Thermoregulatory responses during road races in hot-humid conditions at the 2019 Athletics World Championships

The purpose of this study was to characterize thermoregulatory and performance responses of elite road race athletes while competing in hot humid night time conditions during the 2019 IAAF World Athletic Championships Male and female athletes competing in the 20 km racewalk i n i 20 males 24 females 50 km racewalk i n i 19 males 8 females and marathon i n i 15 males 22 females participated Exposed mean skin T sub sk sub and continuous core body T sub c sub temperature were recorded with infrared thermography and ingestible telemetry pill respectively The range of ambient conditions recorded roadside was 29 3 C 32 7 C air temperature 46 81 relative humidity 0 1 1 7 m s sup 1 sup air velocity and 23 5 C 30 6 C wet bulb globe temperature T sub c sub increased by 1 5 0 1 C but mean T sub sk sub decreased by 1 5 0 4 C over the duration of the races T sub sk sub and T sub c sub changed most rapidly at the start of the races and then plateaued with T sub c sub showing a rapid increase again at the end in a pattern mirroring pacing Performance times were between 3 and 20 mean 113 6 longer during the championships compared with the personal best PB of athletes Overall mean performance relative to PB was correlated with the wet bulb globe temperature WBGT of each race i R i sup 2 sup 0 89 but not with thermophysiological variables i R i sup 2 sup 0 3 As previously reported in exercise heat stress in this field study T sub c sub rose with exercise duration whereas T sub sk sub showed a decline The latter contradicts the commonly recorded rise and plateau in laboratory studies at similar ambient temperatures but without realistic air movement b NEW amp NOTEWORTHY b This paper provides a kinetic observation of both core and skin temperatures in 108 elite athletes during various outdoor competition events adding to the very limited data so far available in the literature taken during elite competitions The field skin temperature findings contrast previous laboratory findings like