Table 1.

Suggested areas for investigation to enhance understanding of the role of carbohydrates in the diet of athletes

Research topic	Research question	Practical relevance
Before intense workouts	How can glycogen storage be optimized when there is less than 24 h between 2 bouts of prolonged high-intensity exercise?	This is relevant for athletes competing day after day (e.g., cycling grand tours) or undertaking strenuous training sessions (e.g., training camps)
	To what extent can liver glycogen content be increased prior to exercise and is liver glycogen supercompensation possible?	This would advance our knowledge about liver glycogen—an important glycogen reservoir within the body
	Can ingesting multiple type monosaccharides (i.e., glucose with galactose and/or fructose) at breakfast help replenish liver glycogen quicker than glucose based carbohydrates?	Possible improvement of performance and/or exercise capacity due to higher glycogen availability; could influence incidence of hypoglycemia due to different intestinal absorption kinetics and subsequent metabolism
During intense exercise	How does carbohydrate ingestion during exercise affect compartmentalized muscle glycogen use (i.e., intermyofibrillar, intramyofibrillar or subsarcolemmal glycogen)?	Knowing this would provide further information on the mechanistic basis of carbohydrate ergogenicity
	Are exogenous carbohydrate oxidation rates during exercise absolute exercise intensity dependent?	We currently recommend athletes to ingest carbohydrate at certain rates without specific adjustments for energy turnover
	Can more than 60 g/h of exogenous glucose be oxidized if exercise intensity is sufficient and should carbohydrate recommendations during exercise be based on absolute exercise intensity and thus energy turnover rates?	Current knowledge is based on moderately trained athletes; exercise intensity and carbohydrate requirements are higher in elite athletes
	What is the role and what are the mechanisms of action of hydrogel forming carbohydrates in gastrointestinal comfort and exogenous carbohydrate oxidation rates?	Conflicting evidence exists regarding this form of delivery of carbohydrates during exercise
	What is the best strategy to offset higher total carbohydrate oxidation and lower exogenous carbohydrate oxidation rates in extreme environments (i.e., hypoxia and heat)?	Competitions often take place in stressful environmental conditions such as in the heat or in hypoxia. It is therefore important to optimize carbohydrate availability in those scenarios
After intense exercise	Would elite athletes benefit from higher short-term hourly carbohydrate ingestion rates as currently recommended 1.2 g·kg−1BM·h−1?	Current knowledge is based on moderately trained athletes whose muscle glycogen storage capacity is lower than in elite athletes
	When is it advisable to ingest a mixture of different monosaccharides (i.e., glucose, fructose and galactose) in recovery?	Relevant for athletes competing with short recovery times (< 24 h)
Carbohydrate periodization	Do low-carbohydrate availability training sessions improve training adaptations in a training program in which training volume is unrestricted (i.e., professional athletes) and are they thus more than just a time-efficient way of training?	Current evidence points towards this approach being efficient in athletes training up to 12 h per week, and it remains to be demonstrated whether it enhances adaptations when training volumes are higher
RED-S and overtraining	Is carbohydrate availability the most important factor in occurrence of RED-S and associated overtraining?	This would advance our understanding about RED-S and overtraining and provide better advice for prevention of these conditions
Personalization	What tools can be used to precisely prescribe carbohydrate intakes before/during/after exercise to improve performance and/or recovery?	While current carbohydrate guidelines offer a fair degree of personalization, knowing exact carbohydrate requirements (i.e., oxidation rates and endogenous carbohydrate availability) and exogenous carbohydrate oxidation limitations during exercise could lead to better individualization of carbohydrate intake during exercise
	What can be learnt from continuous blood glucose monitoring throughout the day and during exercise in athletes?	Better understanding of daily blood glucose profile in athletes could enable refined adjustment of carbohydrate availability in real time, resulting in optimizing recovery and/or performance

BM body mass, RED-S relative energy deficiency in sport