CrossFit® is a high-intensity functional training method consisting of daily workouts called “workouts of the day.” No nutritional recommendations exist for CrossFit® that are supported by scientific evidence regarding the energetic demands of this type of activity or dietary and supplement interventions. This systematic review performed in accordance with PRISMA guidelines aimed to identify studies that determined (a) the physiological and metabolic demands of CrossFit® and (b) the effects of nutritional strategies on CrossFit® performance to guide nutritional recommendations for optimal recovery, adaptations, and performance for CrossFit® athletes and direct future research in this emerging area. Three databases were searched for studies that investigated physiological responses to CrossFit® and dietary or supplementation interventions on CrossFit® performance. Various physiological measures revealed the intense nature of all CrossFit® workouts of the day, reflected in substantial muscle fatigue and damage. Dietary and supplementation studies provided an unclear insight into effective strategies to improve performance and enhance adaptations and recovery due to methodological shortcomings across studies. This systematic review showed that CrossFit® is a high-intensity sport with fairly homogenous anaerobic and aerobic characteristics, resulting in substantial metabolic stress, leading to metabolite accumulation (e.g., lactate and hydrogen ions) and increased markers of muscle damage and muscle fatigue. Limited interventional data exist on dietary and supplementation strategies to optimize CrossFit® performance, and most are moderate to very low quality with some critical methodological limitations, precluding solid conclusions on their efficacy. High-quality work is needed to confirm the ideal dietary and supplemental strategies for optimal performance and recovery for CrossFit® athletes and is an exciting avenue for further research.

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