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Differential effects of attentional focus strategies during long-term resistance training

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Abstract

The purpose of this study was to investigate the effects of using an internal versus external focus of attention during resistance training on muscular adaptations. Thirty untrained college-aged men were randomly assigned to an internal focus group (INTERNAL) that focused on contracting the target muscle during training (n = 15) or an external focus group (EXTERNAL) that focused on the outcome of the lift (n = 15). Training for both routines consisted of 3 weekly sessions performed on non-consecutive days for 8 weeks. Subjects performed 4 sets of 8–12 repetitions per exercise. Changes in strength were assessed by six repetition maximum in the biceps curl and isometric maximal voluntary contraction in knee extension and elbow flexion. Changes in muscle thickness for the elbow flexors and quadriceps were assessed by ultrasound. Results show significantly greater increases in elbow flexor thickness in INTERNAL versus EXTERNAL (12.4% vs. 6.9%, respectively); similar changes were noted in quadriceps thickness. Isometric elbow flexion strength was greater for INTERNAL while isometric knee extension strength was greater for EXTERNAL, although neither reached statistical significance. The findings lend support to the use of a mind–muscle connection to enhance muscle hypertrophy.
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European Journal of Sport Science
ISSN: 1746-1391 (Print) 1536-7290 (Online) Journal homepage: http://www.tandfonline.com/loi/tejs20
Differential effects of attentional focus strategies
during long-term resistance training
Brad Jon Schoenfeld, Andrew Vigotsky, Bret Contreras, Sheona Golden,
Andrew Alto, Rachel Larson, Nick Winkelman & Antonio Paoli
To cite this article: Brad Jon Schoenfeld, Andrew Vigotsky, Bret Contreras, Sheona Golden,
Andrew Alto, Rachel Larson, Nick Winkelman & Antonio Paoli (2018): Differential effects of
attentional focus strategies during long-term resistance training, European Journal of Sport
Science, DOI: 10.1080/17461391.2018.1447020
To link to this article: https://doi.org/10.1080/17461391.2018.1447020
Published online: 13 Mar 2018.
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ORIGINAL ARTICLE
Differential effects of attentional focus strategies during long-term
resistance training
BRAD JON SCHOENFELD
1
, ANDREW VIGOTSKY
2
, BRET CONTRERAS
3
,
SHEONA GOLDEN
1
, ANDREW ALTO
1
, RACHEL LARSON
4
, NICK WINKELMAN
5
,&
ANTONIO PAOLI
6
1
Department of Health Sciences, CUNY Lehman College, Bronx, NY, USA;
2
Department of Biomedical Engineering,
Northwestern University, Evanston, IL, USA;
3
Sport Performance Research Institute, AUT University, Auckland, New
Zealand;
4
Department of Exercise Science & Health Promotion, Arizona State University, Phoenix, AZ, USA;
5
Irish Rugby
Football Union, Dublin, Ireland &
6
Department of Biomedical Sciences, University of Padova, Padova, Italy
Abstract
The purpose of this study was to investigate the effects of using an internal versus external focus of attention during resistance
training on muscular adaptations. Thirty untrained college-aged men were randomly assigned to an internal focus group
(INTERNAL) that focused on contracting the target muscle during training (n= 15) or an external focus group
(EXTERNAL) that focused on the outcome of the lift (n= 15). Training for both routines consisted of 3 weekly sessions
performed on non-consecutive days for 8 weeks. Subjects performed 4 sets of 812 repetitions per exercise. Changes in
strength were assessed by six repetition maximum in the biceps curl and isometric maximal voluntary contraction in knee
extension and elbow flexion. Changes in muscle thickness for the elbow flexors and quadriceps were assessed by
ultrasound. Results show significantly greater increases in elbow flexor thickness in INTERNAL versus EXTERNAL
(12.4% vs. 6.9%, respectively); similar changes were noted in quadriceps thickness. Isometric elbow flexion strength was
greater for INTERNAL while isometric knee extension strength was greater for EXTERNAL, although neither
reached statistical significance. The findings lend support to the use of a mindmuscle connection to enhance muscle
hypertrophy.
Keywords: Mind-muscle connection,cueing,muscle hypertrophy
Highlights
.An internal focus enhances hypertrophy of the elbow flexors during single joint elbow flexion, conceivably by increasing
activation of the musculature.
.Attentional focus did not affect hypertrophy of the quadriceps during single joint knee extension; this may be due to a
reduced ability for untrained individuals to develop a mind-muscle connection with the lower body musculature.
.It is not clear how adopting an internal versus external focus during resistance training over time affects maximal isometric
strength when testing is carried out under neutral attentional focus conditions.
Introduction
Attentional focus is a well-established concept of
motor learning, and its use has potentially important
implications for promoting exercise-induced muscu-
lar adaptations (Schoenfeld & Contreras, 2016).
Attentional focus can be operationally defined as
what an individual thinks about when performing a
given activity (Schoenfeld & Contreras, 2016). The
topic can be sub-classified into two primary focus-
related strategies: internal focus and external focus.
An internal attentional focus involves thinking
about bodily movements when performing an
activity; for example, directing an individual to
squeezetheir muscle. Conversely, an external
attentional focus involves visualizing the outcome
during the performance; for example, directing an
individual to move the weight.
