Cold water submersion attenuates post-submersion aerobic performance and orthostatic tolerance irrespective of partial rehydration with water

Abstract

Purpose: This study examined the independent effects of cold-water submersion and a rehydration strategy on an aerobic endurance performance and orthostatic tolerance following a four-hour dive in cold water (10°C). Methods: Nine male subjects completed a control (CON) performance and lower-body negative pressure test (LBNP) and two water immersion visits with either no rehydration (NR) or a post-immersion rehydration (RH) with 1 L of water. Following submersion, subjects ran to exhaustion and submitted to LBNP. Results: Core body temperature declined during submersion and remained reduced from baseline until the run (P <0.001) and was not different between NR and RH (P = 0.13). Total urine output during submersion was not different between groups (1.69 ± 0.49 (NR), 1.75 ± 0.52 (RH) L; P = 0.74) eliciting a body mass reduction of -2.2 ± 0.3 and -0.8 ± 0.3% (P < 0.01), respectively. Run duration was not different (547 ± 141 (NR), 566 ± 152 (RH) s; P = 0.79); however, both NR and RH run duration was shorter compared to CON (722 ± 170 s; P = 0.04). Cumulative stress index was suppressed in NR (534 ± 163 mmHg*min) and RH (591 ± 129 mmHg*min) compared to CON (707 ± 170 mmHg*min, P ≤ 0.03), with no differences between submersion trials (P = 0.23). Conclusions: Compared to a non-submersed state, run duration and orthostatic tolerance was reduced following a four-hour, cold-water submersion. Rehydration with 1 L of water following submersion did not offer a performance advantage over no rehydration.