Article

Substantial evidence exists for the age-related decline in maximal strength and
strength development. Despite the importance of knee extensor strength for
physical function and mobility in the elderly, studies focusing on the underlying
neuromuscular mechanisms of the quadriceps muscle weakness are limited. The aim
of this study was to investigate the contributions of age-related neural and
muscular changes in the quadriceps muscle to decreases in isometric maximal
voluntary torque (iMVT) and explosive voluntary strength. The interpolated twitch
technique and normalized surface electromyography (EMG) signal during iMVT were
analyzed to assess changes in neural drive to the muscles of 15 young and 15
elderly volunteers. The maximal rate of torque development as well as rate of
torque development, impulse and neuromuscular activation in the early phase of
contraction were determined. Spinal excitability was estimated using the H reflex
technique. Changes at the muscle level were evaluated by analyzing the
contractile properties and lean mass. The age-related decrease in iMVT was
accompanied by a decline in voluntary activation and normalized surface EMG
amplitude. Mechanical parameters of explosive voluntary strength were reduced
while the corresponding muscle activation remained primarily unchanged. The
spinal excitability of the vastus medialis was not different while M wave latency
was longer. Contractile properties and lean mass were reduced. In conclusion, the
age-related decline in iMVT of the quadriceps muscle might be due to a reduced
neural drive and changes in skeletal muscle properties. The decrease in explosive
voluntary strength seemed to be more affected by muscular than by neural changes.
CI - Crown Copyright (c) 2013. Published by Elsevier Ltd. All rights reserved.

Langue : ANGLAIS

Tiré à part : OUI