Characterizing Strains in the Tibia of Hindlimb Unloaded Rats During Combined Isometric and Eccentric Stimulated Muscle Contraction

We have conducted a series of studies for NASA sponsored by the NSBRI using the hindlimb unloaded (HU) rat model to simulate micro-gravity. Studies have focused on various questions related to specific effects on both bone and muscle in the unloaded limbs. In some cases, a muscle stimulation technique has been used to simulate resistive exercise as a countermeasure during HU. Results have been generally quite positive for bone but not as effective for muscle. Consequently, a series of successive alterations have been made to the muscle stimulation protocol parameters in an attempt to maintain benefits for bone while reducing the overall level of exercize in order to minimize fatigue effects on muscle.