Table 1.

Summary of current knowledge and guidelines for optimizing fuel needs for training and competition nutrition

Issue	Current knowledge and guidelines
CHO intake in the training diet	Previous focus on ‘high-CHO diets’ should be replaced by consideration of ‘CHO availability’, in which the daily amount and timing of CHO intake is compared with muscle fuel cost of training: ‘high CHO availability’ = intake providing adequate fuel for training needs, while ‘low CHO availability’ = intake is likely to be associated with CHO depletion [53]
	Daily CHO intake should not be static but should be periodized across training microcycles and macrocycles according to fuel cost of training load and the importance of training with high CHO availability [53]
	When workouts involve high-intensity/volume/quality/technique, the day’s eating patterns should provide high CHO availability [53]
	When workouts involve exercise of lower intensity/quality, it is less important to follow patterns that achieve high CHO availability [53]
	Deliberately manipulating diet/training to exercise with low CHO availability can enhance the adaptive response to the training stimulus, and may be periodized into the training program according to individual goals and experience [14, 59]

Issue	Strategy	Targeted event(s)	Current knowledge and guidelines
Optimizing competition performance by increasing fuel availability (especially to addressing the scenario of limited fuel availability)	Increasing muscle phosphocreatine stores to enhance recovery during period between repeated high-intensity intervals: creatine loading	Stop and go sports: e.g., team sports, racket sports	Likely to be effective in sports/positions in which gradual depletion of phosphocreatine stores is limiting to movement patterns [62] Recommended protocol [63]: Rapid loading: 5 days @ 20 g/day creatine in split doses Slow loading: 30 days @ 3 g/day Maintenance: 3 g/day
	Increasing muscle glycogen stores in day(s) prior to event: CHO loading	Prolonged sustained or intermittent sports (usually >90 min) in which muscle glycogen stores become depleted: e.g., marathon, cycling road races, mid-field positions in some team games	Likely to be effective if event would otherwise deplete muscle glycogen stores, leading to reduction in speed and distance covered [64] Recommended protocol [53]: 36–48 h @ 10–12 g/kg/day CHO + taper
	Increase in muscle/liver glycogen in hours prior to event: pre-event meal	Prolonged sustained or intermittent sports (usually >45 min), especially where pre-exercise muscle/liver glycogen are not optimized by other strategies	Likely to be effective if intake increases CHO availability (increase in liver/muscle glycogen > increase in rate of CHO oxidation during exercise) especially in CHO-limited event [53, 65] Recommended protocol [53]: 1–4 g/kg CHO at 1–4 h pre-event
	Increase in exogenous supply of CHO: intake of CHO just prior to and during event Not needed for metabolic effects in events of more than ~75 min, but may be useful for central effects in events greater than ~45 min	Prolonged sustained or intermittent sports (usually >75 min) in which additional fuel source can replace/spare otherwise limited muscle glycogen stores: e.g., marathon, cycling road races, triathlons, team and racket sports	Likely to be effective if intake provides a readily available CHO supply to the muscle, particularly if muscle glycogen becomes depleted. May also address CNS impairment in events or individuals in which reductions in blood glucose concentrations occur [24, 66] Recommended protocol [53]: 1–2.5 h: 30–60 g/h CHO, >2.5–3 h: up to 90 g/h CHO
		Sustained high-intensity sports (45–75 min) not typically considered to be limited by muscle glycogen stores, e.g., cycling time trial, half marathon	Likely to be effective in enhancing pacing strategy via effect on ‘reward centers’ in brain [61, 67] Recommended protocol [53]: frequent exposure of mouth and oral cavity to CHO, including mouth rinse
	Increase in fatty acid availability: fasting or short-term (1–3 days) high-fat diet	Prolonged sustained or intermittent sports (usually >75 min) in which additional fuel source can replace/spare otherwise limited muscle glycogen stores: e.g., marathon, cycling road races, triathlon, team and racket sports	Typically unable to increase (and may even impair) exercise capacity/performance since enhanced fat oxidation is unable to compensate for low muscle glycogen stores Protocol: not recommended [25, 26]
	Increase in fatty acid availability: high-fat pre-event meal (+heparin) or intralipid infusion		No clear performance benefit despite increased fat oxidation. Use of intralipid infusions and heparin to ensure high fatty acid availability is not practical Protocol: not recommended [25, 26]
	Increase in fatty acid availability: feeding of medium chain triglycerides during exercise		Typically unable to increase (and may even impair) exercise capacity/performance since the large amounts needed to impact fuel metabolism cause gut problems [68] Protocol: not recommended [25, 26]

CHO carbohydrate, CNS central nervous system