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High-level athletes are always looking at ways to maximize training adaptations for competition performance, and using altered environmental conditions to achieve this outcome has become increasingly popular by elite athletes. Furthermore, a series of potential nutrition and hydration interventions may also optimize the adaptation to altered environments. Altitude training was first used to prepare for competition at altitude, and it still is today; however, more often now, elite athletes embark on a series of altitude training camps to try to improve sea-level performance. Similarly, the use of heat acclimation/acclimatization to optimize performance in hot/humid environmental conditions is a common practice by high-level athletes and is well supported in the scientific literature. More recently, the use of heat training to improve exercise capacity in temperate environments has been investigated and appears to have positive outcomes. This consensus statement will detail the use of both heat and altitude training interventions to optimize performance capacities in elite athletes in both normal environmental conditions and extreme conditions (hot and/or high), with a focus on the importance of nutritional strategies required in these extreme environmental conditions to maximize adaptations conducive to competitive performance enhancement.

Endurance exercise can disturb intestinal epithelial integrity, leading to increased systemic indicators of cell injury, hyperpermeability, and pathogenic translocation. However, the interaction between exercise, diet, and gastrointestinal disturbance still warrants exploration. This study examined whether a 6-day dietary intervention influenced perturbations to intestinal epithelial disruption in response to a 25-km race walk. Twenty-eight male race walkers adhered to a high carbohydrate (CHO)/energy diet (65% CHO, energy availability = 40 kcal·kg FFM⁻¹·day⁻¹) for 6 days prior to a Baseline 25-km race walk. Athletes were then split into three subgroups: high CHO/energy diet (n = 10); low-CHO, high-fat diet (LCHF: n = 8; <50 g/day CHO, energy availability = 40 kcal·kg FFM⁻¹·day⁻¹); and low energy availability (n = 10; 65% CHO, energy availability = 15 kcal·kg FFM⁻¹·day⁻¹) for a further 6-day dietary intervention period prior to a second 25-km race walk (Adaptation). During both trials, venous blood was collected pre-, post-, and 1 hr postexercise and analyzed for markers of intestinal epithelial disruption. Intestinal fatty acid-binding protein concentration was significantly higher (twofold increase) in response to exercise during Adaptation compared to Baseline in the LCHF group (p = .001). Similar findings were observed for soluble CD14 (p < .001) and lipopolysaccharide-binding protein (p = .003), where postexercise concentrations were higher (53% and 36%, respectively) during Adaptation than Baseline in LCHF. No differences in high CHO/energy diet or low energy availability were apparent for any blood markers assessed (p > .05). A short-term LCHF diet increased intestinal epithelial cell injury in response to a 25-km race walk. No effect of low energy availability on gastrointestinal injury or symptoms was observed.