The effects of co-ingestion of highly branched cyclic dextrin and dietary nitrate on physiological responses and endurance capacity in recreational endurance runners

Abstract

This study aimed to investigate the effects of co-ingestion of HBCD and dietary nitrate on physiological responses and endurance capacity in recreational endurance runners compared with an isocaloric HBCD beverage, a maltodextrin-dietary nitrate beverage, and a maltodextrin beverage during high-intensity prolong running. Nine male marathon runners (age 35.00 ± 4.00 years) participated in a double-blind crossover design, where they were randomly assigned to receive either the co-ingesting 1.5 g HBCD·kg-1 BM and 500 mg dietary NO3- (~8.00 mmol NO3-) beverages (HBCD+NO3-), the ingesting 1.5 g HBCD·kg-1 BM (HBCD), the co-ingesting 1.5 g MD·kg-1 BM and 500 mg dietary NO3- (~8.00 mmol NO3-) beverages (MD+NO3-) or the ingesting 1.5 g MD·kg-1 BM beverage (MD) 60 min prior to the running economy test following by a 60-min constant load running at a speed equivalent to 70% of V̇O2peak. Measurements of substrate oxidation, muscle oxygenation, and oxygen cost were taken to assess running economy as well as serum glucose concentration, serum insulin concentration and blood lactate concentration, gastrointestinal symptoms, and rate of perceived exertion (RPE). The results showed no significant differences in the serum insulin concentration, serum glucose concentration, blood lactate concentration, oxygen cost, muscle oxygenation, among the HBCD+NO3-, HBCD, MD+NO3-, and MD conditions. However, it was found that the ingesting HBCD it had increase fat oxidation rate and lower the RER compared to the HBCD+NO3-, the MD+NO3-, or MD. This indicate that the ingesting HBCD may modulate fat metabolism and affect the lower RER compared to the co-ingesting of HBCD+NO3- or other CHO sources.