AIM: This study explored the effects of blood flow restriction (BFR) on mRNA responses of PGC-1α (total, 1α1, and 1α4) and Na⁺ ,K⁺ -ATPase isoforms (NKA; α_1-3 , β_1-3 , and FXYD1) to an interval running session, and determined if these effects were related to increased oxidative stress, hypoxia, and fibre type-specific AMPK and CaMKII signalling, in human skeletal muscle.

METHODS: In a randomised, crossover fashion, eight healthy men (26 ± 5 y and 57.4 ± 6.3 mL∙kg^-1 ∙min^-1 ) completed three exercise sessions: without (CON) or with blood flow restriction (BFR), or in systemic hypoxia (HYP, ~3250 m). A muscle sample was collected before (Pre) and after exercise (+0h, +3h) to quantify mRNA, indicators of oxidative stress (HSP27 protein in type I and II fibres, and catalase and HSP70 mRNA), metabolites, and α-AMPK Thr¹⁷² /α-AMPK, ACC Ser²²¹ /ACC, CaMKII Thr²⁸⁷ /CaMKII, and PLBSer¹⁶ /PLB ratios in type I and II fibres.

RESULTS: Muscle hypoxia (assessed by near-infrared spectroscopy) was matched between BFR and HYP, which was higher than CON (~90% vs. ~70%; p<0.05). The mRNA levels of FXYD1 and PGC-1α isoforms (1α1 and 1α4) increased in BFR only (p<0.05) and were associated with increases in indicators of oxidative stress and type-I fibre ACC Ser²²¹ /ACC ratio, but dissociated from muscle hypoxia, lactate, and CaMKII signalling.

CONCLUSION: Blood flow restriction augmented exercise-induced increases in muscle FXYD1 and PGC-1α mRNA in men. This effect was related to increased oxidative stress and fibre type-dependent AMPK signalling, but unrelated to the severity of muscle hypoxia, lactate accumulation, and modulation of fibre type-specific CaMKII signalling. This article is protected by copyright. All rights reserved.