Changes In Muscle Volume And Strength Following 16 Weeks Of Training Using The Advanced Resistive Exercise Device (ARED) And Free Weights

Abstract

Spaceflight-induced muscle atrophy and loss of muscle strength, particularly in the postural and locomotory muscles, might impair task performance during long-duration space missions and planetary exploration. High-intensity free weight (FW) resistive exercise training attenuates muscle atrophy and strength loss during bed rest, a space flight analog. NASA developed the Advanced Resistive Exercise Device (ARED) to simulate the characteristics of FW exercise (i.e. constant resistance, inertial forces) and to be used as a countermeasure during International Space Station (ISS) missions. PURPOSE: To compare the efficacy of ARED and FW training for inducing muscle hypertrophy and strength gains in ambulatory subjects prior to deploying ARED on the ISS. METHODS: Twenty untrained subjects were assigned to either the ARED (8 males, 3 females) or FW (6 males, 3 females) training group and participated in a periodized training protocol consisting of squat (SQ), heel raise (HR), and deadlift (DL) exercises 3 d·wk-1 for 16 wks. SQ, HR, and DL muscle strength (1RM) was measured before, after 8 wks, and after 16 wks of training. Muscle volume of the vasti group (V), hamstring group (H), hip adductor group (ADD), medial gastrocnemius (MG), lateral gastrocnemius (LG), and deep posterior muscles including soleus (DP) was measured using MRI at pre- and post-training. Consecutive cross-sectional images (10mm slices) were analyzed and summed. Anatomical references insured that the same muscle sections were analyzed pre- and post-training. Two-way repeated measures ANOVAs (p<0.05) were used to test for differences in muscle strength and volume between training devices. RESULTS: SQ, HR, and DL 1RM increased in both FW (mean±SE; SQ: 49±6%, HR: 12±2%, DL: 23±4%) and ARED (SQ: 31±4%, HR: 18±2%, DL: 23±3%) groups. Both groups increased muscle volume in the V (FW: 13±2%, ARED: 10±2%), H (FW: 3±1%, ARED: 3±1%), ADD (FW: 15±2%, ARED: 10±1%), LG (FW: 7±2%, ARED: 4±1%), MG (FW: 7±2%, ARED: 5±2%), and DP (FW: 2±1%; ARED: 2±1%) after training. There were no between-group differences in muscle strength or volume. CONCLUSIONS: The increase in muscle volume and strength following ARED training is not different than FW training. These findings indicate that ARED will likely protect against spaceflight-induced muscle atrophy and strength loss.