© 2018 European College of Sport Science
Correspondence: Brad Jon Schoenfeld, Department of Health Sciences, CUNY Lehman College, Bronx, NY, USA. E-mail: brad@
workout911.com
European Journal of Sport Science, 2018
https://doi.org/10.1080/17461391.2018.1447020
The body of the literature appears to indicate that
an external focus of attention optimizes the execution
of performance-oriented tasks. A recent review by
Wulf (2013) concluded that an external focus
showed better improvements in motor learning com-
pared to an internal focus in more than 90% of pub-
lished studies on the topic. Superior outcomes were
observed across an array of physical activities in a
variety of different populations, providing strong
support for the use of an external focus for enhancing
performance-related measures.
While a myriad of data on attentional focus exists
for performance-oriented tasks, research into the
use of attentional focus during resistance training
(RT) is in its infancy. Acutely, the external focus is
beneficial for force production, while internal focus
increases agonist and antagonist surface electromyo-
graphy (sEMG) amplitudes (Marchant, Greig, &
Scott, 2009). Although the more economical move-
ment patterns observed during external focus con-
ditions appear to enhance skill acquisition, they may
be suboptimal for hypertrophic adaptations. Indeed,
electromyographic (EMG) studies report greater
EMG amplitudes of the target musculature during
resistance exercise with the use of an internal focus
(Snyder & Fry, 2012; Snyder & Leech, 2009).
Thus, it has been speculated that an internal focus,
referred to as a mind-muscle connectionin body-
building circles, should be adopted when the goal is
to maximize muscle development (Schoenfeld &
Contreras, 2016). However, drawing inferences con-
cerning adaptation from previous studies should not
be met without scrutiny. First, previous acute
studies that employ isoinertial loading do not
control for relative loading; effort differed between
conditions because the same absolute external load
was used, while one cue produces more economi-
calmovement than another. This means partici-
pants may have been utilizing a different percentage
of maximum for each condition, which is supported
by isokinetic data (Marchant et al., 2009). Second,
drawing inferences from acute measures, such as
sEMG, has recently been a topic of criticism, and a
call has been made for more longitudinal research
to draw more definitive conclusions (Halperin, Vig-
otsky, Foster, & Pyne, 2017).
Currently, there is a paucity of data investigating
the effects of attentional focus during RT on long-
term changes in strength. Moreover, to the authors
knowledge, no study to date has compared RT-
induced hypertrophic outcomes when employing
different attentional focus strategies, as is needed
for training recommendations. Thus, the purpose of
this study was to investigate the effects of using an
internal versus external focus during RT on muscular
adaptations. We hypothesized that the internal focus
would lead to greater increases in muscle hypertrophy
while the external focus would result in greater
strength gains.
Materials and methods
Subjects
Subjects were 30 male volunteers (age = 21.7 ± 3.7
years; height = 176.3 ± 9.1 cm; mass = 78.2 ±
18.4 kg)recruited from a university population. Sub-
jects were between the ages of 1835, had no existing
cardiorespiratory or musculoskeletal disorders,
claimed to be free from consumption of anabolic
steroids or any other legal or illegal agents known to
increase muscle size currently and for the previous
year, and had not performed any regimented RT
for at least the past year. Table I provides anthropo-
metric data for each group.
Participants were pair-matched according to base-
line muscle thickness (MT) (a composite of values of
the elbow flexors and quadriceps) and then randomly
assigned to one of two experimental groups using
online software (randomizer.org): an internal focus
group (INTERNAL) that focused on contracting
the target muscle during training (n= 15) or an exter-
nal focus group (EXTERNAL) that focused on the
outcome of the lift during training (n= 15). Approval
for the study was obtained from the college Insti-
tutional Review Board. Informed consent was
obtained from all participants prior to beginning the
study.
Experimental design
The investigation was carried out over a period of 10
weeks, with 8 weeks dedicated to the RT programme
and 2 weeks allocated for testing. Pre-study testing
was carried out in week 1 and post-study testing
was carried out in week 10. A supervised progressive
RT was performed between weeks 29.
RT procedures
The RT protocol consisted of two exercises: Standing
barbell curl and machine leg extension. These exer-
cises were chosen because it is easier to direct focus
internally during the performance of single-joint move-
ments, therefore helping to preserve internal validity.
Subjects were instructed to refrain from performing
any additional resistance-type or high-intensity
anaerobic training for the duration of the study.
Training for both conditions consisted of 3 weekly
sessions performed on non-consecutive days for 8
weeks. All routines were directly supervised by the
2B.J. Schoenfeld et al.
research team, which included a National Strength
and Conditioning Association Certified Strength and
Conditioning Specialist and certified personal trainers,
to ensure proper performance of the respective rou-
tines. Subjects performed 4 sets of 812 repetitions
per exercise. The supervising research staff member
provided relevant cues to subjects on each repetition
to reinforce the given focus of attention. For
INTERNAL, subjects were cued to squeeze the
muscle!on each repetition; for EXTERNAL, sub-
jects were cued to get the weight up!on each rep-
etition. All sets were carried out to the point of
momentary concentric muscular failure, operationally
defined as the inability to perform another concentric
repetition while maintaining proper form. Cadence of
the concentric portion of repetitions was carried out in
a fashion that allowed subjects to best achieve the given
attentional focus; eccentric actions were performed at
a2 second tempo to ensure controlled lowering of
weights. Subjects were afforded 2 min rest between
sets. The loads were adjusted for each exercise as
needed on successive sets to ensure that subjects
achieved failure in the target repetition range.
Attempts were made to progressively increase the
loads lifted each week within the confines of maintain-
ing the target repetition range. Prior to training, sub-
jects underwent 10-repetition maximum (RM)
testing to determine individual initial training loads
for each exercise. The RM testing was consistent
with recognized guidelines as established by the
National Strength and Conditioning Association
(Baechle & Earle, 2008).
Dietary adherence
To avoid potential dietary confounding of results,
subjects were advised to maintain their customary
nutritional regimen and avoid taking any sup-
plements other than that provided in the course of
the study. Dietary adherence was assessed by self-
reported 5-day food records using MyFitnessPal.-
com (http://www.myfitnesspal.com), which were col-
lected twice during the study: 1 week before the first
training session (i.e. baseline) and during the final
week of the training protocol. Subjects were
instructed on how to properly record all food items
and their respective portion sizes consumed for the
designated period of interest. Each item of food
was individually entered into the programme, and
the programme provided relevant information as to
total energy consumption, as well as the amount of
energy derived from proteins, fats, and carbo-
hydrates for each time period analysed. To help
ensure that protein needs were met for anabolism,
subjects were supplied with a supplement on training
days containing 25 g protein and 1 g carbohydrate
(Iso100 Hydrolyzed Whey Protein Isolate, Dymatize
Nutrition, Dallas, TX) immediately following the
RT session (Aragon & Schoenfeld, 2013).
Measurements
Body composition and anthropometry. Participants
height was measured using a Detecto Physicians
Scale (Cardinal Scale Manufacturing Company,
Webb City, MO). Assessment of fat mass, fat-free
mass, and skeletal muscle mass was carried out
using an InBody 770 multi-frequency bioelectrical
impedance device (Biospace Co. Ltd., Seoul,
Korea) according to the manufacturers instructions.
Subjects were told to refrain from eating for 12 h
prior to testing, eliminate alcohol consumption for
24 h, abstain from strenuous exercise for 24 h, and
void immediately before the test. Prior to each
measurement, the subjects palms and soles were
cleaned with an electrolyte tissue. Subjects then
stood on the InBody 770, placing the soles of their
feet on the electrodes. The instrument derived the
subjects body mass, and their age and sex subject
were manually entered into the display by the
researcher. Subjects then grasped the handles of the
unit ensuring that the palm and fingers of each hand
made direct contact with the electrodes. Arms were
fully extended and abducted approximately 20°.
Analysis of body composition was determined by the
unit with subjects remaining as motionless as possible.
Muscle thickness. Ultrasound imaging was used to
obtain measurements of MT. A trained technician
performed all testing using a B-mode ultrasound
imaging unit (ECO3, Chison Medical Imaging,
Ltd, Jiang Su Province, China). The technician
applied a water-soluble transmission gel (Aquasonic
100 Ultrasound Transmission gel, Parker Labora-
tories Inc., Fairfield, NJ) to each measurement site,
and a 5 MHz ultrasound probe was placed parallel
Table I. Participant demographics.
nAge (years) Stature (cm) Mass (kg)
INTERNAL 14 21.7 ± 3.7 175.8 ± 9.3 75.9 ± 20.1
EXTERNAL 13 21.8 ± 3.1 176.8 ± 9.1 81.0 ± 16.6
Combined 27 21.5 ± 3.3 176.3 ± 9.1 78.2 ± 18.4
Differential effects of attentional focus strategies during long-term resistance training 3
to the tissue interface without depressing the skin.
When the quality of the image was deemed to be sat-
isfactory, the technician saved the image to a hard
drive and obtained MT dimensions by measuring
the distance from the subcutaneous adipose tissue-
muscle interface to the muscle-bone interface, as
described previously (Abe, DeHoyos, Pollock, &
Garzarella, 2000). Measurements were taken on the
right side of the body at three sites: (1) elbow
flexors, (2) mid-thigh (a composite of the rectus
femoris and vastus intermedius), and (3) lateral
thigh (a composite of the vastus lateralis and vastus
intermedius). For the anterior upper arm, measure-
ments were taken 60% distal between the lateral epi-
condyle of the humerus and the acromion process of
the scapula; for the mid- and lateral thigh, measure-
ments were taken 50% between the lateral condyle
of the femur and greater trochanter for the quadriceps
femoris. In an effort to ensure that swelling in the
muscles from training did not obscure results,
images were obtained 4872 h before commence-
ment of the study, as well as after the final training
session. This is consistent with research showing
that acute increases in MT return to baseline within
48 h following a RT session (Ogasawara, Thiebaud,
Loenneke, Loftin, & Abe, 2012). To further ensure
the accuracy of measurements, three images were
obtained for each site and then averaged to obtain a
final value.
Isometric muscle strength. Strength assessments were
carried out using isometric dynamometry testing
(Biodex System 4; Biodex Medical Systems, Inc.
Shirley, NY, USA). After familiarization with the
dynamometer and protocol, subjects were seated in
the chair and performed isometric actions of the knee
extensors and elbow flexors. All isometric testing was
carried out on the subjectsdominant limbs.
During knee extension trials, subjects sat with their
backs flush against the seat back pad and maintained
hip joint angles of 85° with the centre of their lateral
femoral condyles aligned with the axis of rotation of
the dynamometer. The dynamometer arm length
was adjusted for each subject to allow the shin pad
to be secured with straps proximal to the medial mal-
leoli. Subjects were instructed to hold onto handles
for stability and were also strapped in across the ipsi-
lateral thigh, hips, and torso to help prevent
extraneous movement during performance. Testing
was carried out at a knee joint angle of 70° (Knapik,
Wright, Mawdsley, & Braun, 1983).
