greatest improvement after YWU (F2,12 = 47.042, p < 0.001; SWU= 3.63 ± 0.11; LWU= 4.15 ± 0.122; YWU= 4.89 ±0.12 m/s). After YWU, it took the subjects less time to cover a distance of five meters (F2,12 = 24.453, p < 0.001) and fifteen meters (F2,12 = 4.262, p < 0.04). Subjects also achieved a higher mean angular velocity of the knee extension (F2,12 = 23.286, p < 0.001) and a reduction of the time on the block (F2,12 = 6.595, p < 0.05).These results demonstrate that muscle performance in the execution of an SS is enhanced after a warm up with specific PAP protocols. YWU leads to the greatest improvement in the performance of the swimmer's start and, therefore, may be especially beneficial in short events.Journal of strength and conditioning research / National Strength & Conditioning Association. 09/2014;
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ABSTRACT: This study examined the effects of a gluteal activation protocol (GA) on the performance of drop jumps performed on a force sledge apparatus. Fifteen sprinters performed 10 single-leg drop jumps on three days with a unilateral GA performed within the warm up on day 2. Ground contact time (CT), height jumped (HJ), maximum vertical ground reaction force (GRFmax) and vertical leg-spring stiffness (K vert) were calculated on all three days. A repeated measures ANOVA was used to examine mean differences on all variables across days. The results show significant differences on all variables between days 1 and 2 and on HJ and K vert between days 1 and 3 but no differences in any varables between days 2 and 3. This suggests that the improvements in day 2 were due to a practice/learning effect rather than the GA protocol. INTRODUCTION: This paper examines the use of low-load unilateral gluteal exercises on subsequent single leg drop jump performance to assess whether a post activation potentiation effect occurs. Postactivation potentiation (PAP) is the "transient increase in muscle contractile performance after previous contractile activity" (Sale, 2002). Previous research in complex training has examined whether the performance of heavy resistance exercise prior to explosive type movements such as plyometrics invokes a PAP effect. Comyns et al, (2011) reported acute improvements in ground contact time and leg stiffness following complex training. Recently, Crow et al (2012) examined the effect of low load gluteal exercises on countermovement jump performance and found an acute enhancement of peak power output. This enhancement has been attributed to PAP. According to the fitness-fatigue paradim (Plisk and Stone, 2003) a typical PAP effect should involve a reduction in performance immediately after the exercise stimulus followed by an enhancement some time later. Various research designs involving skills such as countermovement jumps and drop jumps to examine PAP, have failed to account for improvements in performance due to learning or practice effects that may occur in participants that are unaccustomed to performing these skills. The use of simple pre-test post-test designs may not be entirely suitable and therefore a 3 day design where participants complete a third bout of testing which mirrors that of the pre-test may allow researchers to identify whether improvements in performance occur due to learning or whether they can be attributed solely to PAP. It would be expected that learning effects would present as sustained improvement in performance on the 3 rd test day or a score similar to the 2 nd test day. The aim of this study was to determine the effects of a low load unilateral gluteal activation protocol on single leg drop jump performance parameters including HJ, CT, GRFmax and K vert and determine, through the use of a 3 day design, if these effects can be attributed solely PAP or simply due to a learning effect. METHODS: Subjects: Fifteen participants were recruited for this study. All participants were sprint trained males (n=8) and females (n=7); age: 19.9 ±1.6 years; height: 173.9 ±11.7 cm; body mass: 67.5 ±11.1 kg (mean ±SD) and were injury free at the time of testing. Ethical approval was granted by the local University Research Ethics Committee and all participants completed an informed consent form before testing. Equipment: Force time data were collected using a force sledge angled at 30° to horizontal as described by Comyns et al, (2011). Force data were sampled at 1000 Hz and filtered using a Butterworth filter with a cut-off frequency of 50 Hz. Participants were secured in the sledge chair with their arms crossed to constrain potential involvement of the upper body in the performance of the drop jump.International Society of Biomechanics in Sport 2013; 07/2013
