Low‐volume muscle endurance training prevents decrease in muscle oxidative and endurance function during 21‐day forearm immobilization

Aim: To examine the effects of low‐volume muscle endurance training on muscle oxidative capacity, endurance and strength of the forearm muscle during 21‐day forearm immobilization (IMM‐21d). Methods: The non‐dominant arm (n = 15) was immobilized for 21 days with a cast and assigned to an immobilization‐only group (Imm‐group; n = 7) or an immobilization with training group (Imm+Tr‐group; n = 8). Training comprised dynamic handgrip exercise at 30% of pre‐intervention maximal voluntary contraction (MVC) at 1 Hz until exhaustion, twice a week during the immobilization period. The duration of each exercise session was 51.7 ± 3.4 s (mean ± SE). Muscle oxidative capacity was evaluated by the time constant for phosphocreatine recovery (τ_offPCr) after a submaximal handgrip exercise using ³¹phosphorus‐magnetic resonance spectroscopy. An endurance test was performed at 30% of pre‐intervention MVC, at 1 Hz, until exhaustion. Results: τ _offPCr was significantly prolonged in the Imm‐group after 21 days (42.0 ± 2.8 and 64.2 ± 5.1 s, pre‐ and post‐intervention respectively; P < 0.01) but did not change for the Imm+Tr‐group (50.3 ± 3.0 and 48.8 ± 5.0 s, ns). Endurance decreased significantly for the Imm‐group (55.1 ± 5.1 and 44.7 ± 4.6 s, P < 0.05) but did not change for the Imm+Tr‐group (47.9 ± 3.0 and 51.7 ± 4.0 s, ns). MVC decreased similarly in both groups (P < 0.01). Conclusions: Twice‐weekly muscle endurance training sessions, each lasting approx. 50 s, effectively prevented a decrease in muscle oxidative capacity and endurance; however, there was no effect on MVC decline with IMM‐21d.