During elbow flexion trials, subjects were seated
with the dominant arm flexed to 30° and supported
in the sagittal plane to eliminate the effects of
gravity. The dominant forearm was strapped into
the upper extremity attachment, and the wrist was
placed in a supinated position. The hip and knee
joint angles were maintained at 85° and 90°, respect-
ively. The non-dominant arm was kept pinned to the
left side of the trunk with the forearm on the
abdomen. Subjects were strapped in by crossover
shoulder harnesses and an abdominal belt to help
prevent extraneous movement during performance.
Testing was carried out at an elbow joint angle of
90° (Knapik et al., 1983).
Each maximum voluntary contraction trial lasted
5 s, followed by 30 s rest, for a total of three to four
trials in each position (if a participants net joint
moment continued to increase in the third trial, then
a fourth trial was performed). Participants were verb-
ally encouraged to produce maximal force throughout
each bout. The highest peak net extension moment
from each of the three trials for each maximum volun-
tary contraction position was used for analysis.
Statistical analyses
Data were imported into Jamovi (version 0.7.7.3,
Jamovi team) for statistical analysis. Before carrying
out analyses, equality of variances (homogeneity) was
ensured using Levenes test. Rather than comparing
baseline values statistically, using independent t-tests,
baseline values were used as covariates in analyses of
covariance (ANCOVA), from which the differences
in the magnitude of changes from baseline were com-
pared (de Boer, Waterlander, Kuijper, Steenhuis, &
Twisk, 2015; Vickers & Altman, 2001). No within-
group comparisons from baseline were made (Bland
&Altman,2011,2015). Effect sizes were calculated
using partial eta squared (
h
2
p), which represents the
variance in the model accounted for by the difference
between groups. Because this model is analogous to a
multiple regression or partial correlation (Vickers &
Altman, 2001),
h
2
pcan be interpreted as the square
of a Pearsonsreffect size. As such, the correlation
coefficient interpretations as defined by Hopkins
(Hopkins, 2002) were adapted (squared) for qualitat-
ive interpretation: 0
h
2
p< 0.01 is trivial; 0.01
h
2
p<
0.09 is small; 0.09
h
2
p< 0.25 is moderate;
0.25
h
2
p< 0.49 is large; 0.49
h
2
p<0.81 is very
large; 0.81
h
2
p< 1 is nearly perfect; and
h
2
p=1 is
perfect. Alpha was set apriorito 0.05 for determining
statistical differences between groups.
Results
Of the 30 initial participants, 27 ultimately completed
the study; 2 subjects dropped out for personal reasons
and data for another subject were discarded due to
lack of compliance. Demographics of the included
4B.J. Schoenfeld et al.
participants can be found in Table I. Adherence to
the protocol was good for both INTERNAL and
EXTERNAL groups, with a mean attendance of
93% and 92% of sessions, respectively.
Hypertrophy
Of the three muscles that were measured, only elbow
flexor hypertrophy differed statistically between
groups, with a large effect size favouring the internal
focus condition (F
1,24
=10.64;
h
2
p= 0.307; p=
0.003). Small and trivial effect sizes favouring external
and internal focus were observed for rectus femoris
and vastus lateralis, respectively (F
1,22
=0.68;
h
2
p=
0.030; p= 0.418 and F
1,24
0;
h
2
p0; p= 0.999)
(Table II).
Strength
No statistical differences between groups were found
for any of the strength measures. Small effect sizes
favouring the external focus condition were observed
for isometric knee extension strength (F
1,22
= 1.50;
h
2
p= 0.064; p= 0.234), while a moderate effect size
favouring internal focus was observed for isometric
elbow flexion strength (F
1,22
= 2.82;
h
2
p= 0.114; p=
0.107) (Table II).
Body composition
No statistical differences between groups were found
for any body composition measures. Small and trivial
effect sizes favouring internal focus were noted for
increases in body fat and body weight, respectively
(F
1,24
= 0.618;
h
2
p= 0.025; p= 0.439 and F
1,24
=
0.179;
h
2
p= 0.007; p= 0.676). A small effect size
favouring external focus was noted for increases in
skeletal muscle mass (F
1,24
= 0.288;
h
2
p= 0.012; p=
0.596) (Table II).
Nutritional intake
Despite attempts to counsel subjects on how to prop-
erly log nutritional information, analysis of the food
diaries indicated gross misreporting of data. We
thus were unable to determine if/how changes in
dietary practices may have impacted results.
