Leg-drive Does Not Affect Upper Extremity Muscle Activation during a Bench Press Exercise

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International Journal of Human Movement and Sports Sciences 7(1): 12-17, 2019 http://www.hrpub.org
DOI: 10.13189/saj.2019.070103
Leg-drive Does Not Affect Upper Extremity Muscle
Activation during a Bench Press Exercise
Jacob K. Gardner1,*, Justin T. Chia2, Kelsey L. Miller1
1Department of Kinesiology and Health Science, Biola University, USA
2Department of Health and Human Development, Western Washington University, USA
Copyright©2019 by authors, all rights reserved. Authors agree that this article remains permanently open access under
the terms of the Creative Commons Attribution License 4.0 International License
Abstract The purpose of this study was to determine if
muscle activity of upper extremity muscles differed
depending on the involvement of the legs during a bench
press. The study included 15 male and 12 female
recreationally trained, college age participants. There were
2 testing sessions. Session 1: Participants performed a
1-repetition maximum in a standard bench press followed
by a leg-drive familiarization. For the familiarization,
participants were instructed in the leg-drive technique
(buttocks remained on the bench) and given ample time to
practice until comfortable and which satisfied the
researchers. Leg-drive pressing force was verified by
measuring anterior-posterior and vertical ground reaction
forces measured by a force plate. Session 2: Outfitted with
surface electromyography (EMG), participants performed
3 repetitions in the bench press with 75% of the standard
bench press 1-repetition maximum (1RM) under three
conditions: 1) standard 2) leg-drive, 3) legs-in-the-air. The
normalized average of the peaks of the three reps for each
muscle were analyzed using a 2 x 3 (gender x condition)
ANOVA. The ANOVA revealed no significant differences
across groups or conditions (pectoralis major p = 0.405,
anterior deltoid p = 0.297, triceps brachii p = 0.092). When
comparing a standard bench press to leg-drive, our results
indicate that similar amounts of muscle activation are
required for the task regardless of the leg involvement. This
work indicates that using a leg-drive technique that does
not allow the buttocks to rise from the bench, does not
result in a change in upper extremity muscle activity
compared to a standard bench press. Due to lack of
differences across conditions, athletes and strength coaches
should base their decision on the use of leg-drive on their
personal preference.
Keywords Lower-extremity, Electromyography,
Resistance Training, Muscle Contraction
1. Introduction
Resistance exercise is an essential component to the
training regime of athletes and the general public alike. The
bench press is commonly used as a measure of upper-body
strength with the prime movers being the pectoralis major,
the triceps brachii, and the anterior deltoids (1). While it is
clear that the bench press is an upper-body exercise, it is
less clear to what extent the lower extremities are, or
should be, involved in the exercise. Professional
organizations such as the National Strength and
Conditioning Association instruct that the left and right feet
of the lifter are to remain on the floor during the lift for
stability as 2 (out of 5) points of contact (13). Anecdotal
evidence in weight rooms suggest that it may be beneficial
to use the lower extremities as a performance enhancing
driving mechanism in addition to stability. To accomplish
such a task, lifters flex at the knee to move the foot behind a
vertical plane at the knee joint in order to press with their
legs (leg-drive) while performing the lift.
Observationally, many weight-training participants
indicate that leg-drive while performing the bench press
gives them a sense of improved performance. In an article
about inter-subject variability of muscle synergies during a
bench press, authors Kristiansen et al. discovered that
experienced power lifters utilized the vastus lateralis
muscle while lifting 75% of a 3 repetition maximum (RM)
load (8). Interestingly, untrained individuals in the same
study did not exhibit this same muscle activation pattern in
the lower extremities. The authors suggested that the use of
the vastus lateralis in experienced lifters acts to
isometrically extend the knee, resulting in increased
stability and stiffness of the torso, allowing greater strength
expression (8). However, these authors did not control for
participant posture and it was noted that the experienced
lifters tended to arch their backs during the lift. Thus, the
increased vastus lateralis activation could partly be due to
driving the legs but also could be due to the effort required
to maintain an arched position.

