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DETERMINATION OF OPTIMAL LOADING DURING THE
POWER CLEAN,IN COLLEGIATE ATHLETES
PAUL COMFORT,CAROLINE FLETCHER,AND JOHN J. MCMAHON
Human Performance Laboratory, University of Salford, Salford, Greater Manchester, United Kingdom
ABSTRACT
Comfort, P, Fletcher, C, and McMahon, JJ. Determination of
optimal loading during the power clean, in collegiate athletes.
J Strength Cond Res 26(11): 2970–2974, 2012—Although
previous research has been performed in similar areas of study,
the optimal load for the development of peak power during
training remains controversial, and this has yet to be established
in collegiate level athletes. The purpose of this study was to
determine the optimal load to achieve peak power output during
the power clean in collegiate athletes. Nineteen male collegiate
athletes (age 21.5 61.4 years; height 173.86 67.98 cm; body
mass 78.85 68.67 kg) performed 3 repetitions of power
cleans, while standing on a force platform, using loads of 30,
40, 50, 60, 70, and 80% of their predetermined 1-repetition
maximum (1RM) power clean, in a randomized, counter-
balanced order. Peak power output occurred at 70% 1RM
(2,951.7 6931.71 W), which was significantly greater than the
30% (2,149.5 6406.98 W, p= 0.007), 40% (2,201.0 6
438.82 W, p= 0.04), and 50% (2,231.1 6501.09 W, p=
0.05) conditions, although not significantly different when
compared with the 60 and 80% 1RM loads. In addition, force
increased with an increase in load, with peak force occurring at
80% 1RM (1,939.1 6320.97 N), which was significantly
greater (p,0.001) than the 30, 40, 50, and 60% 1RM loads
but not significantly greater (p.0.05) than the 70% 1RM load
(1,921.2 6345.16 N). In contrast, there was no significant
difference (p.0.05) in rate of force development across loads.
When training to maximize force and power, it may be
advantageous to use loads equivalent to 60–80% of the
1RM, in collegiate level athletes.
KEY WORDS peak power, peak force, rate of force development
INTRODUCTION
Power can be expressed as the product of force and
velocity (18), with the highest power during
a movement, peak power, being achieved while
neither force nor velocity are at their peak.
Muscular power is considered one of the main determinants
of dynamic athletic performance, especially in sporting
events that require high force generation in a short amount of
time (18). Training power could therefore have important
implications for improving peak power output and have
great effects on sport performance. Generally, weight lifting
movements and their derivatives are considered highly
specific to actual sports performance, because they involve
large muscle mass, multijoint movements, and fast move-
ment velocity (2). Such exercises have been suggested to
increase an athlete’s performance by imitating sport-specific
movements, while concurrently using explosive power
(22,23), with performance in the hang power clean being
correlated to both 20-m sprint and countermovement jump
performance (13).
The load at which peak power is produced in lower-body
exercises, such as the squat and jump squat, has been reported
to vary from 0% (body mass [BM] with no external load)
to 60% of 1-repetition maximum (1RM) back squat
(3,7,8,17,20,21,23). In contrast to the squat jump, optimal
loading during variations of the clean tend to occur between
60 and 80% 1RM power clean (7,11,14–16). Haff et al. (11)
found that peak power in the hang power clean also occurred
at 80% 1RM, but this was not significantly different from 90
and 100% 1RM; however, testing was not conducted at loads
,80% 1RM. Kawamori et al. (15) found that peak power
output is achieved at 60% of 1RM (power clean) during the
midthigh clean pull, when compared with 30, 90, and 120%
of the 1RM power clean. Previously, Kawamori et al. (14)
found that peak power output during the hang power clean is
achieved using a load of 70% of 1RM power clean. More
recently, however, Kilduff et al. (16) found that peak power
output during the hang power clean was not significantly
(p.0.05) different between loads of 50, 60, 70, 80, or 90% of
the 1RM power clean.
It is clear that differing results have been reported, and
there is no set agreement among researchers, which may
be attributed to technical proficiency of the subjects or
methodological issues relating to assessing power during
Address correspondence to Paul Comfort, p.comfort@salford.ac.uk.
