Effect of tubocurarine on static and dynamic muscle contractions in man

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Abstract
The effect of a bolus injection of tubocurarine (0.1 mg .times. kg-1 i.v.) was followed in 6 young subjects by registration of static and slow (30.degree. .times. s-1) and fast (150.degree. .times. s-1) dynamic (isokinetic) maximal voluntary leg extensions. Mechanograms from both unblocked and curarized muscle contractions showed a notch after about 440 ms separating 2 relative maxima. The mechanograms were divided by an arbitrary straight line connecting the starting point of the contraction curve and the notch. The line separated an area (Nm .times. s) above and to the left (.alpha.-component) from an area below and to the right (.beta.-component) of the line. Tubocurarine affected the .beta.-component selectively until about 70% reduced in the static contractions. With further curarization the .alpha.-component was also reduced in size. The .alpha.-component was equally affected during the 3 types of contractions, while the faster the contraction the more the .beta.-component was reduced. Static as well as dynamic human msucle contractions can be divided into 2 parts with a different sensitivity for tubocurarine, 1 of which seems to have a sensitivity which depends on the contraction velocity.