A comparison of muscle activity and 1-RM strength of three chest-press exercises with different stability requirements

Abstract

The purpose of this study was to compare one-repetition maximum (1-RM) and muscle activity in three chest-press exercises with different stability requirements (Smith machine, barbell, and dumbbells). Twelve healthy, resistance-trained males (age 22.7 ± 1.7 years, body mass 78.6 ± 7.6 kg, stature 1.80 ± 0.06 m) were tested for 1-RM of the three chest-press exercises in counterbalanced order with 3-5 days of rest between the exercises. One-repetition maximum and electromyographic activity of the pectoralis major, deltoid anterior, biceps, and triceps brachii were recorded in the exercises. The dumbbell load was 14% less than that for the Smith machine (P ≤ 0.001, effect size [ES] = 1.05) and 17% less than that for the barbell (P ≤ 0.001, ES = 1.11). The barbell load was ∼3% higher than that for the Smith machine (P = 0.016, ES = 0.18). Electrical activity in the pectoralis major and anterior deltoid did not differ during the lifts. Electrical activity in the biceps brachii increased with stability requirements (i.e. Smith machine <barbell <dumbbells; P ≤ 0.005; ES = 0.57, 1.46, and 2.00, respectively), while triceps brachii activity was reduced using dumbbells versus barbell (P = 0.007, ES = 0.73) and dumbbells versus Smith machine (P = 0.003, ES = 0.62). In conclusion, high stability requirements in the chest press (dumbbells) result in similar (pectoralis major and anterior deltoid), lower (triceps brachii) or higher (biceps brachii) muscle activity. These findings have implications for athletic training and rehabilitation.

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A comparison of muscle activity and 1-RM strength of three chest-press
exercises with different stability requirements
ATLE H. SAETERBAKKEN
1
, ROLAND VAN DEN TILLAAR
1
, & MARIUS S. FIMLAND
2
1
Faculty of Teacher Education and Sports, Sogn og Fjordane University College, Sogndal, Norway and
2
Norwegian University
of Science and Technology, Trondheim, Norway
(Accepted 26 November 2010)
Abstract
The purpose of this study was to compare one-repetition maximum (1-RM) and muscle activity in three chest-press exercises
with different stability requirements (Smith machine, barbell, and dumbbells). Twelve healthy, resistance-trained males (age
22.7 +1.7 years, body mass 78.6 +7.6 kg, stature 1.80 +0.06 m) were tested for 1-RM of the three chest-press exercises in
counterbalanced order with 3–5 days of rest between the exercises. One-repetition maximum and electromyographic activity
of the pectoralis major, deltoid anterior, biceps, and triceps brachii were recorded in the exercises. The dumbbell load was
14% less than that for the Smith machine (P0.001, effect size [ES] ¼1.05) and 17% less than that for the barbell
(P0.001, ES ¼1.11). The barbell load was *3% higher than that for the Smith machine (P¼0.016, ES ¼0.18). Electrical
activity in the pectoralis major and anterior deltoid did not differ during the lifts. Electrical activity in the biceps brachii
increased with stability requirements (i.e. Smith machine 5barbell 5dumbbells; P0.005; ES ¼0.57, 1.46, and 2.00,
respectively), while triceps brachii activity was reduced using dumbbells versus barbell (P¼0.007, ES ¼0.73) and dumbbells
versus Smith machine (P¼0.003, ES ¼0.62). In conclusion, high stability requirements in the chest press (dumbbells) result
in similar (pectoralis major and anterior deltoid), lower (triceps brachii) or higher (biceps brachii) muscle activity. These
findings have implications for athletic training and rehabilitation.
Keywords: Electromyography, resistance exercise, free weights, bench press, one-repetition maximum
Introduction
Bench press, also known as chest press, is a strength-
training exercise that is typically performed lying
supine on a bench using a Smith machine, barbell or
dumbbells. Unstable strength training exercises (e.g.
free weights) increase stabilization requirements of
the joints compared with the use of more stable
exercises (e.g. machines) (Garhammer, 1981). Thus,
proponents of instability resistance training claim
that unstable training modalities stress the neuro-
muscular system to a greater extent than more stable
strength-training exercises (Behm & Anderson,
2006).
