## 1 Introduction
These neural mechanisms could explain the benefits of WBV intervention on muscle strength, gait, and balance [29; 32; 33; 34]. The central nervous system's capacity to recruit motor units is closely correlated with functional gains. The nervous system can generate and modulate a greater amount of force when a greater number of motor units are activated, which aids in the better control of fine movements [35; 36]. This results in more precise and rapid postural adjustments and more well-regulated gait patterns [37]. The ability to perform functional daily activities through purposeful and coordinated movements is contingent upon the possession of adequate muscle strength (or force). Furthermore, some studies have found changes in the hormone profile following WBV training, thus showing increased secretion of brain-derived neurotrophic factor (BDNF) [38] testosterone and growth hormone, and decreased cortisol levels [32; 39; 40; 41]. Several studies have investigated the effects of WBV in PwMS [42; 43; 44; 45; 46; 47; 48; 49]. [PERSON] et al. [43] reported that a 3 weeks of WBV training improved muscle strength but not the functional mobility (i.e., 3 min walk test) of people with MS. On the other hand, [PERSON] et al. [42] showed that 20 weeks of WBV did not positively affect the muscular performance of the lower limbs or the functional ability of the lower limb. [PERSON] et al. [46] pointed out that the WBV training improves standing balance and walking time without negative effects. Other recent studies suggest that WBV has a beneficial impact on the functional and physical indices of PwMS [50] and improves gait parameters [51]. Thus, WBV exercise has been indicated in PwMS that report prevalent symptoms of motor impairment [52]. However, the results of these studies do not show conclusive evidence regarding the efficacy of WBV [42; 43; 44; 45; 46; 47; 48; 49]. WBV has been applied without considering the individual response of the PwMS to the magnitude of the vibration load; in other words, a dose-response relationship has not been determined [39; 53; 54; 55; 56] and the WBV intervention did not follow the principle of load progression over time [47; 48]. In many cases, WBV has been administrated by using a fixed value of magnitude for the entire duration of the intervention (i.e., frequency and/or amplitude) for all the people involved. In addition, no studies have investigated a multi-year WBV intervention in people with relapse remitting (RR) MS. Therefore, the present study aims to apply a five-year individualized WBV intervention, in which a dose-response relationship was determined, to a 68-year-old man with RRMS. The effectiveness of the individualized stimulus was quantified by determining the acute and residual biochemical profile of specific markers (growth hormone, testosterone, cortisol and creatine kinase). Additionally, the handgrip strength assessment was included in the current study because it can be regarded as a comprehensive measure of physical impairment [57], even though the WBV stimuli are not directly applied to the upper limbs. This is due to its association with neuromuscular integrity and overall brain health [58]. Adjustments in grip strength may be linked to a decrease in independence in activities of daily living (e.g., drinking, eating, and buttoning a shirt) [59] due to the impairment in the upper limb function observed in PwMS [58]. Low grip strength may serve as an indicator of neuromuscular impairment on a global scale in individuals with multiple sclerosis [60]. The 5-year follow-up was monitored by assessing locomotion, handgrip strength and postural control synchronized with the EMG activity. We hypothesized that a multi-year strategy of individualized WBV improves gait, balance, and handgrip strength in a person with RRMS.