Development of practical and effective hybrid exercise for use in weightless environment

Bedrest and spaceflight are associated with profound losses of muscle bulk and strength which hinder patient's or astronaut's health and reintegration into daily life. We attempted to do two things in this small pilot study. First, we assessed the potential of hybrid electrical stimulation-volitional contraction exercise program to increase proximal lower extremity strength, muscle bulk, and bone mineral density (BMD). Second, we assessed the utility of unilateral lower limb suspension (ULLS) in producing losses in these quantities comparable to those that occur during bedrest and spaceflight. More specifically, this study made an initial evaluation of (1) ability of hybrid exercise program to preserve knee extensor and flexor maximum volitional contraction (MVC), cross-sectional area (CSA), and BMD in 4 healthy men between ages of 22 and 24, and (2) utility of ULLS in producing decrements in these parameters similar to those that occur in weightless environment in single 38 year-old male. Results show that CSA of rectus femoris and hamstrings increased about 5.3% and femoral BMD by 7%. MVC may have exhibited a more complex behavior with 3.0% at end of training, followed by 9.3% at follow-up. ULLS resulted in dramatic losses of strength (70%), CSA (4.8%), and BMD (8.2%).