Contrasting results have been reported in studies
that compared force output and muscle activation in
exercises on stable and unstable surfaces such as
Swiss balls and BOSU balls (Anderson & Behm,
2004; Marshall & Murphy, 2006; Norwood, Ander-
son, Gaetz, & Twist, 2007). For example, Kornecki
and colleagues (Kornecki, Kebel, & Siemien
´ski,
2001) and Anderson and Behm (2004) reported a
reduction in force output of about 30% and 60%,
respectively, when performing the same exercise on
an unstable surface. In contrast, Goodman and
colleagues (Goodman, Pearce, Nicholas, Gatt, &
Fairweather, 2008) reported no differences in one-
repetition maximum (1-RM) in barbell chest press
on a stable or unstable surface. Similarly, some
investigators have reported augmented electromyo-
graphy (EMG) activity in muscles that contribute to
joint stability (Kornecki et al., 2001; Marshall &
Murphy, 2006), whereas others have reported no
differences between stable and unstable surfaces
(Behm, Leonard, Young, Bonsey, & MacKinnon,
2005; Goodman et al., 2008).
A more common way of training to promote joint
stability is to employ free weights instead of machines
or dumbbells instead of a barbell. However, surpris-
ingly few studies have compared common resistance
training exercises with varying requirements of joint
stability for force output and neural drive. McCaw
and Friday (1994) reported greater neuromuscular
activity in the medial and anterior deltoid in bench
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Correspondence: A. H. Saeterbakken, Faculty of Teacher Education and Sports, Sogn og Fjordane Universi ty College, PB 133, N-6851 Sogndal, Norway.
E-mail: atle.saeterbakken@hisf.no
devia 11/12/10 10:03 RJSP_A_543916 (XML)
Journal of Sports Sciences, Month 2011; 29(0): 1–6
ISSN 0264-0414 print/ISSN 1466-447X online Ó2011 Taylor & Francis
DOI: 10.1080/02640414.2010.543916

press using free weights than machines at 60% but
not 80% of 1-RM. Welsch and colleagues (Welsch,
Bird, & Mayhew, 2005) compared barbell and
dumbbell bench press (6-RM loads) and reported
no differences in the neuromuscular activity of the
pectoralis major and anterior deltoid muscles. The
EMG activity was maintained despite the dumbbell
load being only *63% of the barbell load. This
suggests that increased neural drive was required to
stabilize the dumbbell. However, Welsch and col-
leagues did not record EMG activity of the agonist/
synergist triceps brachii and antagonist biceps brachii
muscles. Thus, it is unclear how the increased
stability requirement and the reduced absolute load
that can be lifted with dumbbells compared with
barbell chest-press influence the neuromuscular
activity of the biceps brachii and triceps brachii.
Thus the purpose of the present study was to
examine the 1-RM strength and EMG activity in
chest-press using a free barbell (conventional bench
press), a Smith machine, and dumbbells. It was
hypothesized that: (1) the increased stability require-
ment would result in lower 1-RM strength (kg) (i.e.
dumbbells 5free barbell 5Smith machine), and (2)
EMG activity would be similar in each chest-press
exercise since 1-RM was tested in each exercise.
Methods
Participants
Twelve healthy, resistance-trained males (age
22.7 +1.7 years, body mass 78.6 +7.6 kg, stature
1.80 +0.06 m) participated in the study. The
participants, none of whom was a competitive power
lifter, had 4.6 +2.2 years of strength-training ex-
perience. All participants were accustomed to the
three exercises and performed them as part of their
regular training programme. Participants were ex-
cluded from the study if they had musculoskeletal
pain, an illness or injury that might reduce maximal
effort during testing. The participants were in-
structed to refrain from any additional resistance
training exercises that targeted the chest, shoulders,
and upper arm muscle groups 72 h before testing.
Prior to the study, the participants were informed of
the test procedures and possible risks, and written
consent was obtained. Ethics approval was obtained
from the local research ethics committee and
conformed to the latest revision of the Declaration
of Helsinki.
Procedure
A within-participants crossover design was used to
examine 1-RM-related EMG activity in the barbell,
dumbbell, and Smith machine chest presses.
Two weeks before the experimental test, partici-
pants had three habituation sessions to identify 1-
RM for each of the three chest-press exercises. Each
session was separated by 3–5 days. The order in
which the exercises were performed was fully
counterbalanced. Participants 1 and 7, 2 and 8, 3
and 9, 4 and 10, 5 and 11, and 6 and 12 performed
the exercises in identical order. The exercises were
performed in the same order in the habituation
sessions and the experimental test. A 4-min rest
period was given between attempts (Schwanbeck,
Chilibeck, & Binsted, 2009). Before each 1-RM test,
a 10-min warm-up was performed on a cycle
ergometer at *60 rev min
–1
and self-selected
intensity (75–125 W) followed by four warm-up sets:
(1) 20 repetitions at 30% of 1-RM, (2) 12 repetitions
at 50% of 1-RM, (3) 6 repetitions at 70% of 1-RM,
and (4) 1 repetition at 85% of 1-RM. The percentage
of the 1-RM was estimated based on the self-
reported 1-RM of the participants in each of the
three exercises. A 3-min rest period was given
between warm-up sets (Goodman et al., 2008).
The tempo of each 1-RM lift was self-selected.
Similarly, the position of the hands on the barbell
was individually selected, but the forefinger had to be
inside the marks on the standard Olympic bar used.
Positioning of the hands was identical in the barbell
and Smith machine exercises. The position of the
arms was individually selected using the dumbbells.
The participants achieved 1-RM for the three
exercises in 3–6 attempts. The hips, shoulders, neck,
and head had to be in contact with the bench for each
of the exercises, with the feet on the floor, shoulder
width apart. Two test-leaders acted as spotters and
assisted the participants in the preload phase by
lifting the barbell or dumbbells and stabilizing the
weight until participants had fully extended arms.
On audio command, the participants lowered the
barbell to the middle of the sternum until it touched
the chest (eccentric phase). During dumbbell tests,
a 2-mm wide rubber band was placed on each
dumbbell. In the eccentric phase, the band was
stretched and had to touch the chest to make sure
the participants lowered the weights to the same
position as for the barbell. After lowering the
weights to the chest, the participants had to lift
the barbell/dumbbells back to the starting position
with fully extended elbows (concentric phase). No
bouncing of the weights was allowed. If the dumb-
bells or barbell were not lifted at the same vertical
position in the concentric phase, the lift was not
considered successful.
Recordings
A linear encoder (Ergotest Technology AS, Lange-
sund, Norway) was used to assess the vertical
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2A. H. Saeterbakken et al.

position and lifting time of the dumbbell or barbell
during all exercises. The linear encoder was syn-
chronized with the EMG recordings using a Mu-
sclelab 3010e and analysed with software V8.10
(Ergotest Technology AS, Langesund, Norway).
Before the 1-RM experimental test, the skin was
prepared (shaved, washed with alcohol, abraded) for
placement of gel-coated surface EMG electrodes.
Electrodes were placed according to the recom-
mendations of SENIAM (Hermens, Freriks, Dis-
selhorst-Klug, & Rau, 2000). The electrodes were
placed on the dominant side of the body (Marshall
& Murphy, 2006). The electrodes (11-mm contact
diameter) were placed on the belly of the muscle in
the presumed direction of the underlying muscle
fibres with a centre-to-centre distance of 2 cm. Self-
adhesive electrodes (Dri-Stick Silver circular sEMG
Electrodes AE-131, NeuroDyne Medical, USA)
were positioned at the pectoralis major, the anterior
deltoid, the triceps brachii, and biceps brachii. To
minimize noise from external sources, the raw
EMG signal was amplified and filtered using a
preamplifier located as near to the pickup point as
possible. Signals were low-pass filtered with a
maximum cut-off frequency of 8 Hz and high-pass
filtered with a minimum cut-off frequency of
600 Hz, rectified, and integrated. The raw EMG
signal was root-mean square (RMS) converted to an
RMS signal using a hardware circuit network
(frequency response 450 kHz, with a mean constant
of 12 ms, total error +0.5%). The RMS-converted
signal was sampled at a rate of 100 Hz using a 16-
bit analog-to-digital converter with a common mode
rejection rate of 100 dB. The stored data were
analysed using commercial software (Musclelab
V8.10, Ergotest Technology AS, Langesund, Nor-
way). Traces from the linear encoder and EMG
were overlaid and marked to identify the beginning
and end of the eccentric and concentric phase of
the lifts. The overall mean RMS EMG was
calculated for the entire movement as well sepa-
rately for the eccentric and concentric phases.
