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 untrained men get stronger during dynamic leg extensions, the biggest factor is how much they can turn on their thigh muscles — bigger muscles and fiber angles help a little, but turning on the muscles harder matters most.

When untrained men get stronger during dynamic leg movements like standing up, the biggest factor is how much their thigh muscles fire, especially when combined with changes in the deep thigh muscle’s fiber angle and overall muscle size.

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.

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.

If new guys do leg exercises with slow reps (6 seconds) instead of faster ones (2 seconds), they might get stronger in a specific knee position—even if they do the same number of sets and their muscles grow the same amount.