Scheduling Cycles of Work for Hot Ambient Conditions

Publisher Website
Google Scholar
Abstract
Schedules of working and resting periods were designed separately for work at 40% [Vdot] O2maxand for work at 60% [Vdot] O2max each under the two following ambient conditions: (a) warm-humid, T db 36°C, T wb31°C and; (b) hot-dry, T db50°C, T wb25°C. Two conditions were provided for the resting period: (1) under the same ambient conditions as for the working conditions: (2) under neutral ambient conditions of T db 23°C, T wb 16°C. The working periods were determined by the total sum of the expected work specific heart rate (HR) and the expected heat induced increments in HR. The total sum of the HR was treated in terms of its equivalence to the fraction of [Vdot] O2max, based on the linear relationship between the two parameters. The limiting factor was taken to be the lower end of the 95th percentile maximal HR for the population of the 20–30 yr old participants. Six heat acclimatized male subjects participated in testing the adequacy of the design of the work and rest periods. The schedule of work and rest periods were 20 min for each session of work at 40% [Vdot] O2max and, 10 min and 20 min respectively for the session of work at 60% [Vdot] O2max. A session at each work level included four to five cycles of work and rest. The results showed that based on the levelling off of HR and rectal temperature ( T re), and setting the limit of T re rise to 38°C, the work and rest periods were adequate for ihe hot-dry ambient conditions irrespective of the resting area, but were adequate for the warm-humid conditions only when the resting periods were under the neutral ambient conditions.