Background and objective:
Previous studies suggest that error augmentation may be used as a strategy to achieve longer-term changes in gait deficits after stroke. The purpose of this study was to determine whether longer-term improvements in step length asymmetry could be achieved with repeated split-belt treadmill walking practice using an error augmentation strategy.
13 persons with chronic stroke (>6 months) participated in testing: (1) prior to 12 sessions of split-belt treadmill training, (2) after the training, and (3) in follow-up testing at 1 and 3 months. Step length asymmetry was the target of training, so belt speeds were set to augment step length asymmetry such that aftereffects resulted in reduced step length asymmetry during overground walking practice. Each individual was classified as a "responder" or "nonresponder" based on whether their reduction in step length asymmetry exceeded day-to-day variability.
For the group and for the responders (7 individuals), step length asymmetry improved from baseline to posttesting (P < .05) through an increased step length on both legs but a relatively larger change on the shorter step side (P < .05). Other parameters that were not targeted (e.g., stance time asymmetry) did not change over the intervention.
This study demonstrates that short-term adaptations can be capitalized on through repetitive practice and can lead to longer-term improvements in gait deficits poststroke. The error augmentation strategy, which promotes stride-by-stride adjustment to reduce asymmetry and results in improved asymmetry during overground walking practice, appears to be critical for obtaining the improvements observed.
"In most existing motor based gait rehabilitation approaches, the gait intervention is either applied during the swing phase movement of the affected limb –, , , or is applied at the foot level using a split-belt treadmill to provide a speed constraint during walking . The goals of these studies have been to target the spatio-temporal gait symmetry through these interventions. "
[Show abstract][Hide abstract] ABSTRACT: In this work, we study locomotor adaptation in healthy adults when an asymmetric force vector is applied to the pelvis directed along the right leg. A cable-driven Active Tethered Pelvic Assist Device (A-TPAD) is used to apply an external force on the pelvis, specific to a subject's gait pattern. The force vector is intended to provide external weight bearing during walking and modify the durations of limb supports. The motivation is to use this paradigm to improve weight bearing and stance phase symmetry in individuals with hemiparesis. An experiment with nine healthy subjects was conducted. The results show significant changes in the gait kinematics and kinetics while the healthy subjects developed temporal and spatial asymmetry in gait pattern in response to the applied force vector. This was followed by aftereffects once the applied force vector was removed. The adaptation to the applied force resulted in asymmetry in stance phase timing and lower limb muscle activity. We believe this paradigm, when extended to individuals with hemiparesis, can show improvements in weight bearing capability with positive effects on gait symmetry and walking speed.
"The asymmetrical gait features that have been studied can be divided into two categories: (1) discrete parameters, such as swing time  and stride length , and (2) continuous signals, such as joint displacement , GRF  and electromyography  signals. Compared with the discrete parameters, a distinct advantage of the continuous signals is that they can be analyzed by both time and frequency domain methods. "
[Show abstract][Hide abstract] ABSTRACT: This study introduces gait asymmetry measures by comparing the ground reaction force (GRF) features of the left and right limbs. The proposed features were obtained by decomposing the GRF into components of different frequency sub-bands via the wavelet transform. The correlation coefficients between the right and left limb GRF components of the same frequency sub-band were used to characterize the degree of bilateral symmetry. The asymmetry measures were then obtained by subtracting these coefficients from one. To demonstrate the effectiveness of these asymmetry measures, the proposed measures were applied to differentiate the walking patterns of Parkinson's patients and healthy subjects. The results of the statistical analyses found that the patient group has a higher degree of gait asymmetry. By comparing these results with those obtained by conventional asymmetry measures, it was found that the proposed approach can more effectively distinguish the differences between the tested Parkinson's disease patients and the healthy control subjects.
Biomedical Signal Processing and Control 04/2015; 18. DOI:10.1016/j.bspc.2014.11.008 · 1.42 Impact Factor
"Errors attributed to oneself are more likely to be generalized to other movements. These differences in generalization suggest that the neural substrates for motor adaptation to small vs large errors may be different , and is worth pursuing in the future, particularly with respect to training of walking after injury, when transfer to other related walking environments is highly desirable . "
[Show abstract][Hide abstract] ABSTRACT: Children can modify learned motor skills, such as walking, to adapt to new environments. Movement errors in these new situations drive the learning. We used split-belt walking to determine whether size of the error affects the degree of learning. Twenty-two children (aged 2-5 y) walked on the split-belt treadmill on two separate days spaced 1 week apart. Twenty-eight adults served as controls. On Day 1, children experienced an abrupt change in belt speeds (from 1∶1 to 2∶1 differential) resulting in large errors, or a gradual change (same change in speed over 12-15 min), resulting in small errors. Learning was measured by the size of the aftereffect upon return to a 1∶1 differential. On Day 2 (1 week later), the leg on the fast belt was reversed, as was the method of introducing the speed differential. We found that the error size did not affect learning. Unexpectedly, learning was greater on Day 2 compared to Day 1, especially for children under 4 y of age, despite the fact that the task was opposite to that of Day 1, and did not influence learning in adults. Hence, 11 additional children under 4 y of age were tested with belts running at the same speed on Day 1, and with a 2∶1 speed differential (abrupt introduction) on Day 2. Surprisingly, learning was again greater on Day 2. We conclude that size of error during split-belt walking does not affect learning, but experience on a treadmill does, especially for younger children.
PLoS ONE 03/2014; 9(3):e93349. DOI:10.1371/journal.pone.0093349 · 3.23 Impact Factor
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