Differential in Aerobic Capacity Among Collegiate Distance Runners Consuming a Low Carbohydrate Diet

Abstract

Although current sports nutrition recommendations advocate for a high carbohydrate (CHO) intake among endurance athletes, recent research has suggested that training with low CHO availability may augment adaptations to aerobic training. When adopted during the competitive season, when training intensity and the demand for glycogen replenishment is high, low CHO diets may be detrimental to training adaptations by preventing adequate recovery between concurrent high-intensity endurance sessions. PURPOSE: To observe the dietary habits of collegiate distance runners and to investigate the effects of habitual CHO intake on aerobic performance (PostVO2max) during a competitive season. METHODS: During an 8-week trial period, 12 collegiate track athletes (males, n=8; females, n=4) recorded their self-selected dietary intake via 24-hr recall. Analysis of CHO intake was conducted by a registered dietitian using NutriCalc software. Pre (PreVO2max) and post season aerobic capacity assessments were performed. A one-way ANCOVA with two covariates controlling for PreVO2max and CHO intake compared the variance in PreVO2max and PostVO2max by sex. RESULTS: The average CHO intake was 4.11 ± 1.03 g/kg with only one female athlete meeting dietary recommendations, consuming > 6 g/kg. Male distance runners had a lower CHO intake than females (3.64±0.77g/kg; 5.03±0.91g/kg). After adjusting for PreVO2max and CHO, the male improvement in PostVO2max was 12.62 ml/kg/min (95% CI 2.12-23.12, p = 0.02) greater than the effect observed in females. There were no differences in weight and body composition changes by sex throughout the season (p= 0.48; p= 0.86). CHO accounted for 18% of the variance in PostVO2max. CONCLUSIONS: Collegiate distance runners were able to make improvements in their aerobic capacity during a competitive season while consuming a low CHO diet, with a predominant effect in male athletes. Therefore, it may not be detrimental for endurance athletes to consume low CHO diets while undergoing training at high intensities from an aerobic adaptation standpoint.