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, whereas performing the same exercise with a 1-second eccentric phase does not significantly alter contraction time.
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 increases the contraction time of the quadriceps muscles as measured by tensiomyography, while a 1-second lowering phase does not produce a significant change.
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 eccentric phase does not produce a significant change, suggesting a potential adaptation related to muscle fiber-type composition.
When a person lowers a heavy weight slowly, the muscle fibers under tension stay active longer, which causes the slower-twitch muscle fibers to grow bigger. These bigger fibers take more time to contract and relax, so the muscle takes longer to complete a single contraction.
What the research says
1 studyWhen beginners squat slowly (taking 4 seconds to lower), their thigh muscles take longer to contract after being told to move — this change didn't happen when they squatted quickly. So slow squats may be changing 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.