Effects of L-Arginine and Citrulline Malate Supplementation on Sport Performance in Physically Active Men (ReachSci)

Acute Effects of Combined Supplementation of L-Arginine and Citrulline Malate on Aerobic, Anaerobic, and CrossFit® Exercise Performance

In this randomized, double-blind, placebo-controlled trial we investigated the effects of combined L-arginine (Arg) and citrulline-malate (CM) supplementation on aerobic, anaerobic, and high-intensity interval training in healthy, physically active men. 46 healthy, physically active men were divided into three distinct exercise protocol groups: CrossFit group, the Wingate Anaerobic Test group, and the Harvard Step Test group. The CrossFit performance assessment involved the "Cindy" workout, a high-intensity protocol composed of bodyweight exercises organized in a set sequence: 5 pull-ups, 10 push-ups, and 15 squats. Participants were instructed to perform as many rounds as possible within 20 minutes. The Wingate Anaerobic test involved a 30-second all-out cycling test on a bike ergometer, while the Harvard Step Test The Harvard Step Test was conducted using a 51 cm high platform, with participants stepping at a rate of 30 steps per minute (one second up, one second down) for five minutes or until exhaustion. Each participant attended three separate laboratory sessions. The initial session served for familiarization with the test protocol to minimize learning effects. In the second and the third sessions, participants attended two measurement sessions, conducted in randomized order and under double-blind conditions, where they received either the dietary supplementation or a placebo. Each participant acted as their control, allowing for within-subject comparisons.

Study Overview

• Status: Completed
• Conditions: Healthy
• Intervention / Treatment: Dietary supplement: L-Arginine and Citrulline-Malate Supplementation; Dietary supplement: Placebo consumption

Detailed Description

Consumption of dietary supplements is a common strategy among athletes aiming to optimize recovery after training or competitions and enhance athletic performance. Amino acids L-arginine (Arg) and L-citrulline (Cit) are two of the most widely used supplements in recent times. Their use as nutritional supplements or dietary supplements to improve health and athletic performance has increased dramatically, as both Arg and Cit are essential for the body's synthesis of nitric oxide (NO) and elimination of waste products such as lactate during physical activity. Because it functions as an endogenous precursor to Arg, the primary substrate of nitric oxide, Cit, a non-protein, non-essential amino acid, has attracted a lot of attention lately for its potential to improve exercise performance. Commonly, citrulline is consumed as citrulline malate (CM), which is a mixture of Cit and malic acid in ratios ranging from 1:1 to 2:1. The combined intake of Arg and CM could potentially enhance athletic performance more effectively than using either supplement alone. This synergistic benefit is attributed to Cit's role in synthesizing additional Arg, which in turn elevates NO production, enhancing blood flow and possibly reducing muscle fatigue. Supporting this hypothesis, mixed supplementation of Arg and CM was examined in a previous study and significant increases in both force exertion and fatigue resistance during a 10-minute high-intensity cycling test was found. However, while initial evidence suggests potential ergogenic benefits of combined Arg and CM supplementation, further research is needed to confirm these effects across various exercise modalities. The aim of this study was to investigate the acute effects of combined Arg and CM supplementation on anaerobic performance, aerobic performance, or both through high-intensity interval training (i.e. CrossFit) outcomes in healthy, physically active men. Based on existing research, it was hypothesized that the supplementation would enhance performance by achieving higher peak power in the anaerobic protocol and CrossFit in the CrossFit training protocol, where rapid energy production and resistance to fatigue are critical.

• Study Type: Interventional
• Enrollment (Actual): 46
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Hungary
  • Budapest, Hungary, 1124
    • Hungaria University of Sports Science

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• being healthy, physically active with no history of injuries or illnesses at the time of measurement or within the preceding six months

Exclusion Criteria:

• consumption of any dietary supplements in the last six months to avoid confounding effects

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Supplementation; Supplementation of L-Arginine and Citrulline-malate as a liquid	Dietary supplement: L-Arginine and Citrulline-Malate Supplementation; L-Arginine and Citrulline Malate supplementation was consumed as a liquid one single time to examine the acute effects on sport performance
Placebo Comparator: Placebo; Consumption of a placebo liquid	Dietary supplement: Placebo consumption; Consumption of placebo as a liquid

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mechanical Power	Maximal and mean mechanical power was assessed during the Wingate Anaerobic Test under both conditions (supplementation and placebo).	Day 1 and Day 2
Fitness Score	During the CrossFit exercise and the Harvard Step Test the primare measure of performance was a Fitness Score, which was calculated from the rounds completed for the CrossFit exercise and from the time duration and heart rate for the Harvard Step Test.	Day 1 and Day 2

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Heart Rate	Maximal and mean heart rate was measured for all three exercise protolcols: The Wingate Anaerobic Test, The CrossFit Test, and the Harvard Step Test.	Day 1 and Day 2

Collaborators and Investigators

• Sponsor: Hungarian University of Sports Science

Publications and helpful links

Helpful Links

• Home page of the University of Sports Science

Study record dates

Study Major Dates

• Study Start (Actual): October 1, 2023
• Primary Completion (Actual): May 15, 2024
• Study Completion (Actual): September 30, 2024

Study Registration Dates

• First Submitted: April 7, 2025
• First Submitted That Met QC Criteria: April 14, 2025
• First Posted (Actual): April 22, 2025

Study Record Updates

• Last Update Posted (Actual): April 22, 2025
• Last Update Submitted That Met QC Criteria: April 14, 2025
• Last Verified: April 1, 2025

More Information

Terms related to this study

• Keywords: L-arginine; CrossFit; Citrulline-malate; Sport-performance
• Other Study ID Numbers: TE-KEB/22/2023; HungarianUSportsScience (Other Identifier: Hungarian University of Sports Science)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: All individual data the are included in the study and support the statistical analysis
• IPD Sharing Time Frame: from April 1, 2025 to December 31, 2025
• IPD Sharing Access Criteria: Data are available by the corresponding author
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL

Study Data/Documents

1. Individual Participant Data Set
   Information identifier: TE-KEB/22/2023
   Information comments: For more information please email to: petridis.leonidas@tf.hu

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No