METABOLIC RESPONSES TO EXERCISE IN 3 THERMAL ENVIRONMENTS

  • 1 January 1977
    • journal article
    • research article
    • Vol. 48  (10) , 989-993
Abstract
Male and female physically active but untrained subjects walked on a treadmill grade approximating 58% .ovrhdot.VO2 max [maximal oxygen uptake] as determined in 25.degree. C under 3 environmental conditions. The environments represented thermal neutrality (Ta [ambient temperature] = 25.degree. C), a warm environment Ta = 32.degree. C), and a hot environment (Ta = 40.degree. C). Relative humidity was 50-55%. Exercise .ovrhdot.VO2 values were significantly influenced by increased environmental temperature. In 40.degree. C, male and female .ovrhdot.VO2 increased 12% above values in 25.degree. C. .ovrhdot.VE increased 25% for the female and 32% for the male subjects during exercise in 40.degree. C. In both male and female subjects, true O2 increased slightly in 32.degree. C but decreased in 40.degree. C from values obtained in 25.degree. C. As Ta increased, blood flow was diverted from metabolically active muscle to nonmetabolically active tissue to enhance heat dissipation via conduction and convection. As a result, O2 extraction declined, and an increased respiratory drive was incurred.