The latest myoelectric prostheses have several degrees of freedom and therefore require a large number of myoelectric signals to fully exploit their capabilities. Muscle compartments, which are intra-muscular subdivisions innervated by an individual muscle nerve branch, can be exploited to provide additional independent muscle control sites to operate such prostheses. To explore whether muscle compartments can be voluntarily controlled, electromyographic (EMG) signals are recorded from an array of seven pairs of equally spaced surface electrodes positioned across the biceps brachii of four healthy subjects. The EMG signals are collected in two positions: 1) with the subject seated, right elbow flexed ~100°, and 2) with the subject standing with the right arm extended horizontally in the coronal plane (out to the side). In both positions, the hand is either fully supinated, neutral, or fully pronated. The average root mean square value of the EMG signals obtained from three pairs of electrodes positioned over the biceps short head are compared with the average obtained for the three pairs placed over the biceps long head. Out of the nine hand position/load pairs examined, two pairs are found to elicit larger EMG activity in the long head or in the short head. The potential to preferentially activate either the short or the long head of the biceps suggests that the selective activation of muscle compartments is a promising strategy for facilitating the control of myoelectric prostheses capable of generating many types of movement.