When two different ways of lifting weights are adjusted so that the total time your muscles are under strain is the same, both ways lead to about the same strength gains and muscle growth in people...

If you're already strong and lift weights, training each muscle group either once or five times a week for eight weeks will give you about the same strength gains on the bench press, squat, and row.

If you're a guy who's already used to lifting weights, doing fewer reps with heavier weights and longer rests might boost your bench press more than doing lots of reps with lighter weights and short breaks — at least over 8 weeks.

If you're a regular gym-goer, doing workouts that group similar muscle moves together or alternate them doesn't seem to make a difference in how much stronger or bigger your muscles get after 8 weeks.

If you do push-ups or bench presses with light weights until you can't do another rep, twice a week for two months, your arms and chest will grow just as much — so push-ups can be just as good as gym machines for building muscle, if you push yourself just as hard.

When people who’ve never lifted weights before train their chest and arms with the same total muscle tension time, the back part of their triceps (near the elbow) grows more than the middle or shoulder-end parts.