Preliminary Evidence That Design Fluency Is Related to Dual-Task Treadmill Gait Variability in Healthy Adults.

Evidence supporting a link between gait and cognition is accumulating. However, the relation between executive functioning and spatiotemporal gait parameters has received little attention. This is surprising since these gait variables are related to falls.

We Will, We Will Shock You: Adaptive Versus Conventional Functional Electrical Stimulation in Individuals Post-Stroke.

Functional electrical stimulation (FES) is often used in poststroke gait rehabilitation to address decreased walking speed, foot drop, and decreased forward propulsion. However, not all individuals experience clinically meaningful improvements in gait function with stimulation. Previous research has developed adaptive functional electrical stimulation (AFES) systems that adjust stimulation timing and amplitude at every stride to deliver optimal stimulation.

Adaptive Functional Electrical Stimulation Delivers Stimulation Amplitudes Based on Real-Time Gait Biomechanics.

Functional electrical stimulation (FES) is often used in poststroke gait rehabilitation to decrease foot drop and increase forward propulsion. However, not all stroke survivors experience clinically meaningful improvements in gait function following training with FES. The purpose of this work was to develop and validate a novel adaptive FES (AFES) system to improve dorsiflexor (DF) and plantarflexor (PF) stimulation timing and iteratively adjust the stimulation amplitude at each stride based on measured gait biomechanics.

How Important is Position in Adaptive Treadmill Control?

To more closely mimic overground walking, researchers are developing adaptive treadmills (ATMs) that update belt speed in real-time based on user gait mechanics. Many existing ATM control schemes are solely based on position on the belt and do not respond to changes in gait mechanics, like propulsive forces, that result in increased overground walking speed. To target natural causal mechanisms to alter speed, we developed an ATM controller that adjusts speed via changes in position, step length, and propulsion.

Cognitive Training Improves Joint Stiffness Regulation and Function in ACLR Patients Compared to Healthy Controls.

As cognitive function is critical for muscle coordination, cognitive training may also improve neuromuscular control strategy and knee function following an anterior cruciate ligament reconstruction (ACLR). The purpose of this case-control study was to examine the effects of cognitive training on joint stiffness regulation in response to negative visual stimuli and knee function following ACLR. A total of 20 ACLR patients and 20 healthy controls received four weeks of online cognitive training.

Development and Validation of a Framework for Predictive Simulation of Treadmill Gait.

Treadmill training is a common intervention to promote healthy walking function for individuals with pathological gait. However, because of the heterogeneity of many patient populations, determining how an individual will respond to new treadmill protocols may require extensive trial and error, causing increased patient fatigue. The purpose of this study was to develop and validate a framework for predictive simulation of treadmill gait, which may be used in the design of treadmill training protocols.

Adaptive treadmill walking encourages persistent propulsion.

Background: Adaptive treadmills allow real-time changes in walking speed by responding to changes in step length, propulsion, or position on the treadmill. The stride-to-stride variability, or persistence, of stride time during overground, fixed-speed, and adaptive treadmill walking has been studied, but persistence of propulsion during adaptive treadmill walking remains unknown. Because increased propulsion is often a goal of post-stroke rehabilitation, knowledge of the stride-to-stride variability may aid rehabilitation protocol design.

Adaptive treadmill control can be manipulated to increase propulsive impulse while maintaining walking speed.

Adaptive treadmills (ATM) designed to promote increased propulsion may be an effective tool for gait training since propulsion is often impaired post-stroke. Our lab developed a novel ATM controller that adjusts belt speed via real-time changes in step length, propulsive impulse, and position. This study modified the relative importance of propulsion to step length in the controller to determine the effect of increased propulsive feedback gain on measures of propulsion and walking speed.

Neuroticism and Extraversion Are Related to Changes in Postural Stability During Anatomically-Related Cognitive Tasks.

