The effect of winter clothing ensembles and hypoxia on performance and exercise‐related sensations during uphill walking: A combined and individual stressors approach

Multiple environmental stressors are present at high altitude, including low oxygen availability, decreased atmospheric pressure, cold ambient temperatures, dry air and solar radiation. Rarely considered is the effect that high insulation clothing (i.e. winter ensembles), coupled with high altitude, have on the body during exhaustive exercise. In situations where winter clothing is used during heavy exercise, aerobic mechanical efficiency is reduced, and the potential for heat strain is increased. The aim of this study was two‐fold. First, to investigate the individual and combined effects of winter clothing and normobaric hypoxia on incline walking, when intensity is prescribed using an integrated perception of all exercise‐related signals (ISO‐RPE). The second aim was to establish which is/are the mediating sensations that contribute to ISO‐RPE during exercise. Nine subjects (five male and four female, age 23.4 ± 2.2 years) with moderate‐high fitness levels, completed five self‐regulated exercise stages at an ISO‐RPE rating of 2/10 (‘light’), 4/10 (‘moderate’), 5/10 (‘hard’), 6/10 (‘severe’) and 8/10 (‘very severe’) on a Borg CR10 scale. Each stage lasted 12 minutes at a moderate walking pace on a treadmill, where the intensity of the exercise was self‐regulated using adjustments in the incline only. The subjects were exposed to four different conditions: 1) Normoxic‐Thermoneutrality: 0.21 FIO 2 , 18°C, 50% rH in shorts and t‐shirt; 2) Normoxic‐Winter Clothed: 0.21 FIO 2 , 5°C, 50% rH wearing high insulation clothing; 3) Hypoxic‐Thermoneutrality: 0.13 FIO 2 , 18°C, 50% rH wearing shorts and t‐shirt; 4) Hypoxic‐Winter Clothed: 0.13 FIO 2 , 5°C, 50% rH, wearing high insulation clothing. Core temperature, skin temperature, heart rate, arterial O 2 saturation (SpO 2 ) and oxygen consumption (VO 2 ) were recorded. Subjective ratings of localized discomfort and mental effort were also evaluated using the Borg CR10 scale. The elevation gained (meters climbed/hour) was used to determine the work rate of the participants, calculated using treadmill speed (km/h) and incline (%). The results indicate a significant (p<0.05) reduction in elevation climbed during winter‐clothed conditions at an ISO‐RPE of 8/10 (mean difference = 46.36 ± 58.66 m.hr −1 ). A significant (p<0.05) reduction in elevation climbed was also observed in hypoxia at an ISO‐RPE of 5/10, 6/10 and 8/10 (mean difference = 83 ± 51.39, 121.6 ± 85.24 and 133 ± 150 m.hr −1 respectively). The combined effect of winter clothing and hypoxia was additive on elevation climbed, showing no interaction (p>0.13) at an ISO‐RPE of 5/10, 6/10 and 8/10. Winter clothing significantly (p<0.05) increased skin temperature by 1.6 ± 0.3°C and decreased mechanical efficiency by 0.29 ± 0.11 m.L −1 , while hypoxia significantly (p<0.01) reduced SpO 2 by 17.7 ± 3.6%. VO 2 was not significantly affected by condition. The results also suggest ISO‐RPE is mediated by the highest peripherally and centrally originating sensation (R 2 = 0.90, P<0.05). In this study it is concluded that performance is reduced by both winter clothing and hypoxia individually, with a combined effect that is additive on uphill walking performance. Support or Funding Information Internally funded project This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .