If you're a young adult who hasn't trained much before and you do squats slowly or quickly on the way down for 7 weeks, your thigh muscle gets stiffer either way — and how slow or fast you go doesn't matter.

If you're a young adult who hasn't lifted weights before and you do squats for 7 weeks—whether you lower the bar slowly (4 seconds) or quickly (1 second)—your thigh muscle gets stiffer, and it doesn't matter which speed you use.

If young people who don’t normally lift weights do squats slowly on the way down for 7 weeks, their thigh muscles might start working more like endurance muscles—slower but more tired-resistant.

If you're a young adult who hasn't trained much before, doing squats slowly (4 seconds) or quickly (1 second) on the way down for 7 weeks will make your thigh muscles grow about the same amount — so how slow or fast you lower yourself doesn't really matter as long as you do the same total work.

If you're a young adult who hasn't trained before and you do squats with either a slow (4-second) or fast (1-second) lowering phase for 7 weeks, your thigh muscles will grow about the same amount either way.

If you're a young adult who hasn't trained much before and you do squats slowly on the way down for 7 weeks, your thigh muscles might start contracting more slowly, which could mean they're changing to work more like slow-twitch muscles.