OBJECTIVE: This 12-week pilot study examines the efficacy of applying low frequency sound wave stimulation (between 16-160 Hz) through both hands and feet on relieving pain and improving functional ability in patients with chronic back pain.

METHODS: Twenty-three participants with chronic shoulder (eleven participants) or low back pain (twelve participants) underwent a 12-week vibration therapy program of three sessions per week. A low frequency sound wave device comprising four piezoelectric vibration-type tactile tranducers enclosed in separate 5-cm diameter circular plates, which generate sinusoidal vibratory stimuli at a frequency of 16-160 Hz, was used in this study. Primary outcome measure was pain sensation measured using the Visual Analogue Scale (P-VAS). The secondary outcome measures were pain-related disability measured using the pain disability index (PDI) and quality of life measured using the SF-12.

RESULTS: At week 12, significant reductions in pain sensation and pain-related disability were observed, with mean reductions of 3.5 points in P-VAS and 13.5 points in the PDI scores. Sixty-five percent of the participants had a reduction of at least 3 points on the P-VAS score, while 52% participants showed a decrease of at least 10 points in the PDI score. Significant improvement was observed in the SF-12 physical composite score but not the mental composite score.

METHODS: Six individuals with chronic motor-complete spinal cord injury performed 30-min of sustained FES-leg cycling exercise on two days to induce muscle fatigue. Each participant performed maximum FES-evoked isometric knee extensions before and after the 30-min cycling to determine pre- and post- extension peak torque concomitant with mechanomyography changes.

FINDINGS: Similar to extension peak torque, normalized root mean squared (RMS) and mean power frequency (MPF) of the mechanomyography signal significantly differed in muscle activities between pre- and post-FES-cycling for each quadriceps muscle (extension peak torque up to 69%; RMS up to 80%, and MPF up to 19%). Mechanomyographic-RMS showed significant reduction during cycling with acceptable between-days consistency (intra-class correlation coefficients, ICC = 0.51-0.91). The normalized MPF showed a weak association with FES-cycling duration (ICC = 0.08-0.23). During FES-cycling, the mechanomyographic-RMS revealed greater fatigue rate for rectus femoris and greater fatigue resistance for vastus medialis in spinal cord injured individuals.