Statistical analysis
To assess differences in 1-RM strength, neuromus-
cular activity, and time taken in 1-RM testing
during the three chest-press exercises, a repeated-
measures one-way analysis of variance (ANOVA)
with Bonferroni post-hoc corrections to adjust for
multiple group comparisons was used (SPSS
version 17.0; SPSS, Inc., Chicago, IL). All results
are presented as means +standard deviations, and
we also report Cohen’s deffect sizes (ES). An
effect size of 0.2 was considered small, 0.5
medium, and 0.8 large. Statistical significance
was set as P0.05.
Results
The 1-RM strength was different among the three
chest-press exercises. The participants achieved the
highest 1-RM strength using the free barbell,
followed by the Smith machine and dumbbells
(Figure 1). The intra-class correlation coefficient
for the 1-RM exercises between the practice test and
the experiment was 0.947 (Smith machine), 0.947
(barbell), and 0.862 (dumbbells), respectively.
There were no differences in time spent in the
eccentric lifting phase, concentric lifting phase or in
total time taken in the three exercises (Table I).
The EMG activity for the whole movement
differed between the triceps brachii and biceps
brachii, whereas there were no differences for the
anterior deltoid and pectoralis major among
the different exercises (Figure 2). For dumbbells,
the EMG activity of the triceps brachii was lower
than for the Smith machine (P¼0.007, ES ¼0.62)
and barbell (P¼0.003, ES ¼0.73). For the biceps
brachii, the EMG activity increased with stability
requirements (i.e. dumbbells 4free barbell 4Smith
machine; Figure 2).
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Figure 1. Mean (and standard deviation) 1-RM for Smith
machine, barbell, and dumbbell chest presses. Significant differ-
ence in 1-RM between exercises:
#
P50.01, *P50.05.
Table I. Time taken (seconds) in lowering and lifting the weight
during the three chest-press exercises
Exercise Smith machine Barbell Dumbbells
Eccentric
phase
1.55 +0.38 1.55 +0.43 1.73 +0.74
Concentric
phase
3.14 +1.02 2.89 +0.88 2.75 +0.99
Total time 4.69 +1.16 4.45 +0.86 4.49 +1.39
Note: No differences were observed in time taken (P0.91) in the
different phases and total time between the three exercises.
Comparison of three chest-press exercises 3

When the EMG activity was calculated for the
eccentric phase, differences were observed between
exercises for the biceps brachii, anterior deltoid, and
pectoralis major (Figure 3a). The EMG activity was
lower when lifting with the Smith machine than with
the free barbell for the biceps brachii (P¼0.002,
ES ¼1.06), anterior deltoid (P¼0.004, ES ¼0.24),
and pectoralis major (P¼0.041, ES ¼0.33). The
EMG activity was also lower with the Smith machine
than with dumbbells for the biceps brachii
(P¼0.019, ES ¼0.94) and pectoralis major
(P¼0.012, ES ¼0.66). There were no differences
between the free barbell and dumbbells.
In the concentric phase, there were differences
between the triceps brachii and biceps brachii (Fig.