The relationship between personality and postural stability has received little attention. This study addressed whether neuroticism and extraversion correlate with changes in postural stability while performing cognitive tasks related to brain regions selectively associated with neuroticism and extraversion. Thirty-two adults stood on a foam mat in tandem stance and completed a 2-back task and a weather prediction task (WPT).

Combined user-driven treadmill control and functional electrical stimulation increases walking speeds poststroke.

The variety of poststroke impairments and compensatory mechanisms necessitate adaptive and subject-specific approaches to locomotor rehabilitation. To implement subject-specific, adaptive training to treadmill-based gait training, we developed a user-driven treadmill (UDTM) control algorithm that adjusts the user's speed in real-time. This study examines the response of individuals poststroke to the combination of UDTM control and electrical stimulation of the paretic ankle musculature to augment forward propulsion during walking.

User-driven treadmill walking promotes healthy step width after stroke.

Background: Walking with user-driven treadmill control is believed to be more like overground walking than fixed-speed treadmill walking. Walking speed and ground reaction forces differ between overground and fixed-speed treadmill walking, but not between overground and user-driven treadmill walking in healthy and post-stroke subjects. However, studies assessing spatiotemporal gait parameters during user-driven treadmill walking are limited.

Nonlinear net ankle quasi-stiffness reduces error and changes with speed but not load carried.

Background: Natural ankle quasi-stiffness (NAS) is a key metric used to personalize orthotic and prosthetic ankle-foot devices. NAS has traditionally been defined as the average slope (i.e.

Walking speed changes in response to user-driven treadmill control after stroke.

The objective of this study was to determine how individuals poststroke respond to user-driven treadmill (UDTM) controlin terms ofwalking speeds, peak anterior ground reaction forces (AGRF), peak posterior ground reaction forces (PGRF), and trailing limb angles (TLA). Twenty individuals with chronic stroke walked overground during a 10-meter walk test to determine their self-selected (SS) speeds before walking on a treadmill in its fixed-speed (FSTM) and UDTM control modes at their SS and fastest comfortable (Fast) speeds. Paired t-tests were used to compare the walking speeds, peak AGRF, peak PGRF, and TLA among test conditions (α = 0.

Negative Emotion and Joint-Stiffness Regulation Strategies After Anterior Cruciate Ligament Injury.

Context: Fear of reinjury after an anterior cruciate ligament (ACL) reconstruction (ACLR) may be associated with persistent deficits in knee function and subsequent injury. However, the effects of negative emotion on neuromuscular-control strategies after an ACL injury have remained unclear.

Objective: To identify how negative emotional stimuli affect neural processing in the brain and muscle coordination in patients after anterior cruciate ligament reconstruction compared with healthy control participants.

Dynamic structure of variability in joint angles and center of mass position during user-driven treadmill walking.

Background: Overground locomotion exhibits greater movement variability and less dynamic stability compared to typical fixed-speed treadmill walking. To minimize the differences between treadmill and overground locomotion, researchers are developing user-driven treadmill systems that adjust the speed of the treadmill belts in real-time based on how fast the subject is trying to walk.

Research Question: Does dynamic structure of variability, quantified by the Lyapunov exponent (LyE), of joint angles and center of mass (COM) position differ between a fixed-speed treadmill (FTM) and user-driven treadmill (UTM) for healthy subjects?

Methods: Eleven healthy, adult subjects walked on a user-driven treadmill that updated its speed in real-time based on the subjects' propulsive forces, location, step length, and step time, and at a matched speed on a typical, fixed-speed treadmill for 1-minute.

Changes in gait mechanics and muscle activity with wedge height in an orthopaedic boot.

Background: Orthopaedic boots with wedging are commonly used in the treatment of individuals with Achilles tendon rupture to immobilize the foot in plantar flexion and approximate tendon ends.

Research Question: To describe changes in muscle activity of the triceps surae and gait mechanics with the use of wedges in an orthopaedic boot immediately and after an accommodation period.

