Neural and muscular factors both contribute to plantar-flexor muscle weakness in older fallers

Plantar-flexor muscles are key muscles in the control of postural sway. Older fallers present lower maximal plantar-flexor performance than older non-fallers; however, the mechanisms underlying this motor impairment remain to be elucidated. This study aimed to determine whether muscular and neural f...

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Vydáno v:	Experimental gerontology Ročník 112; s. 127 - 134
Hlavní autoři:	Cattagni, Thomas, Harnie, Jonathan, Jubeau, Marc, Hucteau, Elyse, Couturier, Catherine, Mignardot, Jean-Baptiste, Deschamps, Thibault, Berrut, Gilles, Cornu, Christophe
Médium:	Journal Article
Jazyk:	angličtina
Vydáno:	England Elsevier Inc 02.10.2018 Elsevier
Témata:	Accidental Falls Aged Aged, 80 and over Biomechanical Phenomena Disability Evaluation Electromyography Evoked Potentials Female Humans Male Muscle Contraction Muscle Weakness / physiopathology Muscle, Skeletal / innervation Muscle, Skeletal / physiopathology Reflex, Abnormal Torque Volition Walking Aged Aged, 80 and over Aging Biomechanical Phenomena Disability Evaluation Electromyography Evoked Potentials Falls Female Hoffmann reflex Human health and pathology Humans Life Sciences Male Muscle Contraction Muscle strength Muscle Weakness Muscle, Skeletal Plantar-flexor muscles Reflex, Abnormal Torque Volition Voluntary activation Walking Falls Plantar-flexor muscles Aging Hoffmann reflex Muscle strength Voluntary activation Falls Aging Plantar-flexor muscles Muscle strength Voluntary activation Hoffmann reflex
ISSN:	0531-5565, 1873-6815, 1873-6815
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Shrnutí:	Plantar-flexor muscles are key muscles in the control of postural sway. Older fallers present lower maximal plantar-flexor performance than older non-fallers; however, the mechanisms underlying this motor impairment remain to be elucidated. This study aimed to determine whether muscular and neural factors are both involved in the lower maximal plantar-flexor performance of older fallers. The maximal voluntary contraction (MVC) torque, resting twitch torque, voluntary activation level (VAL), and electromyographic (EMG) activities for the soleus, gastrocnemius medialis, gastrocnemius lateralis and tibialis anterior during plantar-flexor MVCs were recorded in 23 older non-fallers (age: 83.3 ± 3.9 years) and 25 older fallers (age: 84.0 ± 4.1 years). The maximal plantar-flexor Hoffmann reflex normalized to the maximal motor potential (Hmax/Mmax) was measured to assess the efficacy of spinal transmission from the Ia-afferent fibers to the α-motoneurons. Older fallers presented lower plantar-flexor MVC torque, resting twitch torque, VAL and EMG activity (P < 0.05). No significant differences between older fallers and non-fallers were found for the Hmax/Mmax ratio and dorsi-flexor coactivation. The current findings showed for the first time that both neural and muscular factors associated with the plantar-flexors contributed to the specific alteration of maximal motor performance in older fallers. The lack of a difference in the Hmax/Mmax ratio indicated that the efficacy of spinal transmission from the Ia-afferent fibers to the α-motoneurons was not involved in the lower voluntary muscle activation of older fallers. This suggests that supraspinal centers are likely to be involved in the lower voluntary muscle activation observed in older fallers. •This study provides the plantar-flexor neuromuscular profile of older fallers.•Older fallers present a lower maximal plantar-flexor torque than older non-fallers.•Muscle and neural mechanisms are both involved to this muscle weakness.
Bibliografie:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0531-5565 1873-6815 1873-6815
DOI:	10.1016/j.exger.2018.09.011