Effect of Ketone Supplementation on Glycogen Replenishment and Time Trial Performance Following Glycogen Lowering Exercise

Carbohydrates (starches & sugars) are important muscle fuel for exercise at moderate to high intensities. Low glycogen content (stored form of carbohydrates in the body) is associated with fatigue. Thus, greater initial glycogen content has been associated with better performance not only in high intensity intermittent sports, but also in prolonged endurance sports. Dose-response studies have determined that ingestion of 1.2 g·kg-1·h-1 of CHO is the appropriate acute recovery dose to optimize glycogen repletion, with no apparent benefit at higher doses. Protein in combination with CHO has also been proposed to enhance glycogen resynthesis when 1 part protein is provided with ~4 parts CHO. Both strategies, optimal CHO intake and CHO in combination with protein for glycogen resynthesis, have resulted in better exercise performance a few hours after a depleting exercise bout. A recent study provided athletes with ketone esters in a drink after glycogen depleting exercise and found that in the presence of high glucose availability, ketone esters increased glycogen stores by 50% compared to a no ketone, high carbohydrate treatment. However, the authors of this study provided a large quantity of carbohydrates intravenously to maintain blood glucose at 10Mm/L. Consequently, it is unknown whether or not ingesting glucose at the optimal dosage would have the same effect. Furthermore, it is unclear whether or not this difference would translate into improved performance in efforts of more moderate duration. Therefore, the purpose of this study is to assess the effect of glucose-ketone supplementation on a 20 km cycling time trial with a 2-hour feeding during a 4-hour recovery period following glycogen depleting exercise.