REF-1487 · Kassiano et al., 2022 · Journal of Strength and Conditioning Research · Paper · PubMed

Should I keep changing my gym exercises?

Eight studies, 241 young men, no pooled number: planned variation looks fine, frequent random rotation may cost gains. The abstract does not count the studies behind it. Training status unstated.

Main caveat: The key claim is untraceable from what we hold. "Excessive, random variation" rests on an unstated number of the eight studies.
moderate evidenceMeasured on non-athletes to trained athletes

Kassiano and colleagues reviewed whether varying resistance exercises gives more muscle and strength than a fixed selection. Searching PubMed/MEDLINE, Scopus and Web of Science, they found eight studies with 241 participants in total, all young men, of good or excellent rated quality.

They conclude that variation can influence gains, that some systematic variation seems to enhance regional growth and maximize dynamic strength, and that "excessive, random variation may compromise muscular gains"; exercises giving a redundant stimulus and a high frequency of change may hinder adaptation. Our reading: this is a qualitative synthesis with no pooled number.

The direction is useful but its size is unknown, and the warning against rotation cannot be weighed from the abstract, which neither counts nor names the studies behind it. A guide can use it as one review's conclusion in young men, not as a tested rule on how long to keep an exercise.

Protocol

Search: PubMed/MEDLINE, Scopus, Web of Science; dates not given in the abstract.
Studies and participants: eight studies; combined n = 241, all young men.
Quality: Physiotherapy Evidence Database (PEDro) scale, rated "good" and "excellent" by the authors.
Synthesis: narrative; the abstract reports no pooling, effect sizes or CIs.
Not given in the abstract: the names and designs of the eight studies, their duration, training status, what counted as systematic or as random or excessive variation, and how often exercises changed.
Funding and interests: not available from the abstract.

Key Results

Claim in the abstractNumbers givenStudies behind it
Varying exercise selection can influence hypertrophy and strengthNoneNot stated (eight in the review)
Some systematic variation seems to enhance regional hypertrophy and maximize dynamic strengthNoneNot stated
Excessive, random variation may compromise gainsNoneNot stated: neither how many nor which
Redundant stimulus and excessive rotation may hinder adaptation (the conclusion)NoneNot stated
What we could and could not check: OpenAlex lists the review's cited references by identifier, and among them is a study of exercise variation in resistance-trained men (Baz-Valle 2019, DOI 10.1371/journal.pone.0226989) and one of auto-regulated exercise selection (DOI 10.1519/jsc.0000000000002272). A reference list does not show which studies were included or carry the warning; these are leads, not findings.
The ACSM overview on the same question ([REF-1476], sibling draft): it rates the impact of varied exercise selection as not determinable for strength (one review) and hypertrophy (two reviews). It cites this review, but its table does not name which review fills that row.

Mechanisms

Authors' interpretation: variation should be systematic, with a focus on applied anatomy and biomechanics; exercises that give a redundant stimulus, and changing exercises too often, may hinder adaptation. The abstract gives no mechanism beyond that.
Inference: a motor-learning explanation would fit, since an unfamiliar lift limits the load early on; the abstract does not state it, and the log cannot separate it from fitness either way.
Not measured here: any mechanism; the abstract reports conclusions, not data.

Practical Application

Should I keep changing my gym exercises? Eight studies, 241 young men, no pooled number: planned variation looks fine, frequent random rotation may cost gains. The abstract does not count the studies behind it. Training status unstated.
What it supports: choosing a change for an anatomical or biomechanical reason (the abstract speaks of regional growth), and not rotating for its own sake; a joint or a kit limit as a reason is the base's own practice. Say it as one review's conclusion, with no effect size.
What it does not support: a number for how long an exercise must stay, or how often is too often: the abstract gives none. It tests no rule for substitutions when a station or machine is missing.
For the log: Not from this paper; the base's own practice: keep a movement the same long enough for sessions to compare, and treat a swap as a new baseline. The practical reason is readability of the log, which is the base's own, not this review's finding.

Limitations

The key claim is untraceable from what we hold. "Excessive, random variation" rests on an unstated number of the eight studies. Do not cite this as "the studies show"; the guide should say "one review concludes, in young men".
No pooling and no sizes. Nothing can be said about how much is gained or lost.
One population. All 241 are young men, so no women or older adults; no endurance athletes are named.
Definitions unknown. What counted as excessive, random or redundant is not in the abstract.
Interests. Not available from the abstract.
How this entry was checked and changed
Why this level

its design alone sits at A- (an unpooled review of small trials, as REF-680), held a step lower because it is read from the abstract only (OpenAlex marks it closed, with no repository copy) and the claim the base wants from it cannot be traced to a count of studies; the authors rate study quality "good" and "excellent" on the PEDro scale