Author(s): RAVIKANTI, S., SILANG, K., LOUIS, J., BAMPOURAS, T., OWENS, D., JONES, A., PUGH, J., MORTON, J., Institution: LIVERPOOL JOHN MOORES UNIVERSITY , Country: UNITED KINGDOM, Abstract-ID: 2771

INTRODUCTION:
Carbohydrate (CHO) ingestion enhances endurance performance, yet current fuelling guidelines are largely derived from male cohorts (1) with elite female athletes markedly underrepresented in CHO-feeding research (2). Recent modelling suggests female marathoners may require higher exogenous CHO intakes (108 ± 22 g·h⁻¹) (3). These projections challenge current sex-specific fuelling policies. Indeed, in elite male marathoners, ingestion of 120 g·h⁻¹ increased whole-body and exogenous CHO oxidation and improved running economy but increased peak gastrointestinal (GI) symptoms of nausea, stomach fullness and abdominal cramps (4). In elite female runners, data at intakes ≥90 g·h⁻¹ do not exist. Therefore, the aim of the present study was to investigate the effects of 60, 90, and 120 g·h⁻¹ of CHO on substrate metabolism, exogenous CHO oxidation, and GI symptoms in elite female marathoners.
METHODS:
In a double-blind, randomised crossover design, 8 female marathoners (PB 02:40:18 ± 00:06:19) completed three trials after a 24h high CHO (8 g·kg-1) diet and pre-exercise meal (2 g·kg-1). Participants completed three 120-min trials comprising of 15 min at 95% lactate threshold (LT), 90 min at 94% lactate turnpoint (LTP) and a final 15 min at 95% LT. Every 15 minutes, subjects consumed U-13C enriched CHO drinks at rates of 60 (1:0, maltodextrin: fructose), 90 (2:1) or 120 (1:1) g·h⁻¹. CHO and fat oxidation, blood glucose and lactate, running economy and GI symptoms were measured. Data was analysed using a linear mixed effects model, followed by Holm post-hoc analysis. Significance was set at P<0.05.
RESULTS:
Mean whole-body CHO oxidation (120 g·h⁻¹, 2.51 ± 0.35; 90 g·h⁻¹, 1.83 ± 0.35; 60 g·h⁻¹, 1.53 ± 0.29 g·min⁻¹) and hour-2 exogenous CHO oxidation (120 g·h⁻¹, 1.54 ± 0.10; 90 g·h⁻¹, 1.32 ± 0.10; 60 g·h⁻¹, 0.82 ± 0.13 g·min⁻¹) differed between all trials (P<0.01), such that 120 > 90 > 60 g·h⁻¹. Running economy (mL·kg.km-1) was improved at 120 g·h⁻¹ (214 ± 6) compared to 90 g·h⁻¹ (220 ± 16) and 60 g·h⁻¹ (222 ± 17) (P<0.05). Moderate-to-severe GI symptoms (≥4) occurred across all trials. Peak scores for nausea and abdominal cramps were higher at 90 and 120 g·h⁻¹ compared to 60 g·h⁻¹ (P<0.05). Cumulative GI symptom scores for nausea, and regurgitation were also greater at 120 g·h⁻¹ (P<0.05) compared with 60 g·h⁻¹, while cumulative scores for stomach fullness and abdominal cramps were significantly higher at 120 g·h⁻¹ compared to 90 and 60 g·h⁻¹ (P<0.05).
CONCLUSION:
We report for the first time that CHO ingestion of 120 g·h⁻¹ confers a metabolic advantage to elite female marathoners by maintaining whole-body CHO oxidation, increasing exogenous CHO oxidation and improving running economy. However, due to the high incidence of GI symptoms, particularly 120 g·h⁻¹, gut training strategies before practical application are warranted.