A study presented at the 2005 meeting of the American College of Sports Medicine, however, seems to confirm that muscles can be activated at different points.1 The muscle in question was the familiar biceps. The purpose of the study was to determine whether varying biceps exercises, as commonly used by bodybuilders, produces a differential growth pattern in three regions of the muscle: near the origin (top of the arm), the belly (middle of the upper arm) or near the insertion (at the bottom of the upper arm).
Sixty-eight subjects trained with weights for 12 weeks on a biceps program. They used a progressive, periodized protocol, doing four weeks of 12 reps using 65 to 75 percent of one-rep maximum, or 1RM, weight; five weeks of eight reps using 75 to 82 percent of 1RM; and three weeks of six reps, using 83 to 90 percent of 1RM. Thus, the training required a gradual increase in poundage coupled with a decrease in reps. The exercises were preacher curls, concentration curls and standing barbell curls. To determine changes in the subjects’ biceps as a result of the training, the researchers used magnetic resonance imaging, or MRI.
After 12 weeks all areas of the biceps showed growth, with the greatest change appearing in the lower biceps, near the insertion of the muscle. Investigators thought that was because it’s the part of the biceps most affected by maintaining the hand in a typical curl position. The next most affected portion was the belly, followed by the top of the upper arm.
The study lends weight to the long-held notion that different exercises affect different portions of a trained muscle, despite a common nerve supply. Once again, science has born out the experiences of countless bodybuilders over many years.
©,2013 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited.
