When muscles get bigger from lifting weights, the way we measure it (ultrasound vs. body scan) doesn’t always line up—so they might be capturing different kinds of changes, not just muscle growth.

Even though both muscle thickness and total lean mass went up after training, they didn’t change together in a predictable way—meaning one might not be a perfect stand-in for the other.

Measuring thigh muscle thickness with ultrasound near the top and middle of the thigh is a good way to see if your muscles are growing from training—but measuring near the knee might not show it.

This study only looked at the front and side of the thigh—so we don’t know if doing more sets helps your front thigh or hamstrings grow more.

If you’re already experienced with weightlifting and train your legs twice a week for 8 weeks with hard sets, your muscles will grow whether you take short breaks between reps or not.

Muscles don’t grow evenly—when you train your thigh, the top and middle parts of the front muscle grow more than the bottom, and the side muscle grows the same everywhere.