title: Effect of ageing on the force development in tetanic contractions of motor units in rat medial gastrocnemius muscle.
abstract: 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.
authors.affiliation: Department of Neurobiology, University School of Physical Education, 55 Grunwaldzka Str., 60-352 Poznań, Poland. lochynski@awf.poznan.pl
authors.forename: Dawid
authors.initials: D
authors.lastname: Łochyński
authors.forename: Dominik
authors.initials: D
authors.lastname: Kaczmarek
authors.forename: Piotr
authors.initials: P
authors.lastname: Krutki
authors.forename: Jan
authors.initials: J
authors.lastname: Celichowski
mesh_terms: D000375:Aging; D000818:Animals; D004576:Electromyography; D009046:Motor Neurons / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000473:pathology*; D051381:Rats; D017208:Rats, Wistar; D011999:Recruitment, Neurophysiological; D013314:Stress, Mechanical; D013746:Tetany; D013997:Time Factors