The axillas, or armpits, are framed by three primary muscles on either side of the body. The anterior border of each axilla is formed by the pectoralis major muscle as it crosses the shoulder joint. The posterior is bordered by the lats as it runs from your back to your upper arm. The inferior surface is made up of a finger-like muscle called the serratus anterior. To target your armpits, include dumbbell exercises that focus on your pecs, lats and serratus anterior muscles.
Perform your chest, back and serratus anterior workout routine at the beginning of the week such as on a Monday so you have plenty of energy to target your armpits.
Pair two exercises for different muscles together, alternating sets so one muscle can recover while you're working the other muscle.
Begin your workout with flat dumbbell bench presses by holding a dumbbell each hand and sitting at the edge of the flat exercise bench. Lean back then press the dumbbells directly over the center of your chest for the starting position. Lower the dumbbells until they are about 1 inch from touching your shoulders then contract your pecs to press the dumbbells back over the center of your chest. Complete six sets of six to 12 repetitions per set, focusing on the front of your armpits.
Include single-arm dumbbell rows for your back muscles, enhancing the posterior aspect of your armpits. Hold one dumbbell with your right hand then place your left knee and your left palm on a flat exercise bench to support your body. Keep your back flat as you pool the dumbbell up toward your right shoulder, squeezing your shoulder blade toward your spine. Slowly lower the dumbbell toward the floor and repeat for six sets of six to 12 repetitions per set.
Perform flat dumbbell flies by sitting at the end of a flat bench with a dumbbell in each hand. Lie back then press the dumbbells directly over your chest; rotate your arms so your palms are facing each other. Open your arms as if to give someone a hug while simultaneously bending your elbows to draw the dumbbells part. Contract your pectoral muscles as you simultaneously raise the dumbbells together and straighten your elbows. Do six sets of six to 12 repetitions per set for the front of your armpits.
Hold the bar of a dumbbell with both hands then lie with your back flat on a flat exercise bench; shimmy your body so that the end of your head is in line with end of the bench. Raise the dumbbell directly over your chest then slowly draw the dumbbell behind your head until you feel a pull across the sides of your rib cage. Focus on the serratus anterior muscles along the side of your ribs, contracting them to bring the dumbbell back over your chest. Complete six sets of six to 12 reps per set, toning the inferior section of your armpit.
Keep a workout log to ensure you are continuously challenging the muscles of your armpits by gradually increasing the resistance you are using.