Changes in resistance training performance, rating of perceived exertion, and blood biomarkers after six weeks of supplementation with L-citrulline vs. L-citrulline DL-malate in resistance-trained men: a double-blind placebo-controlled trial.

Abstract

Purpose: This study aimed to investigate and compare the effects of chronic supplementation with L-Citrulline (LC) vs. L-Citrulline DL-malate (CM) on resistance training (RT) performance.

Methods: Thirty-three resistance-trained men were randomly assigned to ingest LC (8 g), CM (12 g), or Placebo (PL) daily, along with participation in a 6-week RT protocol. Muscular strength (1-repetition maximum [1RM] for hack squat [HS] and bench press [BP]), muscular endurance (repetitions to failure [RTF] for HS, leg extension [LE], BP, and incline press [IP]), rating of perceived exertion (RPE), and blood biomarkers (lactate, urea, and nitric oxide metabolites [NO_X]) were assessed before and after the intervention. This study was registered on irct.ir (IRCTID: IRCT20221128056642N1).

Results: Comparing mean ∆ scores revealed a significant difference between LC and PL (p < 0.001) and between CM and PL (p = 0.026) for total upper body (the sum of BP and IP) RTF, but only a trend for difference between LC and PL (p = 0.070) for total lower body (the sum of HS and LE) RTF. A significant time effect for NO_X was detected only for LC (p = 0.014) and CM (p = 0.003). In addition, a significant difference between CM and PL (p = 0.009) and a marginally significant difference between LC and PL (p = 0.057) was detected regarding post-exercise NO_X values at post-intervention. There were no other between-group differences for any outcome measure.

Conclusion: Chronic citrulline supplementation seems to enhance upper body muscular endurance and post-exercise NO_X response to RT, but there is no apparent difference between LC and CM in these aspects.