Effects of caffeine on neuromuscular function in a non‐fatigued state and during fatiguing exercise

Mesquita, Ricardo N., Cronin, Neil ORCID: 0000-0002-5332-1188, Kyröläinen, Heikki, Hintikka, Jukka and Avela, Janne (2020) Effects of caffeine on neuromuscular function in a non‐fatigued state and during fatiguing exercise. Experimental Physiology, 105 (4). pp. 690-706. doi:10.1113/EP088265

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Abstract

Caffeine enhances exercise performance, but its mechanisms of action remain unclear. In this study, we investigated its effects on neuromuscular function in a non‐fatigued state and during fatiguing exercise. Eighteen men participated in this randomized, double‐blind, placebo‐controlled crossover trial. Baseline measures included plantarflexion force, drop jump, squat jump, voluntary activation of triceps surae muscle, soleus muscle contractile properties, M‐wave, α‐motoneuron excitability (H‐reflex), corticospinal excitability, short‐interval intracortical inhibition, intracortical facilitation, silent period evoked by transcranial magnetic stimulation (SP) and plasma potassium and caffeine concentrations. Immediately after baseline testing, participants ingested caffeine (6 mg·kg−1) or placebo. After a 1‐h rest, baseline measures were repeated, followed by a fatiguing stretch–shortening cycle exercise (sets of 40 bilateral rebound jumps on a sledge apparatus) until task failure. Neuromuscular testing was carried out throughout the fatigue protocol and afterwards. Caffeine enhanced drop jump height (by 4.2%) and decreased the SP (by 12.6%) in a non‐fatigued state. A caffeine‐related decrease in SP and short‐interval intracortical inhibition before the fatiguing activity was associated with an increased time to task failure. The participants who benefitted from an improved performance on the caffeine day reported a significantly lower sense of effort during exercise and had an accelerated postexercise recovery of M‐wave amplitude. Caffeine modulates inhibitory mechanisms of the CNS, recovery of M‐wave amplitude and perception of effort. This study lays the groundwork for future examinations of differences in caffeine‐induced neuromuscular changes between those who are deemed to benefit from caffeine ingestion and those who are not.

Item Type: Article
Article Type: Article
Uncontrolled Keywords: Central fatigue; Peripheral fatigue; Rate of perceived exertion; Soleus; Transcranial magnetic stimulation
Subjects: Q Science > QP Physiology
Q Science > QP Physiology > QP301.H75 Physiology. Sport
R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions: Schools and Research Institutes > School of Sport and Exercise > Applied Sport & Exercise Sciences
Research Priority Areas: Sport, Exercise, Health & Wellbeing
Depositing User: Rhiannon Goodland
Date Deposited: 30 Oct 2020 10:50
Last Modified: 30 Oct 2020 11:00
URI: http://eprints.glos.ac.uk/id/eprint/8931

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