Methods: Muscle activity of the triceps surae and gait parameters (vertical ground reaction force, knee extension power, gait speed) were collected using surface electromyography and motion capture in 12 healthy individuals.

The effect of stride length on lower extremity joint kinetics at various gait speeds.

Robot-assisted training is a promising tool under development for improving walking function based on repetitive goal-oriented task practice. The challenges in developing the controllers for gait training devices that promote desired changes in gait is complicated by the limited understanding of the human response to robotic input. A possible method of controller formulation can be based on the principle of bio-inspiration, where a robot is controlled to apply the change in joint moment applied by human subjects when they achieve a gait feature of interest.

Neuroplastic changes in anterior cruciate ligament reconstruction patients from neuromechanical decoupling.

The purpose of this study was to identify how the brain simultaneously perceives proprioceptive input during joint loading in anterior cruciate ligament reconstruction (ACLR) patients, when compared to healthy controls. Seventeen ACLR patients (ACLR) and seventeen controls (CONT) were tested for the somatosensory cortical activation using electroencephalography (EEG) while measuring knee laxity using a knee arthrometer. The relationship between cortical activation and joint laxity within group was also examined.

Walking speed changes in response to novel user-driven treadmill control.

Implementing user-driven treadmill control in gait training programs for rehabilitation may be an effective means of enhancing motor learning and improving functional performance. This study aimed to determine the effect of a user-driven treadmill control scheme on walking speeds, anterior ground reaction forces (AGRF), and trailing limb angles (TLA) of healthy adults. Twenty-three participants completed a 10-m overground walking task to measure their overground self-selected (SS) walking speeds.

Correction to: Coordination of muscles to control the footpath during over-ground walking in neurologically intact individuals and stroke survivors.

In the original publication of the article, the corrections for the typographical errors in the equations for variance that affects the footpath (V) and the total variance (V) should be as following.

Dynamic structure of lower limb joint angles during walking post-stroke.

Background: Variability in joint kinematics is necessary for adaptability and response to everyday perturbations; however, intrinsic neuromotor changes secondary to stroke often cause abnormal movement patterns. How these abnormal movement patterns relate to joint kinematic variability and its influence on post-stroke walking impairments is not well understood.

Objective: The purpose of this study was to evaluate the movement variability at the individual joint level in the paretic and non-paretic limbs of individuals post-stroke.

A mathematical analysis to address the 6 degree-of-freedom segmental power imbalance.

Segmental power is used in human movement analyses to indicate the source and net rate of energy transfer between the rigid bodies of biomechanical models. Segmental power calculations are performed using segment endpoint dynamics (kinetic method). A theoretically equivalent method is to measure the rate of change in a segment's mechanical energy state (kinematic method).

The relationship between the sensory responses to ankle-joint loading and corticomotor excitability.

Purpose: Maintaining joint stability is dependent on the ability of the nervous system to sense and react to potentially injurious loads. In attempts to understand the neurophysiologic mechanisms underlying joint stability, this afferent and efferent activity has been quantified separately at the cortical, segmental and peripheral levels using various electrophysiologic techniques in vivo. However, no studies have attempted to quantify sensory and motor activation at multiple levels of the nervous system in a single subset, to understand potential adaptations for optimizing joint stability.

Toward goal-oriented robotic gait training: The effect of gait speed and stride length on lower extremity joint torques.

Robot-assisted gait training is becoming increasingly common to support recovery of walking function after neurological injury. How to formulate controllers capable of promoting desired features in gait, i.e.

Errors Associated With Utilizing Prescribed Scapular Kinematics to Estimate Unconstrained, Natural Upper Extremity Motion in Musculoskeletal Modeling.

Musculoskeletal modeling is capable of estimating physiological parameters that cannot be directly measured, however, the validity of the results must be assessed. Several models utilize a scapular rhythm to prescribe kinematics, yet it is unknown how well they replicate natural scapular motion. This study evaluated kinematic errors associated with a model that employs a scapular rhythm using 2 shoulder movements: abduction and forward reach.