Dopamine and Muscle Function in the Heat

The Influence of Dopamine Activity on Neuromuscular Function During Passive Heat Stress

our goal is to study the effects of dopamine activity, using Ritalin ingestion, on neuromuscular function over the course of a progressive heating and cooling protocol developed in our lab. We hypothesize that Ritalin will minimize the previously reported progressive impairment in neuromuscular function with hyperthermia compared to placebo, suggesting that dopamine activity preserves neuromuscular capacity with hyperthermia.

Study Overview

• Status: Unknown
• Conditions: Hyperthermia; Muscle Force
• Intervention / Treatment: Drug: Ritalin 20 mg Tablet; Drug: Placebo Oral Tablet

Detailed Description

Increased core temperature (hyperthermia) has been associated with impaired neuromuscular performance, with the majority of research suggesting that the observed fatigue is related to the central nervous system. Small doses of Ritalin has been used to study how changes in dopamine activity affects exercise capacity in the heat. This study found that 20 mg of Ritalin had no effect on exercise capacity in a thermoneutral environment of 18°C. However, when in a hot (30°C) environment, the Ritalin resulted in a 16% improvement in finishing time compared to the placebo trial. Interestingly, the higher output during the Ritalin-hot condition also resulted in higher rates of heat production and a higher (~0.6°C) core temperature, suggesting that dopamine enabled greater voluntary tolerance of hyperthermia. This matches recent work from our own work showing that motivational skills training increased both exercise tolerance and final core temperature, and it is possible that dopamine activity played a role in this improvement.

Ultimately, fatigue is shown in an inability to sustain muscular force. However, the role of dopamine activity on neuromuscular function (e.g., central activation and recruitment of muscle) during hyperthermia is unknown. One study reported that 20 mg of Ritalin did not alter neuromuscular function, but this study was done without thermal stress.

Therefore, our goal is to study the effects of dopamine activity, using Ritalin ingestion, on neuromuscular function over the course of a progressive heating and cooling protocol developed in our lab. We hypothesize that Ritalin will minimize the previously reported progressive impairment in neuromuscular function with hyperthermia (5, 7) compared to placebo, suggesting that dopamine activity preserves neuromuscular capacity with hyperthermia.

• Study Type: Interventional
• Enrollment (Actual): 6
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Ontario
    • St Catharines, Ontario, Canada, L2S 3A1
      • Brock University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 30 years (ADULT)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: Male

Description

Inclusion Criteria:

• High aerobic fitness (>55 mL/kg/min maximal aerobic capacity)

Exclusion Criteria:

• diagnosed cardiovascular, respiratory and/or neuromuscular disease, prescription of Ritalin or any drugs for hyperactivity within the past 1 year, any current prescription medication (except for asthma/allergy inhalers), any contraindications to Ritalin.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: BASIC_SCIENCE
• Allocation: RANDOMIZED
• Interventional Model: SINGLE_GROUP
• Masking: SINGLE

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
EXPERIMENTAL: Ritalin; 20 mg Ritalin, 90 min before testing	Drug: Ritalin 20 mg Tablet; Single dose for all participants
PLACEBO_COMPARATOR: Control; Identical size/taste placebo pill, 90 min before testing	Drug: Placebo Oral Tablet; Placebo with same appearance/taste

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Wrist flexion torque	Maximal voluntary contraction of wrist flexion	2-4 hours after ingestion

Collaborators and Investigators

• Sponsor: Brock University

Study record dates

Study Major Dates

• Study Start (ACTUAL): April 20, 2018
• Primary Completion (ANTICIPATED): December 31, 2021
• Study Completion (ANTICIPATED): December 31, 2021

Study Registration Dates

• First Submitted: April 23, 2018
• First Submitted That Met QC Criteria: April 23, 2018
• First Posted (ACTUAL): May 3, 2018

Study Record Updates

• Last Update Posted (ACTUAL): February 10, 2021
• Last Update Submitted That Met QC Criteria: February 8, 2021
• Last Verified: February 1, 2021

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Wounds and Injuries; Body Temperature Changes; Heat Stress Disorders; Hyperthermia; Physiological Effects of Drugs; Neurotransmitter Agents; Molecular Mechanisms of Pharmacological Action; Neurotransmitter Uptake Inhibitors; Membrane Transport Modulators; Dopamine Agents; Dopamine Uptake Inhibitors; Central Nervous System Stimulants; Methylphenidate
• Other Study ID Numbers: 17-123

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: No sharing planned

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