Author(s): AKTITIZ, S., Institution: HACETTEPE UNIVERSITY, Country: TURKEY, Abstract-ID: 1973

INTRODUCTION:
Optimizing carbohydrate intake during prolonged endurance events is critical for maintaining performance and glycemic stability. However, real-world adherence to planned race-day nutrition strategies and the associated glycemic responses in recreational female endurance athletes remain underexplored. Continuous glucose monitoring (CGM) may provide valuable insights into glucose dynamics during competition.
METHODS:
A 30-year-old recreational female runner (52 kg, 5 years of running experience) completed a 42.6 km mountain marathon with 1100 m of elevation gain in 5 hours 43 mins. A personalized pre-race carbohydrate loading and in-race nutrition strategy was developed in accordance with current endurance nutrition guidelines. Dietary intake was recorded before and during the race, and compliance with the planned strategy was evaluated. Interstitial glucose concentrations were continuously monitored using a CGM device for 14 days, including the pre-race period, race day, and post-race recovery. Planned carbohydrate loading was set at 8 g·kg⁻¹·day⁻¹ for the final two days before the race. Race-morning carbohydrate intake was planned as 2.5 g·kg⁻¹ consumed 2.5 hours before the start. In-race targets were 75 g·h⁻¹ carbohydrate, 500 mL·h⁻¹ fluid, and 300 mg·h⁻¹ sodium. Actual intake was quantified and compared with planned targets. CGM data were analyzed descriptively to assess glycemic trends before and during the race.
RESULTS:
The athlete achieved high compliance with the carbohydrate-loading protocol, consuming 8.5 and 7.5 g·kg⁻¹ on the final two days pre-race. Race-morning carbohydrate intake matched the planned target (2.5 g·kg⁻¹). During the race, mean carbohydrate intake was 69 g·h⁻¹, slightly below the planned 75 g·h⁻¹, while fluid (550 mL·h⁻¹) and sodium intake (310 mg·h⁻¹) closely matched planned values. CGM data indicated transient hyperglycemia during the first two hours of the race, coinciding with a high early carbohydrate intake (~80-100 g·h⁻¹). Subsequent adjustment and reduction in carbohydrate intake were associated with more stable glycemic profiles during the latter stages of the race.
CONCLUSION:
This case study demonstrates high real-world compliance with planned nutrition strategies in a recreational female runner and highlights the impact of early race carbohydrate intake on glycemic responses. CGM appears to be a promising tool for evaluating and individualizing endurance nutrition strategies in prolonged, real-world competition settings.
This study was supported by TÜBİTAK (The Scientific and Technological Research Council of Türkiye).