Taking a lot of creatine for 5 days doesn’t seem to boost muscle repair or growth right after a workout in young, healthy guys—even though it does increase creatine levels in their muscles. So, creatine might help muscles grow in other ways, not by speeding up protein building right after exercise.

Doing a tough leg workout with lots of sets makes your leg muscles start building new proteins much faster—2 to 3 times more than usual—right after the workout.

Doing short bursts of intense exercise can help your muscles make more proteins, especially the ones in energy factories inside cells, but it doesn’t always make your muscles bigger if you only do it for less than six weeks.

Taking 21 grams of creatine a day for 5 days can boost the amount of creatine in your muscles by about 30%, but it doesn’t make your muscles build protein faster or break it down slower, whether you’ve eaten or not.

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.