Physical activity modulates corticospinal excitability of the lower limb in young and old adults

Abstract

Aging is associated with reduced neuromuscular function, which may be due in part to altered corticospinal excitability. Regular physical activity (PA) may ameliorate these age-related declines, but the influence of PA on corticospinal excitability is unknown. The purpose of this study was to determine the influence of age, sex, and PA on corticospinal excitability by comparing the stimulus-response curves of motor evoked potentials (MEP) in 28 young (22.4 ± 2.2 yr; 14 women and 14 men) and 50 old adults (70.2 ± 6.1 yr; 22 women and 28 men) who varied in activity levels. Transcranial magnetic stimulation was used to elicit MEPs in the active vastus lateralis muscle (10% maximal voluntary contraction) with 5% increments in stimulator intensity until the maximum MEP amplitude. Stimulus-response curves of MEP amplitudes were fit with a four-parameter sigmoidal curve and the maximal slope calculated (slope). Habitual PA was assessed with tri-axial accelerometry and participants categorized into either those meeting the recommended PA guidelines for optimal health benefits (>10,000 steps/day, high-PA; = 21) or those not meeting the guidelines (<10,000 steps/day, low-PA; = 41). The MEP amplitudes and slope were greater in the low-PA compared with the high-PA group ( < 0.05). Neither age nor sex influenced the stimulus-response curve parameters ( > 0.05), suggesting that habitual PA influenced the excitability of the corticospinal tract projecting to the lower limb similarly in both young and old adults. These findings provide evidence that achieving the recommended PA guidelines for optimal health may mediate its effects on the nervous system by decreasing corticospinal excitability. Transcranial magnetic stimulation was used to determine whether achieving the recommended 10,000 steps/day for optimal health influenced the excitability of the corticospinal tract projecting to the knee extensor muscles. Irrespective of age and sex, individuals who achieved >10,000 steps/day had lower corticospinal excitability than those who performed <10,000 steps/day, possibly representing greater control of inhibitory and excitatory networks. Physical activity involving >10,000 steps/day may mediate its effects on the nervous system by decreasing corticospinal excitability.

Effects of a 12-Week Aerobic Spin Intervention on Resting State Networks in Previously Sedentary Older Adults

“…Previous research has noted changes in patterns of M1 activity as a function of regular engagement in physical activity ( McGregor et al, 2011 , 2013 ; Hassanlouei et al, 2017 ; Lulic et al, 2017 ). However, we are unaware of any work to date that has addressed interhemispheric connectivity changes between right and left M1 using rsfMRI.…”

Effects of elevated H+ and Pi on the contractile mechanics of skeletal muscle fibres from young and old men: implications for muscle fatigue in humans

“…PA was quantified for each participant with a triaxial accelerometer (GT3X; ActiGraph, Pensacola, FL, USA) worn around the waist for at least 4 days (2 weekdays and 2 weekend days) as reported previously (Hassanlouei et al . 2017). The data were reported for each participant as long as the participant completed at least 3 days of wear time (Hart et al .…”

Baseline White Matter Is Associated With Physical Fitness Change in Preclinical Alzheimer’s Disease

“…The corpus callosum plays an integral role in cognitive, motor, and sensory information between the left and right hemispheres of the brain (Sampaio-Baptista and Johansen-Berg, 2017). There is some evidence that an increase in fitness is associated with an increase in α-neurons caused by increased corticospinal tract excitability in addition to adaptive changes in the primary motor cortex, and/or dormant corticospinal connections (Hassanlouei et al, 2017). Rodent studies (Sampaio-Baptista and Johansen-Berg, 2017) suggest that PA promotes oligodendrocyte precursor cell proliferation and differentiation that contributes to WMM measures.…”