When guys who never lifted weights before started doing leg workouts for 15 weeks, their thigh muscles got 12.7% bigger—and super-precise MRI scans proved it, showing this tech is great for tracking muscle growth.

The study used high-tech scans (MRI) to measure muscle growth in specific parts of the thigh, making the results more accurate than just guessing from body measurements.

If older people who didn’t get stronger from doing just one set of weight exercises start doing four sets instead, their thigh muscles will grow bigger — and this was measured with a detailed scan.

Doing full squats or full arm movements when lifting weights doesn’t necessarily make your thigh muscles grow bigger than doing partial movements—studies show both ways work about the same, so going all the way down or all the way up might not give you extra muscle gains.

When young men do isometric leg exercises for 12 weeks, their thigh muscles get bigger—and that bigger muscle size helps explain about 1 in 5 of their strength gains, even if their nerves aren’t getting better at telling muscles to work harder.

When guys who've never lifted weights before start training, using super detailed muscle scans and taking strength readings twice helps scientists measure changes more accurately—so they can tell for sure if bigger muscles mean stronger muscles.