L-arginine Supplementation and Resistance Exercise

January 30, 2019 updated by: Kyle Hackney, North Dakota State University

The Acute Effects of L-arginine Supplementation on Flow-mediated Dilation After Resistance Exercise to Fatigue

The purpose of this study was to examine the acute endothelial, cardiovascular, and performance responses to L-arginine by assessing flow-mediated dilation (FMD) and heart rate variability (HRV) both before and after resistance exercise to fatigue. Thirty (15 male, 15 female) physically active participants volunteered for a randomized, cross-over, double-blind, placebo- controlled clinical trial. Participants completed five sets of elbow extension-flexion exercise after consumption of either 3 g of placebo or 3 g L-arginine.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Participants Thirty healthy, physically active males (n=15) and females (n=15), 18-25 years of age completed the study. Subjects had not participated in another clinical trial or consumed another study related investigation product within 30 days of enrollment. If a supplement containing L-arginine or other nitrate precursors was being taken, a three-week washout period was conducted before participation. All procedures were approved in advance by the North Dakota State University Institutional Review Board and written consent was obtained.

Protocol A randomized, double-blind, placebo-controlled research design was implemented for this investigation. Prior to the randomized testing sessions, participants completed a anthropometric measurements and familiarization session which included:: collection of participant age, height (Seca 213, Chino, CA), and body mass data (Detecto, Webb City, MO) and familiarization with the Biodex Dynamometer (Biodex Medical Systems, Shirley, NY), ultrasound (Philips Ultrasound, Bothell, WA), and electronic sphygmomanometer (Hokanson Rapid Cuff Inflation System, Bellevue, WA) procedures. Participants then reported to the laboratory for two testing sessions, each separated by at least a 48 hours washout period. Testing sessions were conducted at the same time of day to account for circadian variation. Participants entered the trial sessions on an 8-our fast, but were encouraged to arrive at the session well-hydrated. The participants were instructed not to exercise or consume caffeine 24 hours prior to trial time or use toothpaste, chewing gum, or mouthwash the morning of the trials, due to the possible effects on nitric oxide absorption. All females tested negative for pregnancy based on a urinary pregnancy test (Clinical Guard, Atlanta, GA) prior to each trial session. At the start of the trial, participants rested for 5 minutes while sitting.

Endothelial responses were measured by a technique termed flow mediated vasodilation (FMD) which assessed the maximal vasodilatory response to shear stress. FMD was measured in accordance with recommendations from the International Brachial Artery Reactivity Task Force. A Philips HD11XE ultrasound system (Philips, Amsterdam, NL) equipped with 2D imaging, color and spectral Doppler, and a high-frequency vascular transducer was used for the protocol. The participants laid supine with the right arm inside a pillow for a stabilizer. Probe placement was on the brachial artery, above the antecubital fossa in the longitudinal place. Continuous 2D imaging was used to take an initial brachial artery diameter for 10 seconds to determine the resting artery diameter (to cover the full cardiac cycle). Probe placement was outlined with a marker. A Hokanson E20 electronic sphygmomanometric cuff and rapid cuff inflation system (Bellevue, WA) was placed on the middle of the forearm and inflated to 50 mmHg above systolic blood pressure for five mins and cuff placement was marked with a marker. Upon release of the cuff, the ultrasound probe was placed in the same area in which the first measure was taken. A continuous 2D imaging was used from cuff release to 120 seconds post-release. The average of three diameters measured using RadiAnt DICOM software was used for determination of FMD (%), which was expressed as the change in post-stimulus diameter as a percentage of baseline diameter.

Measures of the cardiovascular system included heart rate variability (HRV). HRV were recorded using a Polar H7 Bluetooth strap (Polar, Bethpage, NY) combined Personal Pro Elite HRV smartphone application (elitehrv.com) over 5 min intervals then further analyzed with Kubios software using the "very low" artifact correction setting. HRV explored the differences in beat-to-beat intervals based on the time (milliseconds) between adjacent R to R (RR) peaks within a PQRST waveform. HRV provides a dynamic, sensitive meter of the balance or tone between the two branches of the autonomic nervous system, sympathetic (SNS) and parasympathetic (PNS), RMSSD and pNN50 are also the most commonly used HRV measures and were used in this study.

After baseline measurements were collected, the participants consumed either 6 capsules (3 g) of L-arginine (NOW Foods, Bloomingdale, IL) or 6 capsules of corn starch, placebo (3 g) which had an identical appearance (InHealth Specialty Pharmacy, Fargo, ND). Each supplement was consumed with 12 oz. of water. The participant then rested for 55 minutes to ensure enough time for digestion, absorption and availability. At 55 minutes post-supplementation, participants completed a 5 minutes warm up using a cycle ergometer (Monark 828E, Vansbro, SV). Sixty minutes post-supplementation, participants completed elbow flexion and extension exercise with their right arm on an isokinetic dynamometer to determine the elbow flexor and extensor peak torque.The exercise protocol, designed to induce fatigue, consisted of five sets of 10 maximal isokinetic extension repetitions of the elbow joint at 90º per second with 30 seconds of rest in between sets. Participants were instructed and encouraged to use full-force for all sets. Isometric peak torque was measured prior to and thirty seconds after exercise to determine the fatigue percentage. Dynamometer settings remained constant for each testing session as recorded during the anthropometric and familiarization session. At 10 minutes post-exercise, which was 120 minutes after supplement consumption, FMD and HRV were measured for the final time.

Study Type

Interventional

Enrollment (Actual)

30

Phase

  • Not Applicable

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 25 years (Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • generally healthy
  • physically active

Exclusion Criteria:

  • previous clinical trial
  • pregnancy

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

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

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Placebo Comparator: placebo
3 grams cornstarch once per day for one day.
Dietary supplement: L-arginine
NOW Foods, Bloomingdale, IL
Dietary supplement: Placebo
InHealth Specialty Pharmacy, Fargo, ND
Other Names:
  • cornstarch
Experimental: L-arginine
3 g L-arginine once per day for one day.
Dietary supplement: L-arginine
NOW Foods, Bloomingdale, IL
Dietary supplement: Placebo
InHealth Specialty Pharmacy, Fargo, ND
Other Names:
  • cornstarch

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in Flow mediated dilation 120 seconds post-cuff release
Time Frame: Change from Baseline and 120 seconds
Flow mediated dilation was measured using a A Philips HD11XE ultrasound system (Philips, Amsterdam, NL) equipped with 2D imaging, color and spectral Doppler, and a high-frequency vascular transducer.
Change from Baseline and 120 seconds
Change in Heart Rate Variability 10 minutes after intervention
Time Frame: Change from Baseline and 10 minutes post-exercise
Hear rate variability was recorded using a Polar H7 Bluetooth strap (Polar, Bethpage, NY) combined Personal Pro Elite HRV smartphone application (elitehrv.com) over 5 minutes intervals then further analyzed with Kubios software
Change from Baseline and 10 minutes post-exercise

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

North Dakota State University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

July 16, 2016

Primary Completion (Actual)

April 30, 2017

Study Completion (Actual)

May 30, 2017

Study Registration Dates

First Submitted

July 1, 2018

First Submitted That Met QC Criteria

January 30, 2019

First Posted (Actual)

February 1, 2019

Study Record Updates

Last Update Posted (Actual)

February 1, 2019

Last Update Submitted That Met QC Criteria

January 30, 2019

Last Verified

January 1, 2019

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • HE16235

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

No

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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