Background: Transcranial magnetic stimulation (TMS) is a non-invasive technique that can be used to evaluate cortical function and corticospinal pathway in normal and pathological aging. Yet, the metrologic properties of TMS-related measurements is still limited in the aging population. Objectives: The aim of this cross-sectional study was to document the reliability and smallest detectable change of TMS measurements among community-dwelling seniors. A secondary objective was to test if TMS measurements differ between elders based on lifestyle, medical and socio-demographic factors. Methods: Motor evoked potentials (MEPs) elicited by single-pulse TMS were recorded in the first dorsal interosseous (FDI) in 26 elderly individuals (mean age = 70 ± 3.8 years). Resting motor threshold (rMT), MEP amplitudes and contralateral silent period (cSP) were measured on two separate occasions (1-week interval), and the standard error of the measurement (SEM_eas), intraclass correlation coefficient (ICC), and smallest detectable change in an individual (SDC_indv) were calculated. Lifestyle, medical and socio-demographic factors were collected using questionnaires. TMS-related outcomes were compared using independent sample t-test based on the presence of chronic health diseases, chronic medication intake, obesity, history of smoking, physical activity levels, gender, and level of education. Results: rMT and cSP measures were the most reliable outcomes, with the lowest SEM_eas and highest ICCs, whereas MEP amplitude-related measures were less reliable. SDC_indv levels were generally high, even for rMT (7.29 %MSO) and cSP (43.16–50.84 ms) measures. Although not systematically significant, results pointed toward a higher corticospinal excitability in elderly individuals who were regularly active, who had no chronic medical conditions and who did not take any medication. Conclusion: Even though SDC_indv levels were relatively high, these results show that rMT and cSP are the most reliable outcomes to investigate age-related changes in the corticomotor system and suggest that the influence of factors such as lifestyle habits and medications on TMS measures should be investigated further.

Purpose: Muscle tendon vibration (MTV) strongly activates muscle spindles and can evoke kinaesthetic illusions. Although potentially relevant for sensorimotor rehabilitation in stroke, MTV is scarcely used in clinical practice, likely because of the absence of standardised procedures to elicit and characterise movement illusions. This work developed and validated a Standardised Kinaesthetic Illusion Procedure (SKIP) to favour the use of MTV-induced illusions in clinical settings. Materials and methods: SKIP scores were obtained in 15 individuals with chronic stroke and 18 age- and gender-matched healthy counterparts. A further 13 healthy subjects were tested to provide more data with the general population. MTV was applied over the Achilles tendon and SKIP scoring system characterised the clearness and direction of the illusions of ankle dorsiflexion movements. Results: All healthy and stroke participants perceived movement illusions. SKIP scores on the paretic side were significantly lower compared to the non paretic and healthy. Illusions were less clear and sometimes in unexpected directions with the impaired ankle, but still possible to elicit in the presence of sensorimotor deficits. Conclusions: SKIP represents an ancillary and potentially useful clinical method to elicit and characterise illusions of movements induced by MTV. SKIP could be relevant to further assess the processing of proprioceptive afferents in stroke and their potential impact on motor control and recovery. It may be used to guide therapy and improve sensorimotor recovery. Future work is needed to investigate the metrological properties of our method (reliability, responsiveness, etc.), and also the neurophysiological underpinnings of MTV-induced illusions.