In untrained young adults, performing barbell squats with a 4-second eccentric phase for 7 weeks results in a greater increase in one-repetition maximum strength (effect size = 1.60) compared to performing barbell squats with a 1-second eccentric phase for 7 weeks (effect size = 0.99), suggesting that prolonged eccentric loading may enhance neural or mechanical adaptations for maximal strength.

Slowing down the downward phase of a squat increases the time muscles are under tension, which causes the slow-twitch muscle fibers to grow larger. These larger fibers produce more force and contract more slowly, improving the muscle's ability to generate maximum strength. At the same time, the repeated stretching under load makes the muscle and its connective tissues stiffer, allowing more force to be transferred efficiently during the upward push.