Mechanical muscle-tendon vibration affects musculature and the nervous system. As the vibrations used in previous studies were varied, consistently determining the effect of mechanical vibration was challenging. Additionally, only a few studies have applied vibrations to dynamic motion. This study investigated whether the vibration based on the sensorimotor response could affect the stability and function of stair climbing. Electroencephalogram (EEG) signals were recorded from the sensorimotor area, and mu rhythms, dependent on the vibration frequencies, were analyzed. Based on the analysis, the vibratory stimulus conditions were set and applied to the Achilles tendon of the lower limb during stair climbing. Simultaneously, electromyogram (EMG) signals from the gastrocnemius lateralis (GL), gastrocnemius medialis (GM), soleus (SOL), and tibialis anterior (TA) were recorded. Activations and co-activations of the shank muscles were analyzed according to the phases of stair climbing. When vibration was applied, the TA activation decreased in the pull-up (PU) phase, and calf muscle activations increased during the forward continuous (FCN) phase. These changes and their degrees differ significantly between stimulus conditions (p < 0.05). Co-activation changes, which differed significantly with conditions (p < 0.05), appeared mostly in the PU. These results imply that the vibration affects stability and function of stair climbing, suggesting that the vibration characteristics should be considered when they are applied to dynamic movement.

Background Although, in daily living, almost all stair ambulation is conducted posterior to level walking, or vice versa, there are only a few studies related to the transition compared to the studies on steady-state stair walking. Furthermore, neuromotor control in the instant of the transition is different from that of the steady-state stair walking. However, there are only a few studies investigating the transition from level walking to stair ascent in the elderly by comparing with young adults, and there is no study on the assistance of the transition movement in the elderly who are experiencing neurophysiological changes. Thus, this pilot study aimed to compare the flat surface-to-stair ascent transition by the elderly to that seen in young adults, and to investigate how vibrotactile somatosensory stimulus (VSS), which has a positive effect on muscle performance and gait, affects the transition tasks in elderly people. Results In the first half of the stance phase, the elderly exhibited a higher moment and power of the hip extensor and a less moment and power of the knee extensor compared with young adults. In the second half of the stance phase, positive plantar-flexor power and support moment was higher in the elderly. In addition, during the single-limb support phase, dorsiflexion was maintained in the elderly, whereas young adults appeared to have decreased dorsiflexion. When the VSS was applied, the moment and power of the hip extensor, the plantar-flexor moment, and the support moment in the entire of the stance phase were increased. In addition, it was found that the degree of the kinetics parameters was different depending on the frequencies of the VSS. Conclusions This pilot study has revealed evident biomechanical differences between elderly people and young adults during the transition from level walking to stair ascent. Additionally, it has shown that the VSS may accentuate the features of the transition movement of the elderly and regulate joint kinetics. The results of the present pilot study can provide a base for further research and understanding of movement, which can be utilized in designing assistance aids for the elderly. Trial registration CRIS, KCT0005434, Registered 25 September 2020, Retrospectively registered.

The purpose of this study was to investigate the influence of sensorimotor-cortex-responsebased vibratory stimulation on stair climbing by the elderly and to reveal the functional assistance effect of vibratory stimulation. To do this, vibratory stimulation conditions (VSCs) were set through the reduction of the mu rhythm, an index of sensorimotor cortex excitability, and applied to elderly people during stair climbing. Joint angle, moment, power, and muscle coactivation (CA) of lower limbs were analyzed to investigate the influence of VSCs on stair climbing. As a result of vibratory stimulation, the biomechanical characteristics of the ankle and hip joints were further developed according to the VSC, and a tendency to compensate the knee joint work appeared. Also, functional improvement of the ankle joint was shown through greater energy transfer from the knee joint to the ankle joint. These results suggested that sensorimotorcortex-response-based vibratory stimulation has the effect of functional assistance of the movement of elderly people and may be useful in research on movement assistance or rehabilitation for people with reduced body functions.

The purpose of this study was to derive the local vibration that the sensorimotor area responds sensitively and to investigate changes in muscle activity of the lower limb when the vibratory stimulus was applied during the stair climbing. The electroencephalogram was measured when vibratory stimulus was applied to each tendon and changes in Mu rhythm activity were analyzed. A specific vibration frequency was selected through the results of the Mu rhythm analysis, and the specific vibratory conditions were set by combining the tendon site, vibration intensity, and frequencies. These vibratory conditions were applied simultaneously with the electromyogram measurement during the stair climbing. As a result, we confirm the specific vibration frequencies in each tendon. Also, we infer that there is a sensitive vibratory stimulus for each tendon. Moreover, the specific vibratory stimulus activates the sensorimotor area and elicits an increase in the muscle activity. This result means that specific vibration frequency and stimulation site should be considered in rehabilitation therapy that used the local vibratory stimulus. Also, local vibratory stimulus can be used to assist in stair climbing.