International Journal of Human Movement and Sports Sciences 7(1): 12-17, 2019 13
Little other scientific evidence exists on the effects of
leg-drive on bench press performance. Therefore, the
purpose of this study was to compare muscle activation of
the pectoralis major, anterior deltoid, and triceps brachii
muscles during three bench press conditions. The three
conditions included: 1. Feet on ground but not driving
(standard (13), figure 1a), 2. Feet on ground and driving
(leg-drive, figure 1b), and 3. Feet off the ground with hips
and knees flexed to 90 degrees (feet-in-the-air, figure 1c).
Due to limited literature on leg-involvement during a bench
press, it was hypothesized that no differences in muscle
activation of the three upper extremity muscles would exist
regardless of lower extremity involvement.
Figure 1. (A) Standard bench press condition. (B) Leg-drive condition.
Note that during the leg-drive, participants aligned their feet behind the
vertical line of the knees while still maintaining a flat foot on the floor. (C)
Feet-in-the-air condition. Note that the hips and knees are flexed to
approximately 90 degrees.
2. Methods
2.1. Approach to the Problem
The protocol was conducted on two separate days, 1
week apart. Participants were asked to refrain from
physical activity 2 days prior to and during the experiment
to avoid cumulative fatigue. On the first day, a bench press
1RM protocol (4) was conducted to determine the
maximum weight the participant could lift in the bench
press exercise. The 1RM was only performed in the
standard bench press condition. A standardized five-point
body contact position was utilized for the 1RM protocol
(13). On day 1, participants were familiarized with the
leg-drive technique and metronome pacing.
On day two, participants performed a maximal voluntary
isometric contraction (MVIC) for the purpose of EMG
normalization followed by 3 bench press reps in the 3
testing conditions. It should be noted that all three lifting
styles are common and are safe for the lifter to perform.
Before MVIC testing, surface EMG electrodes (Noraxon
Dual Ag/AgCl electrodes with inter-electrode distance of
1.75 cm, Noraxon USA Inc., Scottsdale, AZ) were placed
over the muscle bellies of the pectoralis major (sternal
fibers), anterior deltoid, and lateral head of the triceps
brachii on the right side of the body according to the
SENIAM project guidelines (5).
2.2. Subjects
Fifteen males (age 22.1 ± 2.1 yrs, height 1.71 ± 0.04 m,
mass 74.7 ± 6.4 kg, 1RM 103.56 ± 24.11 kg) and twelve
females (age 20.5 ± 1.3 yrs, height 1.63 ± 0.07 m, mass
60.1 ± 11.3 kg, 1RM 48.10 ± 5.65 kg) over the age of 18
participated in this study. Individuals were considered for
inclusion had they been regularly resistance training with
the bench press exercise for at least 6 months prior to the
start of the study while also sustaining no serious lower or
upper body injuries during this time. Participants were
informed of the benefits and risks of the investigation prior
to signing an informed consent approved by the
University’s Protection of Human Rights in Research
Committee (approval number F16-021_SE). This research
was conducted in accordance with the 1964 Declaration of
Helsinki.
2.3. Procedures
In the setup for the leg-drive, participants maintained
five points of contact during the press but flexed their
knees, causing the feet to align behind the knees while
remaining flat on the floor (Figure 1a). The participants
were instructed to drive their feet down and forward as if
performing an isometric knee extension into the floor. It
was emphasized not to allow the buttocks to rise off the
bench during the leg-drive. Participants practiced until

14 Leg-drive Does Not Affect Upper Extremity Muscle Activation during a Bench Press Exercise
comfortable and the investigators were satisfied.
To verify that the participants were driving the legs as
desired, the right foot was placed on a force platform (1200
Hz, Advanced Mechanical Technology Inc. (AMTI),
Watertown, MA) and the vertical and anterior-posterior
ground reaction forces (GRF) were recorded (AMTI
Netforce, Watertown, MA). During the zeroing process,
the participant maintained contact with the force plate
without pressing. The force plate was zeroed with the foot
in place to remove the weight of the leg from the GRF data.
A positive vertical and positive antero-posterior GRF
indicated a successful leg-drive.
