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Na + ‐K + ‐ATPase is not involved in the warming‐up phenomenon in generalized myotonia
Author(s) -
Van Beekvelt Mireille C.P.,
Drost Gea,
Rongen Gerard,
Stegeman Dick F.,
Van Engelen Baziel G.M.,
Zwarts Machiel J.
Publication year - 2006
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.20483
Subject(s) - myotonia , ouabain , isometric exercise , medicine , chemistry , electromyography , endocrinology , anatomy , anesthesia , sodium , myotonic dystrophy , physical medicine and rehabilitation , organic chemistry
The initial temporary weakness that occurs in autosomal‐recessive generalized myotonia diminishes with repetitive contractions. Physiological understanding of this phenomenon is incomplete. The underlying hypothesis of our study was that the “warming‐up” phenomenon relates to the exercise‐related activation of Na + ‐K + ‐ATPase. Three patients performed isometric exercise of the brachioradialis muscle on two separate days. Randomly, on one of these days the contraction was preceded by a 30‐min infusion of the Na + ‐K + ‐ATPase inhibitor ouabain into the brachial artery of the exercising arm (0.4 μg.min –1 .dl –1 ). Force was measured simultaneously with electrical muscle activity using high‐density surface electromyography (HD‐sEMG). A transient rapid decline in force occurred after initiation of exercise, accompanied by electrophysiological changes indicating sarcolemmal conduction block. Ouabain infusion did not affect the recovery from transient paresis or the accompanying electromyographic changes, indicating that the warming‐up phenomenon in generalized myotonia is not mediated by Na + ‐K + ‐ATPase. Muscle Nerve, 2005