26(11)/2970–2974
Journal of Strength and Conditioning Research
Ó2012 National Strength and Conditioning Association
2970
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the
TM
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
variations of the clean. Such large disparity in the research
reported has led to ambiguity surrounding the load power
relationship (7,8,10). Training with the optimal load is sug-
gested to be the most effective method for improving maxi-
mal power and is likely to result in enhancement of a variety
of dynamic athletic performances (27). The aim of the study,
therefore, was to determine the optimal load at which peak
power is achieved during the power clean, in collegiate
level athletes, as previous research has only established the
optimal load in well-trained professional athletes. It was
hypothesized that the optimal load for peak power output,
during the power clean, would be achieved at a load of 70% of
1RM power clean, which is in line with the range identified in
previous research, using well-trained athletes.
METHODS
Experimental Approach to the Problem
This study employed a within-subjects repeated measures
research design, whereby peak power output was determined
during the power clean performed at a variety of loads in
a randomized counterbalanced order (30, 40, 50, 60, 70, and
80% 1RM power clean) to determine which relative load
results in the greatest power output. Dependent variables,
peak vertical ground reaction force (F
z
), peak rate of force
development (RFD), and peak power were measured while
the athletes performed all exercise variations while standing
on a force platform (Kistler, Winterthur, Switzerland, Model
9286AA, SN 1209740). These kinetic variables were selected
as F
z
, and measures such as RFD have been shown to be
strong determinants of sprint performance (24–26).
Subjects
Nineteen healthy male collegiate athletes (age 21.5 61.4
years; height 173.86 67.98 cm; BM 78.85 68.67 kg; 1RM
power clean 84.52 67.35 kg) participated in this study. All the
participants had regularly (.33week) performed structured
strength and conditioning training in preparation for their
sport (rugby, field hockey, soccer), including variations of the
clean, for .1 year. The investigation was approved by the
Institutional Ethics Review Board, and all the subjects
provided informed consent before participation. The study
conformed to the principles of the World Medical Associ-
ation’s Declaration of Helsinki. The participants had
previously conducted technique sessions, supervised by
a certified strength and conditioning coach, within their
normal training to allow familiarization with the protocols
and ensure appropriate technique. Testing took place during
the competitive season, after the participants had completed
a power mesocycle.
Testing
The 1RM power cleans were assessed on 2 separate
occasions, at the same time of the day, 3–5 days apart, to
determine reliability following a standardized protocol (1).
The subjects were asked to replicate their fluid and food
intake on both days and avoid strenuous exercise for 24 hours
before testing. After both the 1RM testing sessions, each
subject was familiarized with the protocols for the power
testing of each exercise. Before power testing, all the subjects
performed a standardized dynamic warm-up, including each
variation of the power clean (4 repetitions, 3 sets) using
a standardized load (30 kg) (Werksan weights and Olympic
bar; Werksan, Morristown, NJ, USA). The participants
were then randomly assigned to perform 1 cluster set of
3 repetitions (60-second rest between repetitions to minimize
fatigue) of the power clean (bar starting midway up the shin
and caught in a shallow squat, for each load. Four minutes of
rest between each load was provided to ensure adequate
recovery time, which is in line with the findings of previous
research (7,8,14).
Each repetition was performed with the subjects standing
on a force plate, sampling at 1,000 Hz, interfaced with a laptop.
Data were later analyzed using Bioware (Version 3.22; Kistler
Instrument Corporation) to determine peak F
z
. Instantaneous
RFD was determined by dividing the difference in
consecutive F
z
readings by the time interval (0.001 seconds)
between readings. Data were smoothed using a moving
average window of 400 milliseconds. Velocity of the center
of gravity (COG) of the system (barbell + body) was calculated
from F
z
time data based on the relationship between impulse
and momentum in which impulse is equal to the changes in
momentum (forward dynamics approach). Lower-body
power applied to the system was calculated as the product
of velocity of the COG of the system and F
z
at each time point
TABLE 1. Intraclass correlation values for mean peak
force, mean peak power, and mean peak rate of
force development at various loads.*
Load (% 1RM) rValue p
30 F
z
0.936 ,0.001
Peak power 0.845 ,0.001
RFD 0.790 ,0.001
40 F
z
0.962 ,0.001
Peak power 0.868 0.001
RFD 0.923 ,0.001
50 F
z
0.971 ,0.001
Peak power 0.836 ,0.001
RFD 0.894 ,0.001
60 F
z
0.936 ,0.001
Peak power 0.893 0.002
RFD 0.887 ,0.001
70 F
z
0.957 ,0.001
Peak power 0.828 ,0.001
RFD 0.912 ,0.001
80 F
z
0.940 ,0.001
Peak power 0.880 0.002
RFD 0.852 ,0.001
*RFD = rate of force development; RM = repetition
maximum.
