Effects of diet interventions, dietary supplements, and performance-enhancing substances on the performance of CrossFit-trained individuals: A systematic review of clinical studies

• Published in: Nutrition (Burbank, Los Angeles County, Calif.) Vol. 82; p. 110994
• Main Authors: dos Santos Quaresma, Marcus V.L., Guazzelli Marques, Camila, Nakamoto, Fernanda Patti
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-02-2021; Elsevier Limited
• Subjects: Aerobic capacity; Athletes; Athletic performance; Betaine; Bias; Body composition; Caffeine; Carbohydrates; Clinical trials; CrossFit; CrossFit training; Diet; Dietary supplementation; Dietary supplements; Epicatechin; Exercise; Green tea; Grey literature; Ingestion; Intervention; Keywords; Medical Subject Headings-MeSH; Muscles; Nutrition research; Parameters; Performance evaluation; Performance-enhancing substances; Physical training; Proteins; Restrictions; Rowing; Sodium bicarbonate; Systematic review; CrossFit; CrossFit training; Dietary supplementation; Athletic performance; Performance-enhancing substances
• ISSN: 0899-9007; 1873-1244
• DOI: 10.1016/j.nut.2020.110994

CrossFit (CF) is characterized as a constantly varied, high-intensity, functional movement training program, performed with little or no rest between bouts, combining strength and endurance exercises, such as running, cycling, rowing, Olympic weightlifting, power weightlifting, and gymnastic-type exercises. Several nutritional strategies are used to improve sports performance of CF practitioners; however, most of them are empirical and lack scientific evidence. Thus, the aim of this review was to determine the effects of diet intervention, dietary supplements, and performance-enhancing substances on exercise-performance parameters of CF practitioners. MEDLINE/PubMed, Web of Science, LILACS, SciELO, and Scopus databases were searched using specific Medical Subject Headings and keywords for clinical studies that enrolled CF athletes in an intervention using diet, dietary supplements, or performance-enhancing substances. Athletic performance was considered as the primary outcome. No other filters were applied. Including grey literature search, 219 studies were identified; however only 14 studies met the eligibility criteria. Two studies evaluated the effects of caffeine supplementation on exercise performance; five studies evaluated high- or low-carbohydrate effects on performance and other parameters. One study verified the effects of multi-ingredient supplementation on CF-specific performance and body composition. One study compared the intake of protein supplements on performance and body composition. Two studies assessed the effect of green tea and (-)-epicatechin on performance and other parameters. One study evaluated the effects of nitrate supplementation on exercise performance. One study investigated the effect of betaine supplementation on body composition and muscle performance. Finally, one study examined the effects of sodium bicarbonate (SB) ingestion on exercise performance and aerobic capacity. Only SB supplementation improved CF performance. These outcomes may have been obtained due to methodological limitations such as small sample size, lack of control over influencing variables, short period of exercise intervention. Despite the popularity and growing evidence about CF, little is known about the relationship between performance-enhancing substances or dietary interventions and CF performance. Given the lack of scientific evidence, new studies with potential ergogenic supplements, a better methodological model, and practical application are required.
•Few studies have investigated the effect of dietary interventions, nutritional supplementation, or performance-enhancing substance strategies on the performance of CrossFit-trained athletes or non-athletes.•Only sodium bicarbonate supplementation improved CrossFit performance; however, this can be attributed to the low internal validity of the other studies included in this review.•Although carbohydrate, caffeine, and nitrate supplementation have been shown to improve performance, the studies that evaluated CrossFit-trained athletes or non-athletes found no improvement in CrossFit performance.•Currently, the main strategies using diet, nutrients, and performance-enhancing substances are merely intuitive.