Effects of d-allulose intake during exercise training on heart rate response to submaximal exercise in untrained young adults: a pilot study

[Purpose] d-Allulose has been reported to enhance fat oxidation during acute aerobic exercise; however, its effects during exercise training in humans remain unclear. We investigated the effects of d-allulose intake during exercise training on physiological responses to submaximal exercise in untrained young adults.[Methods] Eighteen untrained young adults were randomly assigned to receive a beverage with (ALLU) or without (PLA) 5 g of d-allulose 30 min before exercise. Participants exercised on a cycle ergometer at 50% of their estimated V4O2max for 30 min, 4 days per week, for 4 weeks. Heart rate at the end of each session was recorded as an indicator of physiological responses to submaximal exercise. Body composition and estimated V4O2max were measured before and after the intervention.[Results] No significant between-group differences were observed in body composition. The relative change in estimated V4O2max tended to be greater in the ALLU group than in the PLA group, although this difference was not statistically significant (p = 0.09). The temporal pattern of absolute heart rate differed significantly between groups over the 4-week intervention period (treatment × week interaction, p = 0.007), with no significant between-group differences observed at individual weeks. Exploratory analysis showed that relative heart rate was significantly lower at Week 4 in the ALLU group than in the PLA group (p = 0.028).[Conclusion] Repeated d-allulose supplementation before exercise during 4 weeks of training was associated with a different temporal pattern of heart rate responses to submaximal exercise in untrained young adults. These preliminary findings warrant further investigation into the effects of d-allulose supplementation during exercise training.