kristiansen2018

EXTERNAL AND INTERNAL FOCUS OF ATTENTION
INCREASES MUSCULAR ACTIVATION DURING BENCH
PRESS IN RESISTANCE-TRAINED PARTICIPANTS
MATHIAS KRISTIANSEN,1 AFSHIN SAMANI,1 NICOLAS VUILLERME,1,2,3 PASCAL MADELEINE,1 AND
ERNST ALBIN HANSEN1
1
Department of Health Science and Technology, Physical Activity and Human Performance Group, SMI, Aalborg University,
Aalborg, Denmark; 2University of Grenoble Alpes, AGEIS, Grenoble, France; and 3University Institute of France, Paris, France
ABSTRACT
INTRODUCTION
Kristiansen, M, Samani, A, Vuillerme, N, Madeleine, P, and
Hansen, EA. External and internal focus of attention increases
muscular activation during bench press in resistance-trained
participants. J Strength Cond Res XX(X): 000–000, 2018—
Research on the effects of instructed attentional focus during
execution of strength training exercises is limited and has
thus far only been performed on single-joint exercises. The
aim of this study was to compare the effects of instructed
internal (INT) and external (EXT) focus of attention with
a baseline measurement of no instructed focus of attention
(BASE) on the surface electromyographic (EMG) amplitude
during a free-weight bench press exercise in resistancetrained participants. Twenty-one resistance-trained male participants performed bench press at 60% of their 3-repetition
maximum, with BASE, EXT, and INT. The order of EXT and
INT was randomized and counterbalanced. Electromyographic data were recorded from 13 muscles of the upper
and lower body. Subsequently, mean and peak EMG amplitudes were computed. EXT and INT resulted in significantly
increased mean EMG amplitude of 6 upper-body muscles as
compared with BASE (p # 0.05). In addition, EXT and INT
also resulted in increased peak EMG amplitude of 3 upperbody muscles as compared with BASE (p # 0.05). These
results show that muscular activation is increased during
bench press, when applying an instructed focus of attention
compared with a baseline measurement with no focus instructions (BASE).
KEY WORDS movement effectiveness, motor performance,
strength training
Address correspondence to Dr. Mathias Kristiansen, [email protected].
00(00)/1–10
Journal of Strength and Conditioning Research
2018 National Strength and Conditioning Association
T
he use of verbal instructions is common within
training and exercise for facilitation of a specific
movement. Depending on the formulation of the
verbal instructions, the attentional focus of the
athlete may be directed either internally or externally (40).
On the one hand, an internal focus of attention encompasses
the athlete focusing on the movements of his or her own
body (36). An example is to focus on the contraction of the
biceps brachii (BB) muscle (i.e., focal muscle) during a biceps
curl exercise. On the other hand, an external focus of attention requires the individual to focus on the effects of his or
her movement in relation to the environment (36). An example is to focus on the movement of the object being lifted
during a biceps curl exercise. An external focus of attention
has been shown to be superior to an internal focus of attention in terms of performance outcome in a variety of different sports disciplines such as golf (23,32,33), basketball
(2,41), vertical jump (38,39), agility (L-run exercise) (24),
discus throwing (42), volleyball (37), dart throwing
(15,19,27), swimming (6), and gymnastics (1). An external
focus of attention has also been reported to result in better
running economy (26). As an explanation for the superiority
of an external focus of attention, the constrained-action
hypothesis has been proposed (22,35,36). Briefly, the
constrained-action hypothesis suggests that an internal focus
of attention interferes with automatic control processes. This
interference presumably results in a constraint of the degrees
of freedom of the motor system, thus compromising an
effective execution of the motor task at hand. An external
focus of attention, however, is believed to promote a more
automatic and reflexive control process, resulting in
improved motor performance (40).
The effect of attentional focus has not been thoroughly
investigated within the field of strength training. Strength
training is one of the most widely practiced forms of
exercise, being used to, for example, improve sports performance, change body composition, as well as rehabilitate
musculoskeletal disorders and injuries (5). Furthermore, the
use of verbal instructions is also a common practice in
VOLUME 00 | NUMBER 00 | MONTH 2018 |
Copyright ª 2018 National Strength and Conditioning Association
1
Focus of Attention During Bench Press
strength training settings (3). In addition, some studies suggest that when not provided with verbal instructions, athletes seem to direct attention internally (18). Therefore, there
is a need for more research in this area to determine which
type of focus of attention is favorable in tasks requiring high
force production. This is interesting with respect to optimizing sports performance and with respect to improving the
instructions given to participants during experimental studies, just to mention a few examples.
Lower surface electromyographic (EMG) activation of
the BB muscle has been reported during biceps curls at the
same load when adopting an external compared with an
internal focus of attention (17,28). Because of the equivalent
amount of external work being produced across focus conditions, the lower EMG amplitude during an external focus
of attention has been interpreted as greater movement efficiency (17). However, the biceps curl is a relatively simple
single-joint task, especially when performed in a dynamometer. There is currently no knowledge available on the effect
of attentional focus on EMG activity during multijoint
free-weight strength training exercises. Such exercises are
characterized by being more difficult to execute, as well as
resulting in an increased number of degrees of freedom. As
an example, for proper execution of the commonly used
exercise of bench press, the coordinated activation of all
the major muscle groups in the legs, back, and upper body
is required (11). Simultaneously, a considerable amount of
focus should be directed toward controlling the heavy barbell in the desired movement trajectory. The sum of all these
results in a dilemma in terms of where the focus of attention
should be directed. For instance, one can choose to primarily
focus on the focal muscles that are being activated (internal
focus of attention). Alternatively, one can choose to primarily focus on the barbell that is being lifted (external focus of
attention). If the constrained-action hypothesis is indeed
valid, adopting an internal focus of attention during such
a demanding task should have deteriorating effects on motor
control, and consequently on performance.