POSTACTIVATION POTENTIATION FOLLOWING
DIFFERENT MODES OF EXERCISE
JOSEPH I. ESFORMES,1NEIL CAMERON,2AND THEODOROS M. BAMPOURAS3
1Cardiff School of Sport, University of Wales Institute, Cardiff, United Kingdom;2Regional Athletics
Center–North East, England Athletics, United Kingdom; and3School of Sport, Human Performance Laboratory,
University of Cumbria, Lancaster, United Kingdom
Esformes, JI, Cameron, N, and Bampouras, TM. Postactivation
potentiation following different modes of exercise. J Strength
Cond Res 24(7): 1911–1916, 2010—The performance charac-
teristics of skeletal muscle are transient in nature and have been
shown to besignificantly affected by its contractile history, where
the phenomenon of acute enhancement is termed postactivation
potentiation (PAP). Acute enhancement of dynamic activity has
been observedwhenpreceded byresistance exercises;however
little information exists for plyometric activity as a conditioning
stimulus.In addition, nostudy has examinedPAP effectsonmore
than one subsequent performance trial. The purpose of the
present study was to determine whether countermovement jump
(CMJ) performance could be enhanced if preceded by heavy-
resistance exercise or by dynamic plyometric activity over 3 trials.
Thirteen anaerobically trained male subjects (mean 6 SD: age,
22 6 3 years; height, 182.4 6 4.3 cm; body mass, 82.7 6
9.2 kg) performed in a counterbalanced order 3 half squats
using a 3 repetition maximum loading (SQUAT), a set of
24 contacts of lower body plyometric exercises (PLYO), or a
control of no activity (REST) 5 minutes before each CMJ. Three
sets of each treatment and CMJ were performed in total and
maximal displacement (dmax), peak power (Ppeak), and peak
vertical force (Fpeak) were recorded, whereas rate of force
development and relative force (F/body mass) were calculated
for every trial. No significant differences were revealed for any
of the other variables, but greater displacement was found for
SQUAT compared to REST or PLYO, whereas no differences
were revealed for any of the conditions for the repeated trials.
Although heavy resistance–induced PAP seems to enhance
jump height compared to REST or PLYO in repeated CMJ
performance, it has no additional benefit on repeated trials.
KEY WORDS plyometrics, complex training, reactive index,
activity results in decreased neuromuscular force generation
and fatigue (20), having a negative impact on subsequent
strength and power performance. In contrast, optimal pre-
vious muscular activity can increase force generation and im-
prove subsequent strength and power performance, a
phenomenon termed postactivation potentiation (PAP ).
This enhancement has been primarily attributed to 2
mechanisms: regulatory light chain phosphorylation and
increased recruitment of motor units. Regulatory light chain
phosphorylation has been shown to increase the sensitivity
of the actin–myosin interaction to the Ca2+released from the
sarcoplasmic reticulum and alter the structure of the myosin
head, resulting in a higher force–producing state for the
myosin crossbridges (20). For the second mechanism, it is
postulated that previous contractions increase the excitation
potential across the spinal cord, which lasts for several
minutes after the initial contractions, resulting in increased
postsynaptic potentials and, subsequently, increased force
generation capacity (8).
One of the factors affecting PAP is the intensity of the
conditioning activity, with higher intensity activities appear-
ing to be more effective (6,22,27). Indeed, the majority of
studies examining the effect of PAP on athletic performance
have reported positive effects when using heavy weights
before explosive movements such as short sprints, vertical
jumps, or explosive strength jumps (2,16,29). Chiu et al. (2)
used 5 sets of 1 back squat repetition at 90% of the subject’s
1 repetition maximum (1RM) and reported a significant
improvement in jump squat power using 30, 50, and 70% of
1RM. Their results agree with findings by Weber et al. (29),
who reported an increase in vertical ground reaction force
and jump height after 5 repetitions at 85% of 1RM. McBride
et al. (16) used 3 repetitions at 90% of 1RM and reported
a significant improvement in 40-m sprinting times of football
players. Finally, Kilduff et al. (13) using a 3RM back squat set
reported a 6.8% increase in countermovement jump (CMJ)
performance. Conversely, Jones and Lees (12) reported no
erformance of skeletal muscle is significantly
affected by its contractile history, because acute
responses are affected by the muscle contractions
preceding the activity (22). Increased muscular
Address correspondence to Joseph I. Esformes, email@example.com.
