A pilot study: effect of somatosensory loss on motor corrections in response to unknown loads in a reaching task by chronic stroke survivors.

Despite recent studies indicating a significant correlation between somatosensory deficits and rehabilitation outcomes, how prevailing somatosensory deficits affect stroke survivors' ability to correct their movements and recover overall remains unclear. To explore how major deficits in somatosensory systems impede stroke survivors' motor correction to various external loads, we conducted a study with 13 chronic stroke survivors who had hemiparesis. An inertial, elastic, or viscous load, which was designed to impose perturbing forces with various force profiles, was introduced unexpectedly during the reaching task using a programmable haptic robot.

The speed of adaptation is dependent on the load type during target reaching by intact human subjects.

When lifting or moving a novel object, humans are routinely able to quickly characterize the nature of the unknown load and swiftly achieve the desired movement trajectory. It appears that both tactile and proprioceptive feedback systems help humans develop an accurate prediction of load properties and determine how associated limb segments behave during voluntary movements. While various types of limb movement information, such as position, velocity, acceleration, and manipulating forces, can be detected using human tactile and proprioceptive systems, we know little about how the central nervous system decodes these various types of movement data, and in which order or priority they are used when developing predictions of joint motion during novel object manipulation.

Improved cortical activity and reduced gait asymmetry during poststroke self-paced walking rehabilitation.

Background: For patients with gait impairment due to neurological disorders, body weight-supported treadmill training (BWSTT) has been widely used for gait rehabilitation. On a conventional (passive) treadmill that runs at a constant speed, however, the level of patient engagement and cortical activity decreased compared with gait training on the ground. To increase the level of cognitive engagement and brain activity during gait rehabilitation, a self-paced (active) treadmill is introduced to allow patients to actively control walking speed, as with overground walking.

Development of a Planar Haptic Robot With Minimized Impedance.

Several studies have reported that stroke survivors displayed improved voluntary planar movements when forces supporting the upper limb increased, and when impeding forces decreased. Earlier haptic devices interacting with the human upper limb were potentially impacted by undesired residual friction force and device inertia. To explore natural, undisturbed voluntary motor control in stroke survivors, we describe the development of a Decoupled-Operational space Robot for wide Impedance Switching (DORIS) with minimized mechanical impedances.

Biomechanical Evaluation of Virtual Reality-based Turning on a Self-Paced Linear Treadmill.

Background: Patients with brain injuries such as Parkinson's disease or stroke exhibit abnormal gait characteristics especially during gait transitions such as step initiation and turning. Since such transitions could precipitate falls and resultant injuries, evaluation and rehabilitation of non-steady state gait in those patients are important. Whereas body weight supported treadmill training (BWSTT) provides a safe and controlled environment for gait training, it is unable to adequately train for gait transitions since the typical linear treadmill does not allow for changes in walking direction and natural fluctuations in speed.

The bending stiffness of shoes is beneficial to running energetics if it does not disturb the natural MTP joint flexion.

A local minimum for running energetics has been reported for a specific bending stiffness, implying that shoe stiffness assists in running propulsion. However, the determinant of the metabolic optimum remains unknown. Highly stiff shoes significantly increase the moment arm of the ground reaction force (GRF) and reduce the leverage effect of joint torque at ground push-off.

Gait strategy changes with acceleration to accommodate the biomechanical constraint on push-off propulsion.

To maintain steady and level walking, push-off propulsion during the double support phase compensates for the energy loss through heel strike collisions in an energetically optimal manner. However, a large portion of daily gait activities also contains transient gait responses, such as acceleration or deceleration, during which the observed dominance of the push-off work or the energy optimality may not hold. In this study, we examined whether the push-off propulsion during the double support phase served as a major energy source for gait acceleration, and we also studied the energetic optimality of accelerated gait using a simple bipedal walking model.