The effects of mild hypothermia on self-paced exercise performance.

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Summary of "The effects of mild hypothermia on self-paced exercise performance."

This study examined self-paced, high-intensity exercise during mild hypothermia and whether hyperoxia may offset any potential impairment. Twelve trained males each completed 15 km time trials in three environmental conditions: Neutral (23{degree sign}C,
0.21), Cold (0{degree sign}C,
0.21), and Cold+Hyper (0{degree sign}C,
0.40). Cold and Cold+Hyper trials occurred after a 0.5{degree sign}C drop in rectal temperature. Rectal temperature was higher (p{less than or equal to}0.016) throughout Neutral compared to Cold and Cold+Hyper; Cold had a higher (p{less than or equal to}0.035) rectal temperature than Cold+Hyper from 2.5 to 7.5 km, and hyperoxia did not alter thermal sensation or comfort. Oxyhemoglobin saturation decreased from ~98% to ~94% with Neutral and Cold, but was maintained at ~99% in Cold+Hyper (p<0.01). Cerebral tissue oxygenation index (TOI) was higher in Neutral than Cold throughout the time trial (TT) (p{less than or equal to}0.001), while Cold+Hyper were unchanged (p{greater than or equal to}0.567) from Neutral by 2.5 km. Muscle TOI was maintained in Cold+Hyper compared to Neutral, and was higher (p{less than or equal to}0.046) than Cold throughout the entire TT. Power output during Cold (246{plus minus}41 W) was lower than Neutral (260{plus minus}38 W) at all 2.5 km intervals (p{less than or equal to}0.012) except at 12.5 km. Power output during Cold+Hyper (256{plus minus}42 W) was unchanged (p{greater than or equal to}0.161) from Neutral throughout the TT, and was higher than Cold from 7.5 km onwards. Average cadence was higher in Neutral (93{plus minus}8 rpm) than either Cold or Cold+Hyper (Cold: 89{plus minus}7 and Cold+Hyper: 90{plus minus}8 rpm, P=0.031). In conclusion, mild hypothermia reduced self-paced exercise performance; hyperoxia during mild hypothermia restored performance to thermoneutral levels, likely due to a maintenance of oxygen availability rather than any thermogenic benefit.


Journal Details

This article was published in the following journal.

Name: Journal of applied physiology (Bethesda, Md. : 1985)
ISSN: 1522-1601


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