Surprise: The triceps actually make up the bulk of your upper arm (no matter how many biceps curls you do).

โ€œTriceps are the big, primary movers for upper-body โ€˜pushโ€™ motion, meaning extension of the arms,โ€ says personal trainer Chris Clough, based in Baltimore and Washington, DC. โ€œThe most common mistake beginners make is ignoring their triceps.โ€

The second most common mistake? โ€œOverworking your tricepsโ€”that is, not recognizing the work triceps do while youโ€™re bench pressing.โ€

The solution? Do this beginner-focused triceps workout once or twice a week, but make sure you donโ€™t do it the day after you focus on a chest-heavy workout.

Directions: 
Aim for four sets of 12โ€“15 reps, with just 15 to 30 seconds of rest between sets. (Increasing muscle mass requires volume.) Use a load heavy enough so itโ€™ll be challenging to complete your reps, but not so heavy that you canโ€™t maintain good form.

For the sake of clarity: โ€œUpper armโ€ refers to the part thatโ€™s closer to your shoulder.