Discussion
This is the first study to investigate the effects of differ-
ent attentional focus strategies on long-term muscular
adaptations. The study produced several novel and
notable findings. First, an internal focus elicited
superior hypertrophic increases in the elbow flexors
compared to an external focus, but MT in the quadri-
ceps was unaffected by attentional focus strategy. The
differences in changes in elbow flexor size between
INTERNAL and EXTERNAL (12.4% vs. 6.9%,
respectively) translated into a large magnitude of
effect favouring the INTERNAL condition (
h
2
p=
0.307). These findings partially support the common
bodybuilding claim that a mindmuscle connection
enhances muscle growth. Although we did not
attempt to determine mechanistic reasons for discre-
pant findings between the upper and lower limbs, it
can be speculated that subjects found it easier to
focus on the elbow flexor muscles compared to the
thighs a sentiment that was anecdotally expressed
by several participants in the INTERNAL group. Pos-
tulations regarding the mechanisms of this phenom-
enon can be deduced from motor control and
neuroplasticity perspectives. First, neuromuscular
reeducation, at least following tendon transfer,
appears to be more prevalent in upper compared to
lower extremities (Sperry, 1945), suggesting that the
nervous system is better able to alter muscle recruit-
ment patterns of the upper extremity. Second, individ-
uals have greater force control of their elbow flexors
than their knee extensors (Tracy, Mehoudar, &
Ortega, 2007). Indeed, this may relate to why individ-
uals have better control of and coordination with their
upper extremities when compared to their lower extre-
mities (Kauranen & Vanharanta, 1996). Practically
speaking, Gordon and Ferris (Gordon & Ferris,
2004)speculated,
If there are inherent differences in efferent control
between any muscle groups, it would seem likely
that lower limb muscles might be the least accurate.
Humans rarely perform fine motor tasks with their
lower limbs, instead relying on them for gross
power output during locomotion.
Such sentiments do not preclude one from being able
to learn how to effectively utilize an internal focus of
attention. That is, such a phenomenon may be
related to the subjectsuntrained statuses, as individ-
uals with RT experience have been shown to be able
to increase quadriceps EMG amplitude when
directed to focus on the thigh musculature during
knee extension exercise (Marchant & Greig, 2017),
and recent evidence suggests that training status-
dependent control may indeed be muscle-specific
(Calatayud et al., 2016). If true, this would suggest
that trained individuals may be able to enhance quad-
riceps hypertrophy by adopting an internal focus
during lower body RT. Perhaps differences in this
regard would have been borne out with a longer inter-
vention period. Further investigation is needed to test
the validity of this hypothesis.
Differential effects of attentional focus strategies during long-term resistance training 5
Table II. Within- and between-group changes following 8 weeks of strength training with either internal or external focus of attention.
Internal focus External focus Between-group difference
Pre Post Change Pre Post Change Absolute
Effect size
(
h
2
p) Interpretation
p-
value
Elbow flexor thickness
(mm)
39.62 ± 8.07 44.55 ± 8.15 4.93 ± 1.73 40.22 ± 6.53 42.98 ± 6.40 2.77 ± 1.63 2.14 (0.853.43) 0.307 Large 0.003
Rectus femoris
thickness (mm)
55.10 ± 11.57 57.82 ± 10.99 2.72 ± 2.62 55.09 ± 5.90 58.69 ± 5.74 3.60 ± 2.87 0.88 (2.981.22) 0.030 Small 0.418
Vastus lateralis
thickness (mm)
51.81 ± 11.03 55.10 ± 10.80 3.29 ± 2.94 53.82 ± 5.47 56.99 ± 6.09 3.17 ± 3.37 0.00 (2.412.41) 0.000 Trivial 0.999
Isometric elbow flexion
(N m)
57.46 ± 12.96 66.78 ± 17.87 9.32 ± 10.88 62.45 ± 14.56 64.06 ± 11.55 1.61 ± 9.21 6.90 (1.1614.96) 0.114 Moderate 0.107
Isometric knee
extension (N m)
286.99 ± 70.04 316.08 ± 68.82 29.09 ± 55.04 280.99 ± 60.90 338.33 ± 55.38 57.34 ± 52.66 12.80 (33.387.78) 0.064 Small 0.234
Body mass (kg) 76.46 ± 20.60 77.90 ± 20.58 1.44 ± 1.24 80.89 ± 16.60 81.85 ± 15.18 0.95 ± 2.64 0.16 ± (0.580.90) 0.007 Trivial 0.676
Skeletal muscle mass
(kg)
33.66 ± 6.90 34.26 ± 6.78 0.60 ± 0.63 34.55 ± 4.42 35.25 ± 4.33 0.71 ± 0.58 0.06 (0.290.17) 0.012 Small 0.596
Body fat (%) 20.02 ± 10.54 20.36 ± 10.01 0.34 ± 1.46 23.17 ± 8.88 22.82 ± 8.64 0.35 ± 2.01 0.52 (0.771.81) 0.025 Small 0.439
Notes: Pre, post, and change scores are presented as mean ± SD. Between-group, absolute differences are presented as mean (95% CI), with a positive value being in favour of (i.e. a greater or more
positive change score) internal focus, and are corrected for baseline values.
6B.J. Schoenfeld et al.
Attentional focus had markedly different effects
specific to the upper versus lower limbs. With
respect to peak isometric elbow flexion strength,
INTERNAL resulted in a 16.2% increase versus a
2.6% in EXTERNAL, translating into an ES of a
moderate magnitude of effect (
h
2
p= 0.114). These
potential findings are in contrast to acute studies,
wherein an external focus of attention is often
found to result in greater strength performance than
an internal focus of attention (Marchant et al.,
2009); therefore, it is important to note that partici-
pants were not encouraged to utilize specific atten-
tional foci during strength testing. Although
potential mechanisms for these non-statistical differ-
ences in isometric elbow flexion strength were not
studied, two often-proposed mechanisms of strength
gain include peripheral (i.e. muscle hypertrophy and
normalized muscle force) and neural (i.e. neural
drive and excitation) changes (Erskine, Jones, Wil-
liams, Stewart, & Degens, 2010). To explore
muscle size as a potential contributor, an additional
ANCOVA was carried out post hoc, using the
change in elbow flexor thickness as a covariate.
