Biomechanics
Randomized Controlled Trial
2018
Differential effects of attentional focus strategies during long-term resistance training
By Brad J. Schoenfeld, Andrew Vigotsky, Bret Contreras, Sheona Golden, Andrew Alto, Rachel Larson, Nick Winkelman and Antonio Paoli
European Journal of Sport Science, 18(5), pp. 705-712
<h2>Abstract</h2>
<p><strong>Background:</strong> The "<a href="/terms/mind-muscle-connection/" class="term-link" data-slug="mind-muscle-connection" title="mind-muscle connection">mind-muscle connection</a>"—the deliberate direction of attentional focus toward the target muscle during resistance exercise—is widely practiced in bodybuilding but its scientific validity and long-term efficacy for promoting <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="hypertrophy">hypertrophy</a> have been underexplored.</p>
<p><strong>Objective:</strong> To compare the effects of an internal attentional focus (IAF) strategy (focusing on contracting the target muscle) versus an external attentional focus (EAF) strategy (focusing on movement outcome) on muscle hypertrophy and strength over 8 weeks of resistance training.</p>
<p><strong>Methods:</strong> Twenty-nine resistance-trained men were randomized to IAF or EAF conditions for the bicep curl and squat exercises. <a href="/terms/training-volume/" class="term-link" data-slug="training-volume" title="Training volume">Training volume</a> was equated between groups. Bicep brachii and quadriceps muscle thickness were assessed by ultrasound at baseline and post-intervention. <a href="/terms/one-repetition-maximum/" class="term-link" data-slug="one-repetition-maximum" title="One-<a href="/terms/repetition-maximum/" class="term-link" data-slug="repetition-maximum" title="repetition maximum">repetition maximum</a>">One-repetition maximum</a> and isokinetic torque were also measured.</p>
<p><strong>Results:</strong> The IAF group demonstrated significantly greater increases in bicep brachii muscle thickness compared with the EAF group (IAF: +12.4% vs. EAF: +6.9%; p = 0.03). No significant between-group difference was observed for quadriceps thickness. Maximal strength increases did not differ significantly between groups for either exercise.</p>
<p><strong>Conclusions:</strong> Internal attentional focus during single-joint isolation exercises enhances muscle hypertrophy relative to external focus, suggesting that the mind-muscle connection is a trainable skill with practical utility for bodybuilding-oriented resistance training. The benefit appears most pronounced for single-joint exercises targeting specific muscle groups.</p>
<h2>Introduction</h2>
<p>Within the bodybuilding and physique sport communities, the concept of the "<a href="/terms/mind-muscle-connection/" class="term-link" data-slug="mind-muscle-connection" title="mind-muscle connection">mind-muscle connection</a>" (MMC) occupies a prominent place in training philosophy. The MMC describes the deliberate direction of conscious attention toward the sensation of muscular contraction in the target muscle during exercise performance—an internal attentional focus strategy aimed at maximizing <a href="/terms/motor-unit/" class="term-link" data-slug="motor-unit" title="motor unit">motor unit</a> recruitment in the intended muscle [1].</p>
<p>Elite bodybuilders and coaches have long advocated for the MMC as a critical element distinguishing effective from ineffective training. Arnold Schwarzenegger famously described "squeezing the muscle at the top of the movement" and "feeling each rep in the working muscle" as essential elements of bodybuilding practice [2]. However, for decades this concept lacked rigorous scientific investigation.</p>
<p>The broader attentional focus literature in motor learning provides a relevant framework. Wulf and colleagues' OPTIMAL theory proposes that external focus of attention—directing attention to movement effects in the environment rather than body movements—generally produces superior motor performance and learning compared with internal focus [3]. This principle, derived primarily from motor skill learning studies, has been extrapolated by some to suggest that internal focus (i.e., the MMC) is detrimental to resistance training performance.</p>
<p>However, the goals of resistance training for <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="hypertrophy">hypertrophy</a> differ fundamentally from those of motor skill acquisition. In hypertrophy-oriented training, the objective is to maximize <a href="/terms/mechanical-tension/" class="term-link" data-slug="mechanical-tension" title="mechanical tension">mechanical tension</a> and <a href="/terms/metabolic-stress/" class="term-link" data-slug="metabolic-stress" title="metabolic stress">metabolic stress</a> in specific target muscles—not to optimize movement efficiency or trajectory. An internal attentional focus may therefore confer advantages in the resistance training context that are distinct from its effects on motor learning [4].</p>
<p>Cross-sectional evidence suggests that experienced resistance trainers demonstrate higher <a href="/terms/muscle-activation/" class="term-link" data-slug="muscle-activation" title="<a href="/terms/electromyography/" class="term-link" data-slug="electromyography" title="EMG">EMG</a> activity">EMG activity</a> in target muscles when using an internal focus compared with an external focus during isolation exercises, consistent with a practical benefit of the MMC for muscle activation [5]. The present study extends this cross-sectional evidence to a longitudinal training study examining hypertrophic outcomes.</p>
<h3>References</h3>
<p>[1] Schoenfeld BJ, Contreras B. Attentional focus for maximizing muscle development. <em>Strength Cond J</em>. 2016;38:27–29.
