A critical review of citrulline malate supplementation and exercise performance

Lewis A Gough,S Andy Sparks,Matthew F Higgins,Josh W Newbury,Craig A Bridge,Eric Trexler,Lars R Mcnaughton,Mark A Faghy

doi:10.1007/s00421-021-04774-6

Abstract

As a nitric oxide (NO) enhancer, citrulline malate (CM) has recently been touted as a potential ergogenic aid to both resistance and high-intensity exercise performance, as well as the recovery of muscular performance. The mechanism has been associated with enhanced blood flow to active musculature, however, it might be more far-reaching as either ammonia homeostasis could be improved, or ATP production could be increased via greater availability of malate. Moreover, CM might improve muscle recovery via increased nutrient delivery and/or removal of waste products. To date, a single acute 8 g dose of CM on either resistance exercise performance or cycling has been the most common approach, which has produced equivocal results. This makes the effectiveness of CM to improve exercise performance difficult to determine. Reasons for the disparity in conclusions seem to be due to methodological discrepancies such as the testing protocols and the associated test–retest reliability, dosing strategy (i.e., amount and timing), and the recent discovery of quality control issues with some manufacturers stated (i.e., citrulline:malate ratios). Further exploration of the optimal dose is therefore required including quantification of the bioavailability of NO, citrulline, and malate following ingestion of a range of CM doses. Similarly, further well-controlled studies using highly repeatable exercise protocols with a large aerobic component are required to assess the mechanisms associated with this supplement appropriately. Until such studies are completed, the efficacy of CM supplementation to improve exercise performance remains ambiguous.

Highlights

Considerable research attention has recently been placed on the physiological signalling molecule, nitric oxide (NO) (Jones et al 2020)
A direct NO precursor called citrulline malate (CM) has been touted to have ergogenic potential, which is the combination of L-citrulline and malate (Gonzalez and Trexler 2020)
The authors reported ingestion of 6 g of CM 1-h before exercise had no impact on the recovery of lower limb muscular endurance, markers of muscle damage, or electromyographic (EMG) activation compared to a placebo at 24, 48 and 72 h post-exercise

Summary

Introduction

Considerable research attention has recently been placed on the physiological signalling molecule, nitric oxide (NO) (Jones et al 2020). Supplementation of CM is suggested to reduce muscle soreness from exercise, via the purported increased blood flow mechanism (Wax et al 2015; da Silva et al 2017) This could be important for either subsequent performance when recovery between bouts is limited (i.e., track and field) and/ or overall quality and quantity of chronic training. There appears to be limited diversity in the timing of CM ingestion with most studies opting for 1-h ingestion before exercise (Gonzalez and Trexler 2020) This approach seems to be informed by previous research reporting ergogenic effects using similar dosing strategies (Wax et al 2015, 2016; Farney et al 2019), rather than the time to reach peak concentrations of citrulline (Moinard et al 2008; Cunniffe et al 2016). Moinard et al (2008) reported that ingestion of a

Participants

Findings

Conclusions and future directions