Hemodynamic Response of the Supplementary Motor Area during Locomotor Tasks with Upright versus Horizontal Postures in Humans

To understand cortical mechanisms related to truncal posture control during human locomotion, we investigated hemodynamic responses in the supplementary motor area (SMA) with quadrupedal and bipedal gaits using functional near-infrared spectroscopy in 10 healthy adults. The subjects performed three locomotor tasks where the degree of postural instability varied biomechanically, namely, hand-knee quadrupedal crawling (HKQuad task), upright quadrupedalism using bilateral Lofstrand crutches (UpQuad task), and typical upright bipedalism (UpBi task), on a treadmill. We measured the concentration of oxygenated hemoglobin (oxy-Hb) during the tasks. The oxy-Hb significantly decreased in the SMA during the HKQuad task, whereas it increased during the UpQuad task. No significant responses were observed during the UpBi task. Based on the degree of oxy-Hb responses, we ranked these locomotor tasks as UpQuad > UpBi > HKQuad. The order of the different tasks did not correspond with postural instability of the tasks. However, qualitative inspection of oxy-Hb time courses showed that oxy-Hb waveform patterns differed between upright posture tasks (peak-plateau-trough pattern for the UpQuad and UpBi tasks) and horizontal posture task (downhill pattern for the HKQuad task). Thus, the SMA may contribute to the control of truncal posture accompanying locomotor movements in humans.

A new walking orthosis for paraplegics: hip and ankle linkage system

For paraplegics, two major disadvantages of hip-knee-ankle-foot orthotic systems that have a medial single hip joint are the short stride and horizontal rotation of the pelvis. The authors consider the pelvic rotation is caused by two factors; one is the lack of a mechanism to assist hip flexion, and the other is fixed ankle joints that cause instability when the step length becomes longer. Users must rotate their pelvis to initiate a swing in their legs and to achieve stability by making their two legs as parallel as possible in order to avoid losing balance. To overcome those disadvantages, the authors developed a new orthosis named “HALO” (Hip and Ankle Linked Orthosis), which has a linking mechanism that connects both ankle joints with a medial single hip joint. This new orthosis allows users to keep both feet always parallel to the floor while walking, and assists the swinging of the leg when the contralateral ankle is flexed dorsally by loading. Gait analysis revealed that the pelvic rotation with “HALO” either in parallel bars or with Lofstrand crutches was within 20°, which was within the physiologically normal level.