Endurance capacity impairment in cold air ranging from skin cooling to mild hypothermia.

We tested the effects of cold air (0℃) exposure on endurance capacity to different levels of cold strain ranging from skin cooling to core cooling of Δ-1.0℃. Ten males completed a randomized, crossover, control study consisting of a cycling time to exhaustion (TTE) at 70% of their peak power output following: 1) 30-min of exposure to 22℃ thermoneutral air (TN), 2) 30-min exposure to 0℃ air leading to a cold shell (CS), 3) 0℃ air exposure causing mild hypothermia of -0.5℃ from baseline rectal temperature (HYPO-0.5℃), and 4) 0℃ air exposure causing mild hypothermia of -1.0℃ from baseline rectal temperature (HYPO-1.0℃). The latter three conditions tested TTE in 0℃ air. Core temperature and seven-site mean skin temperature at the start of the TTE were: TN (37.0±0.2℃, 31.2 ±0.8℃), CS (37.1 ±0.3℃, 25.5 ± 1.4℃), HYPO-0.5℃ (36.6 ±0.4℃, 22.3 ± 2.2℃), HYPO-1.0℃ (36.4 ±0.5℃, 21.4 ± 2.7℃). There was a significant condition effect (P < 0.001) for TTE, which from TN (23.75 ± 13.75 min) to CS (16.22 ± 10.30 min, Δ-30.9 ± 21.5%, P = 0.055), HYPO-0.5℃ (8.50 ± 5.23 min, Δ-61.4 ± 19.7%, P < 0.001), and HYPO-1.0℃ (6.50± 5.60 min, Δ-71.6 ± 16.4%, P < 0.001). Furthermore, participants had a greater endurance capacity in CS compared with HYPO-0.5℃ (P = 0.046), and HYPO-1.0℃ (P = 0.007), with no differences between HYPO-0.5℃ and HYPO-1.0℃ (P = 1.00). Endurance capacity impairment at 70% peak power output occurs early in cold exposure with skin cooling, with significantly larger impairments with mild hypothermia up to Δ-1.0℃. [ABSTRACT FROM AUTHOR]