Outdoor Sports Nutrition is a sub-field of sports nutrition research that studies optimal dietary and supplementation strategies for hiking, trail running, climbing, and similar outdoor activities. Unlike indoor fitness, outdoor sports face unique nutritional challenges: prolonged continuous activity (8-72 hours), extreme environments (heat, cold, altitude) that alter nutritional metabolism, limited carry weight, and gastrointestinal stress from complex terrain.
## The Logic of Energy Substrate Fuel
**Carbohydrates**: the primary fuel for outdoor sports, especially at moderate-plus intensities. Liver glycogen and muscle glycogen stores total approximately 400-600g (~1,600-2,400 kcal); at consumption rates of 300-500 kcal/hour, they’re significantly depleted in 2-4 hours without supplementation, leading to “bonking” (sudden blood glucose drop causing exhaustion and cognitive decline).
**Fat**: at low intensities (Z1-Z2), fat contributes a higher proportion of energy (up to 50-60%). Body fat stores (even a normal-weight person has 10-20kg of body fat) far exceed glycogen — the primary energy source for ultra-long, low-intensity activity. Prolonged low-intensity training can improve fat oxidation (fat adaptation), but cannot entirely replace carbohydrate supplementation.
**Protein**: protein contributes a small proportion of energy during outdoor sports (<5%), but muscle damage repair requires timely post-exercise supplementation (recommended 20-40g quality protein within 30-60 minutes post-exercise). ## Practical Supplementation Plans **While moving (every 45-60 minutes)**: 30-60g carbohydrates. Options: energy gels (~25g carbs/pack), energy bars (50-70g carbs/bar), dates/banana/rice cake (natural foods, more stable digestion but heavier). **Hydration management**: sweat rate approximately 500-1,500ml/hour (varies with temperature, exercise intensity, individual differences); generally recommended 150-250ml every 15-20 minutes; during heat or intense exercise, supplement sodium-containing electrolyte drinks (500-700mg sodium/liter) to avoid hyponatremia. **Recovery nutrition**: within 30 minutes post-exercise: 1-1.5g/kg body weight carbohydrates (replenish glycogen) + 20-40g quality protein (promote muscle repair); ensure 8 hours of sleep (sleep is the most important recovery factor, outweighing any nutritional intervention). See [Ultramarathon Sports Science](https://sunqi.org/ultramarathon-science-en/) and [International Society of Sports Nutrition (ISSN) position statements](https://jissn.biomedcentral.com/).