The aim of this study was to compare instructed internal
and external focus of attention with no instructed focus of
attention during a free-weight bench press exercise in
resistance-trained participants. In particular, we focused on
the EMG amplitude. We hypothesized that the internal
focus of attention would result in higher EMG amplitudes
compared with external focus of attention and a control
condition. As the physical work performed across focus
conditions was equal, a higher EMG amplitude would be
interpreted as an indication of reduced movement efficacy
(18).
METHODS
Experimental Approach to the Problem
The bench press, which is one of the most popular and widely
used strength training exercises, was chosen for this study, as
proper execution of this exercise requires a coordinated
2
the
activation of all major muscles of the legs, back, and upper
body while handling a high load (10–12). The large number of
phasic and postural muscles involved throughout the body
makes bench press a complex bilateral arm movement and
thus an appropriate strength training exercise for assessment
of the effect of different instructed foci of attention. The study
consisted of a familiarization session and a test session. The
goal of the familiarization session was to familiarize the participants with the test protocol, laboratory environment, and
test equipment, as well as to minimize learning effects in the
subsequent test session. One week after the familiarization
session, all participants performed the test session in which
they were tested extensively in bench press. Testing was performed to address the role of internal and external focus of
attention on EMG amplitude of 13 muscles during bench
press.
Subjects
Twenty-one male participants (age 24.5 6 2.2 years [mean
6 SD], range 21–28, height 1.81 6 0.07 m, body mass 89.0 6
12.8 kg, and 3-repetition maximum [3RM] in bench press
109.4 6 25.9 kg) were recruited for participation in the current study. All participants had performed full-body strength
training for at least 2 years, with 2–3 training sessions per
week. The study was approved by the local ethics committee
of the North Denmark region (N-20120036), and all participants gave their written informed consent after having been
explained the experimental methods and risks. The participants in the current study are the same as the ones involved
in a previous study from our group, focusing on reliability of
muscle synergies during bench press (12). Therefore, the
number of participants was determined using an a level set
to 0.05, b level to 0.20, p0 to 0.7, p1 to 0.9, and n to 2 (30). p0
and p1 denotes the minimally acceptable level of reliability
and the expected level of reliability, respectively. a level and
b level denotes the probability of making a type 1 and type 2
error, respectively.
Procedures
The test session consisted of the following: mounting of
electrodes, warm-up, a 3RM test in bench press, one set of 3
repetitions at 75% of the 3RM load for normalization
purposes, and 12 sets of 8 repetitions at 60% of the 3RM
load.
Before mounting the electrodes, the skin areas covering
the muscles of interest were shaved, abraded, and cleaned
with alcohol. Surface EMG electrodes (Ambu Neuroline 720
01-K/12, Ag/AgCl, interelectrode distance 20 mm, Ambu
A/S, Ballerup, Denmark) were mounted on the skin over the
following muscles on the right side of the body: pectoralis
major (PM), anterior deltoideus, BB, triceps brachii lateral
head (TBL), triceps brachii medial head (TBM), latissimus
dorsi (LD), erector spinae (ES), rectus femoris (RF), biceps
femoris (BF), gastrocnemius lateral head (GML), soleus
(SOL), vastus lateralis (VL), and vastus medialis (VM). All
electrodes were mounted along the muscle fiber direction in
TM
Journal of Strength and Conditioning Research
Copyright ª 2018 National Strength and Conditioning Association
the
TM
Journal of Strength and Conditioning Research | www.nsca.com
a bipolar configuration. Most of the electrodes were
mounted according to the SENIAM recommendations (7).
For PM and LD (not listed in the SENIAM recommendations), the electrodes were mounted 4 fingerbreadths below
the clavicle, medial to the anterior axillary border, and 3
fingerbreadths distal to and along the posterior axillary fold,
parallel to the lateral border of scapula (14), respectively. A
reference electrode was mounted on the ankle, at the ipsilateral lateral malleolus. The impedance level of the electrodes was checked before proceeding. Electrodes were
replaced in case of an electrode-skin impedance .10 kV.
Furthermore, an interelectro distance of 20 mm was chosen
in line with SENIAM recommendations to ensure SEMG
selectivity and thereby reduce cross talk (7).
After the placement of the electrodes, participants performed a progressive warm-up regimen by lifting increasingly heavier loads in bench press. Bench press was
performed using an ER-Equipment power rack (ER Equipment, Albertslund, Denmark). Subsequent for the 3RM test,
the load was increased by 2.5–10 kg per set of 3 repetitions,
until 3RM was found. On average, 4 sets were required for
the determination of the 3RM. A 4-minute rest was applied
between all sets to avoid development of muscle fatigue (10).
After successful completion of the 3RM test, the load was
decreased to 75% of the 3RM load and a single set of 3
repetitions were performed. For this (and the 3RM test),
participants were instructed to perform the eccentric phase
in approx. 1 second and the concentric phase as fast as
possible. The EMG data obtained during this set at 75% of
the 3RM were used for normalization purpose (11).
The 12 sets of 8 repetitions at 60% of the 3RM load
included 4 different ways (I–IV, see below) of performing
bench press. All sets were separated by 4-minute rest periods. To avoid the confounding use of previously instructed
focus strategies, the sets described under I and II were always
performed first (13,15,20,24). Thereafter, the sets described
under III and IV were performed in a counterbalanced order.
(I) Three sets of 8 repetitions were completed, in which
the participants were carefully instructed to time the
top and bottom position of the barbell to the auditory
input of a metronome set to 1 Hz. This resulted in a 1second eccentric and a 1-second concentric phase.
The objective of these sets was to practice this specific
tempo of execution rigorously, so that it could be replicated during the latter sets without the use of auditory input.
(II) Three sets of 8 repetitions were completed as a baseline measurement with no focus instructions (BASE).
The objective of these sets was to maintain the same
tempo, which had just been practiced.
(III) Three sets of 8 repetitions were completed with an
external focus of attention (EXT). The instructions to
the participants before performing bench press with an
EXT were as follows: “Perform 8 repetitions while
moving the barbell up and down as smooth as possible
and replicating the same tempo as you applied earlier.
While performing the bench press, the focus of attention should be on the movement of the barbell. The
movement of the barbell should be as smooth as possible.”
(IV) Three sets of 8 repetitions were completed with an
internal focus of attention (INT). The instructions to
the participants before performing bench press with
INT were as follows: “Perform 8 repetitions while
moving the barbell up and down as smooth as possible
and replicating the same tempo (1 Hz) as you applied
earlier. While performing the bench press, the focus of
attention should be on the contraction of your pectoral muscle. The concentric contraction and eccentric
contraction of the pectoral muscle should be as
smooth as possible.”
All instructions were provided in detail by the same
researcher for all subjects. Instructions were provided before
each condition (I, II, and III) and repeated before each set.
After each instruction, the subjects were asked to explain in
their own words what they were supposed to do. If they
failed in giving a satisfactory answer, the instructions were
repeated.
During all sets of bench press, a potentiometer (model
KS60; NTT Nordic Transducer, Hadsund, Denmark) was
connected to the middle of the barbell for measurement of
the vertical position. This enabled the identification of the
top and bottom positions of the barbell. To avoid any initial
transition, the first bench press repetition of each set was
removed from the data. This resulted in 21 repetitions per
participant, for each condition of BASE, EXT, and INT.
To evaluate the participants effort to adopt the instructed
focus of attention, a 10-point numerical rating scale (NRS),
ranging from 0 (completely uninvolved, not trying hard at
all) to 10 (extremely involved, trying as hard as possible), was
applied (29). Participants were asked to rate their effort to
adopt the instructed focus of attention immediately after
each set of EXT (III) and INT (IV).
Data Recording and Processing. The EMG signals were
recorded using an EMG amplifier (EMG-USB; LISiN—
OT Bioelectronica, Turin, Italy). Electromyographic signals
were amplified using an individual-specific gain factor
(100–500) and band-pass filtered (10–750 Hz) before being
sampled at 2,048 Hz. Furthermore, a notch filter (fourth
order Butterworth band stop with rejection width of 1 Hz
centered at the first 3 harmonics of the power line frequency
of 50 Hz) was used to remove line interference. Electromyographic data were then segmented into 21 bench press
cycles, using the data obtained from the potentiometer. A
bench press cycle was defined as the period between 2 successive top positions (equivalent to one bench repetition per
2 seconds). The linear envelopes of the EMG signals across
each of the 21 bench press cycles were obtained by low-pass
filtering (zero-lag Butterworth, second order, 4 Hz) of the
VOLUME 00 | NUMBER 00 | MONTH 2018 |
Copyright ª 2018 National Strength and Conditioning Association
3
Focus of Attention During Bench Press
rectified EMG. Each of the EMG envelopes was then interpolated into 100 time points, and the average for each time
point across the 21 repetitions was calculated for each participant. The EMG amplitude at each time point was then
divided by the normalization factor (see description below)
obtained during the set performed at 75% of 3RM. Next, the
mean EMG envelope was calculated in 10 consecutive
epochs for each cycle. As a measure of mean amplitude
across the entire cycle, the mean of the 10 EMG amplitude
values was calculated. As a measure of peak muscle activity
during the cycle, peak EMG amplitude was computed as the
highest EMG amplitude value.
To normalize the recorded EMG data, a task-specific
submaximal dynamic normalization procedure was applied.
This procedure has previously been used in a similar
experimental setup (11). Briefly, the task-specific submaximal dynamic normalization procedure consisted of recording the maximal surface EMG envelope from the
aforementioned muscles during the execution of a submaximal bench press at 75% of 3RM. The obtained value in this
procedure was then used as a normalization factor.
Two analyses were performed to check for the effects of
fatigue in the data set. First, the mean and peak EMG
amplitudes of all muscles obtained in III and IV were
reordered independent of focus instruction, in the chronological sequence in which they were recorded. If fatigue was
present, the latter EMG amplitudes should be higher than
the former. Second, using the same chronological reordering
sequence as described above, the time of execution of the
first and the seventh repetition for all sets in II, III, and IV
was calculated. If fatigue was present, the duration should
increase between the first and the seventh repetition in each
set and between repetitions of different sets. The seventh
repetition was used instead of the eighth because the barbell
was replaced in the bench press rack immediately after the
eighth repetition, making the precise duration of this
repetition difficult to reliably establish.
