The Claim
In untrained young adults, performing barbell squats with a 4-second eccentric phase for 7 weeks increases the contraction time (Tc) of the vastus lateralis and rectus femoris muscles, as measured by tensiomyography, compared to a 1-second eccentric tempo.
What the research says
Supports is higher
Support is ahead, but a single strong opposing study can change this.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
In untrained young adults, performing barbell squats with a 4-second lowering phase for 7 weeks results in longer muscle contraction time in the quadriceps compared to using a 1-second lowering phase.
See the scientific wording
In untrained young adults, performing barbell squats with a 4-second eccentric phase for 7 weeks increases the contraction time (Tc) of the vastus lateralis and rectus femoris muscles, as measured by tensiomyography, while a 1-second tempo does not, suggesting a potential adaptation related to muscle fiber-type composition.
When muscles are stretched slowly under load, the slow-twitch fibers grow larger because they are better suited to handle long-lasting tension. These larger fibers take longer to contract because they release and recapture calcium more slowly and their muscle fibers cycle through contractions at a slower pace. This makes the whole muscle respond more slowly when electrically stimulated, which is measured as longer contraction time.
What the research says
1 studyPeople who did squats slowly (taking 4 seconds to lower) ended up with thigh muscles that took longer to contract after being zapped with electricity, while those who did squats quickly didn't. This suggests slow squats might change how the muscles work.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.