Metabolic habituation following repeated resting cold-water immersion is not apparent during low-intensity cold-water exercise

Abstract

This project examined the effects of repeated, resting cold-water immersion on metabolic heat production and core temperature defence during subsequent rest and exercising immersions. Seven males undertook 15 days of cold-water adaptation, immersed to the fourth intercostal space, with cold-water stress tests (CWST) on days 1, 8 and 15 (18.1 SD 0.1°C: 60 min seated, followed by 30 min cycling (1 W-kg-1)), and 90-min resting immersions (18.4 SD 0.4°C) on each of the intervening days. Adaptation elicited an habituated thermogenic response during the rest phase of CWST3 beyond 20 min, compared to CWST1 (P<0.05), with oxygen consumption averaging 11.15 (± 0.25) ml-kg-1-min-1 and 8.61 (± 0.90) ml-kg-1-min-1 by 50 min, for CWST1 and CWST3, respectively. During exercise, this metabolic blunting was only apparent over the first 10-min period (60-70 min). No significant differences were observed during either the rest or exercise phases of the CWSTs for oesophageal temperature (Tes). While repeated cold-water exposures produced an habituated-thermogenic response, for an equivalent drop in Tes during rest, neither this response, nor an elevated thermogenesis, were apparent during subsequent cold-water exercise.