Whether you train both legs together or one at a time, your thigh muscles grow about the same amount after 12 weeks of heavy lifting.

When people train one leg at a time, that leg gets much stronger than the other leg, even if the other leg didn’t do any training.

Doing leg exercises with both legs at the same time for 12 weeks makes you stronger at lifting with both legs together, while doing them one leg at a time makes you stronger at lifting with each leg separately.

If young guys who’ve never lifted weights before do regular strength training twice a week for two months using moderate weights, their thigh muscles get bigger and stronger—whether or not they use special bands to restrict blood flow.

If you lift weights the same total amount each week, it doesn’t matter if you do it in one big session or split into three smaller ones—you’ll get just as strong and build just as much muscle.

If a guy does leg workouts with just one leg, three times a week for two months using heavy weights, that one leg gets noticeably bigger in muscle size—especially the fast-twitch fibers—while the other leg stays the same.