Effects of aging on transmission from Ia afferents to α-motoneurons and presynaptic mechanisms across muscle lengths and contraction types.

Yohan Betus, Julian Colard, Marc Jubeau, Anne-Sophie Boureau, Guillaume Chapelet, Christophe Cornu, Thomas Cattagni

Movement - Interactions - Performance, MIP, UR 4334, Nantes Université, F-44000, Nantes, France.Movement - Interactions - Performance, MIP, UR 4334, Nantes Université, F-44000, Nantes, France. · pubmed

Paper

Abstract

Presynaptic inhibition of Ia afferents, particularly via primary afferent depolarization (PAD), plays a crucial role in modulating transmission from Ia afferents to α-motoneurons according to task demands. In young adults, PAD is enhanced during eccentric contractions and at longer muscle lengths, supporting adaptable motor control. However, aging is associated with reduced muscle spindle sensitivity, which may impair the regulation of presynaptic inhibition via PAD. This study investigated whether aging alters the modulation of PAD according to contraction type and muscle length. Nineteen older adults (69 ± 4 years) and 16 young adults (23 ± 2 years) participated in three experimental sessions. The maximal H-reflex (H

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Research summary

Aging reduces the modulation of presynaptic inhibition via primary afferent depolarization in Ia afferents, affecting motor control. The study addresses how aging impacts fundamental neuromuscular mechanisms, which is relevant to understanding the biological processes of aging and potential interventions.

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