Acute L-Carnitine Supplementation Does Not Improve CrossFit Performance: A Randomized, Double-Blind, Placebo-Controlled Crossover Study

L-carnitine supplementation is thought to enhance exercise performance, particularly in moderate and high-intensity activities, but evidence supporting this is mixed. This study aimed to assess whether acute L-carnitine tartrate supplementation could improve CrossFit performance, specifically during the "Cindy" workout, a high-intensity exercise protocol. In a randomized, double-blind, placebo-controlled crossover design, 20 trained male recreational CrossFit athletes completed the "Cindy" workout within a 20 min period after ingesting either 3 g of L-carnitine tartrate or a placebo 90 min before exercise. Performance was measured by total repetitions completed. Secondary outcomes included ratings of perceived exertion (RPE), gastrointestinal issues, and blood pressure (BP) measurements. The results showed that L-carnitine supplementation did not significantly affect the number of repetitions performed (202.4 ± 69.9 vs. 204.5 ± 78.8, = 0.810) compared to the placebo. There were also no significant differences in RPE (6.3 ± 1.5 vs. 6.9 ± 1.4, = 0.180) or BP changes between groups. However, 10% of participants reported difficulty sleeping after L-carnitine supplementation.