Direct policy search methods offer the promise of automatically learning controllers for complex, high-dimensional tasks. However, prior applications of policy search often required specialized, low-dimensional policy classes, limiting their generality. In this work, we introduce a policy search algorithm that can directly learn high-dimensional, general-purpose policies, represented by neural ...

BACKGROUND Humans normally dissipate significant energy during walking, largely at the transitions between steps. The ankle then acts to restore energy during push-off, which may be the reason that ankle impairment nearly always leads to poorer walking economy. The replacement of lost energy is necessary for steady gait, in which mechanical energy is constant on average, external dissipation is...

Rapid unloading and a peak in power output of the ankle joint have been widely observed during push-off in human walking. Model-based studies hypothesize that this push-off causes redirection of the body center of mass just before touch-down of the leading leg. Other research suggests that work done by the ankle extensors provides kinetic energy for the initiation of swing. Also, muscle work is...

Current commercially available prosthetic feet have succeeded in decreasing the metabolic cost and increasing the speed of walking compared to walking with conventional, mostly solid prosthetic feet. However, there is still a large discrepancy when compared with a non‐disabled gait, and the walking pattern remains strongly disturbed. During the stance phase of the leg, t...

Background: Forward head posture is one of the most prevalent abnormal postures in patients with neck disorders. The aim of this study was to evaluate the effects of forward head posture on gait ground reaction force characteristics in children. Methods: Twelve children with forward head posture (age: 11.8±1.3 years) and sixteen healthy control children (...

In human walking, each transition to a new stance limb requires redirection of the center of mass (COM) velocity from one inverted pendulum arc to the next. While this can be accomplished with either negative collision work by the leading limb, positive push-off work by the trailing limb, or some combination of the two, physics-based models of step-to-step transitions predict that total positiv...

Previous studies have identified differences in gait kinetics between healthy older and young adults. However, the underlying factors that cause these changes are not well understood. The objective of this study was to assess the effects of age and speed on the activation of lower-extremity muscles during human walking. We recorded electromyography (EMG) signals of the soleus, gastrocnemius, bi...

Residual hip impairments, such as decreased hip muscle moment and power during walking, have been reported in patients with total hip arthroplasty (THA). Meanwhile, greater ankle power has also been reported in these patients. We investigated the interaction between hip and ankle joints during walking to determine the effects of different ankle pushoff instructions on hip biomechanics in patien...

BACKGROUND In stroke and multiple sclerosis patients, gait is frequently hampered by a reduced ability to push-off with the ankle caused by weakness of the plantar-flexor muscles. To enhance ankle push-off and to decrease the high energy cost of walking, spring-like carbon-composite Ankle Foot Orthoses are frequently prescribed. However, it is unknown what Ankle Foot Orthoses stiffness should b...