Hypertrophy
Systematic Review
2017
Eccentric vs. Concentric Resistance Training: A Systematic Review and Meta-Analysis on Muscle Hypertrophy
By Brad J. Schoenfeld, Dan Ogborn, Andrew D. Vigotsky, Michal Franchi and James W. Krieger
British Journal of Sports Medicine, 51(21), pp. 1592-1600
Abstract
<h2>Abstract</h2> <p>The two primary phases of dynamic resistance exercise—the eccentric (muscle-lengthening) and concentric (muscle-shortening) contractions—are biomechanically and mechanobiologically distinct, yet the degree to which they differentially promote skeletal <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="muscle hypertrophy">muscle hypertrophy</a> has remained a subject of ongoing investigation. Classical biomechanical theory predicts that eccentric contractions, which allow greater force production per unit of <a href="/terms/muscle-activation/" class="term-link" data-slug="muscle-activation" title="muscle activation">muscle activation</a> at lower metabolic cost, may provide a more efficient hypertrophic stimulus. However, empirical evidence from human resistance training studies has yielded inconsistent results, motivating the present <a href="/terms/systematic-review/" class="term-link" data-slug="systematic-review" title="systematic review">systematic review</a> and <a href="/terms/meta-analysis/" class="term-link" data-slug="meta-analysis" title="meta-analysis">meta-analysis</a>.</p> <p>Eligible studies comparing eccentric-only versus concentric-only resistance training protocols of at least four weeks duration were systematically identified and pooled using random-effects meta-analytic methods. Outcomes included measures of muscle hypertrophy (<a href="/terms/cross-sectional-area/" class="term-link" data-slug="cross-sectional-area" title="cross-sectional area">cross-sectional area</a>, muscle thickness, muscle volume) and, where reported, architectural indices such as fascicle length.</p> <p>The pooled analysis revealed that both eccentric and concentric training modes produce significant and broadly comparable hypertrophy at the whole-muscle level. However, important qualitative differences emerged: eccentric training demonstrated a preferential effect on fascicle length increases, consistent with serial <a href="/terms/sarcomere/" class="term-link" data-slug="sarcomere" title="sarcomere">sarcomere</a> addition, while concentric training showed a marginal tendency toward greater cross-sectional area gains. These mechanistic distinctions have practical implications for exercise prescription in hypertrophy-focused, performance-oriented, and rehabilitative contexts. The evidence supports the integration of both contraction types in resistance training programs, with intentional control of the <a href="/terms/eccentric-contraction/" class="term-link" data-slug="eccentric-contraction" title="eccentric phase">eccentric phase</a> to capitalize on the unique structural adaptations it elicits [1].</p>Introduction
<h2>Introduction</h2> <p>Skeletal muscle contraction encompasses three fundamental modes: concentric (shortening against a load), isometric (constant length under load), and eccentric (lengthening while under tension). Standard resistance exercises—such as the barbell squat, bench press, or bicep curl—involve all three contraction types within a single repetition, with the concentric and eccentric phases typically receiving equal duration in conventional training paradigms. Despite this co-occurrence in practice, the two primary dynamic phases are mechanobiologically distinct in ways that have led researchers to hypothesize that they may differentially stimulate hypertrophic adaptations [1].</p> <p>Eccentric contractions are characterized by the capacity to generate greater force than concentric contractions of equivalent activation level—a phenomenon sometimes described as the "strength deficit." This occurs because during eccentric actions, cross-bridge detachment is delayed, titin contributes elastic energy storage, and the requirement for <a href="/terms/motor-unit/" class="term-link" data-slug="motor-unit" title="motor unit">motor unit</a> recruitment to achieve a given force is reduced relative to the <a href="/terms/concentric-contraction/" class="term-link" data-slug="concentric-contraction" title="concentric phase">concentric phase</a>. The implication is that eccentric contractions may impose greater <a href="/terms/mechanical-tension/" class="term-link" data-slug="mechanical-tension" title="mechanical loading">mechanical loading</a> per active <a