Statistical Analyses
Normal distribution of all data was evaluated using
a Shapiro-Wilks test, histograms, and QQ-plots. For normally distributed outcomes, a 1-way repeated-measures
Figure 1. Surface electromyographic (EMG) normalized envelopes from muscles of the upper body obtained during bench press with no instruction (BASE),
external focus (EXT), and internal focus (INT). The EMG amplitudes were normalized with respect to the normalization factor obtained during a submaximal
dynamic normalization procedure. The black bold line represents the mean profile for each group, whereas the thin lines represent the individual profiles. The
cycle of the bench press is characterized as follows: 0% = start position with barbell above chest on straight arms. Fifty percent = bottom position, with barbell
touching chest. Zero percent = start position. Hundred percent = end position, identical to start position. PM = pectoralis major, DA = anterior deltoideus, BB =
biceps brachii, TBL = triceps brachii lateral head, TBM = triceps brachii medial head, LD = latissimus dorsi, ES = erector spinae.
4
the
TM
Journal of Strength and Conditioning Research
Copyright ª 2018 National Strength and Conditioning Association
the
TM
Journal of Strength and Conditioning Research | www.nsca.com
analysis of variance (RM-ANOVA) with a Bonferroni post
hoc test was applied to test for an effect of type of
instructed focus of attention (i.e., BASE, EXT, and INT)
on EMG amplitude. If the assumption of sphericity was
violated, a Greenhouse-Geisser correction was applied.
For the outcomes that were not normally distributed,
a nonparametric statistical approach was applied. A
Friedman test was used to test for an effect of type of
instructed focus of attention (i.e., BASE, EXT, and INT)
on EMG amplitude. A Wilcoxon signed-rank test was
used as post hoc test. For NRS data, the 3 NRS scores
obtained in EXT and INT, respectively, were averaged for
each participant. A Wilcoxon signed-rank test was then
used to test for differences between focus conditions. The
reordered mean and peak EMG values of all muscles for
the fatigue analysis were compared using a Wilcoxon
signed-rank test. To test for differences in the time of
execution of the first and last repetitions in all sets, a RMANOVA with a Bonferroni post hoc test was applied. A
step-down Holm-Bonferroni adjustment was applied to
all post hoc p values obtained, to retain the familywise
error rate for multiple comparisons (8). The SPSS Version
23.0 (IBM Corp., Armonk, NY, USA) was used for all
statistical analyses. Statistical significance was accepted
at p # 0.05. Results are presented as mean 6 SD.
RESULTS
The peak and mean EMG amplitude of all muscles
obtained in session III (independent of focus instructions)
was not significantly different from the values obtained in
session IV (p , 0.05). Likewise, there was no significant
difference in time of execution of the first and last repetition of all sets performed across all focus types (BASE,
EXT, and INT; p . 0.05).
The NRS score was 8.9 6 0.8 for EXT and 8.7 6 0.9 for
INT. The Wilcoxon signed-rank test showed no significant difference in the NRS score between EXT and INT
(p = 0.537). All scores were on average above 8, which
suggested that participants in general made a considerable
and consistent effort in adopting the instructed focus of
attention during all sets in bench press.
Figure 2. Normalized surface electromyographic (EMG) envelopes from muscles of the lower body obtained during bench press with no instruction (BASE),
external focus (EXT), and internal focus (INT). The EMG amplitudes were normalized with respect to the normalization factor obtained during a submaximal
dynamic normalization procedure. The black bold line represents the mean profile for each group, whereas the thin lines represent the individual profiles. The
cycle of the bench press is characterized as follows: Zero percent = start position with barbell above chest on straight arms. Fifty percent = bottom position, with
barbell touching chest. Zero percent = start position. Hundred percent = end position, identical to start position. RF = rectus femoris, BF = biceps femoris, GML
= gastrocnemius lateral head, SOL = soleus, VL = vastus lateralis, and VM = vastus medialis.
VOLUME 00 | NUMBER 00 | MONTH 2018 |
Copyright ª 2018 National Strength and Conditioning Association
5
Focus of Attention During Bench Press
Mean Electromyographic Amplitude
Individual EMG envelopes and the mean envelope across
all participants, for all upper-body muscles and lowerbody muscles, are illustrated in Figures 1 and 2, respectively. A bar plot of the mean normalized EMG amplitude
is depicted in Figure 3. The 1-way RM-ANOVA revealed
a significant effect of instructed focus on the mean normalized EMG amplitude values of PM (p = 0.007),
whereas the Friedman test revealed a significant effect
for DA (p # 0.001), BB (p = 0.002), TBL (p = 0.035),
TBM (p # 0.001), LD (p # 0.001), and ES (p = 0.010).
Post hoc analyses showed that, for PM, the mean normalized EMG amplitude values were significantly higher for
EXT (44.0 6 16.4%) than for BASE (40.7 6 15.6%) (p =
0.003). Besides, INT (43.9 6 16.6%) was not significantly
different from BASE (p = 0.068) for PM. With regard to
DA, the mean normalized EMG amplitude values were
significantly higher for EXT (43.0 6 18.4%) and INT
(43.3 6 18.5%) as compared to BASE (37.6 6 16.6%)
(p # 0.001 and p = 0.002, respectively). With regard to
BB, the mean normalized EMG amplitude values were
significantly higher for INT (30.4 6 17.8%) as compared
to BASE (27.7 6 16.0%) (p = 0.006). With regard to TBL,
the post hoc tests did not reach statistical significance.
