Toning your underarms is a common goal. So common, in fact, that it led the American Council on Exercise to sponsor a women-only study in 2011 to determine which underarm exercises best tone the triceps. Researchers at the University of Wisconsin, La Crosse, studied different exercises and ranked the results based on the amount of triceps activation produced by each exercise.
Read more: The Best Arm-Toning Pilates Exercises
Perform a variety of triceps-toning exercises to firm up your underarm area.
1. Triangle Push-Up
Do the underarm exercise the study ranks as the most effective exercise for challenging the underarms. Triangle push-ups also strengthen the chest, abdominal and lower back muscles.
HOW TO DO IT: Kneel on all fours and place your hands on the floor, under your shoulders. Bring your hands together, forming a triangle with your thumbs and forefingers. Extend your feet behind you and lift onto your toes. Tighten your abdominal muscles, aligning your shoulders, lower back, hips, knees and ankles. Don't sag your back or hips during the push-ups.
Slowly lower your upper body toward the floor, bending and flaring your elbows as you descend. Stop before your chest touches the floor, push through your arms and lift your body to the start position. Drop to your knees to make the push-ups easier. Complete 12 to 15 repetitions, stopping when your muscles fatigue.
2. Triceps Kickback
Include the study's second-best underarm exercise in your workouts — triceps kickbacks.
HOW TO DO IT: Hold a dumbbell in your right hand, stand up straight and stagger your stance: left foot forward, right foot back. Pointing both feet forward, lean forward 45 degrees and place your left hand on the top of your left leg. Press your right arm against your right side, then lift your right forearm parallel to the floor.
Slowly push the weight behind you and straighten your arm. Bring the weight back to the start position. Complete 12 to 15 repetitions, stopping when your arm fatigues. Switch sides and do 12 to 15 reps with your left arm.
Read more: 10-Minute Arm-Sculpting Workout
3. Triceps Dip
Do triceps dips, the underarm exercise ranked third most effective for training the triceps.
HOW TO DO IT: Sit on a workout bench, place your hands next to your hips and wrap your fingers around the edge of the bench. Straighten your wrists and tuck your elbows by your sides.
Relax your shoulders, tighten your stomach muscles and walk your feet forward 24 inches. Lift your hips off the bench and position them directly in front of it.
Lower your hips slowly toward the floor, bending your elbows as you descend. Don't let your elbows flare — tucked elbows keep the emphasis on the triceps. Stop when the back of your arms are parallel to the floor, push through your hands and lift your hips in front of the bench.
Complete 12 to 15 repetitions, stopping when the back of your arms fatigue. Lift one foot off the floor to make the dips harder.