Beach muscles refer to a group of muscles that lie on the front of the human body. These include the major muscles of the chest, shoulders, quadriceps, abdominals and biceps.
The name comes from the fact that these muscles are commonly emphasized using a weight or resistance training routine in order to look good in a situation where a shirt is not required or a bathing suit is worn, such as at the beach. In order to judge the development of these muscles, a person will need to observe him or herself in a mirror. However, by observing in a mirror, the person is unable to view the muscles of the back of his or her body and, as such, frequently either under-emphasizes or forgoes the training of these muscles. This neglect of significant number of other muscles can lead to frequent injury (or risk of injury). Hence, it is always advisable to train for symmetry and proportion.