A rat resistance exercise regimen attenuates losses of musculoskeletal mass during hindlimb suspension

ABSTRACT Exposure to microgravity and/or spaceflight causes dramatic losses in both muscle and bone mass. In normal gravity, resistance exercise has been effectively used to increase muscle and bone mass. We tested a novel form of resistance exercise training using flywheel technology as a countermeasure to offset the loss of musculoskeletal mass during 4 weeks of adult rat hindlimb suspension (HS), an unloading model of microgravity. Male, Sprague–Dawley rats (6‐month old) were operantly conditioned to perform resistance exercise, and then randomly assigned to groups of sedentary control (CON), HS, and HS with resistance exercise training (HSRT; 2 sets of ∼21 repetitions, 3 days week−1 for 4 weeks during suspension). In soleus, HS resulted in lower (P