To minimize compounding effects of delayed onset
muscle soreness (DOMS), testing days were separated by 1
week. Each EMG site was shaved (if applicable), abraded
with sandpaper, cleansed with alcohol, and treated with an
electrode skin prep gel (Nuprep, Weaver and Company,
Aurora, CO) (6). Electrode impedances were maintained
below 10 kOhms as verified by the EL-Check electrode
checker (Biopac Systems Inc., Goleta, CA).
For the MVIC procedure, positioning was identical to
the standard bench press but with the pressing apparatus
configured to restrict the participant to a 90-degree elbow
angle. Participants performed 3 sustained pulses of
maximal isometric contractions for approximately 3
seconds separated by another 3-second pause. The highest
recorded value in each muscle for any of the three
contractions was used as the normalization value for
subsequent EMG data (6).
Following the MVIC test, participants performed 3
bench press repetitions at 75% of their 1RM in each of the
three aforementioned testing conditions: standard (figure
1a), leg-drive (figure 1b), and feet-in-the-air (figure 1c).
The 3 repetitions for each randomly ordered condition were
performed to a metronome set at 60 beats per minute to
standardize lifting velocity across participants. Starting
with the barbell in the upward position the participant
began the eccentric phase of the lift on a metronome beep,
reached the bottom of the lift at the next beep, started the
concentric movement on the third beep, and finished the
rep on the fourth beep. This procedure was repeated for the
following 2 reps. Participants had 4 minutes of rest
between conditions. If any of the trials failed to meet the
metronome timing, participants were given 4 minutes of
rest and the trial was repeated. During the standard and
leg-drive conditions, the right leg of the participant was
positioned on a force plate to record vertical and
antero-posterior GRF data.
The raw EMG data were collected and processed
through Biopac’s Acknowledge 4.4 software (Biopac
Systems Inc., Goleta, CA). Data were band pass filtered at
10-500 Hz, full wave rectified, and smoothed using a root
mean square (RMS) moving window of 100 ms (6). The
processed EMG data were then exported to Microsoft
Excel for calculation and extraction of the variables of
interest. The average of the peak EMG muscle activations,
across the 3 reps for each condition, was calculated and
then normalized to the peak muscle activation value from
the MVIC. Thus, normalized muscle activation values are
presented as a percentage of MVIC.
The GRF data were collected in AMTI’s NetForce
software (AMTI Inc., Watertown, MA) and exported to be
used in Matlab (v. R2017b, Mathworks, Natick, MA) for
processing. Ground reaction force data were smoothed
using a 4th order Butterworth filter with a cutoff frequency
set at 20 Hz (16). Peak vertical and antero-posterior GRF
were determined for each rep and then averaged across reps
for the leg-drive condition. The standard bench press
condition did not result in 3 distinct peaks like in the
leg-drive condition, thus, for the standard condition, the
maximum GRF values were used for analysis. The GRF
values were then normalized to body weight to determine
the percentage of body weight at which the participant was
pressing.
2.4. Statistical Analyses
For the EMG data, between group and within group
differences for peak muscle activations were analyzed
using a 2 x 3 (gender x condition) analysis of variance
(ANOVA). In the presence of a significant F-value, a
Bonferroni post-hoc analysis was conducted to determine
where, if any, differences occurred. The criterion level for
significance was set at p ≤ 0.05.
In addition, averaged peak vertical and antero-posterior
GRF variables were analyzed using a 2 x 2 (gender x
condition) ANOVA. This only included 2 conditions
because force plate data was not collected for the
feet-in-the-air condition. The criterion level for
significance was set at p ≤ 0.05. In the presence of a
significant finding, 95% confidence intervals (95% CI) and
Cohen’s D effect sizes (ES) were reported. Cohen’s D
effect sizes were interpreted as 0.20 = small, 0.50 =
moderate, and 0.80 = large (2).
3. Results
Figure 2 shows mean muscle activation values, in %
MVIC, for each of the three muscles, across gender and
condition. The results of the ANOVA revealed no
statistically significant differences across gender or
condition for any of the three muscles analyzed (pectoralis
major gender p = 0.939, condition p = 0.405; anterior
deltoid gender p = 0.734, condition p = 0.297; triceps
brachii gender p = 0.456, condition p = 0.092). Graphically,
there is a trend with the feet-in-the-air condition resulting
in higher muscle activations than the other two conditions.
