Quantitative analysis of muscle hardness in tetanic contractions induced by electrical stimulation in rats

Authors: Morisada, Makoto; Okada, Kaoru; Kawakita, Kenji

Source: European Journal of Applied Physiology, Volume 97, Number 6, August 2006 , pp. 681-686(6)

Publisher: Springer

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Abstract:

The purpose of this study was to investigate the in vivo relation between muscle hardness during an electrically induced contracting state and neuromuscular functions (M-wave and developed tension). Sixteen Sprague-Dawley rats were deeply anesthetized with urethane. Muscle hardness was measured quantitatively at the mid-portion of the gastrocnemius (GS) muscle during tetanic contractions induced by electrical stimulation (50 Hz, 100 μs duration) of the sciatic nerve or of the muscle directly. The M-wave was recorded with a pair of wire electrodes inserted into the muscle, and the developed tension was monitored with a push-pull gauge. Muscle hardness, M-wave amplitude and developed tension increased rapidly with the onset of nerve stimulation. Similar but intensity-dependent increases in muscle hardness and tension were observed following direct tetanic stimulation of the muscle. The hardness measured during nerve stimulation was correlated with the amplitude of the M-wave (r = 0.62, P < 0.0001) and the developed tension (r = 0.85, P < 0.0001). These phenomena were suppressed by pancuronium treatment (2 mg/ml, i.v.). These results suggest that muscle tension might be the most important factor for transcutaneously measured muscle hardness induced by tetanic muscle contraction.

Keywords: Muscle hardness; M-wave; Muscle tension; Electrical stimulation; Pancuronium

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s00421-006-0225-6

Affiliations: 1: Email: k_kawakita@meiji-u.ac.jp

Publication date: 2006-08-01