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(12). When calculating power using F
z
, the impulse-
momentum approach is used to calculate power, where
impulse is equal to a change in momentum, or force multiplied
by time. Because the force, system mass, and initial velocity
conditions are known, the instantaneous velocity can be
calculated using this approach. Power can then be calculated
as force multiplied by velocity, and the peak of these values
can be determined for the propulsive phase of each variation
of the power clean. For each i, or time point based on
sampling frequency (equation set for the force data only):
vð0Þ¼0;
FðiÞt¼mv
ðiþ1Þv
;
¼FðiÞt
=m;
PðiÞ¼FðiÞ3vðiÞ;
where Fis the force, tis the 1/sampling frequency, mis the
mass of body 1 load, vis the velocity, and Pis the power.
To implement this calculation method, the sampling rate
and F
z
are needed, along with an initial velocity of the system
of zero. To calculate power in this way, it was important that
the initial F
z
represented sys-
tem load (athlete’s BM plus
load lifted); consequently, the
bar was held slightly above
ground level before the onset
of the power clean, in line with
what was done in previous
research (5,6). Power is calcu-
lated along the vertical axis
only and is the result of
lower-body force production
and not representative of the
power applied to the bar.
Statistical Analyses
Intraclass correlation coeffi-
cients (ICCs) were calculated
to determine reliability between 1RM power cleans and to
establish reproducibility between repetitions during each
exercise variation. A 1-way analysis of variance and
Bonferroni post hoc analysis were conducted to determine
if there were any significant differences in dependent variables
(peak power output, RFD, and F
z
) between relative loads.
Statistical power was calculated between 0.89 and 0.92
for each loading condition. An apriori alpha level was set to
p#0.05.
RESULTS
The ICCs show a high reliability for peak F
z
(r.0.936,
p,0.01) and peak power output (r.0.828, p,0.001), with
a moderate to high reliability for RFD (r.0.790, p,0.001)
across all loads, in line with the recommendations of Cortina
(9) (Table 1).
Force Production
Force production increased as load increased, with the peak
F
z
produced at 30% (1,561.1 6220.18 N, p,0.001), 40%
(1,621.1 6249.61 N, p,0.001), and 50% (1,695.9 6296.26 N,
p,0.003) being significantly
lower than the 60, 70, and 80%
1RM loading conditions. Peak
F
z
occurred at 80% 1RM
(1,939.1 6320.97 N), which
was significantly greater (p,
0.001) than the 30, 40, 50, and
60% 1RM loads but not signif-
icantly greater (p.0.05) than
the 70% 1RM load (1,921.2 6
345.16 N) (Table 2).
Peak Power
Peak power output occurred at
70% 1RM (2,951.7 6931.71 W),
which was significantly greater
than the 30% (2,149.5 6
406.98 W, p= 0.007), 40%
TABLE 2. Mean and SD values for peak force production during the power clean at
various loads.*
Load (% 1RM) Mean (SD) (N)
95% Confidence interval
Lower bound Upper bound
30 1,561.105 (220.18) 1,454.982 1,667.228
40 1,621.184 (249.61) 1,500.875 1,741.493
50 1,695.921 (296.26) 1,553.127 1,838.715
60 1,817.588 (271.98) 1,686.499 1,948.677
70 1,921.245 (345.16) 1,754.881 2,087.608
80 1,939.167 (320.97) 1,784.465 2,093.869
*RM = repetition maximum.
TABLE 3. Mean and SD values for peak power production during the power clean at
various loads.*
Load (% 1RM) Mean (SD) (W)
95% Confidence interval
Lower bound Upper bound
30 2,149.544 (406.98) 1,953.384 2,345.704
40 2,201.009 (438.82) 1,989.500 2,412.571
50 2,231.114 (501.09) 1,989.596 2,472.632
60 2,705.281 (624.47) 2,404.296 3,006.265
70 2,951.702 (931.71) 2,502.631 3,400.774
80 2,918.614 (1022.58) 2,425.744 3,411.483
*RM = repetition maximum.
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Optimal Loading during the Power Clean
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(2,201.0 6438.82 W, p= 0.04), and 50% (2,231.1 6501.09 W,
p= 0.05) 1RM conditions, although not significantly different
(p.0.05) than the 60 and 80% 1RM conditions (Table 3).
Rate of Force Development
In general, the peak RFD increased as load increased, with the
greatest peak RFD occurring at 70% 1RM (10,741.9 6
4,291.02 Ns
21
); however, this was not significantly different
(p.0.05) to the RFD produced with any other load
(Table 4).
