Developing a stiffness treatment device and finding an optimal parameter setting

Hypertonia is one of the major causes of movement disorder in individuals with central nerve system lesion. The cause of hypertonia can be divided into two components, reflexive and non reflexive. The purpose of this study was to design a stiffness treating device utilizing concepts of reducing both reflexive and non-reflexive muscle tone. A custom-made stiffness treating device was developed which oscillated the ankle at various speed from 0 to 3.7 cycles/sec. A force transducer was mounted to measure the real-time total oscillation resistance. Ten individuals with spinal cord injury at levels above T10 participated. Each subject received 8 minutes of repeated contractions elicited by electrical stimulation, oscillation at low speed (1.5 cycles/sec), and oscillation at high speed (3.7 cycles/sec) at 3 consecutive weeks. Maximum electrical stimulation elicited isometric force, M waves, H reflex, and total oscillation resistance were measured before, and at 10 and 20 minutes after the interventions. The results demonstrated a significant fatigue after 8 minutes of repeated contractions. The M waves were not significantly altered after any of the three interventions. The size of H reflex reduced after oscillations at both speeds but not after repeated electrical stimulated isometric contractions. The effects of three interventions on the total oscillation resistance were varied. This study successfully developed a stiffness treatment device which is effective in both the reflexive and non-reflexive components. This stiffness treatment device is not only able to evaluate stiffness but also potentially applicable for rehabilitation purposes. Related mechanisms are discussed.