Cold water immersion attenuates anabolic signalling and skeletal muscle fiber hypertrophy, but not strength gain, following whole-body resistance training.

We determined the effects of CWI on long-term adaptations and post-exercise molecular responses in skeletal muscle before and after resistance training.Sixteen males (22.9 ± 4.6 y; 85.1 ± 17.9 kg; mean ± SD) performed resistance training (3 d·wk) for 7 wk, with each session followed by either CWI (15 min at 10°C, COLD group, = 8) or passive recovery (15 min at 23°C, CON group, = 8). Exercise performance [one-repetition maximum (1-RM) leg press and bench press, countermovement jump, squat jump and ballistic push-up], body composition (dual x-ray absorptiometry), and post-exercise (i.e., +1 and +48 h) molecular responses were assessed before and after training.Improvements in 1-RM leg press were similar between groups [130 ±69 kg, pooled effect size (ES): 1.53; ±90% confidence interval (CI) 0.49], while increases in type II muscle fiber cross-sectional area were attenuated with CWI (-1959 µM; ±1675; ES: -1.37; ±0.99). Post-exercise mTORC1 signalling (rps6 phosphorylation) was blunted for COLD at POST +1 h (-0.4-fold, ES: -0.69; ±0.86) and POST +48 h (-0.2-fold, ES: -1.33; ±0.82), while basal protein degradation markers (FOX-O1 protein content) were increased (1.3-fold, ES: 2.17; ±2.22). Training-induced increases in HSP27 protein content were attenuated for COLD (-0.8-fold, ES, -0.94 ±0.82), which also reduced total HSP72 protein content (-0.7-fold, ES: -0.79, ±0.57).CWI blunted resistance training-induced muscle fiber hypertrophy, but not maximal strength, potentially via reduced skeletal muscle protein anabolism and increased catabolism. Post-exercise CWI should therefore be avoided if muscle hypertrophy is desired.