If you're a young guy who's never lifted much before, doing push-ups and light bench presses until you can't do any more, twice a week for two months, will make you just as strong on the bench press as if you were lifting heavier weights — and you don't even need dumbbells or barbells.

You can make push-ups easier or harder by changing how you do them—like bending your knees or putting your hands on a raised surface—to match the same effort as lifting 40% of your max bench press weight, so you can still build strength without any gym equipment.

Doing push-ups with light weights until you can't do more doesn't make your biceps bigger, but doing the same kind of light-weight bench presses does — so your arms respond differently to these two exercises.

Whether you do chest and back exercises together or separately, lifting weights for 8 weeks will make you stronger on the bench press and lat pulldown.

If you're a young guy who already lifts weights, doing workouts until you can't do another rep for 12 weeks will make your legs and shoulders just as strong whether you use light or heavy weights—but for the bench press, heavy weights make you stronger than light ones.

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.