Interstitial glucose during sanctioned competition and during high-intensity training in highly trained collegiate male endurance athletes: A real-world continuous glucose monitoring study.

Abstract

Real-world evidence on glucose behavior during competition in highly trained athletes is scarce. We characterized interstitial glucose dynamics in collegiate endurance athletes during sanctioned competitions using continuous glucose monitoring (CGM), with within-subject comparisons to high-intensity training performed at the same prescribed race pace. Twenty male runners and race walkers (Tier 3: Highly Trained/National) wore CGM during 36 races, contributing 20 paired race-versus-training comparisons. Glucose rose from baseline to 8.3 ± 1.5 mM 1 h pre-race, peaked at 11.2 ± 2.2 mM during competition (mean difference + 3.12 mM, 95% CI +2.72 to +3.53; Cohen's dz. = 1.45), and declined to 6.7 ± 1.7 mM post-race (F(2,220) = 225.79, p < 0.001, partial η² = 0.67). Within-subject maximum glucose was higher during competition than during training (12.91 ± 1.93 vs. 11.02 ± 1.18 mM; mean difference + 1.89 mM, 95% CI 1.06-2.72; Cohen's dz. = 1.07), with a geometric mean ratio of 1.166 (95% CI 1.088-1.249), approximately 17% higher peaks in competition. These findings describe a reproducible pattern of higher peak glucose in competition than in training matched on the recorded external characteristics. Internal exercise load was not measured, so the difference cannot be attributed to the competitive context rather than to differing internal exercise intensity.