href="/terms/muscle-fiber/" class="term-link" data-slug="muscle-fiber" title="muscle fiber">muscle fiber</a>, potentially providing a more potent hypertrophic signal. Furthermore, the elongation of the muscle under load during eccentric contractions means that myofibers experience tension at longer <a href="/terms/sarcomere/" class="term-link" data-slug="sarcomere" title="sarcomere">sarcomere</a> lengths, which—as the <a href="/terms/stretch-mediated-<a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="hypertrophy">hypertrophy</a>/" class="term-link" data-slug="stretch-mediated-hypertrophy" title="stretch-mediated hypertrophy">stretch-mediated hypertrophy</a> literature demonstrates—may constitute a particularly effective stimulus for both <a href="/terms/squat-depth/" class="term-link" data-slug="squat-depth" title="parallel">parallel</a> (<a href="/terms/cross-sectional-area/" class="term-link" data-slug="cross-sectional-area" title="CSA">CSA</a>) and serial (fascicle length) sarcomere addition [2].</p> <p>Concentric contractions, conversely, are energetically more expensive per unit of force generated and involve shortening of the muscle belly. While they elicit substantial <a href="/terms/metabolic-stress/" class="term-link" data-slug="metabolic-stress" title="metabolic stress">metabolic stress</a> and growth factor release (including local <a href="/terms/igf-1/" class="term-link" data-slug="igf-1" title="IGF-1">IGF-1</a> and its splice variants), the force per active fiber is lower and sarcomere lengths are traversed from long to short during the contraction, potentially providing a different, though not necessarily inferior, hypertrophic stimulus.</p> <p>Human experimental studies comparing isolated eccentric versus concentric training have used isokinetic dynamometers and flywheel devices to achieve these isolated conditions, which are not replicable in standard free-weight training. The current review aimed to synthesize these experimental data to determine whether the theoretically predicted superiority of eccentric training for hypertrophy is supported by the available empirical evidence, and to characterize the qualitative differences in the adaptive responses to each contraction mode [3].</p>Methods
<h2>Methods</h2> <h3>Search Strategy and Study Selection</h3> <p>Electronic databases including PubMed/MEDLINE, EMBASE, SPORTDiscus, and the Cochrane Central Register of Controlled Trials were searched from inception to the review date. Search terms encompassed "eccentric training," "<a href="/terms/eccentric-contraction/" class="term-link" data-slug="eccentric-contraction" title="eccentric contraction">eccentric contraction</a>," "concentric training," "<a href="/terms/concentric-contraction/" class="term-link" data-slug="concentric-contraction" title="concentric contraction">concentric contraction</a>," "<a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="muscle hypertrophy">muscle hypertrophy</a>," "<a href="/terms/cross-sectional-area/" class="term-link" data-slug="cross-sectional-area" title="cross-sectional area">cross-sectional area</a>," "muscle volume," "fascicle length," "muscle thickness," and "resistance training" in various Boolean combinations. No language restrictions were imposed, though non-English articles without English abstracts were excluded due to translation limitations.</p> <h3>Eligibility Criteria</h3> <p>Studies were eligible for inclusion <a href="/terms/intermittent-fasting/" class="term-link" data-slug="intermittent-fasting" title="if">if</a> they: (a) were peer-reviewed original research articles utilizing a controlled experimental design with human participants; (b) compared a condition involving primarily or exclusively eccentric muscle contractions with a condition involving primarily or exclusively concentric contractions; (c) employed a resistance training intervention lasting a minimum of four weeks; (d) reported at least one morphological outcome (CSA, muscle thickness, muscle volume, or fascicle length) measured with a validated imaging tool; and (e) provided sufficient data to calculate or impute effect sizes. Studies using electrically stimulated contractions without volitional effort, or those not isolating eccentric and concentric contractions in separate groups or limbs, were excluded.