Passive dehydration increases oxidative stress and mTOR signalling pathway activation in young men following resistance exercise

Dehydration is prevalent and adversely affects exercise performance; however, its influence on cellular responses to exercise remains unclear. Thus, this study examined the intramuscular responses to resistance‐exercise (RE) in RE‐trained men under dehydrated and euhydrated states. Eleven men (21 ± 1 years, 175.9 ± 6.2 cm, 79.2 ± 12.3 kg, 18.4% ± 6.7% fat) completed two identical lower‐body RE sessions, either with (DEHY) or without (EUHY) fluid‐restriction from 24 h before to 3 h after RE. At pre‐RE (PRE), 1 h, and 3 h post‐RE, muscle samples were collected and analysed for protein content of AKT/mTOR/p70S6K/rpS6 and their corresponding phosphorylation sites, REDD1 and selected autophagy markers, cathepsin L, H₂O₂ concentration, fibre cross‐sectional area (CSA), and muscle water content. Significant time × condition interaction effects revealed that p‐rpS6^S240/244 was greater in DEHY than EUHY at PRE and increased from PRE to 1 h and 3 h in both conditions. In DEHY, REDD1 increased from PRE to 1 h and 3 h, active‐cathepsin L decreased from 1 h to 3 h and was greater than EUHY at 1 h, and muscle water content increased from 1 h to 3 h. Significant condition main effects revealed that p‐S6K^T389 and H₂O₂ were greater, and CSA was smaller, in DEHY versus EUHY. Significant time main effects revealed that p‐AKT^S473 and p‐mTOR^S2448 increased from PRE to 1 h and 3 h, LC3‐I decreased from PRE and 1 h to 3 h, LC3‐II decreased from PRE to 1 h and 3 h, and LC3‐II/LC3‐I decreased from PRE to 1 h and increased from 1 h to 3 h. These results suggest that performing RE in a dehydrated state imposes additional stress on the muscle, leading to greater cellular stress and growth signalling. image

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