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Influence of age and posture on spinal and corticospinal excitability.

par Baudry, Stéphane ;Collignon, Sarah;Duchateau, Jacques
Référence Experimental gerontology, 69, page (62-69)
Publication Publié, 2015-06

Article révisé par les pairs

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Résumé :

This study investigated the modulation of the excitability of spinal and corticospinal pathways from seated to upright standing across adult lifespan. The input-output relations for the Hoffmann (H) reflex and motor-evoked potential (MEP) were recorded in soleus muscle during seated and upright posture in 40 subjects assigned to either young (range: 19-39yrs, n=16), middle-aged (40-59yrs, n=12), and elderly group (60-76yrs, n=12). In seated posture, H reflex and MEP were recorded during voluntary contractions of the ankle plantar flexors inducing similar soleus electromyographic activity that during upright standing. Maximal H-reflex and MEP amplitude (Hmax, MEPmax), and the change in response amplitude from seated to standing were analyzed. The Hmax decreased with age (p=0.001) and from seated to standing (p<0.001). The change in Hmax from seated to standing was greater in elderly (-40.1%; p<0.05) compared with young (-20.7%) and middle-aged groups (-23.7%). MEPmax increased with age and from seated to standing (p<0.001). The change in MEPmax from seated to standing did not differ (p>0.05) between young (+53.6%), middle-aged (+43.2%) and elderly groups (+77.3%). These results indicate a posture-related modulation of the excitability of spinal and corticospinal pathways regardless of age, with a more pronounced modulation of spinal pathway in elderly adults. This study further documents the time course of decrease and increase in spinal and corticospinal excitability, respectively, across adult lifespan.