In our previous post we discussed the benefit of ingesting multiple transportable carbs when CHO intake rates exceed >60 g/h. Ingestion of ~90 g CHO/h in the form of glucose or maltodextrin-fructose can increase exogenous CHO utilization and improve endurance performance. However, the majority of research in this area has been completed in males, but do women require different CHO intake recommendations during endurance exercise?
In general, women are able to oxidize a greater percentage of fat versus stored CHO (glycogen), compared to men completing endurance exercise at the same relative intensity. However, current research does not suggest a sex-difference in exogenous CHO oxidation during exercise after ingesting a glucose solution. What about the ingestion of multiple-transportable CHO (e.g. glucose-fructose solution) > 60 g/h?
A recent study provided elite male and female cross-country ski athletes an 18% maltodextrin and fructose hydrogel beverage at a rate of 2.2 g/min (132 g/h) during a 2 h roller skiing protocol in cold ambient conditions at 70% max. Neither group experienced GI symptoms and there were no significant differences in glycogen utilization change, peak rate of exogenous CHO oxidation (though females tended to have lower peak oxidation rates than males, 1.2 vs 1.5 g/min), RPE, or performance between males and females in response to CHO ingestion.
Results from other studies measuring exogenous CHO oxidation in females vs. males are mixed. Some indicate that exogenous CHO oxidation is ~2-4% higher in females compared to males while others found the opposite or no difference. More research is needed to answer this question specifically, but at this point there is insufficient evidence to indicate CHO intake recommendations should be different for females and males engaging in endurance exercise. Further, it has been demonstrated that both male and female athletes can tolerate high rates (>90 g/h) of CHO (glucose-fructose) intake without experiencing GI symptoms in cool conditions.
Finally, because hormonal changes throughout the menstrual cycle may induce changes in fuel utilization, eating a pre-exercise CHO meal in addition to ingesting ~90 g of multiple transportable CHO per hour during endurance exercise > 2.5 h may help minimize hormonal effects and help support performance.
PMID: 10953068, 12070184, 14750011, 14967866, 16278245, 20019632, 31655603, 3401523
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