Cold-water immersion after training sessions: Effects on fiber type-specific adaptations in muscle K transport proteins to sprint-interval training in men

Abstract

Effects of regular use of cold-water immersion (CWI) on fiber type-specific adaptations in muscle K transport proteins to intense training, along with their relationship to changes in mRNA levels after the first training session, were investigated in humans. Nineteen recreationally active men (24 6 yr, 79.5 10.8 kg, 44.6 5.8 ml·kg1·min1) completed six weeks of sprint-interval cycling, either without (passive rest; CON) or with training sessions followed by CWI (15 min at 10°C; COLD). Muscle biopsies were obtained before and after training to determine abundance of Na, K-ATPase isoforms (1–3, 1–3) and phospholemman (FXYD1) and after recovery treatments (0 h and 3 h) on the first day of training to measure mRNA content. Training increased (P 0.05) the abundance of 1 and 3 in both fiber types and 1 in type-II fibers and decreased FXYD1 in type-I fibers, whereas 2 and 3 abundance was not altered by training (P 0.05). CWI after each session did not influence responses to training (P 0.05). However, 2 mRNA increased after the first session in COLD (0 h, P 0.05) but not in CON (P 0.05). In both conditions, 1 and 3 mRNA increased (3 h; P 0.05) and 2 mRNA decreased (3 h; P 0.05), whereas 3, 1, and FXYD1 mRNA remained unchanged (P 0.05) after the first session. In summary, Na,K-ATPase isoforms are differently regulated in type I and II muscle fibers by sprint-interval training in humans, which, for most isoforms, do not associate with changes in mRNA levels after the first training session. CWI neither impairs nor improves protein adaptations to intense training of importance for muscle K regulation. cold-water immersion; fiber type; FXYD1; Na,K-ATPase; single-fiber western blotting; training.