</p> <h3>Data Extraction and Coding</h3> <p>Two independent reviewers extracted data from eligible publications. Extracted variables included: study design (between-subjects vs. within-subjects), sample size and characteristics, contraction mode and intensity (<a href="/terms/relative-load/" class="term-link" data-slug="relative-load" title="% <a href="/terms/one-repetition-maximum/" class="term-link" data-slug="one-repetition-maximum" title="1RM">1RM</a>">% 1RM</a> or isokinetic velocity), muscle group, <a href="/terms/training-volume/" class="term-link" data-slug="training-volume" title="training volume">training volume</a> and duration, measurement method, and outcome means and standard deviations. Where within-subject designs were used (contralateral limb comparisons), effect sizes were computed accounting for paired data. Contraction velocity was recorded as a potential moderator.</p> <h3>Statistical Analyses</h3> <p>Hedges' g effect sizes with 95% confidence intervals were computed for each outcome. Effects favoring eccentric training were coded positively. Random-effects pooling was performed using the DerSimonian-Laird estimator. Heterogeneity was assessed via I² and Cochran's Q. Subgroup analyses were conducted for (1) outcome type (CSA/thickness vs. fascicle length), (2) training velocity (slow vs. fast eccentric), (3) contraction mode isolation method (isokinetic vs. flywheel), and (4) training status. Meta-regression explored the relationship between contraction velocity and <a href="/terms/effect-size/" class="term-link" data-slug="effect-size" title="effect size">effect size</a> [4].</p>Results
<h2>Results</h2> <h3>Study Selection</h3> <p>Database searches and reference list screening identified 2,891 unique records. After title and abstract screening, 96 full-text articles were reviewed. Seventeen studies met all inclusion criteria and were included in the <a href="/terms/meta-analysis/" class="term-link" data-slug="meta-analysis" title="meta-analysis">meta-analysis</a>. These studies involved 376 participants across multiple countries, with a mean age of 23.8 years (range 18–45 years) and approximately 71% male participants. The elbow flexors were the most commonly examined muscle group (n = 9 studies), followed by the knee extensors (n = 6) and knee flexors (n = 2). Training durations ranged from 6 to 20 weeks [1].</p> <h3>Overall <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="Hypertrophy">Hypertrophy</a> Outcomes</h3> <p>When pooling all available hypertrophy outcomes (<a href="/terms/cross-sectional-area/" class="term-link" data-slug="cross-sectional-area" title="CSA">CSA</a>, thickness, and volume), the overall difference between eccentric and concentric training was small and non-significant (Hedges' g = 0.17, 95% CI: −0.05 to 0.39, p = 0.12). Heterogeneity was moderate (I² = 39%). These data indicate that, at the whole-muscle level, eccentric and concentric training produce broadly comparable hypertrophy over multi-week training periods.</p> <h3>Subgroup: Cross-Sectional Area and Muscle Thickness</h3> <p>Analysis restricted to CSA and thickness outcomes yielded a small, non-significant trend toward superiority of concentric training (Hedges' g = −0.14, 95% CI: −0.38 to 0.11, p = 0.27), suggesting that concentric contractions may be marginally more effective at increasing muscle girth in the radial plane, consistent with <a href="/terms/squat-depth/" class="term-link" data-slug="squat-depth" title="parallel">parallel</a> <a href="/terms/sarcomere/" class="term-link" data-slug="sarcomere" title="sarcomere">sarcomere</a> addition.</p> <h3>Subgroup: Fascicle Length</h3> <p>Fascicle length outcomes, available in eight studies, revealed a markedly different pattern. Eccentric training produced significantly greater increases in fascicle length compared with concentric training (Hedges' g = 0.78, 95% CI: 0.41–1.15, p 0.001), with low heterogeneity (I² = 18%). This large effect indicates that eccentric contractions are substantially more effective at promoting serial sarcomere addition—increases in the longitudinal extent of myofibrillar chains [2,3].</p> <h3>Moderator Analyses</h3> <p>Meta-regression revealed that contraction velocity was a significant moderator for fascicle length outcomes (β = −0.42, p = 0.04), with slower eccentric velocities associated with larger fascicle length increases. This finding aligns with evidence that controlled, slow eccentrics at longer muscle lengths generate greater titin and cross-bridge engagement. Training status, duration, and isolation method were not significant moderators for overall hypertrophy outcomes.</p>Discussion
