Muscle from aged rats is resistant to mechanotherapy during atrophy and reloading

Massage is a viable mechanotherapy to improve protein turnover during disuse atrophy and improve muscle regrowth during recovery from disuse atrophy in adult muscle. Therefore, we investigated whether massage can cause beneficial adaptations in skeletal muscle from aged rats during normal weight-bearing (WB) conditions, hindlimb suspension (HS), or reloading (RE) following HS. Aged (30 months) male Fischer 344/Brown Norway rats were divided into two experiments: (1) WB for 7 days (WB, n = 8), WB with massage (WBM, n = 8), HS for 7 days (HS7, n = 8), or HS with massage (HSM, n = 8), and (2) WB for 14 days (WB14, n = 8), HS for 14 days (HS14, n = 8), reloading (RE, n = 10), or reloading with massage (REM, n = 10) for 7 days following HS. Deuterium oxide (D₂O) labeling was used to assess dynamic protein and ribosome turnover in each group and anabolic signaling pathways were assessed. Massage did have an anabolic benefit during RE or WB. In contrast, massage during HS enhanced myofibrillar protein turnover in both the massaged limb and contralateral non-massaged limb compared with HS, but this did not prevent muscle loss. Overall, the data demonstrate that massage is not an effective mechanotherapy for prevention of atrophy during muscle disuse or recovery of muscle mass during reloading in aged rats.