Journal
MECHANISMS OF AGEING AND DEVELOPMENT
Volume 131, Issue 9, Pages 545-553Publisher
ELSEVIER IRELAND LTD
DOI: 10.1016/j.mad.2010.07.001
Keywords
Motor unit; Rate of force development; Doublet; Impulse; Ageing
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Funding
- Polish Ministry of Science and Informatization [2 P050 109 29]
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The purpose of this study was to determine the effect of ageing on the rate of force generation of motor units, and the mechanical efficiency of contraction produced by a doublet discharge. The study was carried out on isolated motor units of rat medial gastrocnemius muscle of young (5-10 mo) and two groups of old (24-25 and 28-30 mo) Wistar rats. Motor units were classified into the fast fatigable (FF), fast resistant (FR) and slow (S) ones. The force output and rate of force development were determined for non-doublet unfused tetanic contractions evoked by a series of a constant-rate trains of pulses and corresponding doublet contractions starting with an initial brief interpulse interval of 5 ms, and for maximal tetanic contraction. In FF motor units the rate of force development and the force produced by the doublet discharge increased transiently at the age of 24-25 mo, while in S and FR motor units this increase was observed at the age of 28-30 mo. Age-related decrease in the rate of force development of skeletal muscle cannot be attributed to a decline in efficiency of force production by functioning motor units. (C) 2010 Elsevier Ireland Ltd. All rights reserved.
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