The Study
Assessing differential responders and mean changes in muscle size, strength, and the cross-over effect to two distinct resistance training protocols.
This study compared two ways of lifting weights and found that, on average, one way made arms stronger and another made muscles bigger. But it didn't prove that one caused the other, or that some people are just 'naturally better' at getting stronger—it might just be random luck.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Two ways to train your arm: do many reps until tired, or lift the heaviest weight you can once. Both made arms stronger, but only the heavy-lift group made the other arm stronger too — and only the many-reps group made muscles bigger.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 558 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — this means muscle size doesn't always predict strength, and practicing the exact movement you're tested on matters more than just building muscle.
- 2Both groups got 2.4 kg stronger.
- 3The heavy-lift group made the other arm 1.5 kg stronger.
- 4The many-reps group made muscles 0.23 cm thicker.
- 5Only strength gains showed real individual differences (1.80 kg).
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme
Year
2020
Authors
S. Dankel, Z. Bell, Robert W Spitz, Vickie Wong, R. Viana, Raksha N. Chatakondi, S. Buckner, M. Jessee, K. Mattocks, J. Mouser, T. Abe, J. Loenneke
Related Content
Claims (5)
After six weeks of strength training, some untrained adults gain about 1.80 kg more in one-repetition maximum strength than can be explained by measurement error, indicating that individual responses to training differ in a way that reflects biological variation.
Resistance training that mimics the exact movements and weights used in strength tests leads to greater increases in strength than training that does not, even when muscle size does not change, because the nervous system becomes more efficient at performing those specific movements.
In untrained adults, two different weightlifting routines produce the same strength gain in the trained arm, but only one routine also increases strength in the opposite untrained arm.
Training with four sets of resistance exercises to failure causes measurable muscle growth, while training with one maximum-effort repetition does not, even though both types of training improve strength equally.
In people who regularly lift weights, differences in muscle growth and strength gains between individuals are often no larger than the natural inaccuracies in measurement tools, so some people are incorrectly labeled as responders or non-responders based on measurement error rather than real biological differences.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.