The Effects of Nicotine on Cortical Excitability After Exercise: A Double-Blind Randomized, Placebo-controlled, Crossover Study.

Abstract

Purpose: The use of smokeless tobacco/nicotine products is common among athletes, but clear evidence for their positive or negative effect on sports performance is lacking. Nicotine is a psychoactive substance involved in numerous neuronal processes including cortical excitability. The aim of this study was to evaluate its effect on cortical excitability associated with aerobic exercise in nicotine-naive healthy volunteers. Methods: Ten nicotine-naive healthy volunteers were recruited for this double-blind, randomized, crossover study to compare the effect of snus (8 mg nicotine), an oral, smokeless tobacco product, to placebo on cortical excitability before and after aerobic exercise. Transcranial magnetic stimulation (TMS) was used to measure changes in corticomotor excitability (motor-evoked potentials, MEPs) and electromyography of leg muscles duringmaximal voluntary contractions (MVC) to assess changes inmuscle contractions. Before and after aerobic exercise and with or without nicotine treatment, MEPs and MVCs were measured. Results: Analysis of TMS data showed lower motor cortex activation (lower MEP amplitude) after snus administration compared with placebo, whereas electromyography data showed no difference in muscle contraction between snus and placebo treatment. Conclusions: These findings suggest a general reduction in cortical excitability, without no relevant effect on physical performance.