Effects of caffeine on neuromuscular function
| Autor: | J. M. Kalmar, E. Cafarelli |
|---|---|
| Rok vydání: | 1999 |
| Předmět: |
Adult
Male medicine.medical_specialty Physiology Neuromuscular Junction Neuromuscular transmission Electromyography Placebo chemistry.chemical_compound Double-Blind Method Caffeine Physiology (medical) Humans Medicine Muscle Skeletal Electric stimulation Motor Neurons medicine.diagnostic_test business.industry Quadriceps muscle musculoskeletal system Electric Stimulation chemistry Physical performance Anesthesia Muscle Fatigue Physical therapy Tibial Nerve H-reflex business Muscle Contraction |
| Zdroj: | Journal of Applied Physiology. 87:801-808 |
| ISSN: | 1522-1601 8750-7587 |
| DOI: | 10.1152/jappl.1999.87.2.801 |
| Popis: | This double-blind, repeated-measures study examined the effects of caffeine on neuromuscular function. Eleven male volunteers [22.3 ± 2.4 (SD) yr] came to the laboratory for control, placebo, and caffeine (6 mg/kg dose) trials. Each trial consisted of 10 × 1-ms stimulation of the tibial nerve to elicit maximal H reflexes of the soleus, four attempts at a maximal voluntary contraction (MVC) of the right knee extensors, six brief submaximal contractions, and a 50% MVC held to fatigue. Isometric force and surface electromyographic signals were recorded continuously. The degree of maximal voluntary activation was assessed with the twitch-interpolation technique. Single-unit recordings were made with tungsten microelectrodes during the submaximal contractions. Voluntary activation at MVC increased by 3.50 ± 1.01 (SE) % ( P < 0.01), but there was no change in H-reflex amplitude, suggesting that caffeine increases maximal voluntary activation at a supraspinal level. Neither the force-EMG relationship nor motor unit firing rates were altered by caffeine. Subjects were able to hold a 50% MVC for an average of 66.1 s in the absence of caffeine. Time to fatigue (Tlim) increased by 25.80 ± 16.06% after caffeine administration ( P < 0.05). There was no significant change in Tlim from pretest to posttest in the control or placebo trials. The increase in Tlim was associated with an attenuated decline in twitch amplitude, which would suggest that the mechanism is, at least in part, peripheral. |
| Databáze: | OpenAIRE |
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