Magdalena Kaszuba

Background/Objectives: While traditional sports nutrition emphasizes high carbohydrate intake for endurance athletes, trained athletes may achieve metabolic adaptation to low-carbohydrate and ketogenic diets with maintained or improved performance outcomes. This systematic review and meta-analysis synthesize evidence on the effects of low-carbohydrate (≤130 g·day⁻¹ or ≤25% total energy) and ketogenic (−1 or 1 week consistently demonstrated maintained or improved performance. Conclusions: Low-carbohydrate diets reliably induce metabolic adaptation characterized by dramatically increased fat oxidative capacity. However, aerobic performance responses are nuanced, with preserved maximal aerobic power, transient submaximal efficiency impairments, and context-dependent endurance effects. Adaptation involves initial acute-phase decrements (≤7 days) followed by recovery. Evidence supports periodized carbohydrate strategies balancing metabolic adaptation benefits from low-carbohydrate training phases with carbohydrate requirements during competition.

Biathlon is a winter Olympic sport that combines high-intensity cross-country skiing with precise rifle shooting. These dual demands require athletes to develop exceptional aerobic capacity while maintaining fine motor accuracy under physiological stress. Despite its complexity, nutritional strategies in biathlon remain under-explored and recommendations are often extrapolated from related endurance sports. This narrative review aims to summarise existing knowledge on nutrition in biathlon, highlight sport-specific challenges and identify areas for future research. The main findings indicate that biathletes face very high energy demands, with daily expenditure exceeding 7000 kcal during intensive training. Carbohydrates are the primary fuel source, with intake recommendations based on training intensity and duration (6–12 g/kg/d). Furthermore, protein is essential for muscle repair, recovery and adaptation. To achieve the recommended intake of 1.6 g/kg/day, it is advisable to consume meals containing approximately 0.3 g/kg of high-quality protein every three to four hours. Given the frequency of training sessions, effective recovery strategies are important in biathlon. When recovery is a priority, biathletes should consume a meal comprising protein (approximately 0.3 g/kg) and carbohydrates (approximately 1.2 g/kg) before key training sessions. Micronutrient and vitamin deficiencies are not commonly observed in biathletes due to their high calorie intake. However, concerns regarding iron and vitamin D are common among endurance athletes due to the high risk of low energy intake, diets lacking in iron, and insufficient exposure to sunlight. On the day of the race, it is recommended that biathletes plan their meals to ensure that they meet their nutritional needs and begin recovery as soon as possible after the race is over. Biathletes may use specific supplements to enhance performance and health during preparation and competition. However, it is important to note that some supplements that improve performance may harm shooting accuracy. Current guidance is provisional, and future research should adopt a dual-performance framework that evaluates both endurance output and shooting precision under realistic competition conditions.

No previous study analyzed the effect of caffeinated chewing gum on volleyball-specific skills and physical performance in volleyball players. Twelve volleyball players participated ina randomized, crossover, and double-blind experiment after ingestion of (a) ~3.2 ± 0.4 mg/kg of body mass (BM) of caffeine via chewing gum or (b) non-caffeinated chewing gum (placebo) and performed: (a) a countermovement jump, (b) a squat jump, (c), an attack jump, (d) a block jump, (e) 5 and 10 m sprints, (f) a modified agility t-test, (g) an attack and service speed test, and (h) a spike and serve accuracy test. Compared to the placebo, the caffeine chewing gum supplementation significantly improved the accuracy of the attack (15 ± 4 vs. 18 ± 3 points, p = 0.02). However, the ingestion of caffeinated chewing gum had no effect on the remaining other performance tests (p from 0.12 to 1.00). A caffeine-containing chewing gum with a dose of ~3 mg/kg BM effectively improved the attack’s accuracy in volleyball players. However, this effect was not observed in better results in jumping, running, and other skill-based volleyball tests.