This is only a noted trend and not substantiated statistically
by the ANOVA.

International Journal of Human Movement and Sports Sciences 7(1): 12-17, 2019 15
Figure 2. Mean muscle activation values normalized to MVIC across gender and condition. There were no statistically significant differences found
across any of the conditions.
Figure 3. Peak (for standard condition) and mean peak (for the leg-drive condition across the three reps) antero-posterior and vertical ground reaction
forces normalized to body weight. Note, no data are presented for the feet-in-the-air condition because the feet were not in contact with the ground. All
condition comparisons were found to be statistically significant at the α = 0.05 level.
Figure 3 shows the mean GRF data across gender and
conditions. The results of the ANOVA for the GRF data
revealed a significant increase in both vertical (mean
difference = 19.03 %BW, 95% CI = 16.46 – 21.30 %BW, p
< 0.001, ES = 4.81) and antero-posterior (mean difference
= 8.85 %BW, 95% CI = 7.11 – 10.60 %BW, p < 0.001, ES
= 6.99) GRF in the leg-drive compared to the standard
bench press condition. Additionally, there were no
statistically significant differences between genders for the
vertical (p = 0.095) or antero-posterior (p = 0.528) GRF.
4. Discussion
The intent of this study was to examine the effects of
leg-drive on upper extremity muscle activation during the
bench press exercise. It was hypothesized that no
differences in muscle activation of the three upper
extremity muscles would exist regardless of lower
extremity involvement and leg position. The hypothesis
was supported in that there were no statistically significant
findings in any of the muscle activations of the pectoralis
major, anterior deltoid, or triceps brachii during the three
conditions of the bench press.
From an observational standpoint, lifters who utilize
leg-drive feel as if they are capable of lifting more weight,
or, performing a better lift when compared to a standard
technique. This is further evidenced by Kristiansen et al.
who demonstrated that experienced lifters utilized the
vastus lateralis muscle more during a bench press at 75% of
a 3-RM while inexperienced lifters did not (8). The authors
suggest that this posture led to a greater strength expression
in the experienced lifters. While this current work did not
result in a greater strength expression, it is worth noting
that Kristiansen et al. did not control the participants’
posture on the bench. In their observations, they reported
that experienced lifters tended to arch their backs during
the lift, while the inexperienced lifters did not. It is
probable that the “greater strength expression” they are
describing was a result of an increase in the torso angle to

16 Leg-drive Does Not Affect Upper Extremity Muscle Activation during a Bench Press Exercise
mimic a decline bench press. For example, Lauver et al.
showed that compared to a flat bench press, a decline
position results in more utilization of the lower fibers of the
pectoralis major and simultaneously places less emphasis
on the anterior deltoids (10). A decline position places
more demand on the larger musculature of the pectoralis
major, which better handles that demand and removes
some demand from the smaller musculature of the anterior
deltoids.
Within this study, the participants were required to
maintain 5 points of body contact (in the leg-drive and
standard conditions), one of which was the buttocks on the
bench. This variable was controlled in order to minimize
the effects of spinal posture in the lift. It is clear from the
GRF data that the participants pressed harder into the
ground during the leg-drive (anteroposterior = 11.00 %
BW, vertical = 22.85 % BW) compared to the standard
bench press condition (anteroposterior = 2.16 % BW,
vertical = 3.82 % BW). Thus, any expected changes in
muscle activity would be attributed to the leg-drive
technique. If leg-drive was easier from a muscle activation
perspective, one of two different scenarios may be
expected: 1. there might be increased muscle activations
with the leg-drive technique, indicating that the positioning
would cause the central nervous system (CNS) to recruit
more motor units to perform the lift. 2. with leg-drive, the
body is placed into a mechanical advantage thereby
reducing demand placed on the central nervous system.
This would result in less motor unit recruitment necessary
for the lift. If the lift were “easier,” then this scenario would
make more sense, as it would take less muscular effort to
lift the given weight. The latter theory is more consistent
with Ploutz et al. who showed that after 9 weeks of
resistance training, the quadriceps utilized less muscle for a
given lift when compared to pre-training (15). Thus, the
more a muscle is prepared for, or capable of performing a
demanding task, the less effort is required of that muscle to
complete that task.
