Lifting weights slowly (eccentric) or quickly (concentric) both make your quads stronger in about 10 weeks — and you don’t need to be sore or damaged to get stronger.

You can get just as strong by pushing weights up as by lowering them slowly—even if lowering them doesn’t make your muscles sore or damaged.

If young, healthy guys do strength training for 12 weeks using different types of muscle contractions—whether slow or fast—they’ll get significantly stronger in their thigh muscles, no matter which style they pick.

Men who started with a longer tendon lever arm and could already activate their thigh muscles better tended to get stronger in eccentric movements after training — their starting point mattered.

Doing slow, low-effort weight training three times a week for 12 weeks can make your thigh muscles bigger and stronger, just as much as doing fast, high-effort weight training.

If young guys stick to the same exercises every time they work out for about two months, they get stronger in a specific leg test than if they keep switching up their routine.