When guys get stronger from doing isometric leg exercises, their hamstring muscles don’t start working differently alongside their quads—so the way their hamstrings fire doesn’t predict whether they’ll get stronger or not.

When untrained men get stronger in a static leg press, the main reason is that their thigh muscle near the hip gets bigger and its fibers angle more, which helps push harder.

When guys who’ve never lifted weights before train their legs for 15 weeks, the more their muscles grow, the stronger they get—so muscle growth is mostly why they get stronger.

When guys who’ve never lifted weights before start training their legs for 15 weeks, the more their thigh muscles grow, the stronger they get—so muscle growth is probably why they’re getting stronger, not just better at lifting.

If you lift heavy weights with either short or long breaks between sets—while doing the same total work—you’ll get about the same stronger in your leg muscles after 10 weeks.

Whether you train one leg or both legs at once for 12 weeks, your legs get just as big and strong overall — the way you do the exercise doesn’t change how much muscle you build or how strong you become in general.