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Effects of a Modified Coconut Water–Based Isotonic Beverage on Energy Intake, VO2max, and Abdominal Muscular Endurance among Indonesian Adolescent Soccer Players: A Randomized Controlled Trial
Rahmadani N.
Nutricion Clinica Y Dietetica Hospitalaria
Q4Abstract
Background: Fluid loss and inadequate energy intake are common among adolescent soccer players and may negatively affect physical performance. Modified isotonic beverages have been proposed as a nutritional strategy to support hydration and energy balance; however, evidence regarding their effects on nutritional intake and physical performance remains limited. Objective: To evaluate the effects of a modified coconut water–based isotonic beverage compared with young coconut water on energy intake, aerobic capacity (VO₂max), and abdominal muscle endurance among adolescent soccer players. Methods: A randomized controlled trial with a two-group pretest–posttest design was conducted among 43 adolescent soccer players from a specialized sports high school in Indonesia. Participants were assigned to an intervention group (n = 23), which received a modified isotonic beverage formulated from mature coconut water, sweet orange juice, and palm sugar, or a control group (n = 20), which received young coconut water as an active comparator rather than a placebo. Assessments were performed at baseline, day 8, and day 15. Energy intake was assessed using 24-hour dietary recalls, aerobic capacity (VO₂max) was measured using the Balke test, and abdominal muscle endurance was evaluated using the sit-up test. Within-group changes from baseline were analyzed using paired t-tests, while between-group differences in outcome changes were compared using independent t-tests. Results: Baseline characteristics were comparable between groups (p > 0.05). Both groups demonstrated significant increases in energy intake during the intervention period; however, the mean increase was significantly greater in the intervention group than in the control group (660.9 ± 493.4 vs. 366.9 ± 396.5 kcal; p = 0.039). Similarly, VO₂max improved significantly in both groups, with a significantly greater mean increase observed in the intervention group compared with the control group (2.71 ± 1.54 vs. 1.90 ± 0.89 mL/kg/min; p = 0.048). Abdominal muscle endurance also increased significantly from baseline in both groups; however, the magnitude of improvement did not differ significantly between groups (p = 0.419). Conclusion: Consumption of a modified coconut water–based isotonic beverage was associated with greater improvements in energy intake and aerobic capacity compared with young coconut water among adolescent soccer players. Although abdominal muscle endurance improved within both groups, no significant difference in the magnitude of change was observed between groups. These findings suggest that a modified natural isotonic beverage may serve as a practical nutritional strategy to support hydration, energy availability, and aerobic performance in adolescent soccer players.