Repeated-sprint exercise delays gastric emptying independently of hypoxia and heat exposure

[Purpose] The present study examined the effects of repeated-sprint exercise in normoxia, hypoxia, and combined heat and hypoxia on the gastric emptying rate.[Methods] Eleven physically active males completed four experimental trials, consisting of a resting control (REST) and three exercise trials; three sets of 5 × 6-s maximal sprints in normoxia (NOR; 23℃, FiO₂: 20.9%), hypoxia (HYP; 23℃, FiO₂: 14.5%), and combined heat and hypoxia (HH; 35℃, FiO₂: 14.5%) in a randomized order. Post-exercise gastric emptying rate was assessed by the ¹³C-sodium acetate breath test.[Results] The ¹³C excretion was significantly lower in the exercise trials (NOR, HYP, and HH) than in the REST during 10-35 min after exercise (p < 0.05). Time to peak ¹³C excretion was significantly delayed in all exercise trials (NOR, HYP, and HH) compared with the REST (p < 0.05), with no difference among the exercise trials. The magnitude of the gastric emptying delay was correlated with power output and blood glucose during the exercise.[Conclusion] Repeated-sprint exercise significantly delayed gastric emptying, while additional hypoxic or heat stress did not exacerbate the delay, suggesting that hypoxic or heat stress can be applied during repeated-sprint training without negative impacts on gastric emptying.