A lateral raise is a resistance training exercise that involves lifting your arms out to your sides. It is an isolation movement with motion occurring at the shoulder only. This exercise is typically performed with dumbbells or cables. It can also be done while seated on a machine designed for the purpose. Lateral raises work the muscles on the side of your shoulder.
Shoulder Muscles
Eleven muscles cross and act at your shoulder joint. Some of these originate on your trunk, while others are attached to your shoulder blade. All of these muscles insert on your arm. This orientation allows these muscles to move your arm in a variety of directions in relation to your body. When you raise your arm to the side while performing lateral raises, two of these muscles are favored. These are the middle head of the deltoid and the supraspinatus of the rotator cuff.
Middle Deltoid
The deltoid muscle has three heads that allow it to pull your arm in distinctly different directions. The front portion aids all forward movements and also rotates your arm inward. Consequently, this head would be favored when you raise your arm to the front. Conversely, when you raise it to the side, the fibers making up the middle portion will be targeted. The greatest activity of theses fibers when performing lateral raises is between 90 and 120 degrees.
Supraspinatus
There are four muscles of the rotator cuff that serve as both movers and stabilizers of the shoulder. These are the subscapularis, supraspinatus, infraspinatus and teres minor. The supraspinatus acts with the middle deltoid to raise your arm to the side throughout the entire range of motion. It is also an important shoulder stabilizer as it helps prevent downward dislocation.
Shoulder Development
The supraspinatus is an underlying muscle that typically will not grow substantially. It is important to strengthen it for functional purposes because it is a very important stabilizer that is often injured. The middle deltoid is more prominent and when developed, provides width to your shoulders. For aesthetic purposes, this is an important muscle to train.
References
- "Kinesiology: Scientific Basis of Human Motion, Twelfth Edition"; N. Hamilton et al.; 2008
- "ACE Personal Trainer Manual, 4th Edition"; American Council on Exercise; 2010
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