Effect of diet interventions, dietary supplements and performance-enhancing substances on CrossFit-trained individuals’ performance: a systematic review of clinical studies
Marcus V.L. dos SantosQuaresma Nutrition Available online 28 August 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 effect of diet intervention, dietary supplements, and performance-enhancing substances in 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 which enrolled CF athletes in a diet, dietary supplements, or performance-enhancing substances intervention. Athletic performance was considered as the primary outcome. No other filters were applied. Including grey literature search, a total of 217 studies and 2 abstracts were identified, however only 14 studies met the eligibility criteria.
Two studies evaluated the effect of caffeine supplementation on exercise performance and performance parameters; five studies evaluated high or low carbohydrate effect on performance and other parameters. One study verified the effect of multi-ingredient supplementation on CF-specific performance and body composition. One study compared protein supplements intake 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 sodium bicarbonate (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 the 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, good methodological model, and practical application are required.