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

Abstract

Background: 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 (R) performance, specifically during the Cindy workout, a high-intensity exercise protocol. Methods: In a randomized, double-blind, placebo-controlled crossover design, 20 trained male recreational CrossFit (R) 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. Results: 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, p = 0.810) compared to the placebo. There were also no significant differences in RPE (6.3 +/- 1.5 vs. 6.9 +/- 1.4, p = 0.180) or BP changes between groups. However, 10% of participants reported difficulty sleeping after L-carnitine supplementation. Conclusions: The findings suggest that 3 g of L-carnitine tartrate does not enhance CrossFit (R) performance in recreational athletes. Further research is needed to clarify its potential benefits, especially with larger samples and consideration of factors like sex and carbohydrate co-ingestion.