To date, many rehabilitative therapies have been proposed to help with muscle function and spasticity, such as passive standing, muscle strengthening, and electrical stimulation (Ji et al. 2016). Recently, interest has focused on muscle vibration, which aims to prevent/treat muscle atrophy and spasticity through the application of mechanical oscillations to skeletal muscles (Ji et al. 2016). The application of vibration to muscle-tendon complexes results in a stretch-shortening action, in turn, activating muscle spindles to trigger a reflexive muscle contraction (Menendez et al. 2016). The vibratory stimulus may be applied in a variety of ways including focal muscle vibration and whole-body vibration. Focal muscle vibration applies low-amplitude and high-frequency vibration stimulation to a specific muscle through a small portable device (Celletti et al. 2017), while whole-body vibration involves standing, sitting or performing various tasks on a vibration platform (Liao et al. 2015; Park et al. 2018). The effects of muscle vibration therapy have been well documented in stroke patients and demonstrate an improvement in motor function, as well as balance, gait, and mobility. However, the effects of muscle vibration therapy on functional outcomes in individuals with SCI are not well known.
The methodological details and results from one randomized controlled trial are presented in Table 15.
Currently, there is very little evidence to draw any conclusions about muscle vibration as a rehabilitative therapy in SCI. Given the evidence presented by Gomes-Osman & Field-Fote and Backus et al. (2014), vibration therapy is feasible in an SCI population. Pinch strength, muscle strength, and grasp strength were temporarily improved with vibration therapy, however, no significant changes were observed with the nine-hole peg test or other measures of functional improvement. Based on the current evidence, muscle vibration therapy has little effect on functional outcomes in SCI patients. As such, future research is necessary in this area to determine the efficacy of muscle vibration therapy in SCI patients.
There is level 1a evidence (from one randomized controlled trial: Gomes-Osman & Field-Fote 2015) that pinch strength significantly improves with vibration therapy but this does not translate to improvements in functional outcomes.
There is level 4 evidence (from one pre-post study: Backus et al. 2014) that an end effector utilizing muscle vibration can be safely used in patients with tetraplegia to significantly improve upper limb function.