DISCUSSION
The primary finding from this study was that peak power
output (2,951.7 6931.71 W) was maximized at 70% 1RM in
the power clean, which is in line with the original hypothesis;
however, peak power output at 60, 70, and 80% of 1RM were
not significantly (p.0.05) different, in line with the findings
of previous research using the hang power clean (14). This
confirms suggestions that peak power output may be a very
individual response and can occur at any of the 3 relative
loads of 60, 70, and 80% of 1RM, although Kilduff et al. (16)
found that peak power output occurred at 80% 1RM. In fact,
individual results in this study show that 5 subjects achieved
their peak F
z
, RFD, and Power at 60%, 6 at 70%, and 9 at 80%,
demonstrating the aforementioned individual response.
The results of this study are also comparable with results
found by Haff et al. (11), who reported that peak power
output occurred at 80% 1RM (2,440.23 6236.90 W);
however, they only tested at loads of 80, 90, and 100% of
1RM, and therefore, it cannot be discounted that peak power
may have occurred at a load ,80% 1RM. Although the
peak power output (2,951.7 6931.71 W) achieved in this
study is similar to the findings of Haff et al. (11) (2,440.23 6
236.90 W), it was substantially lower than the peak power
outputs achieved in the studies of Kilduff et al. (15) (4,460.7 6
477.2 W) and Kawamori et al. (14) (4,281.15 6634.84 W).
This may be attributed to the higher BM and absolute
strength (BM = 102.4 611.4 kg, 1RM = 107 613 kg;
BM = 89.4 614.7 kg, 1RM =
107.0 618.8 kg, respectively) of
the subjects of the later studies
compared with this study
(BM = 78.85 68.67 kg; 1RM
84.52 67.35 kg). It is suggested,
therefore, that collegiate level
athletes should perform the
power clean with a load of
60–80% 1RM maximize power
output, which is in line with
previous research using more
experienced athletes (4,14–16)
and to account for the individ-
ual variation noted above.
The F
z
increased as load
increased, with the greatest
peak F
z
(1,939.1 6320.97 N), occurring at the highest
load (80% 1RM), although this was not significantly
different from the peak F
z
produced at 70% 1RM
(1,921.2 6345.16 N), which is in agreement with previous
findings (14,16). Individual results also showed some
individual variation with peak F
z
and RFD occurring
between 60 and 80% 1RM, mirroring the individual
variations in peak power already discussed. In contrast
the higher absolute peak F
z
reported by Kilduff et al.
(15) (F
z
= 3,487.0 6526.6 N) compared with this study
(1,939.1 6320.97 N) may be attributable to the lower
system mass (BM + bar mass) in this study.
Peak RFD occurred at 70% of the 1RM, although
interestingly this was not significantly different from any of
the other loads tested, which may be explained by
Schmidtbleicher (19) who reported the peak RFD was equal
for all loads .25% of peak F
z
.
It is suggested that further research be conducted to
determine whether training at the load that maximizes
individual peak power output, compared with training at
higher, or lower relative loads, results in a greater adaptive
response. It would also be advantageous to see if any
improvements in F
z
, power, or RFD are related to any
subsequent changes in sprint or jump performance.
PRACTICAL APPLICATIONS
The findings of this study indicate that when training to
maximize peak power output, a load of 70% 1RM power clean
may be advantageous; similarly, if the focus is developing or
maintaining peak F
z
80% 1RM may be optimal. It is
noteworthy, however, that individual responses to loading
varied with peak values occurring between 60 and 80% 1RM
across individuals. It is suggested, therefore, that when
developing training programs for collegiate athletes which
include the power clean, a range of loads, between 60–80%
1RM, and identification of the loads that elicit peak power in
individual athletes may be advantageous, because of the
individual responses noted.
TABLE 4. Mean and SD values for peak rate of force development during the power
clean at various loads.*
Load (% 1RM) Mean (SD)(Ns
21
)
95% Confidence interval
Lower bound Upper bound
30 8,839.912 (3,185.64) 7,304.482 10,375.342
40 8,748.123 (3,328.16) 7,144.000 10,352.245
50 9,288.509 (3,600.49) 7,553.126 11,023.892
60 10,227.227 (3,750.86) 8,419.369 12,035.086
70 10,741.912 (4,291.02) 8,673.709 12,810.115
80 10,700.746 (2,946.02) 9,280.811 12,120.681
*RM = repetition maximum.
VOLUME 26 | NUMBER 11 | NOVEMBER 2012 | 2973
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