Clinical Trial Details
— Status: Active, not recruiting
Administrative data
NCT number |
NCT04283877 |
Other study ID # |
EEL124 |
Secondary ID |
|
Status |
Active, not recruiting |
Phase |
Phase 4
|
First received |
|
Last updated |
|
Start date |
December 15, 2019 |
Est. completion date |
December 31, 2021 |
Study information
Verified date |
February 2021 |
Source |
Brock University |
Contact |
n/a |
Is FDA regulated |
No |
Health authority |
|
Study type |
Interventional
|
Clinical Trial Summary
The purpose is to study the effects of dopamine activity, using methylphenidate ingestion, on
exercise and cognitive function over the course of a progressive cooling protocol. The
investigators hypothesize that methylphenidate will minimize the previously reported
impairment in exercise performance and cognitive function with mild hypothermia and cold
stress (air temperature: 0˚C) compared to placebo, suggesting that dopamine activity
preserves exercise and cognitive capacity with mild hypothermia.
Description:
Temperature regulation and decision-making are vital aspects of human survival where
relatively small deviations in whole-body heat balance lead to decrements in physical
performance and cognitive function. Prolonged exposure to cold stress combined with
inadequate clothing and/or insufficient heat production can lead to decreases in body
temperature causing mild hypothermia (≤ -1.0˚C in body temperature). Performance in the cold
is more physically demanding compared to neutral environments (~22˚C) as there is increased
cardiovascular strain due to a strong peripheral vasoconstriction reducing cerebral and
muscle blood flow and oxygenation, reduced neuromuscular capacity, as well as changes in
energy metabolism during shivering and increased catecholamine release. Additionally, there
is an increased psychological strain where perceptually there is a high thermal discomfort,
alterations in neurotransmitters (e.g. dopamine, norepinephrine), and alterations in mood.
These changes lead to decreases in self-paced cycling time-trial performance in the cold with
mild hypothermia compared to thermoneutral environments. Additionally, there appears to be
task-dependent cognitive changes with acute cold stress, where higher-order functions such as
executive function, working memory, and inhibitory control decrease before simple task
performance such as reaction time and visual recognition/awareness. Currently, it is unknown
what the potential mechanisms are that lead to these performance decrements.
The decrements in both self-paced exercise and cognitive function may be due to alterations
in neurotransmitters caused by hypothermia. Exposure to cold leads to alterations in
dopamine, and norepinephrine which may affect prefrontal cortex function, which may explain
why higher-order executive function tasks such as inhibitory control and spatial planning are
impaired compared to simple task performance. Previously, it has been determined that the use
of tyrosine (amino acid precursor to dopamine and norepinephrine neurotransmitters)
supplementation improves working memory and executive function despite a -2.0˚C drop in body
temperature through cold-water immersion, but not in thermoneutral conditions. However, it is
unknown what the role of dopamine or central nervous system stimulants are in the cold.
Methylphenidate is a central nervous system stimulant through dopamine re-uptake inhibition
is demonstrated to improve executive function task performance in healthy adults in
thermoneutral conditions. Additionally, methylphenidate has been demonstrated to improve
self-paced cycling performance by 16% in the heat (30˚C) but not thermoneutral environments
(1). Methylphenidate is also demonstrated to improve maximal force production during
fatiguing exercise, indicating it may play a role in reducing the effects of fatigue during
endurance exercise. The investigators aim to determine the role of the central nervous system
using methylphenidate on cognitive function and self-paced exercise in the cold.