3b). Triceps brachii EMG activity was lower with
dumbbells than with the Smith machine (P¼0.005,
ES ¼0.54) and barbell (P¼0.003, ES ¼0.65). Bi-
ceps brachii EMG activity was higher with dumbbells
than with the Smith machine (P0.001, ES ¼2.32)
and barbell (P¼0.001, ES ¼1.79).
Discussion
In this study, we examined 1-RM strength and
neuromuscular activation in three chest-press ex-
ercises with different joint stability requirements.
The main findings were that 1-RM strength (i.e.
dumbbells 5Smith machine 5free barbell) and neu-
romuscular activity of the arm flexor/extensor mus-
cles, but not the pectoralis major and deltoid
anterior, differed among the three chest-press ex-
ercises.
For 1-RM strength, the dumbbells chest-press
load, which had the highest joint stability require-
ments, was substantially lower than for both Smith
machine and barbell chest-press (–14% and –17%
respectively; Figure 1). Furthermore, the load lifted
with the free barbell was slightly (*3%) higher than
with the Smith machine. The differences in 1-RM
strength between the free barbell and dumbbells in
the present study are in line with those of Welsch
et al. (2005). They reported that the maximal
dumbbells chest-press load was approximately 63%
of the maximal barbell load. Our finding of 83% is
broadly similar.
The stability requirements were lowest with the
Smith machine, which creates a guided one-dimen-
sional movement pattern, and thus the highest force
should theoretically be exerted in this exercise (Behm
& Anderson, 2006). However, contrary to the
hypothesis this was not the case in the present study.
The unnatural barbell path of the Smith machine
forced the participants to press the barbell in a linear
path similar to a novice barbell path (Madsen &
McLaughlin, 1984). Muscle use of the upper body
could be reduced and, therefore, limits the 1-RM
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400
405
410
415
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430
435
440
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450
455
Figure 2. Mean (and standard deviation) root mean square
(muscle activity) of the whole movement of the triceps, biceps,
anterior deltoid, and pectoralis major during three chest-press
exercises (free barbell, in a Smith machine, and with dumbbells).
Significant difference in 1-RM between exercises:
#
P50.01,
*P50.05.
Figure 3. Mean (and standard deviation) root mean square
(muscle activity) of (a) the eccentric phase (a) and the concentric
phase (b) of the triceps, biceps, anterior deltoid, and pectoralis
major during three chest-press exercises (free barbell, in a Smith
machine, and with dumbbells). Significant difference in 1-RM
between exercises:
#
P50.01, *P50.05.
4A. H. Saeterbakken et al.

strength using the Smith machine versus a barbell
(Cotterman, Darby, & Skelly, 2005).
The difference in 1-RM strength between the free
barbell and the Smith machine is similar to that
reported by Cotterman et al. (2005) – that is, a
higher 1-RM strength with the barbell. Cotterman
et al. (2005) reported differences in 1-RM strength
both for men (*11%) and women (*22%) among
the exercises, which were much greater than in the
present study. However, these differences could
simply be because of the inexperience of the
participants. In the study of Cotterman et al.
(2005), 72% of the participants had never used a
Smith machine for bench press, whereas 97% of the
participants had used the free barbell previously. In
the present study, all participants had experience
with all three exercises, though the free barbell was
preferred by the participants for their daily training,
and the results could be attributable to training-
specific adaptation.
As regards the second hypothesis of no differences
in EMG activity, we anticipated that reduced 1-RM
strength would be compensated by increased stabi-
lization demands of the muscles. In line with the
hypothesis, EMG activity of the pectoralis major and
the anterior deltoid muscles was similar for all three
exercises when an overall mean value was taken for
both lifting phases (Figure 2). However, EMG
activity in the biceps brachii and triceps brachii
differed among exercises, indicating different de-
mands on activation patterns. The EMG activity of
the triceps brachii was lower, while that of the biceps
brachii was greater with the dumbbells than both
barbell and Smith machine (Figure 2). There was
greater biceps brachii antagonist co-activation with
the dumbbells than both the Smith machine and free
bar. This is probably attributable to the increased
stabilization demands for this exercise to maintain
the integrity of the joint (Lehman, MacMillan,
MacIntyre, Chivers, & Fluter, 2006). Furthermore,
it might be that the reduced triceps brachii EMG
activity during dumbbells lifting is a result of
reciprocal inhibition that arises from increased arm-
flexor activation (Folland & Williams, 2007). The
dumbbell chest press is typically used as a supple-
ment to more frequently used chest-press exercises,
such as the free barbell. Based on the present results,
this could have influenced the neuromuscular
activation of the biceps brachii and triceps brachii
more than the Smith machine and free barbell.
