Windproof outer-garment Density impacts thermal sensation and mean body temperature during exercise in the cold C.R. Carriker1,2, S. Campbell1, L. Stark1, T.R. Burnham1, V.M. Nethery1, R.C. Pritchett3 1Central Washington University, Ellensburg, WA. 2University of New Mexico, Albuquerque, NM. 3The University of Georgia, Athens, GA

In a cold environment, body heat loss naturally occurs due to the temperature gradient between ambient air and core/skin temperature. A windproof outer-garment may prevent disruption of the inner air layer and mitigate heat loss. The base layer (underwear) thermal insulation has been previously reported as minimal. PURPOSE: To investigate the impact that outer-garment ‘shells’ of different linear density (without added insulated properties) have on thermal sensation (TS) and mean body temperature (MB) during exercise (~50% METmax; 45 min) in the cold (2±1°C; 66±6% humidity). METHODS: Nine men (23±2 yr., 11.72±5.95 %Fat, VO2max 49.83±3.23 ml/kg/min) wore two treatment outer-garments, Light (CL): 20 Denier and Heavy (CH): 70 Denier, in a random crossover design (>48 hours apart). All participants wore a standard base layer pant/long sleeve shirt (100% polyester) composing a 2-layer ensemble (hat/gloves not permitted). Exercise consisted of 3 repeated series of 10 min treadmill walking at 10% grade and 5 min bench stepping (height at distal patella) with simulated wind (~1.5 m/s). ACSM walking/step equations (~50% METmax) determined pace/cadence. A four site (chest, upper arm, thigh, and calf) mean skin temperature (Tsk) was employed while core temperature (Tre) was measured via rectal thermistor probe. MB=.33Tsk + .67Tre. The TS scale ranged from -7 (unbearably cold) to +7 (unbearably hot). RESULTS: TS was significantly lower in CL (-2.33±.34) compared to CH (-.89±.30) during the initial 15 minutes of exercise (p<.05). Over the remaining 30 minutes, TS was similar (p>.05), but remained lower in CL (.54±.16) from 20 to 45 minutes. Tre increased similarly (p=0.924) for CL and CH over 45 min (1.23±0.31 and 1.12°C±0.25; respectively) and was greater than rest after 15 min (p≤0.05) for both conditions. Compared to CL, MB was higher in CH at all time points with minute 30 significantly greater (p=0.04) (34.42°C and 34.67°C; respectively). Tre and TS were moderately correlated (r=0.573, p<0.05). CONCLUSION: The higher comfort levels conferred by the heavier shell were temporally restricted to the initial 15 minutes of moderate exercise in the cold. Exercise induced thermogenesis negated any further comfort benefits of the heavier shell beyond this time frame.

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