Effects of Grape Syrup Intake on Metabolic Rate and Substrate Oxidation During and After Sprint Intermittent Exercise

Abstract

Background: Regarding sports drinks' role in substrate oxidation, the present study investigated the effect of grape syrup intake on metabolic rate and substrate oxidation after sprint intermittent exercise in active male students. Methods: In a double-blind, placebo-controlled, crossover study, 12 active male college students (body mass = 62.77 ± 9.05 kg; height = 173 ± 6.78 cm; BMI = 21 ± 2.5 kg/m2) performed two separate exercise sessions after grape syrup (1.1 mL/kg. body weight) or placebo intake. In each of the intervention sessions, the subject first took the desired dose of the supplement or placebo and after 60 minutes performed Sprint Intermittent Exercise or SIE protocol (four 30-second Wingate tests (75g/kg body weight) with a 5-minute rest period). Energy expenditure (EE), respiratory exchange ratio (RER), fat oxidation (FO), heart rate (HR), and oxygen intake (VO2) were assessed 5 minutes before, during, and 30 minutes after exercise. Statistical analysis was performed using mixed-model ANOVA with repeated measures. Results: The results showed only between-group differences in respiratory exchange ratio (P = 0.04). However, the effect of time was significant between different situations (before, during, and after SIE) on all variables (P < 0.05). No time-group interaction effect was also observed in investigated variables (P > 0.05). The effect of different measurement times showed that in the post-SIE period, RER and fat oxidation rate values respectively decreased and increased compared to pre-SIE (P < 0.05) in both situations. Conclusions: The grape syrup intake improved metabolic rate and substrate oxidation during the recovery period after SIE, comparable to the placebo-containing synthetic carbohydrates. Therefore, it is recommended to use this herbal supplement as a substitute for a carbohydrate drink during SIE. However, more research is needed in this case.