Author(s): AJJIMAPORN, A., YOMMANA, T., NANA, A., Institution: SPORTS SCIENCE AND TECHNOLOGY, Country: THAILAND, Abstract-ID: 497

INTRODUCTION:
Energy gels are widely used to support endurance performance, yet the optimal glycemic index (GI) formulation remains unclear. High-GI (HGI) gels provide rapid glucose availability but may induce early glycemic fluctuations, whereas medium-GI (MGI) gels may promote more stable metabolic responses. Evidence comparing these formulations in recreational runners during prolonged exercise followed by maximal sprint effort is limited. This study compared the acute metabolic responses to MGI and HGI energy gels, with performance and perceptual outcomes included for practical interpretation.
METHODS:
Eleven male recreational runners (22 ± 3 years) completed a randomized, double-blind, crossover trial. Participants ingested either an MGI or HGI energy gel before a 60-minute treadmill run at 60% VO2max, followed immediately by a 30-second Wingate test. Metabolic variables included blood glucose (BG) and respiratory exchange ratio (RER). Heart rate (HR), ratings of perceived exertion (RPE), palatability, gastrointestinal comfort, and anaerobic performance (peak power, mean power, fatigue index) were also assessed. Data were analyzed using repeated-measures ANOVA.
RESULTS:
BG increased significantly after ingestion in both conditions (p < 0.05); however, the HGI gel showed a greater early decline at exercise onset compared with MGI (p < 0.05). RER was consistently lower in the MGI condition throughout exercise (p < 0.05), indicating greater fat oxidation and improved metabolic stability. HR and RPE increased progressively during running (p < 0.001) with no between-condition differences. Anaerobic performance and post-exercise blood lactate did not differ between gels (p > 0.05). Palatability ratings were higher for HGI compared with MGI (p < 0.05), while gastrointestinal comfort was similar between conditions.
CONCLUSION:
MGI energy gel ingestion promoted greater metabolic stability during prolonged exercise without compromising anaerobic performance. Although HGI gels were perceived as more palatable, both formulations supported performance. These findings highlight the importance of considering metabolic responses alongside sensory acceptance when selecting carbohydrate strategies for recreational endurance athletes.