Journal of Strength and Conditioning Research
? 2010 National Strength and Conditioning Association
VOLUME 24 | NUMBER 7 | JULY 2010 | 1911
improvement in CMJ after 5 squat repetitions at 85% of 1RM.
Nevertheless, there was no reduction in performance,
suggesting that execution of heavy-resistance exercise before
CMJ was not detrimental. It is possible, therefore, that Jones
and Lees did not observe fatigue because of an induced PAP,
as fatigue and PAP are initiated together after muscular
There is little evidence in the literature to indicate that PAP
canaffectmaximumforcegeneration(26). However, PAP can
improve rate of force development (RFD [6,22,26]), which is
an important factor in explosive sport activities where high
power outputs are required. Such high power output in
explosive sports is usually achieved by substantial use of the
stretch-shortening cycle (plyometrics). Despite the potential
of plyometric exercises as a PAP stimulus, little is known
about the acute effect plyometric exercises have on sub-
sequent muscular performance. Masamoto et al. (15) exam-
ined the effect of 3 double-leg tuck jumps and 2 depth jumps
on subsequent 1RM squat performance and reported a 3.5%
improvement in the load lifted. McBride et al. (16) used
a loaded CMJ for a single set of 3 repetitions at 30% of 1RM
before a 40-m sprint but found no differences. The lack of any
difference in performance was attributed to the single set
being insufficient to induce PAP. The small number of studies
and the contradicting results merit further investigation of the
ability of plyometric exercises to induce PAP.
The potential impact of PAP on explosive sports raises
another issue that merits further investigation. Many explo-
to gain an understanding of PAP effects on repeated perfor-
mances, for example, repeated CMJ trials. Smilios et al. (25)
assessed the jump height of a CMJ at 6 time points. These
time points were at baseline, after each set of conditioning
jumps (3 sets) and at 5 and 10 minutes of recovery. The
findings indicated that after an initial improvement in CMJ
performance, the jump height subsequently remained similar
or decreased after the first loaded jump squat. However,
because heavy weights have been shown to elicit PAP more
effectively (6,22,27), a higher load may have yielded different
results. Lastly, no information exists on the ability of
plyometric exercises to elicit PAP on repeated performances.
Therefore, the aim of the present study was to (a) examine
PAP effects induced by heavy weight or plyometric exercises
on repeated trials and (b) compare performances in repeated
(a) both heavy weights and plyometric exercises would induce
PAP and (b) plyometric exercises would have a greater impact
on subsequent performance than heavy-weight exercise.
Experimental Approach to the Problem
The PAP effects induced by heavy-weight and plyometric
exercises on repeated trials, and any potential differences
between the 2 conditioning stimuli were examined using
a randomized, counterbalanced, repeated-measures design.
Subjects performed 3 CMJs on 3 separate occasions. On each
with the sequence repeated 3 times (Figure 1). The condi-
tioning stimuli were (a) resistance exercise (SQUAT),
(b) plyometric exercise (PLYO), or (c) inactivity (REST).
The plyometric exercise conditioning stimulus consisted of
4 different plyometric exercises totaling 24 foot contacts,
whereas 1 set of 3 repetitions at 3RM was used as the
resistance exercise conditioning stimulus. REST served as
a control condition and was used to compare the effects of
contractile history between subjects using inactive recovery
and those using a preconditioning stimulus. Maximal
displacement (dmax), peak power (Ppeak), and peak vertical
force (Fpeak) were recorded from a force plate, whereas RFD
and relative force (F/body mass) were calculated for every
trial. The variables examined were selected as they are
commonly used for assessing explosive performance and can
provide an indication of any PAP effects.
