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.

Partial and Complete Fluid Replacement Maintains Exercise Performance in a Warm Environment Following Prolonged Cold-Water Immersion

“…Postimmersion running performance (.70% V Ȯ2max ) is reduced in a temperate environment with ;2% immersion-induced hypohydration (10,11). The compromising effects of dehydration were expected to be augmented with cold-water immersion and exercise in a warm environment.…”

“…Previous research in our laboratory has shown that 4 hours of thermoneutral water immersion results in mild hypohydration (∼1.6% body mass loss) and that fluid replacement during or following water immersion has no effect on run time to exhaustion at 70% age-predicted heart rate max (11). In a similar study, 4 hours of cold-water immersion (10°C) resulted in >2% body mass loss and a 23% reduction in run time to exhaustion at ∼85% maximal oxygen consumption (V̇O 2max ) in thermoneutral conditions compared with a no-immersion control (10). Postimmersion fluid replacement (1 L of water) failed to rescue these performance decrements despite correcting body mass loss to ∼0.8% of baseline.…”

“…The magnitude of these fluid shifts and diuretic stimulus (13,22) are even greater in cold water (10-18°C) (32) because of increased peripheral vasoconstriction when compared with thermoneutral water (4,12). During prolonged immersion, total urine output can exceed 1.7 L, resulting in body mass loss that is sufficient to impair aerobic performance on land (4,10).…”