Your shoulders are capable of rotating 360 degrees, allowing you to move your arms in all directions from front to back and side to side. Thanks to your main shoulder joint, the glenohumerus, you can also move your arms across your body. This movement is called shoulder horizontal flexion. Horizontal refers to the transverse plane of motion and flexion refers to the forward movement of your arms. There are many exercises that use this movement to build your chest and shoulder muscles.
There are several muscles responsible for shoulder horizontal flexion. The main muscles are the pectoralis major clavicular head, pectoralis major sternocostal head, pectoralis major abdominal head, anterior deltoid and coracobrachialis. The pec majors are also known as the chest muscles. The anterior deltoid is more simply referred to as the front shoulder muscle, and the coracobrachialis is a muscle running from your upper arms up to your shoulder region.
Pushup and Bench Press
The two most common shoulder horizontal flexion exercises are the pushup and the bench press. The bench press is basically the same exercise as the pushup, except you are lifting an external resistance rather than your own body weight. To do the bench press using a barbell, lie face up on a flat bench holding the barbell shoulder-with apart. Horizontally extend your shoulders and bend your elbows to lower the barbell toward your chest. Then, horizontally flex your shoulders and extend your elbows to drive the barbell back up to the start.
If you take out the elbow-extending movement from the pushup or bench press, then you're left with an exercise known as the flye. This exercise is literally strict shoulder horizontal flexion, because there is minimal movement in your other joints. To do flyes, lie face up on a flat bench holding a pair of dumbbells over your thorax. From this position, turn your elbows out and keep them in a slightly bent position throughout the movement. You're now ready to begin strict shoulder horizontal flexion. First, lower your arms out to your sides by extending your shoulders horizontally. Don't let your elbows travel behind your shoulders during this downward movement. Then, lift the dumbbell over your thorax by flexing your shoulders horizontally.
You don't want your elbows traveling behind your shoulders during shoulder horizontal flexion because that places too much stress on your shoulder joint. And it places the pec major tendon in a vulnerable position for either a strain or a tear. You will have a difficult time seeing the extent to which your arms travel during the downward phase of the aforementioned exercises. However, you will feel a deep stretch in your pec major muscles. When you feel this stretch, stop the downward motion. You should not feel pain during this phase, only a stretching sensation.
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