Thirteen male, competitive athletes (mean 6 SD: age, 22 6
3 years; height, 182.4 6 4.3 cm; and body mass, 82.7 6
9.2 kg) volunteered to participate in the current investigation
and provided written, informed consent. The subjects
participated in sports or events where explosive power was
a significant aspect (100/200/400 m, n = 7; 400-m hurdles,
n = 1; pole vault, n = 1; long jump, n = 2; and rugby, n = 2).
When testing took place, all subjects were in the competitive
phase of their training cycle, although at different points,
because the athletics season finishes in the summer, whereas
the rugby season starts in spring. All subjects included regular
Figure 1. Schematic diagram of experimental procedures. The solid squares sequence was executed 3 times in total for each conditioning stimulus. Condition-
specific warm-up or exercises refer to the inactivity (REST), plyometric exercises (PLYO), or heavy-weight squatting (SQUAT) modes of exercise.
Journal of Strength and Conditioning Research
Postactivation Potentiation After Exercise
and planned resistance training as part of their sport-training
program for at least 2 years before the study. Their training
included a minimum of 3 sessions per week, with training
loads ranging from 30 to 90% of 1RM, depending on the
phase of their training cycle. Finally, the subjects were free of
any medical conditions or lower limb injuries in the 6 months
before the investigation. The study was approved by the
University of Wales Institute, Cardiff Ethics Committee.
All subjects initially visited the laboratory to ensure
familiarity with the half squat, the plyometric exercises,
and the CMJ technique and to have their age, height, and
weight recorded. Height was measured to the nearest
0.1 cm using a stadiometer (Harpenden, Burgess Hill,
United Kingdom), and weight was measured using
a calibrated balance beam scale (Seca, Birmingham, United
Kingdom) and recorded to the nearest 0.1 kg.
Subjects were then required to complete a set of stabiliza-
tion tests to determine whether they had sufficient stabiliza-
tion strength to perform the plyometric exercises. These tests
comprised a static stand (hip flexed), single-leg squat, hop for
test, and to be able to squat 1.5 times their body mass (23).
Form and technique were observed and used to identify
successful completion of the tests, with all subjects success-
fully completing all the stabilization strength tests. Each
subject’s 3RM half squat was then determined, with 3RM
defined as a load that caused failure on the third repetition
without loss of proper exercise technique. To establish the
3RM load, subjects attempted 3 repetitions of a load and, if
successful, increased the loading. A 5-minute rest interval was
allowed between trials, with 3–5 trials typically required for
determining each subject’s 3RM.
The subjects then visited the
laboratory on 3 separate ses-
sions. A standardized dynamic
warm-up protocol was used for
all sessions, which consisted of
400-m jogging and 4 repetitions
of dynamic drills over 15 m
(heel flicks, high knee jogging,
walking lunges, and walking
hamstring sweeps). After the
standardized warm-up, the sub-
1 of the experimental groups;
inactivity (REST), plyometric
exercise (PLYO), or heavy-
REST executed no additional
warm-up. PLYO performed 1
set of 6 contacts of alternate
speed bounds, right leg speed
hops, left leg speed hops, and
vertical bounds (total foot contacts = 24), with a 15-second
resting interval allowed between each exercise. SQUAT
at 60 and 85% of 3RM, respectively, with a minimum of 2-
minute rest between sets. After the condition-specific warm-
up, a minimum rest of 2 minutes was allowed.
The subjects then performed the conditioning stimulus
(described below) with 5-minute rest and, subsequently,
3 CMJs with 10 minute-rest. This sequence was performed
of events in Athletics have repeated attempts. A schematic
diagram of the experimental procedure can be seen in
The conditioning stimulus for the PLYO group was 1 set of
6 foot contacts per plyometric exercise (alternate speed
bounds, right leg speed hops, left leg speed hops, and vertical
bounds), totaling 24 foot contacts per subject per trial. A 15-
second resting interval between each exercise was allowed.
