REF-1176 · Schoenfeld et al., 2015 · Sports Medicine · Paper · PubMed

Does a slow tempo grow more muscle?

A meta-analysis of 8 trials to failure found similar growth for reps of 0.5-8 s; reps over 10 s looked worse (few studies). Muscle size only: no fibre-type, mitochondrial or endurance data.

A-fairly strong evidenceMeasured on non-athletes and recreational people

Schoenfeld, Ogborn and Krieger asked whether the duration of a repetition (the sum of its concentric, eccentric and isometric parts, set by the tempo) changes how much muscle grows.

They included experimental trials in English-language refereed journals that compared different tempos in dynamic exercise with both concentric and eccentric actions, measured muscle morphology by biopsy, imaging or densitometry, lasted at least 6 weeks, trained to muscular failure, and studied people without chronic disease or injury. Eight studies qualified.

Hypertrophy was similar across repetition durations from 0.5 to 8 s. The authors suggest that volitionally very slow repetitions (more than 10 s) are inferior for hypertrophy, but say the lack of controlled studies makes that hard to conclude.

How this bears on the Russian static-dynamic method (Seluyanov): indirect. The method's claims (practice descriptions, not this paper) are that slow, continuous-tension sets of roughly 30-60 s at a light load, taken to a burning sensation with short rests, grow type I (slow) fibres and their mitochondria and so improve endurance.

This review tested only whole-muscle size, at matched effort (failure), across tempos. The slow tempos used in the closest tested form of the method, low-intensity slow movement with tonic force generation (LST, typically 3 s down and 3 s up), fall inside the 0.5-8 s band where tempo made no measurable difference.

On this evidence a slow tempo does not add growth by itself; it neither confirms nor refutes the fibre-type and mitochondrial claims.

Included studies

Search and eligibility (abstract): experimental trials in English-language refereed journals; direct comparison of different tempos in dynamic exercise with concentric and eccentric repetitions; morphology measured by biopsy, imaging and/or densitometry; at least 6 weeks; training to muscle failure (inability to complete another concentric repetition with proper form); human participants without chronic disease or injury.
Studies: 8 met the criteria. The abstract does not give the number of participants, the populations, the loads, the per-phase tempos or the effect sizes.
Load, relaxation and range: not reported in the abstract. Training to failure was an inclusion criterion, so effort was matched by design across tempos.

Key Results

QuestionResult (abstract)Evidence
Hypertrophy across repetition durations of 0.5-8 ssimilar8 studies, all to failure, at least 6 weeks
Volitionally very slow repetitions (>10 s)"inferior from a hypertrophy standpoint"the authors flag a lack of controlled studies; no pooled estimate in the abstract
Pooled effect sizes, confidence intervals, sample sizesnot given in the abstractfull text closed

Mechanisms

Authors' interpretation: a fairly wide range of repetition durations can be used if the goal is maximal growth; tempo is a minor variable once sets reach failure.
Inference: because every included study trained to failure, the result says that at matched effort the time each repetition takes is not what drives growth. Long time under tension is not itself an independent hypertrophy signal in this evidence.
Inference: the >10 s penalty is consistent with very slow repetitions forcing a lighter load and fewer repetitions, but the abstract does not test why.
Not measured: fibre-type-specific growth, mitochondrial content or function, capillaries, metabolic markers, endurance.

Practical Application

Does a slow tempo grow more muscle? A meta-analysis of 8 trials to failure found similar growth for reps of 0.5-8 s; reps over 10 s looked worse (few studies). Muscle size only: no fibre-type, mitochondrial or endurance data.
For hypertrophy, pick a tempo you can control and take sets close to failure; do not slow down for its own sake. Repetitions over about 10 s are the one tempo this review warns against.
Static-dynamic method: this is an indirect test only. Its 3 s down / 3 s up style of slow repetition sits inside the range where tempo did not change growth, so on this evidence slowness by itself is unlikely to be what adds size; the method's no-relaxation (continuous-tension) element was not tested by this review. Its claims about slow-fibre mitochondria and endurance are untouched by this review.
For endurance athletes the base's default for strength work remains heavy, few repetitions, short of failure (SYNTH-43, SYNTH-44); this paper does not argue for slow-tempo work.

Limitations

Read from the abstract only; the included studies, their loads, populations, effect sizes and heterogeneity could not be checked.
Only eight studies (sample sizes not given in the abstract); the >10 s conclusion rests on very few controlled comparisons, as the authors state.
Only English-language refereed journals; only training to failure, so the result may not hold for sets stopped short of failure.
Muscle size is the only outcome; nothing on strength, fibre type, oxidative capacity or performance.
Funding and conflicts of interest: not stated in the abstract or the PubMed record.
How this entry was checked and changed
Why this level

meta-analysis of only 8 trials (their sizes are not in the abstract; tempo trials are typically small, base inference), and the authors themselves say the >10 s comparison rests on too few controlled studies; from the abstract (the full text is not open)