Research Highlights

Neuromechanical principles underlying movement modularity and their implications for rehabilitation

Neuromechanical principles define the properties and problems that shape neural solutions for movement. Although the theoretical and experimental evidence is debated, we present arguments for consistent struc- tures in motor patterns, i.e., motor modules, that are neuromechanical solutions for movement particular to an individual and shaped by evolutionary, developmental, and learning processes. As a consequence, motor modules may be useful in assessing sensorimotor deficits specific to an individual and define targets for the rational development of novel rehabilitation therapies that enhance neural plasticity and sculpt motor recovery. We propose that motor module organization is disrupted and may be improved by therapy in spinal cord injury, stroke, and Parkinson’s disease. Recent studies provide insights into the yet-unknown under- lying neural mechanisms of motor modules, motor impairment, and motor learning and may lead to better understanding of the causal nature of modularity and its underlying neural substrates. [download PDF]

Evaluation by expert dancers of a robot that performs partnered stepping via haptic interaction

Our long-term goal is to enable a robot to engage in partner dance for use in rehabilitation therapy, assessment, diagnosis, and scientific investigations of two-person whole-body motor coordination. Partner dance has been shown to improve balance and gait in people with Parkinson's disease and in older adults, which motivates our work. During partner dance, dance couples rely heavily on haptic interaction to convey motor intent such as speed and direction. In this paper, we investigate the potential for a wheeled mobile robot with a human-like upper-body to perform partnered stepping with people based on the forces applied to its end effectors. [download PDF]

Directional acuity of whole-body perturbations during standing balance

The ability to perceive the direction of whole-body motion during standing may be critical to maintaining balance and preventing a fall. Our first goal was to quantify kinesthetic perception of whole-body motion by estimating directional acuity thresholds of support-surface perturbations during standing. The directional acuity threshold to lateral deviations in backward support-surface motion healthy, young adults was quantified as 9.5 ± 2.4° using the psychometric method (n = 25 subjects). The directional acuity threshold was estimated at 11.7° ± 3.8° from the PEST method (n = 11 of 25 subjects, psychometric threshold = 10.1 ± 3.1°) using only one-third the number of trials compared to the psychometric method. Computational modeling of both techniques revealed similar variance in the estimated thresholds across simulations of about 1°. Our results suggest that the PEST algorithm can be used to more quickly quantify whole-body directional acuity during standing in individuals with balance impairments.[download PDF]

Feasible Muscle Activation Ranges Based on Inverse Dynamics Analyses of Human Walking

Although it is possible to produce the same movement using an infinite number of different muscle activation patterns owing to musculoskeletal redundancy, the degree to which observed variations in muscle activity can deviate from optimal solutions computed from biomechanical models is not known.  Here, we examined the range of biomechanically permitted activation levels in individual muscles during human walking using a detailed musculoskeletal model and experimentally-measured kinetics and kinematics. Feasible muscle activation ranges define the minimum and maximum possible level of each muscle’s activation that satisfy inverse dynamics joint torques assuming that all other muscles can vary their activation as needed. Our results demonstrate that joint torque requirements from standard inverse dynamics calculations are insufficient to define the activation of individual muscles during walking in healthy individuals. Identifying feasible muscle activation ranges may be an effective way to evaluate the impact of additional biomechanical and/or neural constraints on possible versus actual muscle activity in both normal and impaired movements.[download PDF]

Balance, Body Motion and Muscle Activity after High Volume Short Term Dance-Based Rehabilitation in Individuals with Parkinson's Disease: a Pilot Study

BACKGROUND AND PURPOSE: The objectives of this pilot study were to 1) evaluate the feasibility and investigate the efficacy of a 3-week, high volume (450 minutes / week) Adapted Tango intervention for community dwelling individuals with mild-moderate PD, and to 2) investigate the potential efficacy of Adapted Tango in modifying electromyographic (EMG) activity and center of body mass (CoM) displacement during automatic postural responses to support surface perturbations. METHODS: Individuals with PD (n=26) were recruited for high volume Adapted Tango (fifteen, 1.5 h lessons in 3 weeks). DISCUSSION AND CONCLUSIONS: Compliance was acceptable and improvements on clinical measures of balance and gait were comparable to lesser volume, 12-week programs. Post-Adapted Tango, changes in kinematic and some EMG measures of perturbation responses were observed in addition to improvements observed in clinical measures. We conclude that 3-week, high volume Adapted Tango is feasible; randomized Adapted Tango trials using laboratory-assessed measures of postural responses are feasible and justified.