The effects of low and normal dose ice slurry ingestion on endurance capacity and intestinal epithelial injury in the heat

Abstract

Objectives: Compare the effects of ice slurry ingestion at low and normal doses on endurance capacity and exertional heat stress-induced gastrointestinal perturbations.

Design: Randomised, cross-over design.

Methods: Twelve physically active males completed four treadmill running trials, ingesting ice slurry (ICE) or ambient drink (AMB) at 2 g·kg^-1 (Normal; N) or 1 g·kg^-1 (Low; L) doses every 15-min during exercise and 8 g·kg^-1 (N) or 4 g·kg^-1 (L) pre- and post-exercise. Pre-, during and post-exercise serum intestinal fatty-acid binding protein ([I-FABP]) and lipopolysaccharide ([LPS]) concentrations were determined.

Results: Pre-exercise gastrointestinal temperature (T_gi) was lower in L + ICE than L + AMB (p < 0.05), N + ICE than N + AMB (p < 0.001) and N + ICE than L + ICE (p < 0.001). Higher rate of T_gi rise (p < 0.05) and lower estimated sweat rate (p < 0.001) were observed in N + ICE than N + AMB. Rate of T_gi rise was similar at low dose (p = 0.113) despite a lower estimated sweat rate in L + ICE than L+AMB (p < 0.01). Time-to-exhaustion was longer in L + ICE than L + AMB (p < 0.05), but similar between N + ICE and N + AMB (p = 0.142) and L + ICE and N + ICE (p = 0.766). [I-FABP] and [LPS] were similar (p > 0.05).

Conclusions: L + ICE elicited a lower heat dissipation compensatory effect with similar endurance capacity as N + ICE. Ice slurry conferred no protection against exertional heat stress-induced gastrointestinal perturbations.

Keywords: Endotoxin; Heat mitigation; Intestinal fatty acid binding protein; Per-cooling; Pre-cooling; Thermoregulation.