The Study
Comparison of muscle activation and kinematics during free-weight back squats with different loads
This study watches a small group of strong young men do squats with different weights and measures how their muscles behave. It can tell us what happened during the squats, but not why it happened or if it would be the same for other people.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
When doing squats, people tried lifting weights from light to super heavy, all as fast as they could. Their muscles were checked to see how hard they worked.
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 521 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1You don't need to always lift the heaviest weight to make most muscles work hard—lifting lighter weights very fast can give similar muscle effort, which is safer and useful for training or rehab.
- 2- Lifting heavier weights made the bar move slower.
- 3- Quadriceps muscles worked about the same at 40%–90% of max weight, but worked hardest at 100%.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
PLoS ONE
Year
2019
Authors
R. van den Tillaar, V. Andersen, A. Saeterbakken
Related Content
Claims (6)
When strong guys do squats as fast as they can, the heavier the weight, the slower they move — even if they're trying to go fast. The heaviest weights always result in the slowest lifts, and this seems to be true for everyone.
When strong guys do fast squats with heavy weights, their leg muscles don't work harder the heavier the weight gets—until they go all the way up to their max. At max weight, two of the three main quad muscles actually fire way more.
When strong guys do fast squats, their thigh muscles turn on in a set order—one muscle first, then another, then a third—and that order doesn’t change no matter how heavy the weight is.
When strong guys do fast back squats with heavy weights, their butt and hamstring muscles work harder the heavier the weight gets — especially the butt muscle, which really kicks in when the weight is 80% or more of their max lift.
When you squat with heavier weights, your butt muscles (glutes) have to work way harder than your thigh muscles (quads), more than you'd expect just from the added weight.
When strong guys do fast squats with heavy weights, their butt muscles kick in later during the upward push compared to when they use lighter weights — it’s like their body adjusts how it uses those muscles depending on how heavy the weight is.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.