A MINIMALISTIC MODEL OF RESISTANCE TRAINING: EFFECTS ON SKELETAL MUSCLE FUNCTION DURING UNLOADING

1657 Since astronaut time and energy are at a premium, effective countermeasure programs must be designed to maximize benefits while minimizing the time/energy cost. Therefore, our intent was to design and evaluate a low volume, high intensity resistance training program (RTP) on the preservation of knee extensor and plantar flexor strength and size in response to unloading. Eight men underwent 21 days of unilateral lower limb suspension (ULLS) and were assigned to no exercise (NE, n=4) or countermeasures (CM, n=4). CM was performed every third day over the 21 d period (total of 6 sessions). CM consisted of 2 maximal isometric contractions, 1 set of 10 concentric (CON) and eccentric (ECC) isotonic repetitions, and 1 set to exhaustion, at 80% of the CON 1-repetition maximum (1RM). Maximal CON and ECC 1RM strength and maximal isokinetic strength across 6 CON (1.05-8.73 rad·sec−1) and ECC velocities (1.05-5.24 rad·sec−1) were assessed. Knee extensor work capacity (WC) was evaluated during 30 maximal CON contractions at 3.14 rad·sec−1. Neural activation of v. lat, v. med, gast and sol was measured by electromyography (EMG). Muscle cross sectional area (CSA) was measured by computed tomography (CT). NE CON and ECC isokinetic strength decreased at all velocities (range. 13-30%) and peak isometric and 1RM strength declined 19% and 20%, respectively (p<0.05). CM showed no strength changes. Knee extensor WC decreased 15% in NE (p<0.05), and was unaltered in CM. Submaximal v. lat EMG increased and maximal v. lat, gast and sol EMG decreased in NE (p<0.05). CSA decreased 8% (quadricep) and 9% (calf) in NE, while no changes in CM were observed. These data suggest muscle strength and size are preserved during unloading using a low volume, high intensity RTP performed every third day. Supported by NASA and the Indiana Space Grant Consortium.