If you're already used to lifting weights, using free weights like dumbbells or barbells gives you about the same muscle growth in your thighs, chest, and abs as using weight machines — after 8 weeks of training.

If you're already used to lifting weights, whether you use free weights or machines, you'll gain about the same amount of muscle in your thighs, chest, and abs after 8 weeks — the type of equipment doesn't make a meaningful difference.

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 lift weights until you can't do another rep, or stop just before failure, your thigh muscles grow about the same amount after eight weeks — but stopping short feels less exhausting each time.

Doing a lot more leg workouts—over 50 sets a week—doesn’t make your thigh muscles grow bigger than doing 20–40 sets a week, even if you train for 12 weeks.

After nine weeks of lifting weights—whether heavy or light—men who work out casually don’t get bigger pectoral muscles, even though other muscles in their body do grow. This might mean some muscles just don’t respond the same way, or maybe they’re not doing the exercises right.