Objective: 1) To determine rectal temperature (Tre) and fluid loss (FL) of obese men (OM) compared to non-obese men (NM)
during exercise in cool conditions (CC) and hot and humid conditions (HC), and 2) to investigate the effects of cold water (CW; 0.5+0.5°C) ingestion before exercise in HC in OM.
Material and Method: Twelve OM and 12 NM completed 2 treadmill exercise sessions, in CC and HC, in a randomized
order. Each session was performed for 30 minutes at 45-50% of heart rate reserve with a 5-minute warm up and 5-minute cool down.
Results: There were no differences in Tre in response to exercise between OM and NM both in CC (OM 37.77+0.08°C, NM
37.68+0.08°C; p = 0.463) and in HC (OM 37.82+0.06°C, NM 37.85+0.06°C; p = 0.725). Heart rate, perceived exertion and
thermal sensations were not significantly different between OM and NM. However, compared to NM, fluid loss (FL) was
approximately 160 mL greater in OM (OM 443.33+98.65 mL, NM 283.33+108.15 mL; p<0.001) in CC, and was 194 mL
greater (OM 632.50+126.57 mL, NM 438.33+126.62 mL; p<0.001) in HC. In HC, the 12 OM performed additional 2 bouts
of exercise, with CW vs. ambient temperature water (AW; 30.5+0.5°C) ingestions prior to the start of exercise. Precooling
with CW ingestion, compared to AW ingestion, showed no significant difference in Tre but CW was able to reduce FL (CW
646.67+139.82 mL, AW 735+126.95 mL; p = 0.010).
Conclusion: OM may continuously exercise about 30 minutes at moderate intensity in HC without the increase of Tre to dangerous levels. However, OM should drink approximately 200 mL more water in HC and 160 mL more water in CC than
NM. Precooling with CW ingestion is a good method of reducing risk of exertional heat illnesses in obese individuals during
exercise in HC, as it decreases the amount of FL induced by exercise.

Keywords: Obesity, Exercise, Precooling, Thermoregulation, Core temperature, Fluid loss, Hot environment