After accounting for the change in elbow flexor thick-
ness, the magnitude of the group effect decreased
substantially, from moderate (
h
2
p= 0.114) to trivial
(
h
2
p= 0.006). In contrast to recent criticisms of the
theory that hypertrophy is related to changes in
strength (Buckner et al., 2016), it appears that, in
this study, differences in hypertrophy accounted for
potential differences in strength between groups.
As opposed to isometric elbow flexion strength,
peak isometric knee extension strength favoured
EXTERNAL versus INTERNAL (20.4% vs.
10.1%, respectively), with the ES indicating a small
magnitude of effect (
h
2
p= 0.064). Although the
observed effect size was small and did not reach the
a priori alpha, in the interest of consistency, another
post hoc ANCOVA was carried out, utilizing both
changes in vastus lateralis and rectus femoris thick-
ness as covariates, but unlike elbow flexion strength,
the change in magnitude of the effect size was minus-
cule (
h
2
p= 0.052).
The study had several notable limitations. First,
the exercise protocol employed a moderate repetition
range and thus the results cannot necessarily be
extrapolated to training with heavier or lighter
loads, especially because the acute effects of internal
cueing are load-dependent (Calatayud et al., 2016).
Second, although we provided explicit instructions
on the focus of attention and supplemented the
instructions with cueing throughout each set, there
is no way to be sure that subjects were actually focus-
ing as directed. It remains possible that some subjects
did not adhere to the proper focus in at least some of
the sets, which in turn may have altered results. That
said, the marked between-group differences in elbow
flexor muscle growth favouring the internal focus
condition provides strong evidence that cueing strat-
egies affect hypertrophic outcomes. Third, MT was
measured only at the mid-portion of the muscles.
Although this region is widely considered to be
indicative of overall muscle growth, some studies
report that hypertrophy manifests in a regional-
specific manner, with greater adaptations seen proxi-
mally and/or distally (Wakahara et al., 2012; Waka-
hara, Fukutani, Kawakami, & Yanai, 2013). Thus,
we cannot discount the prospect that greater proxi-
mal or distal increases in MT occurred in one proto-
col versus the other. Fourth, we were not able to
obtain accurate reporting on dietary practices
throughout the study and thus cannot rule out the
possibility that differences in nutritional intake
unduly confounded results. Finally, the findings are
specific to untrained subjects; future research is
needed to determine the strength- and hypertrophy-
related effects of different attentional focus strategies
on those with previous RT experience.
Conclusion
Our findings indicate that an internal focus of atten-
tion is superior to an external focus of attention
when the goal is to maximize hypertrophy of the
elbow flexors. Attentional focus does not seem to
affect lower extremity hypertrophy, which may be
due to the difficulty for untrained individuals to
establish a mind-muscle connectionin the thigh
musculature during resistive exercise.
Acknowledgements
The authors gratefully acknowledge the contributions
of the research assistants who facilitated data collec-
tion and without whom this project could not have
been carried out: Harold Belen, Jesus Martinez,
Audrey Rivera, Alyssa Dumlao, Ezenwa Emerjuru,
Anthony Masner, Lauren Colenso-Semple, Mario
Rosario, Sussan Soto, Chris Morrison, Anthony
Rambarran, Denise Flores, Teshawna Smith,
Andrea Mene, Ronnie Guerra, Miguel Melendez,
Kyron Slater, Bryan Taveras, Greg Andronico, and
Leila Nasr. We also would like to express our grati-
tude to Dymatize Nutrition for providing the
protein supplements used in this study. The authors
declare no conflicts of interest.
Disclosure statement
No potential conflict of interest was reported by the authors.
Differential effects of attentional focus strategies during long-term resistance training 7
Funding
This study was supported by a grant from Dymatize Nutrition.
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8B.J. Schoenfeld et al.
... Such a greater muscle excitation was suggested to be used for hypertrophic purposes . Indeed, greater hypertrophic response in elbow flexor muscle thickness after an internal vs external focus-based long term training was shown, albeit no between-focus difference in gains in knee extensors thickness was observed (Schoenfeld et al., 2018). As such, an internal focus could be used to vary the training stimuli and possibly enhance the hypertrophic response. ...
... Additionally, it was proposed that the greater muscle excitation elicited by an internal focus could be used to hypertrophic purposes . To date, the only longitudinal study that has compared the long-term effects of internal vs external squat using elbow flexion and knee extension exercises, showed that internal focus resulted in greater elbow flexors thickness, albeit similar gains were observed in quadriceps (Schoenfeld et al., 2018). For hypertrophic purposes, back-squat does not seem to be suitable for promoting any increase in biceps femoris size (Kubo et al., 2019). ...
... Moreover, an internal focus was shown as disadvantageous for the acute maximum force production (Neumann, 2019;Wulf, 2013). However, no difference in strength gains were reported in elbow flexors and knee extensors after a longitudinal internal vs external focus training (Schoenfeld et al., 2018). As such, an external focus is preferable to enhance the force production, while an internal focus might be more useful to elicit a hypertrophic response. ...
