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Caffeine increases spinal excitability in humans
Author(s) -
Walton C.,
Kalmar J.,
Cafarelli E.
Publication year - 2003
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.10457
Subject(s) - caffeine , h reflex , reflex , anesthesia , medicine , excitatory postsynaptic potential , placebo , electrophysiology , electromyography , neuroscience , psychology , endocrinology , physical medicine and rehabilitation , inhibitory postsynaptic potential , alternative medicine , pathology
The Hoffman reflex (H reflex) has long been established as a measure of spinal excitability. Caffeine is one of the most widely consumed drugs in the world. Because it is known to increase excitatory neurotransmission, we hypothesized that caffeine would increase spinal excitability and thus alter the H reflex by increasing its amplitude. Seven subjects each attended the laboratory on 2 days. Caffeine (6 mg/kg) was administered on one day and a placebo was administered on the other. The tibial nerve was stimulated at incremental intensities to create an H‐reflex recruitment curve prior to capsule administration (pretest) and 1 h later (posttest) on each day. The slope of H‐reflex recruitment curve normalized to that of the M wave (H slp /M slp ) was compared (pretest to posttest). Caffeine increased spinal excitability 43 ± 17% ( P < 0.05). Thus, caffeine may be used to safely increase spinal excitability in electrophysiological studies of the human neuromuscular system. Our results also suggest that caffeine intake should be controlled when the H reflex is used in diagnostic and experimental situations. Muscle Nerve 28: 359–364, 2003