With regard to TBM, the mean normalized EMG amplitude values were significantly higher for EXT (39.6 6
18.8%) and INT (40.3 6 19.2%) as compared to BASE
(35.1 6 17.0%) (p # 0.001 and p # 0.001, respectively).
With regard to LD, the mean normalized EMG amplitude
values were significantly higher for EXT (40.0 6 16.8%)
and INT (42.9 6 18.4%) as compared to BASE (36.2 6
15.8%) (p # 0.001 and p # 0.001, respectively). Besides,
INT was also significantly higher than EXT (p = 0.028) for
LD. With regard to ES, the mean normalized EMG amplitude values were significantly higher for EXT (24.2 6
14.6%) and INT (26.8 6 16.8%) as compared to BASE
(22.3 6 13.9%) (p = 0.024 and p = 0.024). Besides, INT
was also significantly higher than EXT (p = 0.025) for ES.
No significant effect of instructions was found for the
muscles of the lower-body RF (p = 0.625), BF (p = 0.596),
Figure 3. Bar plot of the normalized EMG amplitude (mean + SD) obtained during bench press with no instruction (BASE), external focus (EXT), and internal
focus (INT). *Significant difference (p # 0.05). PM = pectoralis major, DA = anterior deltoideus, BB = biceps brachii, TBL = triceps brachii lateral head, TBM =
triceps brachii medial head, LD = latissimus dorsi, ES = erector spinae, RF = rectus femoris, BF = biceps femoris, GML = gastrocnemius lateral head, SOL =
soleus, VL = vastus lateralis, and VM = vastus medialis.
6
the
TM
Journal of Strength and Conditioning Research
Copyright ª 2018 National Strength and Conditioning Association
the
TM
Journal of Strength and Conditioning Research | www.nsca.com
GML (p = 0.554), SOL (p = 0.795), VL (p = 0.640), and VM
(p = 0.554).
Peak Electromyographic Amplitude
With regard to the peak normalized EMG amplitude, the 1way RM-ANOVA revealed a significant effect of instructed
focus for PM (p = 0.019), DA (p = 0.018), TBM (p # 0.001),
and LD (p # 0.001). The post hoc analysis showed that, for
PM, the peak normalized EMG amplitude was significantly
higher for EXT (64.8 6 15.6%) as compared to BASE (61.5
6 14.0%) (p = 0.030). With regard to DA, the post hoc tests
did not reach statistical significance. With regard to TBM,
the peak normalized EMG amplitude was significantly higher for EXT (60.1 6 18.3%) and INT (62.7 6 18.5%) as
compared to BASE (54.9 6 17.5%) (p # 0.001 and p #
0.001, respectively). With regard to LD, the peak normalized
EMG amplitude was significantly higher for EXT (55.2 6
17.5%) and INT (57.2 6 19.9%) as compared to BASE
(49.5 6 17.5%) (p # 0.001 and p # 0.001, respectively).
No significant effect of instructions was found for the
following muscles: BB (p = 0.269), TBL (p = 0.098), ES (p =
0.132), RF (p = 0.855), BF (p = 0.315), GML (p = 0.390),
SOL (p = 0.661), VL (p = 0.615), and VM (p = 0.587).
DISCUSSION
In this study, EMG data were recorded from 13 muscles
during bench press performed at 60% of 3RM, with 3
different foci of attention (BASE, EXT, and INT). We
showed that EXT and INT resulted in significantly increased
mean and peak EMG amplitudes of 6 upper-body muscles as
compared with BASE. These results were mostly in contrast
to our initial hypothesis and may suggest that, for resistancetrained participants at least, adopting either an external or an
internal focus of attention reduces the movement efficacy
during submaximal bench press.
Previous studies in various force production tasks have
shown that external focus of attention led to decreased
muscular activity and increased performance compared with
an internal focus of attention or a control condition of no
instruction (16,20,21,28). For example, an external focus of
attention decreased EMG activity of the antagonist muscle
and increased performance in an isometric plantar flexion of
the ankle (16). Similarly, compared with an internal focus of
attention, an external focus of attention has been shown to
increase force production and reduce muscular activity during an isokinetic biceps curl task (17) and to reduce muscular
activity during a dynamic biceps curl task with a barbell
using both a controlled and an uncontrolled tempo of execution (28). In a test to determine the maximal amount of
repetitions that could be performed in the Smith machine
bench press, during free-weight bench press, and during free
weight squat, an external focus of attention improved performance in all 3 tasks compared with an internal focus of
attention (20). In a more recent study, an external focus of
attention significantly reduced muscular activity during an
isokinetic concentric leg extension exercise compared with
an internal focus of attention (21), whereas force output
remained the same between the 2 focus conditions. Most
research in this area has demonstrated an external focus of
attention to be superior to either an internal focus of attention or a control condition of no instructed focus in terms of
performance and movement efficacy (18,40).
In the aforementioned studies (16,17,20,21,28), conclusions have been drawn on the effects of different foci of
attention on performance by measuring force production.
This study, on the other hand, compared EMG amplitudes
recorded during bench press using the same weight in all
sets, but with different foci of attention. While acknowledging that the focal point of this study and those of
(16,17,20,21,28) was not identical, the results of this study
do not support any benefit on applying an external focus
of attention during bench press performed at 60% of 3RM.
This discrepancy may be explained by the fact that the multijoint free-weight exercise used in this study is more challenging than performing a unilateral isokinetic biceps curl in
a dynamometer or an isometric plantar flexion of the ankle.
Thus, multiple degrees of freedom must be efficiently controlled to successfully complete the bench press. Furthermore, the participants in this study had a minimum of 2
years of strength training experience and a relatively high
performance level (3RM = 109.4 6 25.9 kg), whereas most
of other studies have recruited participants with either very
little or no previous experience in the task that they were
being tested on (34). In resistance-trained individuals, such
as those recruited for this study, considerable adaptations are
bound to have occurred in the motor control of the neuromuscular system through years of training, for the participants to attain such an efficient solution for controlling the
multiple degrees of freedom (11). For resistance-trained individuals with extensive muscle strength and experience, it is
therefore plausible that any focus of attention, which is
markedly different from what they are used to, will act as
a perturbation. This may in turn decrease the movement
efficacy as reflected in this study by the significantly higher
EMG amplitude of the upper-body muscles, when either an
external or internal focus of attention was applied (Figure 3).
An alternative explanation for the results is that the complexity of the instructions given in EXT and INT was higher
compared with BASE. More specifically, the subjects had to
focus on both the tempo of execution combined with either
an external or internal cue in EXT and INT, while only
focusing on the tempo of execution in BASE. The decreased
movement efficacy in EXT and INT compared with BASE
could then be explained by the complexity of the instructions given resulting in an increased mental load affecting the
EMG amplitude (9). However, the idea that highly skilled
athletes may not benefit from an external focus of attention
is supported by a previous study (34) in which balance measures were investigated in world-class acrobats. While standing on an inflated rubber disk, the acrobats showed no
VOLUME 00 | NUMBER 00 | MONTH 2018 |
Copyright ª 2018 National Strength and Conditioning Association
7
Focus of Attention During Bench Press
differences in postural sway among the 3 focus of attention
conditions (control condition, external focus of attention,
and internal focus of attention), but automaticity (as measured by the mean power frequency of their center of pressure movements) was perturbed by the external and internal
focus of attention instructions. Similar results were found in
performance of expert dart players, where performance deteriorated when an external or internal focus of attention was
applied compared with baseline measurements consisting of
dart throws with no instructions on focus of attention (25).
And finally, the level of experience has also been shown to
play a role in sprinting performance, as collegiate soccer
players benefit from an external focus of attention during
a 10-m sprint, while highly experienced sprinters do not (31).
The constrained-action hypothesis has been proposed as
an explanation for the superiority of an external focus of
attention (22,35,36). Thus, it has been inferred that an internal focus of attention interferes with automatic control processes, whereas an external focus is believed to promote
a more automatic and reflexive type of control, resulting in
improved motor performance (22,35,36). With regard to our
results, it seems, at least for the participants in this study, that
when participants already have developed a focus of attention through rigorous practice, this particular focus of attention promotes a more automatic and reflexive type of
control, resulting in optimal movement efficacy, whereas
any new type of focus of attention, whether it be external
or internal, seems to interfere with automatic control processes. A decreased EMG amplitude has, thus, previously
been used to advocate for a more efficient motor strategy,
when the external force produced was kept constant
between focus conditions (17,28). Continuing this line of
argumentation, our results clearly indicate that, for
resistance-trained participants, an acute change in the focus
of attention induced by instructions does not promote more
efficient motor strategies compared with a control focus of
attention (BASE). To the best of our knowledge, only one
other study has provided similar results in which the control
condition yielded better outcomes than either an instructed
external or internal focus of attention (34).
There was no significant effect of different foci of attention
on muscle activity of the lower body. When creating a stable
setup in the bench press exercise, plantar flexors of the ankle
joint and knee extensor muscles are activated to push the
lower body in the vertical direction. This increases stability
and stiffness of the whole body, thereby creating a rigid base
from which maximal strength of the upper body can be
expressed. The isometric contractions produced by these
muscles during bench press did not seem to be affected by
different attentional foci. This may be because this is an
essential part of performing the bench press for the
resistance-trained participants recruited for this study (11),
or because the activity of the lower-body muscles remain
unaffected, when the focus of attention is directed at or
toward part of the upper body. These results are in contrast
8
the
to previous studies, which suggest the effects of focus of
attention to be general in nature, and to be able to “spread”
to muscle groups that are not in the performers focus of
attention (41).
There are some limitations to this study. First, the lifting
intensity was submaximal (60% of 3RM). Thus, it is
unknown whether or not the results would have been the
same, had an intensity closer to a 100% of 1RM been used.
This was, however, a very deliberate choice to avoid muscle
fatigue during data recording as fatigue causes the EMG
amplitude to increase (4). Second, the tempo of execution
was rehearsed before data collection using a metronome to
control for the effects of different velocities on the recorded
EMG data. As this tempo of execution may have been different from the preferred tempo of execution, this could
potentially affect the results. Furthermore, as the objective
in the baseline measurement (II) was to maintain the same
tempo that had been rehearsed, focusing on the tempo of
execution could be interpreted as a sort of an external focus.
