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Investigating Voluntary Wheel Running as a Recovery Method for Tail Suspension Induced Sarcopenia.   A.M. Hanson, S.J. Simske, L.S Stodieck, C.A. Cannon, V.L Ferguson. BioServe Space Technologies, Univ. of Colorado.

   Tail-suspension is a commonly used method to induce sarcopenia in mice. This study examines voluntary cage wheel running following muscle loss after tail suspension. Forty-eight 12-week old C57BL/6J male mice were evenly divided into four groups: unsuspended (US)-wheel recovery (R), US-non-wheel recovery (NR), tail-suspended (TS)-(R), and TS-NR. The soleus, extensor digitorum longus (EDL) and gastrocnemius muscle wet weights were recorded at sacrifice. Instrumented running wheels measured distance run/day. Muscle performance was assessed in vivo by measuring the force exerted by the hind limbs and ex vivo by electrophysiological testing of the soleus and EDL. Data were analyzed using two-way ANOVA with followed by Tukey group-group comparison. The soleus, EDL and gastrocnemius muscles of the NR mice decreased by 27.6% (p<0.001), 11.1% (p=0.013) and 13.1% (p=0.002) respectively, with TS. After 7 days of wheel running, the effect of TS on muscle mass was much less pronounced (11.7% p=0.040, 11.4% NS and 3.5% NS respectively). After one day of running, US mice ran 46.9% further than TS mice. TS performance improved after 7 days, such that US mice ran 24.9% further than TS mice. Ex vivo EDL strength exhibited no significant change with TS or R, whereas the soleus demonstrated a 31.8% (p=0.002) decrease in strength with TS in NR mice and a 21.7% (p=0.039) decrease in R mice. Overall, measurements of in vivo strength decreased with both TS (17.1%, p<0.001) and R (10.0%, p=0.042). In vivo hind limb strength significantly increased (13.5%, p=0.031) after 7 days of running in US mice and no significant difference in TS mice. TS significantly decreases muscle masses, distance run/day during recovery, and measurements of in vivo and ex vivo soleus strength. 7 days of voluntary wheel running aids in recovery of lost muscle mass and strength due to TS, but is not a sufficient length of time for total, functional recovery.

(Supported by NASA: NCC8-242)