Subjects were specifically instructed to minimize ground
contact time and maintain technique on each repetition.
The total time required for each subject to complete the
plyometric exercises was approximately 70 seconds.
The conditioning stimulus for the SQUATgroup was 1 set
a standard 20-kg Olympic barbell and weight plates (Ivanko,
Reno, NV, USA). All resistance exercises were performed
within the confines of a weightlifting safety cage. Subjects
support knee wraps and weightlifting body suits was not
permitted. According to the International Powerlifting
Federation rules, a lift was deemed to be successful if the
subject could descend until the inguinal fold was lower than
the patella and rise without help. Approximately 15 seconds
was required by each subject to complete the squat exercise.
Figure 2. Maximal displacement for each trial for the inactivity (REST), plyometric exercises (PLYO), or heavy-
weight squatting (SQUAT) conditioning stimuli. Square brackets indicate paired significant differences (p , 0.05).
Values are mean 6 SD.
VOLUME 24 | NUMBER 7 | JULY 2010 | 1913
Journal of Strength and Conditioning Research
After the conditioning stimulus, subjects remained inactive
for a period of 5 minutes, before performing 3 CMJs, sepa-
rated by approximately 8 seconds each. The CMJ is com-
monly used for assessing lower limb explosive power and has
been shown to be highly reliable (intraclass correlation
to ours, intraclass correlation coefficients were also high (r =
0.95 ). Countermovement jumps were initiated from an
upright standing position, and upon command, the subjects
squatted (the degree of knee bend used by each subject was
self-determined) and then immediately after jumped verti-
cally. The subjects were specifically instructed to aim for
maximum height. To isolate the contribution from the lower
limbs, subjects were requested to place their hands on their
hips throughout each jump. A 10-minute rest interval was
provided between the CMJs and the following conditioning
stimulus. This rest interval was used to replicate the approxi-
mate temporal demands during the events of Athletics
competitions. After the third and final set repetition, subjects
were asked to undertake a cool down consisting of light
jogging and stretching.
Maximal displacement (dmax), peak power (Ppeak), and peak
vertical force (Fpeak) were measured on a Kistler force platform
with an internal charge amplifier (Model 9287ba, Kistler,
Winterthur, Switzerland). The force data were sampled at
1,000 Hz for 3 seconds and analyzed using Bioware software
(version 3.2.6, Kistler). Rate of force development was calcu-
lated as maximum force/time to maximum force (30). Finally,
relative force (RelF) was calculated as absolute force/body
mass. For all measurements, the highest CMJ was used from
each trial for each condition to reduce variability (18).
Subjects refrained from any strenuous activities or re-
sistance training at least 24 hours before testing. All tests took
place at the same time of the day and with a minimum of 24
Data were checked for normality using the Shapiro–Wilks
test. Because data were found to deviate from normal distri-
bution, Friedman’s test was used to examine for differences
within trials for all performance measures (dmax, Ppeak, Fpeak,
RFD, and RelF). Where a difference was revealed,
Wilcoxon’s test was used to identify those differences.
Significance level was set at p # 0.05. Because the measure-
ments were directly or indirectly intercorrelated, no adjust-
ments were made for multiple comparisons, but caution was
exercised in the interpretation of the results (19,21). All
statistical analyses were conducted using SPSS v14.0.
Figure 2). The pairwise comparisons indicated differences
between SQUAT trial 1 with PLYO trial 1 (p = 0.044) and
REST trial 3 (p = 0.010), and SQUAT trial 3 with PLYO trial 1
(p = 0.018) (Figure 2).