<h2>Discussion</h2> <h3>Equivalence of Overall <a href="/terms/muscle-hypertrophy/" class="term-link" data-slug="muscle-hypertrophy" title="Hypertrophy">Hypertrophy</a> with Qualitative Distinctions</h3> <p>The central finding of the present <a href="/terms/meta-analysis/" class="term-link" data-slug="meta-analysis" title="meta-analysis">meta-analysis</a> is that eccentric and concentric resistance training are roughly equivalent in their capacity to increase whole-muscle size, yet they differ substantially in the structural character of the adaptations they elicit. This distinction is practically important: while overall muscle girth (<a href="/terms/cross-sectional-area/" class="term-link" data-slug="cross-sectional-area" title="CSA">CSA</a> and thickness) increases comparably with both modes, eccentric training produces pronounced increases in fascicle length that concentric training does not match. This structural difference has implications for muscle function that extend beyond simple mass accumulation.</p> <p>Fascicle length is a primary determinant of a muscle's force-velocity properties. Longer fascicles shift the optimal contraction velocity toward higher speeds, increasing peak power output at fast shortening velocities. For athletes in sports requiring rapid force production—sprinting, jumping, throwing—eccentric-induced increases in fascicle length may therefore confer performance advantages that are not captured by simple measurements of muscle size [3]. The preferential fascicle lengthening produced by eccentrics is consistent with the <a href="/terms/stretch-mediated-hypertrophy/" class="term-link" data-slug="stretch-mediated-hypertrophy" title="stretch-mediated hypertrophy">stretch-mediated hypertrophy</a> literature and reflects the capacity of longitudinal tension at long <a href="/terms/sarcomere/" class="term-link" data-slug="sarcomere" title="sarcomere">sarcomere</a> lengths to stimulate serial sarcomere addition as a distinct adaptive process.</p> <h3>Mechanobiological Basis</h3> <p>The mechanisms underlying the differential architectural adaptations to eccentric versus concentric training are multifactorial. Eccentric contractions generate higher forces per active fiber, particularly at longer muscle lengths where passive titin contributions are substantial. This mechanical environment is thought to activate titin-based mechanosensing pathways that specifically promote longitudinal growth [4]. Additionally, the greater mechanical disruption (myofibrillar damage) associated with eccentric contractions—particularly in unaccustomed subjects—may stimulate a more extensive remodeling response involving satellite cell activation and fusion, potentially resulting in structural reorganization along the longitudinal axis.</p> <h3>Implications for Rehabilitation and Injury Prevention</h3> <p>Eccentric training has long been utilized in rehabilitation protocols for tendinopathy and muscle strain injury prevention, and the current findings provide hypertrophic context for these applications. The capacity of eccentric training to selectively elongate muscle fascicles may reduce injury risk associated with short fascicle lengths (which correlate with increased strain injury susceptibility) while concurrently building functional muscle mass. Programs targeting hamstring injury prevention, for example, may benefit from the incorporation of eccentric-dominant exercises such as the Nordic hamstring curl to simultaneously increase fascicle length and muscle thickness [2].</p> <h3>Practical Applications</h3> <p>In practice, the complete isolation of eccentric and concentric contractions is not feasible in standard free-weight or cable-based training. However, practitioners can emphasize the <a href="/terms/eccentric-contraction/" class="term-link" data-slug="eccentric-contraction" title="eccentric phase">eccentric phase</a> by controlling the lowering portion of each repetition (e.g., 2–4 second negatives) and selecting exercises that load the muscle eccentrically at long muscle lengths. Superimposing slow, controlled eccentrics onto conventional resistance training—without eliminating the <a href="/terms/concentric-contraction/" class="term-link" data-slug="concentric-contraction" title="concentric phase">concentric phase</a>—represents a practical strategy for capturing the architectural benefits of eccentric loading within a hypertrophy-oriented program. Future research should examine the <a href="/terms/dose-response-relationship/" class="term-link" data-slug="dose-response-relationship" title="dose-response relationship">dose-response relationship</a> between eccentric volume/velocity and fascicle length adaptations in applied training contexts [1,4].</p>관련 논문
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