The Study
Fatigue and Motor Unit Activation Are Determined by Neither Load Nor Time Under Tension During Resistance Exercise
This study watched how muscles worked during different kinds of weightlifting, but it didn't test if one way makes you stronger or bigger over time. It only saw what happened during one workout, so we can say certain things are linked, but not that one thing causes another.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
This study tested whether lifting light or heavy weights to exhaustion affects muscle activation differently.
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 533 / 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 suggests you don’t need heavy weights to fully activate your muscles; going all-out with light weights works just as well for muscle recruitment.
- 2Light weights (30% max) led to 27% more total muscle activation (iEMG) than heavy weights (80% max), even though heavy weights felt harder per rep.
- 3Everyone got equally tired no matter the weight.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
The FASEB Journal
Year
2017
Authors
Robert W. Morton, Michael W. L. Sonne, A. Zuniga, Amanda Jones, P. Keir, C. McGlory, Stuart M Phillips
Related Content
Claims (6)
In young men, muscle fatigue occurs during resistance exercise when effort is pushed to complete exhaustion, whether the weight is light or heavy or the movement speed is fast or slow.
During resistance exercise to muscle failure, longer muscle contraction time is associated with higher total electrical activity in the muscles, reflecting greater cumulative activation of motor units.
When lifting weights until exhaustion, heavy weights produce higher peak muscle electrical activity per repetition than light weights, but the total muscle activation across all repetitions is the same for both weights.
Performing resistance exercises with light weights until muscle fatigue activates the same high-threshold motor units as heavy weights.
When young men lift light weights until they can no longer continue, the total electrical activity in their muscles is higher than when they lift heavy weights until failure.
When lifting lighter weights until muscle failure, acute muscle protein synthesis is higher than when lifting heavier weights without matching the total volume of work.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.