You've been diligently doing barbell bench presses with every grip imaginable — wide, narrow, standard — and increasing in weight. You're getting stronger. However, when you look in the mirror, you notice a slight disparity between the two sides of your chest and you're not just interested in how much weight you can push. You want symmetry to look good on the bodybuilding stage or at the beach when you strip down to a swimsuit.
Uneven pec development isn't always your fault. You might have a slight genetic difference between the sides, fewer nerves might run to the smaller side or you may have suffered an injury that impeded development.
Your mistake when trying to even out your chest is relying only on exercises that use both sides of your pecs together. Bench presses, cable flyes and chest dips all allow your stronger side to compensate for a weaker one; the larger, stronger pec ends ups bearing a little more weight and grows at a faster rate.
Make up for your lagging pec development by switching up your exercises to isolate one side with dumbbells or a single arm presses.
Trade your barbell in for dumbbells so each side of your chest has to work independently. A single-arm press is especially valuable because you can choose a weight that's appropriate for each side without feeling completely wonky by trying to press two different weights together at the same time.
When you're trying to even out your pecs, don't just work the weaker or smaller side. Continue to work both sides, but challenge the weak side a bit more. Don't max out on weight on the stronger side — use a weight that is challenging but doable for about 12 reps. For your weak side, use a dumbbell that's heavier and fatigues you after about eight reps.
Hold a dumbbell in one hand at your hip and lie back on a workout bench. Extend the arm holding the dumbbell over your chest. Plant your feet and let your other arm rest in a comfortable position.
Bend your elbow to lower the dumbbell just outside your chest wall. The elbow should create a 45-degree angle with the torso.
Extend the elbow back up to straighten the arm. Repeat for your desired number of sets.
The cable column provides you with an opportunity to isolate one side of your chest at a time. You could also use a seated cable press machine.
Stand in front of a cable column with the pulley set at arm-pit height. Grab the handle in one hand and turn your back to the column.
Point your elbow out to the side as you hold the handle in front of the chest at shoulder height. Walk forward slightly to feel mild tension. Assume a staggered stance.
Press the handle forward until your elbow is fully extended. Bend the elbow to return the handle to the front of your shoulder. Avoid allowing the elbow to pull behind your body as this risks shoulder injury.
Use heavier resistance for your weaker side to help it catch up to your stronger one. Alternatively, use the same weight for each side, but do two or three more sets for your weaker side to increase the stress on the muscle.