Browsing by Subject "Hemiparesis"
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Item An analysis of modular patterns in healthy and post-stroke hemiparetic gait(2014-08) Routson, Rebecca Linn; Neptune, Richard R.Recent studies have suggested the biomechanical subtasks of walking can be produced using a reduced set of co-excited muscles or modules. Individuals post-stroke often exhibit poor inter-muscular coordination characterized by poor timing and merging of modules that are normally independent in healthy individuals. However, whether locomotor therapy can influence module quality (timing and composition) and whether these improvements lead to improved walking performance is unclear. Further, it is unknown whether the same modules that produce self-selected walking can also produce the execution of different mobility tasks. In this study, experimental analyses were used to compare module quality pre- and post-therapy. In subjects with four modules pre- and post-therapy, locomotor training resulted in improved timing of the ankle plantarflexor module and a more extended paretic leg angle that allowed the subjects to walk faster with more symmetrical propulsion. In addition, subjects with three modules pre-therapy increased their number of modules and improved walking performance post-therapy. Thus, locomotor training was found to influence module composition and timing, which can lead to improvements in walking performance. Experimental and simulation analyses were then used to characterize modular organization in specific mobility tasks (walking at self-selected speed with maximum cadence, maximum step length, and maximum step height). We found that the same underlying modules (number and composition) in each subject that contribute to steady-state walking also contribute to the different mobility tasks. In healthy subjects, module timing, but not composition, changed when the task demands were altered. This adaptability in module timing, in addition to the ability to adapt to the changing task demands, was limited in the post-stroke subjects. The primary difference in the execution of the walking biomechanical subtasks occurred in the control of the leg during pre-swing and swing. To increase cadence, the ankle plantarflexors and dorsiflexors contributed more power to the ipsilateral leg in pre-swing and swing, respectively. To increase step height, the hamstrings provided energy to the ipsilateral leg that accelerated the leg into swing in pre-swing and swing. These results provide a first step towards linking impaired module patterns to mobility task performance in persons post-stroke.Item Understanding changes in post-stroke walking ability through simulation and experimental analyses(2010-12) Hall, Allison Leigh; Neptune, Richard R.; Barr, Ronald E.; Crawford, Richard H.; Dingwell, Jonathan B.; Kautz, Steven A.Post-stroke hemiparesis usually leads to slow and asymmetric gait. Improving walking ability, specifically walking speed, is a common goal post-stroke. To develop effective post-stroke rehabilitation interventions, the underlying mechanisms that lead to changes in walking ability need to be fully understood. The overall goal of this research was to investigate the deficits that limit hemiparetic walking ability and understand the influence of post-stroke rehabilitation on walking ability in persons with post-stroke hemiparesis. Forward dynamics walking simulations of hemiparetic subjects (and speed-matched controls) with different levels of functional walking status were developed to investigate the relationships between individual muscle contributions to pre-swing forward propulsion, swing initiation and power generation subtasks and functional walking status. The analyses showed that muscle contributions to the walking subtasks are indeed related to functional walking status in the hemiparetic subjects. Increased contributions from the paretic leg muscles (i.e., plantarflexors and hip flexors) and reduced contributions from the non-paretic leg muscles (i.e., knee and hip extensors) to the walking subtasks were critical in obtaining higher functional walking status. Changes in individual muscle contributions to propulsion during rehabilitation were investigated by developing a large number of subject-specific forward dynamics simulations of hemiparetic subjects (with different levels of pre-training propulsion symmetry) walking pre- and post-locomotor training. Subjects with low paretic leg propulsion pre-training increased contributions to propulsion from both paretic leg (i.e., gastrocnemius) and non-paretic leg muscles (i.e., hamstrings) to improve walking speed during rehabilitation. Subjects with high paretic leg propulsion pre-training improved walking speed by increasing contributions to propulsion from the paretic leg ankle plantarflexors (i.e., soleus and gastrocnemius). This study revealed two primary strategies that hemiparetic subjects use to increase walking speed during rehabilitation. Experimental analyses were used to determine post-training biomechanical predictors of successful post-stroke rehabilitation, defined as performance over a 6-month follow-up period following rehabilitation. The strongest predictor of success was step length symmetry. Other potential predictors of success were identified including increased paretic leg hip flexor output in late paretic leg single-limb stance, increased paretic leg knee extensor output from mid to late paretic leg stance and increased paretic leg propulsion during pre-swing.