| Description |
Twelve competitive cyclists performed 90-minute cycling bouts at 70% Vo2max in normoconvestive (wind speed, <.2 mps) and hyperconvective (wind speed, 4.05 mps) environments with a controlled ambient temperature and humidity. Repeated measures ANOVA (R < .005) revealed that rectal temperature was higher and exhibited a greater rate of increase throughout exercise in the normoconvective trial than the hyperconvective trial. Rectal temperature at min 90 was 39.25 + .50 °C and 38.61 + .30 °C in the normoconvective and hyperconvective trials, respectively. Mean skin temperature was higher (R < .001) in the normoconvective trial (35.09 + .81 °C) than the hyperconvective trial (32.52 + .72 °C) indicating an enhanced skin-to-ambient temperature gradient. Sweat rate was higher (R < .001) in the normoconvective trial than the hyperconvective trial whereas the percentage of sweat that evaporated was 92.8% and 98.7%, respectively. Heat storage during the normoconvective trial (39.35 + 11.07 w*m-2) was 7.2% of waste heat with the remainder dissipated by evaporation (70.6%), radiation (11.4%), respiration (8.7%), and convection (2.2%). The hyperconvective trial revealed that 4.5% of waste heat was stored (22.79 + 7.94 W*m-2) with the remainder dissipated by evaporation (66.5%), convection (10.8%), radiation (9.2%), and respiration (9.0%). Hear.t rate remained higher and had a progressively greater rate of increase (R < .005) during the normoconvective trial as compared to the hyperconvective trial. Oxygen uptake was significantly elevated (R < .003) during the normoconvective trial as compared to the hyperconvective trial. The results of this study indicate that prolonged cycling in a hypoconvective environment requires more reliance on sweat evaporation resulting in greater dehydration. Fan-driven air circulation around the body significantly enhances thermoregulation, deters potential heat illness, and reduces heart rate . |