[2] Schwarzenegger A, Hall DC. <em>Encyclopedia of Modern Bodybuilding</em>. Simon Schuster; 1985.
[3] Wulf G, et al. Attentional focus and motor learning. <em>Psychol Bull</em>. 2010;136:39–73.
[4] Calatayud J, et al. Importance of mind-muscle connection. <em>Eur J Hum Mov</em>. 2016;37:130–145.
[5] Marchetti PH, et al. Muscle activation patterns and the role of mind-muscle connection. <em>Sports Med</em>. 2018;48:71–77.</p>
<h2>Methods</h2>
<h3>Participants</h3>
<p>Twenty-nine resistance-trained men (age: 23.1 ± 3.4 years; resistance training experience: ≥1 year) were recruited and randomized to either an internal <a href="/terms/mind-muscle-connection/" class="term-link" data-slug="mind-muscle-connection" title="attentional focus">attentional focus</a> (IAF) group (n = 14) or external attentional focus (EAF) group (n = 15). Participants were required to have at least 1 year of consistent resistance training experience to ensure baseline familiarity with the target exercises. Exclusion criteria included current upper or lower limb injury, use of anabolic-androgenic steroids, and any neurological condition affecting motor control.</p>
<h3>Attentional Focus Conditions</h3>
<p><strong>Internal Attentional Focus (IAF):</strong> Participants were instructed before each set to "focus on feeling your biceps contract and squeeze against the weight" (for bicep curls) or "focus on feeling your quadriceps push down against the floor" (for squats). Standardized verbal cues were provided by an investigator before each set.</p>
<p><strong>External Attentional Focus (EAF):</strong> Participants were instructed to "focus on pushing the weight up as fast as possible" (for curls) or "focus on pushing the floor away from you" (for squats). These cues directed attention to movement outcomes rather than muscular contractions.</p>
<h3>Training Protocol</h3>
<p>All participants completed an 8-week supervised resistance training program consisting of 3 sessions per week. The training protocol included barbell bicep curls (3 sets × 12 repetitions at 70% <a href="/terms/one-repetition-maximum/" class="term-link" data-slug="one-repetition-maximum" title="1RM">1RM</a>) and barbell back squats (3 sets × 12 repetitions at 70% 1RM). Total <a href="/terms/training-volume/" class="term-link" data-slug="training-volume" title="training volume">training volume</a> was identical between groups. Loads were adjusted bi-weekly based on perceived effort ratings.</p>
<h3>Outcome Measurements</h3>
<p><strong>Muscle thickness:</strong> Bicep brachii thickness and quadriceps (vastus lateralis) thickness were assessed by B-mode ultrasonography at a standardized location using a 7.5 MHz linear transducer. All scans were performed by a single trained sonographer blinded to group assignment.</p>
<p><strong>Strength:</strong> One-<a href="/terms/repetition-maximum/" class="term-link" data-slug="repetition-maximum" title="repetition maximum">repetition maximum</a> (1RM) for both exercises was assessed at baseline and post-intervention following standardized warm-up protocols.</p>
<h2>Results</h2>
<h3>Bicep Brachii <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="Hypertrophy">Hypertrophy</a></h3>
<p>The primary finding of this study was a significant between-group difference in bicep brachii muscle thickness change. The IAF group demonstrated a mean increase of 12.4 ± 4.1% in bicep brachii thickness, compared with 6.9 ± 3.8% in the EAF group (p = 0.03; <a href="/terms/effect-size/" class="term-link" data-slug="effect-size" title="Cohen's d">Cohen's d</a> = 1.37). This represents a clinically meaningful and statistically significant advantage for internal <a href="/terms/mind-muscle-connection/" class="term-link" data-slug="mind-muscle-connection" title="attentional focus">attentional focus</a> in single-joint <a href="/terms/isolation-exercise/" class="term-link" data-slug="isolation-exercise" title="isolation exercise">isolation exercise</a> for the biceps.</p>
<p>Intra-group analyses confirmed that both groups achieved statistically significant increases in bicep brachii thickness from baseline (IAF: p 0.001; EAF: p = 0.004), indicating that training with either attentional strategy produced measurable hypertrophy.</p>
<h3>Quadriceps Hypertrophy</h3>
<p>In contrast to the bicep findings, no significant between-group difference was observed for vastus lateralis muscle thickness change (IAF: +8.1 ± 3.2% vs. EAF: +7.3 ± 3.6%; p = 0.54). Both groups demonstrated significant within-group increases in quadriceps thickness, but the attentional focus manipulation did not differentially modulate this outcome for the multi-joint squat exercise.</p>
<h3>Strength Outcomes</h3>
<p><a href="/terms/one-repetition-maximum/" class="term-link" data-slug="one-repetition-maximum" title="One-<a href="/terms/repetition-maximum/" class="term-link" data-slug="repetition-maximum" title="repetition maximum">repetition maximum</a>">One-repetition maximum</a> strength improved significantly in both groups for both exercises. Bicep curl 1RM increased by 15.3 ± 5.8% in the IAF group and 14.1 ± 6.2% in the EAF group (p = 0.57). Squat 1RM increased by 12.4 ± 4.7% and 13.8 ± 5.1% in IAF and EAF groups, respectively (p = 0.43). These non-significant between-group strength differences indicate that attentional focus strategy did not meaningfully affect maximal force production capacity.</p>
<h3><a href="/terms/training-volume/" class="term-link" data-slug="training-volume" title="Training Volume">Training Volume</a> and Adherence</h3>
<p>Both groups completed equivalent training volumes across the 8-week intervention, and adherence rates did not differ (IAF: 95.2%; EAF: 94.7%). This equivalence confirms that any between-group differences in hypertrophy outcomes are attributable to the attentional focus manipulation rather than differences in total mechanical work performed.</p>
<h2>Discussion</h2>
<p>This study provides the first longitudinal experimental evidence that internal <a href="/terms/mind-muscle-connection/" class="term-link" data-slug="mind-muscle-connection" title="attentional focus">attentional focus</a> (the "mind-muscle connection") produces superior bicep brachii <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="hypertrophy">hypertrophy</a> compared with external attentional focus during bicep curl training in resistance-trained men. The 5.5 percentage point difference in hypertrophy between conditions, representing an 80% greater increase in the IAF group, is practically meaningful for athletes pursuing muscle development.</p>
<h3>Exercise Specificity of the MMC Effect</h3>
<p>The dissociation between bicep and quadriceps findings is theoretically important. The absence of a between-group difference in quadriceps hypertrophy despite the robust bicep effect suggests that the benefit of internal attentional focus is exercise-specific rather than universal. This exercise specificity is consistent with the hypothesis that internal focus enhances selective <a href="/terms/motor-unit/" class="term-link" data-slug="motor-unit" title="motor unit">motor unit</a> recruitment in isolated, single-joint movements where attentional redirection can meaningfully alter the relative contribution of specific muscles [1].</p>
<p>The squat, as a complex multi-joint movement, may be less amenable to attentional manipulation of individual muscle group activation. During squats, motor control demands—balance, coordination, and coordination across multiple joints—may dominate attentional resources, leaving less capacity for deliberate muscle-specific focus. Additionally, the primary muscles in the squat (quadriceps, gluteus maximus) work in coordination with multiple synergists, and selective de-emphasis of any single muscle group may be compensated by others.</p>
<h3>Reconciling with Motor Learning Literature</h3>
<p>This finding appears to contradict the motor learning literature suggesting external focus is superior. However, the goals of hypertrophy training and motor skill learning are fundamentally different [2]. In motor learning, external focus optimizes movement efficiency and trajectory learning. In hypertrophy training, the objective is to maximize <a href="/terms/mechanical-tension/" class="term-link" data-slug="mechanical-tension" title="mechanical tension">mechanical tension</a> in specific target muscles—a goal for which internal attentional focus provides a meaningful advantage for single-joint exercises.</p>
<h3>Practical Recommendations</h3>
<p>Resistance-trained individuals focusing on muscle hypertrophy should employ internal attentional focus (active attention to the contracting muscle) during single-joint isolation exercises such as bicep curls, tricep extensions, lateral raises, and leg curls. For multi-joint compound movements (squats, deadlifts, rows, presses), external focus cues—directing attention to movement outcomes—may be more effective for maximizing total force output and coordinating complex movement patterns.</p>
<p>The mind-muscle connection should be viewed as a trainable skill that develops with practice and body awareness. Beginners may initially struggle to consciously modulate muscle-specific activation, but deliberate practice of isolation exercises with appropriate attentional cues can develop this capacity over time [3].</p>
<h3>References</h3>
<p>[1] Schoenfeld BJ, Contreras B. Attentional focus for maximizing muscle development. <em>Strength Cond J</em>. 2016;38:27–29.
[2] Wulf G. Attentional focus and motor learning. <em>Psychol Bull</em>. 2010;136:39–73.
[3] Calatayud J, et al. Importance of mind-muscle connection during <a href="/terms/progressive-overload/" class="term-link" data-slug="progressive-overload" title="progressive resistance">progressive resistance</a> training. <em>Eur J Hum Mov</em>. 2016;37:130–145.</p>