TABLE 1. Countermovement jump performance variables after the 3 different conditioning stimuli over 3 trials for each stimulus.*†
2,254 6 549
2,079 6 419
2,041 6 372
2,164 6 220
2,174 6 365
2,051 6 233
1,332 6 327
1,240 6 265
1,352 6 382
1,128 6 294
1,258 6 328
1,294 6 288
401,750 6 210,841
462,553 6 231,241
453,722 6 98,521
372,034 6 153,098
461,563 6 90,461
360,124 6 69,572
Relative force (N/BW)
1.66 6 0.39
1.55 6 0.30
1.67 6 0.42
1.52 6 0.31
1.55 6 0.34
1.60 6 0.28
2,254 6 391
2,267 6 368
2,236 6 492
1,332 6 374
1,292 6 347
1,323 6 390
343,965 6 140,920
346,011 6 120,404
310,779 6 161,626
Relative force (N/BW)
1.67 6 0.48
1.59 6 0.36
1.63 6 0.45
*REST = inactivity; PLYO = plyometric exercises; SQUAT = heavy-weight squatting; RFD = rate of force development.
†Values are mean 6 SD.
Journal of Strength and Conditioning Research
Postactivation Potentiation After Exercise
No differences were revealed for any of the other variables.
Descriptives (mean 6 SD) for Ppeak, Fpeak, RFD, and RelF can
be seen in Table 1.
The aim of the present study was to investigate PAP by
examining the effect of heavy-weight or plyometric exercises
on repeated CMJ performance, and to compare CMJ
performances between the 2 modes of exercise. Our findings
show that heavy weight–induced PAP improved to some
extent jump height compared to plyometric exercises or
inactivity, as statistically significant differences were revealed
in some comparisons only, whereas plyometric exercises
presented no additional benefit to inactivity. Finally, neither
heavy-weight nor plyometric exercises showed any signifi-
cant improvements over the course of the 3 trials. To the
authors’ knowledge, this was the first study to directly
compare heavy-weight resistance and plyometric exercises in
relation to PAP over repeated trials preceded by the
Heavy weights have been shown to improve vertical jump
performance, in both intervention (1,17) and acute studies
(7,29). In contrast, previous studies have reported no
difference in acute CMJ performance after heavy-resistance
exercise (12,16). Indeed, in the current study, no difference
was revealed in CMJ jump height over the course of 3 trials.
These results agree with the findings of Jones and Lees (12),
who reported no effect of heavy-resistance exercise on
repeated CMJ performance using similar rest intervals (12). It
is worth noting that both the current study and that of Jones
and Lees (12) employed a similar sample, with all subjects
involved in sports requiring the development of explosive
strength, particularly in the hip, knee extensors, and ankle
plantar flexors and had experience performing resistance
exercises. Although such athletes may have benefited from
improved motor unit synchronization (2,15), this was not
evident in the present study. Notwithstanding the lack of
improvement in jump height, it is worth noting, from
a practical perspective, that no impairment in performance
was evident. As PAP and fatigue are simultaneously initiated
after muscle contractions (20), we posit that the effect of PAP
was sufficient to counteract the effect of fatigue in the
SQUAT group but inadequate for enhancing performance.
One interesting finding of the study was the consistency of
performance over those trials, despite no immediate effect of
the SQUAT stimulus on the repeated CMJs. When the
coefficient of variation (CV) was calculated (SD/average 3
100 ), the SQUAT group demonstrated a much lower
CV (1.3%) compared with PLYO (5.1%) and REST (4.3%).
A similar displacement performance consistency was
calculated from the study of Jones and Lees (12), where
the CVwas 1.2%. Although all the above percentages appear
small, the CV needs to be considered in comparison to
the performance gains expected. Significant differences in
vertical jump height performance are in the region of 4% and
above (14). A CV value above 4% (such as in the PLYO and
RESTgroups), would make the interpretation of results very
difficult, because any performance gain could be attributed to
the variability of the measure. In addition, CVvalues for force
(1.6%) and power (0.7%) indicate high consistency. It is
suggested that in sports involving repeated performances and
in which force and power are crucial, such as long jump (24),
heavy-resistance exercises will assist in maintaining the
required muscle output to allow the athlete to focus on the
technical execution of the skill.
