Objectives: The study aimed to determine the effects of temperature of ingested water during exertional-heat stress on gastrointestinal injury, symptoms and systemic inflammatory responses. Design: Randomised cross-over study. Methods: Twelve endurance runners completed 2 h running at 60% v˙O2max in 35 °C ambient temperature on three separate occasions, consuming 250 ± 40 mL water before and every 15 min during running at either 0.4 ± 0.4 °C (COLD), 7.3 ± 0.8 °C (COOL), or 22.1 ± 1.2 °C (TEMP). Rectal temperature and gastrointestinal symptoms were recorded every 10 min during exercise. Blood was collected pre, immediately and 1 h post-exercise to determine plasma intestinal fatty-acid binding protein (I-FABP), cortisol, and inflammatory cytokine concentrations. Results: Compared to TEMP, COLD and COOL blunted the rise in rectal temperature (2.0 ± 0.5 °C vs. 1.6 ± 0.4 °C and 1.7 ± 0.4 °C, respectively; trial × time, p = 0.033). I-FABP increased post-exercise (419%, p < 0.001), with a trend for reduced I-FABP on COLD and COOL (mean reduction 460 pg mL−1 and 430 pg mL−1, respectively), compared to TEMP (p = 0.066). No differences were observed between trials for gastrointestinal symptoms, albeit a trend for increased upper-gastrointestinal symptoms on TEMP (p = 0.087) compared to COLD and COOL was observed. IL-6, IL-1β, IL-8, IL-10 and IL-1ra increased post-exercise (p < 0.05); however no differences were observed between trials. Conclusions: COLD and COOL water ingestion during exertional-heat stress ameliorates thermoregulatory strain compared to TEMP. However, this appears to have no effect on cytokine profile and minimal effect on intestinal epithelial injury and gastrointestinal symptoms.
- Gastrointestinal symptoms
- Intestinal fatty acid binding protein