The EMG activity of the pectoralis differed in the
concentric and eccentric phases of the exercises,
whereas that of the anterior deltoid muscle differed
in the eccentric phase (Figure 3a). The activity of
these muscles was lower during the eccentric phase
for the Smith machine than for the barbell and
dumbbells. This can be explained again by the
decreased requirements of stabilization of these
muscles in the descending phase withn the Smith
machine (McCaw & Friday; 1994). Madsen and
McLaughlin (1984) reported maintenance of control
when lowering the bar as one of five factors that
affects bench-press performance. However, with
different requirements of stability, there were no
differences in time spent in the different lifting
phases and it would therefore have little influence on
the differences in neuromuscular activity (Table I).
In the concentric phase, there was no difference
for the anterior deltoid and pectoralis muscles
(Figure 3b). These two muscles are prime movers
in the three exercises, which shows that the activity of
these muscles is similar when lifting 1-RM (Schick
et al., 2010; van den Tillaar & Ettema, 2010; Welsch
et al., 2005). Differences between the concentric and
eccentric phase indicate greater neural drive to
stabilize the weights in the eccentric phase.
There were several differences in the EMG activity
of the triceps brachii and biceps brachii among the
three chest-press exercises (Figure 2). When the
eccentric and concentric phases were analysed
separately (Figures 3a and 3b), lower activity was
observed for the triceps brachii only in the concentric
phase with dumbbells. The biceps brachii stabilizes
movement during the three exercises (Lehman et al.,
2006). Thus differences in neuromuscular activity of
the biceps brachii – that is, higher activity in the
eccentric and concentric phase with dumbbells than
in the other exercises (Figures 3a and 3b) – is a result
of the increased stabilizing function of this muscle
during the exercise. However, it should be noted that
we used only one pair of electrodes on each of the
muscles (biceps and triceps). Since these muscles
have multiple heads, other parts of these muscles
could have been active during the different lifts, thus
influencing the differences observed in our study.
The present results are limited by testing only 1-
RM and cannot be generalized to other strength-
training programmes. Surface EMG has inherent
technical limitations and can provide only an
estimate of neuromuscular activation. There is an
inherent risk of crosstalk from neighbouring muscles,
even if a small inter-electrode distance were to be
used. Further research should investigate the neuro-
muscular pattern of exercises with different require-
ment of stability with loads that are more typically
employed in resistance training (e.g. 6- to 12-RM).
In conclusion, this study has shown differences in
1-RM strength (i.e. dumbbells 5Smith machine 5
free barbell) and differences in neuromuscular
activity for the arm flexor/extensor muscles, but not
for the prime movers, among the three chest-press
exercises. As the stability requirements increased, the
neuromuscular activity of the biceps brachii in-
creased. Dumbbell lifting was accompanied by
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Comparison of three chest-press exercises 5

greater biceps brachii activity, but less activity of the
triceps brachii. The prime movers showed similar
EMG activity while lifting 1-RM, but less in the
descending phase using the Smith machine than with
barbell and dumbbells chest-press. This indicates
that greater neural drive is required to stabilize
weights in the eccentric phase. During rehabilitation,
it may in some cases be beneficial to achieve high
levels of muscle activation while lifting a lighter
external load. However, strength trainers/coaches
should be aware that the dumbbell chest press does
not activate the triceps brachii to the same extent as
conventional bench press or bench press performed
in a Smith machine.
Acknowledgements
We would like to thank the participants together with
Alexander Hansen, Kjetil Myklebust, and Sigurd J.
Bergstom for assistance in participant recruitment
and data collection.
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