If young, healthy guys do certain muscle-damaging exercises before their leg is immobilized, their muscles might waste away less—even if their muscle-building activity goes down. Without those exercises, lower muscle-building activity means more muscle loss.

If young, healthy guys do a tough leg workout right before having one leg immobilized for a week, their muscles in that leg keep building protein faster for the first couple of days compared to if they didn’t exercise first.

If young, healthy guys do certain muscle-lengthening exercises before having one leg kept still for a week, their muscles don’t slow down making new proteins as much as those who don’t exercise — which might help prevent muscle loss.

After 10 weeks of working out, men who are already somewhat active don't build muscle as efficiently as before, and their bodies don't respond as strongly to exercise—this happens whether they're doing cardio or weight training.

When young men lift weights to build muscle, their muscle-building process speeds up at first but slows down after 10 weeks, even if they keep increasing the difficulty.

If you lift heavy weights or do lots of reps with lighter weights, your muscles grow at the same rate—so it doesn’t matter which way you train, as long as you’re already fit.