Influence of Physical Exercise on Neuroplasticity and Sensorimotor Networks in Older Adults

Corticospinal excitability

Corticospinal excitability will be assessed using transcranial magnetic stimulation (TMS) applied to the primary motor cortex. Motor evoked potentials (MEPs) are recorded using surface electromyography from the abductor pollicis brevis (APB) muscle of the dominant hand. Single pulses of increasing intensity will be delivered to establish an input-output (I/O) recruitment curve. The stimulation intensity will be increased in steps of 3 to 5%, and 10 stimuli will be delivered per stimulation intensity. I/O curves will be fitted using a Boltzmann sigmoid function. Three parameters will be derived : slope, plateau and S50. These parameters will be compared across experimental conditions. The primary outcome will be the slope of the I/O curve, reflecting the recruitment rate of neurons in the corticospinal tract, indicating the level of corticospinal excitability.

Intracortical and sensorimotor circuits of M1

Sensorimotor circuits of the primary motor cortex (M1) will be assessed using paired-pulse transcranial magnetic stimulation (TMS) applied over the M1 controlling the dominant hand. Short- and long-interval intracortical inhibition and facilitation (SICI, ICF, LICI) : A subthreshold conditioning stimulus (80% RMT) will precede a suprathreshold test stimulus (1mV MEP) at specific interstimulus intervals to quantify intracortical inhibitory and facilitatory processes. Outcome measures are expressed as the ratio of conditioned to unconditioned MEP amplitude. Sensorimotor afferent circuits (SAI, LAI, AIF) : Electrical stimulation of the median nerve at the wrist (SC) will precede TMS over M1 (ST) at defined intervals to evaluate afferent-mediated inhibition or facilitation. Outcome measures are the ratio of conditioned to unconditioned MEP amplitude.

Global Physical Activity Questionnaire

The Global Physical Activity Questionnaire (GPAQ) is used to assess levels of physical activity. Designed for adults, this standardized questionnaire comprises 16 items (P1 to P16) that gather information about physical and sports activities during a typical week. The GPAQ explores three specific categories : activities carried out in a professional context, active travel and leisure activities. It also takes into account time spent sitting, thus reflecting sedentary behaviors. For each of these categories, the frequency, duration, and intensity of activities are recorded.

Edinburgh Handedness Inventory

Measuring handedness is particularly important in studies using transcranial magnetic stimulation (TMS), as manual dominance is often associated with functional and structural asymmetries in the brain. Accurate identification of the dominant hand allows for better targeting of cortical regions of interest and standardization of the interpretation of neurophysiological results. This questionnaire includes a series of common activities (writing, throwing, using scissors, etc.) for which the participant indicates which hand they use most frequently.

Numeric Pain Rating Scale

The Numeric Rating Scale (NRS) will be administered to assess the presence and intensity of pain in daily life, particularly in older participants who may experience pain. This measure is included to document baseline pain status and to explore potential interactions between pain and neurophysiological outcomes. In participants reporting no pain, the scale will not be further analyzed.