title: Influence of age and posture on spinal and corticospinal excitability.
abstract: 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.
authors.affiliation: Laboratory of Applied Biology and Neurophysiology, ULB Neuroscience Institute (UNI), Université Libre de Bruxelles (ULB), 808 route de Lennik, 1070 Brussels, Belgium. Electronic address: sbaudry@ulb.ac.be.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Baudry
authors.affiliation: Laboratory of Applied Biology and Neurophysiology, ULB Neuroscience Institute (UNI), Université Libre de Bruxelles (ULB), 808 route de Lennik, 1070 Brussels, Belgium.
authors.forename: Sarah
authors.initials: S
authors.lastname: Collignon
authors.affiliation: Laboratory of Applied Biology and Neurophysiology, ULB Neuroscience Institute (UNI), Université Libre de Bruxelles (ULB), 808 route de Lennik, 1070 Brussels, Belgium.
authors.forename: Jacques
authors.initials: J
authors.lastname: Duchateau
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D011187:Posture / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology*
keywords: Aging; H reflex; Motor evoked potential; Transcranial magnetic stimulation; Upright standing