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The present study investigated whether or not verbal instruction affects the electromyographic (EMG) amplitude of back-squat prime movers. Fifteen resistance-trained men performed back-squat at 50%1-RM and 80%1-RM and received external (EF) or internal focus (IF) on lower-limb posterior muscles. EMG amplitude of gluteus maximus, biceps femoris, gastrocnemius medialis, vastus lateralis and tibialis anterior was recorded during both concentric and eccentric phase. During the concentric phase, the gluteus maximus and biceps femoris EMG amplitude was greater in IF vs EF at 50% [effect size (ES): 0.63(95%CI 0.09/1.17) and 0.49(0.10/0.78) respectively] and 80% [ES: 1.30(0.29/2.21) and 0.59(0.08/1.10)]. The gastrocnemius medialis EMG amplitude was greater in IF vs EF during the eccentric phase at 50% [ES: 0.73(0.13/1.33)] and at 80% [ES: 0.72(0.10/1.34)]. Concomitantly, vastus lateralis EMG amplitude was lower at 50% [ES: −0.71(−1.38/-0.04)] and 80% [ES: −0.68(−1.33/-0.03)]. During the eccentric phase, the tibialis anterior EMG amplitude was greater in IF vs EF at 50% [ES: 0.90(0.12 to 1.68)] and 80% [ES: 0.74(0.13/1.45)]. Irrespective of the load, in the thigh muscles the internal focus promoted a different motor pattern, increasing the hip extensors and reducing the knee extensor excitation during the concentric phase. Concomitantly, both ankle muscles were more excited during the eccentric phase, possibly to increase the anterior-posterior balance control. The internal focus in back-squat seems to have phase-dependent effects, and it is visible at both moderate and high load.
... Besides acute effects, studies have also conducted training interventions in which participants received either external focus or internal focus cues during each exercise session [15,16]. Some of these studies reported greater gains in muscular strength when adopting an external focus of attention, whereas others found no significant differences between these two motor learning strategies [15,16]. ...
... Besides acute effects, studies have also conducted training interventions in which participants received either external focus or internal focus cues during each exercise session [15,16]. Some of these studies reported greater gains in muscular strength when adopting an external focus of attention, whereas others found no significant differences between these two motor learning strategies [15,16]. Given the inconsistent evidence on the topic, this review aimed to perform a meta-analysis examining: (a) acute effects of adopting an internal focus vs. external focus of attention on muscular strength; and (b) long-term effects of adopting an internal focus vs. external focus of attention during resistance training on gains in muscular strength. ...
... Therefore, 28 full-text papers were read. Nineteen studies were excluded after reading the full texts, and a total of nine studies were included in the review [13][14][15][16][25][26][27][28][29]. There were 555 search results in the secondary searches, and one additional study was included in the review [30]. ...
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This review aimed to perform a meta-analysis examining the following: (a) acute effects of adopting an internal focus vs. external focus of attention on muscular strength; and (b) long-term effects of adopting an internal focus vs. external focus of attention during resistance training on gains in muscular strength. We searched through five databases to find eligible studies. Random-effects meta-analyses of standardized mean differences were conducted to analyze the data. Ten studies were included. In the meta-analysis for the acute effects, there was a significant positive effect of external focus on muscular strength (standardized mean difference: 0.34; 95% confidence interval: 0.22, 0.46). In the meta-analysis for the long-term effects, there was no significant difference between training with an internal focus and external focus on muscular strength gains (standardized mean difference: 0.32; 95% confidence interval: –0.08, 0.73). In the subgroup analysis for lower-body exercises, we found a significant positive effect of training with an external focus on muscular strength gains (standardized mean difference: 0.47; 95% confidence interval: 0.07, 0.87). In summary, our findings indicate an acute increase in muscular strength when utilizing an external focus of attention. When applied over the long-term, using an external focus of attention may also enhance resistance training-induced gains in lower-body muscular strength.
... While an INT focus may decrease certain performance outcomes, attentional focus on a specific muscle group during resistance training may be advantageous to promote skeletal muscle hypertrophy. For instance, utilizing an INT focus has been shown to increase elbow flexor and muscle thickness by ~150% in an untrained male sample over an eight-week resistance training program (26). While an abundance of literature has previously examined sport performance outcomes while using various attentional focus strategies (2,14,32,33,36), less research is available in reference to the application of INT and EXT cues within resistance training (8,20,23,26). ...
... For instance, utilizing an INT focus has been shown to increase elbow flexor and muscle thickness by ~150% in an untrained male sample over an eight-week resistance training program (26). While an abundance of literature has previously examined sport performance outcomes while using various attentional focus strategies (2,14,32,33,36), less research is available in reference to the application of INT and EXT cues within resistance training (8,20,23,26). Furthermore, the studies that have examined resistance training have done so with single or limited outcome variables (e.g., either repetitions-to-failure or motor unit excitation only). ...
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... This finding aligns with the data reported in a recent meta-analysis on the topic [32]. However, the benefits of external focus should not be generalized to muscular hypertrophy, as one study reported that increases in elbow flexor thickness favoured training with an internal focus of attention [33]. Due to the paucity of studies on this topic, more research is still needed before making conclusive recommendations. ...
