Muscle training by means of combined electrical stimulation and volitional contraction

A variety of techniques have been used with variable success in an attempt to reverse the loss of muscle strength, bulk, and endurance that occurs during spaceflight. This study was designed to evaluate a new "hybrid" approach that uses the resistance provided by an electrically stimulated antagonist muscle to resist the volitional contraction of its agonist.

There were 20 subjects who were randomized into 3 groups that received either the new hybrid program (HYB), isotonic weight training (WT), or isometric electrical stimulation (ES). Subjects trained 3 times per week for 8 wk with each session consisting of their non-dominant upper extremity performing 10 sets of 10 reciprocal 2-s elbow flexion and extension contractions separated by 1-min rest intervals. Elbow flexion\extension torques and biceps\triceps cross-sectional areas (CSA) were measured at the beginning, midpoint, and end of training as well as at follow-up 4 wk later.

The HYB group demonstrated statistically significant increases in elbow flexion and extension torques (56% and 31%, respectively) at the end of training that were similar to or larger than the gains in the other groups with benefits that persisted at follow-up 4 wk later. Muscle CSA increases in the HYB group (10%) were comparable or larger than those in WT and ES subjects.

These results suggest that HYB training may be an effective way to maintain and increase muscle bulk and strength for patients during bed rest, as well as astronauts in space.