Impact of Mechanical Load on Recovery from Reloading-Induced Muscle Injury

Abstract

180 Reloading (RL, i.e. weightbearing) of skeletal muscle following hindlimb suspension (HS) or spaceflight is known to induce muscle damage. The significant reduction in maximal isometric force (Po, N/cm2) of the soleus (SOL) muscle following 7 days HS consequent to 24- or 48 hrs RL is shown below: (Table 1)Table 1The purpose of this study was to determine if altered mechanical load impacted on the rate of recovery of contractile properties following RL-induced muscle injury in male Sprague Dawley rats (250-300 gms). Following 7 days of HS, rats were allowed to RL for 48 hrs. Thereafter, rats were randomly assigned to 1 of 4 groups: re-suspended for 7 days (RS × 7D) or 14 days (RS × 14D), or cage-bound with daily treadmill walking (12 m/min, 20 min/day) for 7 days (TM × 7D) or 14 days (TM × 14D). In vitro isometric contractile properties (25°C) of the SOL muscle were measured. The mean Po (± S.D.) for the 4 groups are shown in in the following table: (Table 2)Table 2Compared with RS, cage-bound activity coupled with daily treadmill walking resulted in a significantly higher Po both 7- and 14-days after reloading-induced muscle injury (P < 0.05). These results indicate that the amount of load post-injury significantly impacts on the rate of recovery. Supported by the University @ Buffalo Moir P. Tanner and Mark Diamond Funds.