What is the optimal macronutrient breakdown for a 6-hour gravel ride, and how do the demands of varied terrain and elevation change impact the ideal balance of carbohydrates, protein, and fat intake? Specifically, how do the differences in muscle fiber recruitment and energy expenditure between gravel and road cycling influence the nutritional needs of endurance athletes? Is there a consensus on the use of maltodextrin versus fructose-based energy gels, and what are the implications for gut health and glucose uptake? How do the nutritional needs of gravel riders differ from those of mountain bikers, given the unique demands of each discipline? Can anyone provide evidence-based recommendations for hydration strategies and electrolyte replenishment during prolonged gravel rides, particularly in hot and humid environments?