Altered water vapor and evaporation during exercise in a cold weather garment layering system

Abstract

Water vapor accumulation within a garment layering system during exercise in the cold may alter evaporative heat loss. The objective of this study was to investigate the impact of altered water vapor accumulation within a garment layering system during cold weather exercise. Subjects (N=10) exercised on a treadmill for 45 min (70% VO2max) while wearing a wind impermeable (air permeability: .02 m3/min/m2) running jacket with (open) and without (closed) open mesh fabric (air permeability: 39 m3/min/m2) panels placed at the chest (120 cm2), sides (120 cm2), and back (120 cm2). Jackets were worn over a standard polyester t‐shirt. Average (front and back) water vapor pressure (Pw) was calculated from humidity (%) and air temperature under the running jacket (between t‐shirt and jacket). Whole body temperature (Twb), total sweat loss, and evaporation of sweat were also determined. Average Pw in the running jacket was 13.1±0.4 and 10.4±0.3 mmHg for the closed and open jacket conditions, respectively. The decreased Pw enhanced evaporation in the open (84±2%) compared to the closed jacket condition (79±2%; P <0.05), without a statistical difference in sweat loss (closed: 654±56 vs. open: 642±55 g) or Twb (closed: 36.6±0.1 vs. open: 36.4±0.2 °C). Results suggest a ~3 mmHg reduction in Pw in running jackets enhances sweat evaporation without a significant reduction in whole body temperature. Research support from Nike Inc.