In that case, the results of this study demonstrate differences
in EMG amplitude between an external focus on the movement of the barbell, an internal focus on the pectoral muscle
and an external focus on the tempo of execution. Third, in
this study, the external focus of attention instructions was
focused on the movement of the barbell, and the internal
focus of attention instructions were focused on the contraction of the pectoral muscle. As the formulation of the instructions can have profound effect on the outcome (40), it is
possible that other external and internal focus instructions,
for instance, focusing on pushing against the barbell or focusing on the movement of the arms, respectively, could have
yielded different results. Finally, given this study design, the
baseline trials always preceded the external and internal
focus of attention trials. As mentioned in the methods, the
applied study design did not randomize the BASE sets to
avoid the confounding use of previously instructed focus
strategies (20). It is unlikely that accumulated muscle fatigue
occurred given the low intensity of lifting (60% of 3RM)
coupled with the 4-minute interset rest intervals and the
training status of the participants. Subsequent analyses suggested that muscle fatigue was not present in the data set, as
the peak and mean EMG amplitude of all muscles obtained
in session III (independent of focus instructions), was not
significantly different from that obtained during session IV.
Furthermore, comparing the time of execution of the first
repetition and the last repetition of all sets performed across
all focus types (BASE, EXT, and INT) showed no significant
differences. These underlined a lack of carryover effect over
the sessions of bench press and the absence of fatigue development. The authors acknowledge that the procedure of
always recording the baseline trials before the external and
internal focus of attention trials, in theory, could generate
a statistical order effect. However, this procedure has
previously been used in several studies, with the aim of
avoiding the confounding use of previously instructed focus
TM
Journal of Strength and Conditioning Research
Copyright ª 2018 National Strength and Conditioning Association
the
TM
Journal of Strength and Conditioning Research | www.nsca.com
strategies (13,15,20,24), which, in the opinion of the authors,
would have been detrimental to the results of this study.
In conclusion, this study demonstrated that adopting
either an internal or an external focus of attention during
bench press significantly increased the mean and peak EMG
amplitude in PM, DA, BB, TBM, LD, and ES muscles of the
upper body among resistance-trained participants, when
compared with a control condition of no instruction. These
results suggest that movement efficacy during bench press
can be deteriorated, when adding a focus of attention that is
different from the focus of attention used during a control
condition of no instructed focus (BASE).
PRACTICAL APPLICATIONS
This study provides valuable information on the effects of
instructed focus of attention during submaximal bench press
in resistance-trained participants. Our results show that, for
participants with considerable strength training experience,
adopting either an external or an internal focus of attention
reduces the movement efficacy during submaximal bench
press, as measured by EMG amplitude. It is important to
note that this study design does not allow conclusions to be
drawn on the long-term training effects of incorporating
either an external or internal focus of attention.
ACKNOWLEDGMENTS
10. Kristiansen, M, Samani, A, Madeleine, P, and Hansen, EA. Effects of
five weeks of bench press training on muscle synergies—
a randomized controlled study. J Strength Cond Res 30: 1948–1959,
2016.
11. Kristiansen, M, Madeleine, P, Hansen, EA, and Samani, A. Intersubject variability of muscle synergies during bench press in power
lifters and untrained individuals. Scand J Med Sci Sports 25: 89–97,
2015.
12. Kristiansen, M, Samani, A, Madeleine, P, and Hansen, EA. Muscle
synergies during bench press are reliable across days. J Electromyogr
Kinesiol 30: 81–88, 2016.
13. Landers, M, Wulf, G, Wallmann, H, and Guadagnoli, M. An external
focus of attention attenuates balance impairment in patients with
Parkinson’s disease who have a fall history. Physiotherapy 91: 152–
158, 2005.
14. Lehman, GJ, MacMillan, B, MacIntyre, I, Chivers, M, and Fluter, M.
Shoulder muscle EMG activity during push up variations on and off
a Swiss ball. Dyn Med 5: 7, 2006.
15. Lohse, KR, Sherwood, DE, and Healy, AF. How changing the focus
of attention affects performance, kinematics, and electromyography
in dart throwing. Hum Mov Sci 29: 542–555, 2010.
16. Lohse, KR, Sherwood, DE, and Healy, AF. Neuromuscular effects of
shifting the focus of attention in a simple force production task. J
Mot Behav 43: 173–184, 2011.
17. Marchant, DC, Greig, M, and Scott, C. Attentional focusing
instructions influence force production and muscular activity during
isokinetic elbow flexions. J Strength Cond Res 23: 2358–2366, 2009.
18. Marchant, DC. Attentional focusing instructions and force
production. Front Psychol 1: 210, 2011.
19. Marchant, DC, Clough, PJ, Crawshaw, M, and Levy, A. Novice
motor skill performance and task experience is influenced by
attentional focusing instructions and instruction preferences. Int J
Sport Exerc Psychol 7: 488–502, 2009.
ER Equipment is thanked for loan of the lifting equipment.
This study was supported by the Danish Rheumatism
Association. The authors have no conflicts of interests to
disclose.
20. Marchant, DC, Greig, M, Bullough, J, and Hitchen, D. Instructions
to adopt an external focus enhance muscular endurance. Res Q Exerc
Sport 82: 466–473, 2011.
REFERENCES
21. Marchant, DC and Greig, M. Attentional focusing instructions
influence quadriceps activity characteristics but not force production
during isokinetic knee extensions. Hum Mov Sci 52: 67–73, 2017.
1. Abdollahipour, R, Wulf, G, Psotta, R, and Palomo Nieto, M.
Performance of gymnastics skill benefits from an external focus of
attention. J Sports Sci 33: 1807–1813, 2015.
22. McNevin, NH, Shea, CH, and Wulf, G. Increasing the distance of an
external focus of attention enhances learning. Psychol Res 67: 22–29,
2003.
2. Al-Abood, SA, Bennett, SJ, Hernandez, FM, Ashford, D, and
Davids, K. Effect of verbal instructions and image size on visual
search strategies in basketball free throw shooting. J Sports Sci 20:
271–278, 2002.
23. Perkins-Ceccato, N, Passmore, SR, and Lee, TD. Effects of focus of
attention depend on golfers’ skill. J Sports Sci 21: 593–600, 2003.
3. Campenella, B, Mattacola, CG, and Kimura, IF. Effect of visual
feedback and verbal encouragement on concentric quadriceps and
hamstrings peak torque of males and females. Isokinetics Exerc Sci 8:
1–6, 2000.
4. De Luca, CJ. The use of surface electromyography in biomechanics.
J Appl Biomech 13: 135–163, 1997.
24. Porter, JM, Nolan, RP, Ostrowski, EJ, and Wulf, G. Directing
attention externally enhances agility performance: A qualitative and
quantitative analysis of the efficacy of using verbal instructions to
focus attention. Front Psychol 1: 216, 2010.
25. Schorer, J, Jaitner, T, Wollny, R, Fath, F, and Baker, J. Influence of
varying focus of attention conditions on dart throwing performance
in experts and novices. Exp Brain Res 217: 287–287–297, 2012.
5. Folland, JP and Williams, AG. The adaptations to strength training.
Sports Med 37: 145–168, 2007.
26. Schücker, L, Hagemann, N, Strauss, B, and VÖlker, K. The effect of
attentional focus on running economy. J Sports Sci 27: 1241–1248,
2009.
6. Freudenheim, AM, Wulf, G, Madureira, F, Pasetto, SC, and Corrêa,
UC. Original Research: An external focus of attention results in
greater swimming speed. Int J Sports Sci Coach 5: 533–542, 2010.
27. Sherwood, DE, Lohse, KR, and Healy, AF. Judging joint angles and
movement outcome: Shifting the focus of attention in dart-throwing.
J Exp Psychol Hum Percept Perform 40: 1903–1914, 2014.
7. Hermens, HJ, Freriks, B, Disselhorst-Klug, C, and Rau, G.
Development of recommendations for SEMG sensors and sensor
placement procedures. J Electromyogr Kinesiol 10: 361–374, 2000.
28. Vance, J, Wulf, G, Töllner, T, McNevin, N, and Mercer, J. EMG
activity as a function of the performer’s focus of attention. J Mot
Behav 36: 450–459, 2004.
8. Holm, S. A simple sequentially rejective multiple test procedure.
Scand J Stat 6: 65–70, 1979.
29. Vuillerme, N and Nafati, G. How attentional focus on body sway
affects postural control during quiet standing. Psychol Res 71: 192–
200, 2007.
9. Jensen, BR, Laursen, B, and Sjøgaard, G. Aspects of shoulder
function in relation to exposure demands and fatigue—A mini
review. Clin Biomech 15: S17–S20, 2000.
30. Walter, SD, Eliasziw, M, and Donner, A. Sample size and optimal
designs for reliability studies. Stat Med 17: 101–110, 1998.
VOLUME 00 | NUMBER 00 | MONTH 2018 |
Copyright ª 2018 National Strength and Conditioning Association
9
Focus of Attention During Bench Press
31. Winkelman, NC, Clark, KP, and Ryan, LJ. Experience level
influences the effect of attentional focus on sprint performance. Hum
Mov Sci 52: 84–95, 2017.
37. Wulf, G, McConnel, N, Grtner, M, and Schwarz, A. Enhancing the
learning of sport skills through external-focus feedback. J Mot Behav
34: 171–182, 2002.
32. Wulf, G, Lauterbach, B, and Toole, T. The learning advantages of an
external focus of attention in golf. Res Q Exerc Sport 70: 120–126,
1999.
38. Wulf, G, Zachry, T, Granados, C, and Dufek, J. Increases in jumpand-reach height through an external focus of attention. Int J Sports
Sci Coach 2: 275–284, 2007.
33. Wulf, G and Su, J. An external focus of attention enhances golf shot
accuracy in beginners and experts. Res Q Exerc Sport 78: 384–389,
2007.
39. Wulf, G, Dufek, JS, Lozano, L, and Pettigrew, C. Increased jump
height and reduced EMG activity with an external focus. Hum Mov
Sci 29: 440–448, 2010.
34. Wulf, G. Attentional focus effects in balance acrobats. Res Q Exerc
Sport 79: 319–325, 2008.
40. Wulf, G. Attentional focus and motor learning: A review of 15 years.
Int Rev Sport Exerc Psychol 6: 77–77–104, 2013.
35. Wulf, G, McNevin, N, and Shea, CH. The automaticity of complex
motor skill learning as a function of attentional focus. Q J Exp
Psychol A 54: 1143–1154, 2001.
41. Zachry, T, Wulf, G, Mercer, J, and Bezodis, N. Increased movement
accuracy and reduced EMG activity as the result of adopting an
external focus of attention. Brain Res Bull 67: 304–309, 2005.
36. Wulf, G and Prinz, W. Directing attention to movement effects
enhances learning: A review. Psychon Bull Rev 8: 648–660, 2001.
42. Zarghami, M. External focus of attention enhances discus throwing
performance. Kinesiology 44: 47, 2012.
10
the
TM
Journal of Strength and Conditioning Research
Copyright ª 2018 National Strength and Conditioning Association