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Several studies explored the effects of attentional focus on resistance exercise, but their analysed outcomes most commonly involved surface electromyography variables. Therefore, the effects of attentional focus on resistance exercise performance remain unclear. The aim of this review was to perform a meta-analysis examining the acute effects of external focus vs. internal focus vs. control on muscular endurance. Five databases were searched to find relevant studies. The data were pooled in a random-effects meta-analysis. In the analysis for external vs. internal focus of attention , there were seven comparisons with 14 study groups. In the analyses for external focus vs. control and internal focus vs. control, there were six comparisons with 12 study groups. An external focus of attention enhanced muscular endurance when compared with an internal focus (Cohen's d: 0.58; 95% confidence interval (CI): 0.34 and 0.82) and control (Cohen's d: 0.42; 95% CI: 0.08 and 0.76). In the analysis for internal focus vs. control, there was no significant difference between the conditions (Cohen's d:-0.19; 95% CI:-0.45 and 0.07). Generally, these results remained consistent in the subgroup analyses for upper-body vs. lower-body exercises. From a practical perspective, the results presented in this review suggest that individuals should use an external focus of attention for acute enhancement of muscular endurance.
... The effectiveness of internal focus may be the result of the lighter loads providing a large enough muscle hypertrophy stimulus during exercise, while effectively activating the electrical impulse within the muscle. Evidence from a study by Schoenfeld et al. (11) showed greater muscle thickness in elbow flexor and knee extensor musculature when applying an internal focus during resistance training when compared with an external focus. These findings were more compelling for the elbow flexors than knee extensors, suggesting a potentially stronger mind-body connection with the upper body. ...
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• Explore how attentional focused cues affect performance based on exercise modality and intensity. • Identify how and when to apply cues that target internal or external focus to optimize training for clients.
... 1,3,4 These assessments have allowed researchers to discover scenario-specific benefits of both IFA and EFA. Recently, IFA cueing has facilitated increased hypertrophy in weight lifting tasks, 5 yet most chronicled research emphasizes the benefits of EFA with quantifiable measurements expressing movement efficiency and maximum force production in tasks such as balancing, shooting basketball free throws, throwing darts, jumping, weight lifting, and golfing. 2,6,7 The evidence-based benefits of EFA over IFA are attributed to various theories, including the constrained action hypothesis. 1 In this case, attempting to consciously control a movement process that otherwise operates through automatic learned motor pathways constrains the efficiency of the system. ...
... Internal focus, also known as "muscle-mind connection" under the bodybuilding community, has been popular in the recent decade, but limited research has proven this theory. A recent study by Schoenfeld et al. showed that an internal focus of attention was superior to an external focus of attention when the goal was to maximize hypertrophy of the elbow flexors (32). In order to distinguish two different conditions, participants were cued to "squeeze the muscle" for internal focus and cued to "lift weight up" for external focus. ...
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Chapter
Attention focus plays an essential role in promoting motor performance and motor learning. There are two types of attention focus: internal focus and external focus. Internal focus refers to direct attention inside the body while external focus refers to direct attention outside the body. Several studies have reported that external focus positively affects motor performance and motor learning by promoting automatic control. The mechanisms of attention focus have been examined using electromyography (EMG), electroencephalography (EEG), and functional magnetic resonance imaging (fMRI). During rehabilitation, therapists promote patients’ movement acquisition and motor learning. This chapter reviews the application of attention focus in rehabilitation to promote motor performance and motor learning in patients.
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Researchers often analyze randomized trials and other comparative studies by separate analysis of changes from baseline in each parallel group. This may be the only analysis presented or it may be in addition to the direct comparison of allocated groups. We illustrate this by reference to 3 recently published nutritional trials. We show why this method of analysis may be highly misleading and may produce type I errors far greater than the 5% that we expect. We recommend direct comparison of means between groups with the use of baseline as a covariate if required.
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Over the past 15 years, research on focus of attention has consistently demonstrated that an external focus (i.e., on the movement effect) enhances motor performance and learning relative to an internal focus (i.e., on body movements). This article provides a comprehensive review of the extant literature. Findings show that the performance and learning advantages through instructions or feedback inducing an external focus extend across different types of tasks, skill levels, and age groups. Benefits are seen in movement effectiveness (e.g., accuracy, consistency, balance) as well as efficiency (e.g., muscular activity, force production, cardiovascular responses). Methodological issues that have arisen in the literature are discussed. Finally, our current understanding of the underlying mechanisms of the attentional focus effect is outlined, and directions for future research are suggested.
Article
Purpose: Muscle hypertrophy in response to resistance training has been reported to occur nonuniformly along the length of the muscle. The purpose of the present study was to examine whether the regional difference in muscle hypertrophy induced by a training intervention corresponds to the regional difference in muscle activation in the training session. Methods: Twelve young men participated in a training intervention program for the elbow extensors with a multijoint resistance exercise for 12 wk (3 d · wk(-1)). Before and after the intervention, cross-sectional areas of the triceps brachii along its length were measured with magnetic resonance images. A series of transverse relaxation time (T2)-weighted magnetic resonance images was recorded before and immediately after the first session of training intervention. The T2 was calculated for each pixel within the triceps brachii. In the images recorded after the session, the number of pixels with a T2 greater than the threshold (mean + 1 SD of T2 before the session) was expressed as the ratio to the whole number of pixels within the muscle and used as an index of muscle activation (percent activated area). Results: The percent activated area of the triceps brachii in the first session was significantly higher in the middle regions than that in the most proximal region. Similarly, the relative change in cross-sectional area induced by the training intervention was also significantly greater in the middle regions than the most proximal region. Conclusion: The results suggest that nonuniform muscle hypertrophy after training intervention is due to the region-specific muscle activation during the training session.