The Study
Muscle adaptations following 21 consecutive days of strength test familiarization compared with traditional training
This study watched five people do arm exercises for three weeks and measured how strong they got and if their muscles grew. It didn't prove that one thing caused another — it just showed what happened in those five people. You can't say it's true for everyone else.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Two arms trained differently for 21 days: one lifted weights, the other just practiced lifting without adding weight. Both got stronger — but only the weight-lifting arm got bigger muscles.
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 550 / 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 — you can get nearly as strong just by practicing a movement, even without lifting heavy, which means your brain and nerves get better at recruiting muscles — not just your muscles getting bigger.
- 2Without weights: +1.9 kg stronger.
- 3With weights: +2.2 kg stronger.
- 4Only the weighted arm grew 0.28 cm thicker muscles.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Muscle & Nerve
Year
2017
Authors
S. Dankel, Brittany R. Counts, Brian E. Barnett, S. Buckner, T. Abe, J. Loenneke
Related Content
Claims (5)
In people already trained in strength exercises, repeating the same movement without adding weight produces the same increase in strength as a structured resistance training program over 21 days.
In people who are already trained, lifting weights repeatedly increases strength without increasing muscle size, showing that improvements in nerve signaling play a major role in getting stronger.
In trained individuals, performing daily elbow flexion tests without weights increases maximum strength by 1.9 kg, and performing daily elbow flexion exercises with 70% of maximum weight increases maximum strength by 2.2 kg over 21 days.
After 21 days of daily weight training at 70% of maximum strength, the muscles in the trained arm grow thicker by 0.28 cm on average, while the untrained arm shows no change, indicating that muscle growth occurs only when muscles are subjected to mechanical stress.
After 21 days of daily testing or training, the maximum force produced by isometric contractions is the same in both arms, and any strength improvements from repeated testing occur only in movements that involve full range of motion and dynamic muscle action.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.