Contribution of Corticospinal and Reticulospinal Mechanisms to Neural Adaptations Induced by Muscle Strengthening of Healthy Adults

This controlled trial aims to investigate the neural adaptations induced by a 4-week resistance training program targeting the triceps surae muscles. Specifically, the study will examine the contribution of the corticospinal and reticulospinal pathways to the nervous adaptations associated with resistance training. It will give us more information about the nervous pathways mediating adaptations following this type of training. The main question it aims to answer is: What is the contribution of the cortico- and reticulospinal tracts to the nervous adaptations following a resistance training program? Participants will take part to a resistance training program of the triceps surae for 4 weeks. They will undergo assessments of corticospinal and reticulospinal excitability before and after the training intervention to determine changes in neural pathways The findings will improve our understanding of the neural mechanisms underlying strength gains following resistance training.

Inclusion Criteria: * Male or female participants aged 18 to 40 years * Willing and able to provide written informed consent * No regular participation (\>1 session per week) in resistance training aimed at increasing maximal strength * Affiliated with, or beneficiary of, a social security system Exclusion Criteria: * Personal or family history of epilepsy * Conditions associated with a significantly reduced seizure threshold, including sleep deprivation, extreme fatigue, or jet lag * Use of medications or substances known to lower the seizure threshold * Use of medications that may influence neurophysiological measures (e.g., neuroleptics, anxiolytics, antidepressants, anticonvulsants) * Presence of cardiac pacemakers or other implanted devices that may interfere with magnetic fields * Presence of metallic implants (mechanical or electronic), including cochlear implants, cranial implants, cardiac or neural stimulators, drug infusion pumps, magnetic aneurysm clips, or cerebrospinal fluid shunts * Presence of non-removable metallic objects * Presence of intraocular or intracranial metallic foreign bodies * Known hearing disorders (e.g., tinnitus) * History of psychiatric or neurological disorders * Presence of severe cardiac or respiratory disease * History of severe traumatic brain injury with loss of consciousness * History of brain lesions of vascular, tumoral, infectious, or metabolic origin (e.g., stroke) * History or presence of bleeding disorders (e.g., venous or arterial thrombosis, thrombophlebitis) * Individuals currently under an exclusion period from another research study * Individuals listed under Articles L.1121-5 to L.1121-8 and L.1121-12 of the French Public Health Code, including: * Pregnant, parturient, or breastfeeding women * Women of childbearing potential not using effective contraception * Individuals deprived of liberty by judicial or administrative decision * Adults under legal protection (guardianship, curatorship, or legal safeguard) or unable to provide consent and not under such protection * Minors