Due to the lack of muscle activation variation, it is
plausible that the demand of the task (75% of 1RM) was
too light. Since the weight remained at 75% of 1RM
throughout all conditions, the muscle activation may not
have changed because the demands of the weight remained
the same. It is possible that increasing the number of reps
or the load would tease out muscle activation differences
between lifting techniques since the requirement for the
CNS would be more demanding. As such, perhaps
leg-drive is only beneficial in very heavy, or increasingly
demanding loads. Alternatively, it is possible the leg-drive
technique yielded no muscle activation difference because
the effort to control lifting velocity via metronome
hindered the participant’s power output.
During the feet-in-the-air condition there was a small
trend of higher muscle activation values compared to the
other two conditions. While this trend is not statistically
significant, it is worthy of mention in light of some studies
that show alterations in muscle activity with instability (3,
9, 11, 12, 14, 17). Current literature on the effects of
instability in the bench press is ambiguous. In a study by
Nairn et al., participants performed a bench press on a
stability ball resulting in increased shoulder muscle
activation compared to a standard bench press (12).
However, in a study by Saeterbakken, the standard bench
press condition resulted in greater EMG activity in the
pectoralis major and triceps compared to the unstable
conditions (17). The instabilities created in previous
studies were either at the level of the bench (e.g. using a
stability ball) or at the implement being lifted (e.g. using an
earthquake bar). It appears that a majority of the studies
resulted in more recruitment of stabilizing muscles rather
than the primary movers. Interestingly, in the current study,
instability was not purposely created in the bar or the bench
in the feet-in-the-air condition, but it appeared that there
was some instability in the participants because of not
having their feet on the floor to help maintain balance. This
small finding may be worth exploring more in future bench
press studies.
Since there was not a statistically significant change in
EMG activity levels across the conditions, it begs the
question, why do lifters feel that performing the leg-drive
while lifting is “easier” compared to a standard bench press?
In this study, the EMG activity remained at similar levels
between all three conditions, but it is important to note that
the resistance also remained constant at 75% of the
participant’s 1RM. It is possible that since the weight being
lifted is the same amount across all conditions, the CNS
only recruited the motor units necessary to perform that
task; no more, no less. A study by Korak et al. corroborates
this idea, noting that the strength and neural activations
between two groups performing bench press using the
same load (one utilizing rest-pause method and one
performing a traditional bench press) were not significantly
different (7). Interestingly, they did find that over a 4-week
training period, even though EMG activities were not
different between groups, the group that was trained in the
rest-pause method did increase their lifting volume
compared to the traditionally trained group. Since there
was not a difference in muscle activity across conditions, it
is clear, at least from a muscle activation standpoint that the
use of leg-drive while keeping the buttocks on the bench,
does not lead to a reduction in motor unit recruitment.
However, it is still unknown if leg-drive could feasibly
contribute to an increased maximum load lifted or training
volume. More research is necessary to determine the
effectiveness of this technique.
Future research should examine the effects of leg-drive
utilizing a higher or lower percentage of the participant’s
1RM.Currently, no studies have examined the effects of
leg-drive on any type of performance increases, such as
increasing the load or the number or reps during the bench
press. Examining this in a future study may reveal if a
heavier or lighter weight with leg-drive results in a change

International Journal of Human Movement and Sports Sciences 7(1): 12-17, 2019 17
in muscle activation compared to a standard bench press.
Future training studies could compare an intervention
group utilizing leg-drive to a control group performing a
standard bench press to determine if the maximum amount
of weight lifted or volume lifted, would be different over
several weeks of training.
5. Practical Applications
Based on the findings of the present study, recreational
athletes or individuals utilizing the bench press in their
training could use the leg-drive technique if they prefer it,
or refrain if they do not. Because there were no significant
differences in upper extremity EMG activations found
between conditions, strength and conditioning coaches or
practitioners should base the decision to utilize the
leg-drive on the athlete’s personal preference.
Acknowledgements
No external financial support was received for this
research. The authors would like to thank all of the
volunteers who participated in the study.
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