When you do two different styles of weightlifting—one with heavy weights and fewer reps, and one with lighter weights and more reps—but match the total amount of work done, both can make your arm muscles grow just as much after 8 weeks.

Two different weightlifting styles—one focused on heavy weights with long breaks, the other on lighter weights with short breaks—both grew arm muscles about the same amount when people lifted the same total amount over 8 weeks.

Lifting heavy weights with longer breaks between sets makes young men stronger faster than lifting lighter weights with shorter breaks, based on an 8-week study.

If you do the same total amount of weightlifting work, lifting heavy weights with longer breaks and lifting lighter weights with shorter breaks both build muscle about the same, but lifting heavy gives you more strength.

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.

If you're someone who regularly lifts weights, doing more triceps exercises each week might help your triceps muscles get a little bigger—but only a little, and not as much as it helps your biceps.