Plyometric exercises have been used widely as a training
method to improve the efficiency of the stretch-shortening
cycle as well as the muscle–tendon unit’s ability to tolerate
stretch loads (3). The positive effects obtained by this form of
training on vertical jump performance have been established
(9,23). However, less is known about the acute effects of
plyometric or power exercises as a conditioning stimulus on
subsequent vertical jump performance (26). To the authors’
knowledge, this is the first study to examine the effect of
plyometric exercises on subsequent plyometric activity. Our
study indicated that previous plyometric exercises have no
impact on force and power production and that they present
no additional benefit to resting between trials.
Although no previous studies have examined the effect of
plyometric exercises on subsequent CMJ performance, it was
hypothesized thatPLYOwouldimprovepower performance,
because of PAP increasing RFD in explosive activities (22).
Jensen and Ebben (11) and Ebben et al. (4) proposed that the
concepts of plyometric intensity should be re-examined, as
they reported that ‘‘high’’ intensity plyometric exercises, such
as depth jumps, are recruiting muscle fibers as any other ‘‘less
intense’’ plyometric exercise, such as single-leg hops.
Interestingly, the vertical jump was shown to have higher
muscle fiber recruitment compared to the other plyometric
exercises used in their study (4). It is possible that the PLYO
conditioning exercises used in the present study did not result
in sufficiently high recruitment of muscle fibers to elevate the
postsynaptic potentials (26). This assumption is supported by
Masamoto et al. (15), who used tuck jumps (high muscle fiber
recruitment ), resulting in increased 1RM performance.
However, the opposite could also hold true. The plyometric
conditioning exercises could have resulted in high re-
cruitment of muscle fibers at maximum rate, in which case
PAP would offer little benefit (22). Unfortunately, in the
present study as in Masamoto et al. (15), electromyography
(EMG) was unavailable, making it impossible to accept or
refute any of these contentions. Therefore, future studies
should use EMG to assist in offering an explanation on the
mechanisms by which plyometric exercises enhance sub-
sequent strength and power performance, especially in
activities that involve the stretch-shortening cycle.
exercises (;70 seconds) in the current study was too long.
Vandervoort et al. (28) found that potentiation was partially
suppressed by fatigue in muscle contractions over 10-seconds
VOLUME 24 | NUMBER 7 | JULY 2010 | 1915
Journal of Strength and Conditioning Research
in duration, which may explain why shorter duration
plyometric exercises have previously improved performance
(15). The rest duration used in our study has previously been
shown to be sufficient for allowing fatigue to subside
(10,25,29). However, the duration of the conditioning
exercises in these studies was lower compared to the exercise
duration used in the present study, indicating that the
complex relationship between duration of contractions and
rest interval warrants further investigation.
Although the majority of research into PAP has recom-
mended its use for performance enhancement, few studies
have specifically investigated how such acute augmentation
may be achieved in repeated performances, as those
encountered in athletics competition. The results of the
present study indicated that lower body power performance,
as measured by CMJ height, is enhanced when preceded by
3 half squats at 3RM followed by 5 minutes of rest, compared
to plyometric exercises and rest. Therefore, the inclusion of
sets of squats into a warm-up routine before and during
the early stages of intermittent performance may provide
a beneficial alternative to traditional warm-up practices.
In addition, the inclusion of the above protocol in an athlete’s
preparation for their next performance (e.g., next jump or
throw) will ensure consistent force generation across trials.
The findings of the present study may be of particular
brief efforts are required, such as the jumping events in Track
and Field, where success is a product of force and take-off
velocity (24). Although the extent of performance augmen-
tation noted from the PAP mechanism is relatively small,
the potential benefits that such acute improvements in
performance hold to highly conditioned elite athletes should
not be underestimated (5).
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Journal of Strength and Conditioning Research
Postactivation Potentiation After Exercise