Exercising the Rib Muscles Below the Armpit

Exercising the Rib Muscles Below the Armpit. Part of the series: LS - Physical Therapy. The muscles below your armpit, the serratus anterior, is actually a very important muscle to avoid shoulder injury and rotator cuff tears, very important in throwing and reaching. Find out about exercising the rib muscles below the armpit with help from a fitness professional in this free video clip.