It's one thing to say you're going to build up your chest muscles, but if your intention is to develop a well-sculpted — dare we say, artistic — chest, there's more involved than just maxing out your pecs with bench pressing.
The pectoralis major, the most visible of chest muscles, is one large muscle, but it does have discernible regions. They are more identifiable in terms of upper and lower rather than inside and outside, but for some people, the sides may be the hardest to tone up.
Side Chest Workout
Alas, there are so many exercises for your side chest workout and so little time. Since you can't do all of them at once, it's important to mix them up because different exercises work the muscles from different angles.
The standard barbell bench press is a great place to start for an overall chest workout, but for eliciting activation in all regions of the pecs, it's a good idea to get friendly with dumbbells. You can get more ideas insights from the American Council on Exercise's study of the best chest exercises, but a few exercises that may favor the outer pecs include:
1. Dumbbell Flyes
Dumbbell flyes are one of the best exercises for adding muscle fibers in your side pec workout. Proper form is essential to avoid transferring the load to your shoulders, which diminishes activation in your pecs and can lead to injury.
How to: Lying back on a flat bench, hold dumbbells in each hand over the center of your chest, keeping a slight bend in your elbows. Your palms are facing each other. Lower the dumbbells as far as you can. As you lift them back toward the starting position, pause at about three-quarters of the way up. Do eight to 12 repetitions with enough weight to cause muscle fatigue by the end of the set.
Dumbbell flyes can also be done on both incline and decline bench.
2. Seated Chest Press
The seated chest press machine is more or less the vertical version of dumbbell flyes, but the change in orientation and the push-resist movement will emphasize different muscle fibers as part of your side chest workout.
To boost intensity, do them one arm at a time or sit forward away from the backrest so that it takes more core effort to maintain stability. The seated press machine mainly works the outer pecs and is great for beginners.
Adapt ordinary push-ups to work the outer pecs. The first variation is to use a wider grip than the usual shoulder-width distance between hands. Experiment with different amounts of space between your hands and stay tuned into your outer pecs to see what makes you feel them.
Doing push-ups at an incline with your hands resting on a surface that's higher than your feet will also enhance activation of the outer pecs.
4. Push-Ups Plus
Another key push-up variation that will assist in tapering the outer pecs is the push-up plus, sometimes referred to as serratus anterior (SA) push-ups. These are excellent for toning up the aforementioned SA, the two muscles that flank the sides of the torso, adding broadness to the chest as part of your side pec workout.
How to: Assume plank position with arms at shoulder width. Lower yourself to the floor and back up as you would with a standard push-up. At the top of the position, when your arms are fully extended, press your palms firmly into the floor and broaden your shoulder blades and drive them upward toward the sky. To deepen activation of the serratus anterior, hold in this position for one or two seconds.
The last action — the "plus" part of the push-up — is fairly subtle, but will unglue your shoulder blades and bring your chest forward.
Burn Some Fat
Everybody's different, and a lot of people tend to accumulate fat at the outer region of their pecs. Losing fat almost always means losing weight. Unfortunately, there's no such thing as "spot reduction" for side chest fat — your body mass index doesn't really care where you want to lose it. But as your body becomes leaner overall, flab at the sides of your pecs sooner or later will exit the building.
To lose a pound of fat, you've got to create a deficit of 3,500 calories. A two-pronged approach is best: eat less and burn more with cardio training. High-intensity interval training (HIIT) is an effective way to accomplish that. HIIT means alternating intense bursts of activity with intervals of lesser exertion or complete rest. For example, you might jam hard on the treadmill for two minutes and walk for one minute at two or three workouts during the week.