Browsing by Author "Schmit, Brian D."

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    Exercise-Induced Alterations in Sympathetic-Somatomotor Coupling in Incomplete Spinal Cord Injury
    (Mary Ann Liebert, Inc., publishers, 2019-09-15) Onushko, Tanya; Mahtani, Gordhan B.; Brazg, Gabrielle; Hornby, T. George; Schmit, Brian D.; Physical Medicine and Rehabilitation, School of Medicine
    The aim of this study was to understand how high- and low-intensity locomotor training (LT) affects sympathetic-somatomotor (SS) coupling in people with incomplete spinal cord injury (SCI). Proper coupling between sympathetic and somatomotor systems allows controlled regulation of cardiovascular responses to exercise. In people with SCI, altered connectivity between descending pathways and spinal segments impairs sympathetic and somatomotor coordination, which may have deleterious effects during exercise and limit rehabilitation outcomes. We postulated that high-intensity LT, which repeatedly engages SS systems, would alter SS coupling. Thirteen individuals (50 ± 7.2 years) with motor incomplete spinal cord injuries (American Spinal Injury Association Impairment Scale C or D; injury level >T6) participated in a locomotor treadmill training program. Patients were randomized into either a high-intensity (high-LT; 70–85% of maximum predicted heart rate; n = 6) group or a low-intensity (low-LT; 50–65% of maximum predicted heart rate; n = 7) group and completed up to 20 LT training sessions over 4–6 weeks, 3–5 days/week. Before and after taining, we tested SS coupling by eliciting reflexive sympathetic activity through a cold stimulation, noxious stimulation, and a mental math task while we measured tendon reflexes, blood pressure, and heart rate. Participants who completed high- versus low-LT exhibited significant decreases in reflex torques during triggered sympathetic activity (cold: −83 vs. 13%, p < 0.01; pain: −65 vs. 54%, p < 0.05; mental math: −43 vs. 41%; p < 0.05). Mean arterial pressure responses to sympathetic stimuli were slightly higher following high- versus low-LT (cold: 30 vs. −1.5%; pain: 6 vs. −12%; mental math: 5 vs. 7%), although differences were not statistically significant. These results suggest that high-LT may be advantageous to low-LT to improve SS coupling in people with incomplete SCI.
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    High intensity variable stepping training in persons with motor incomplete spinal cord injury: a case series
    (Lippincott, Williams & Wilkins, 2020-04-05) Holleran, Carey L.; Hennessey, Patrick W.; Leddy, Abigail L.; Mahtani, Gordhan B.; Brazg, Gabrielle; Schmit, Brian D.; Hornby, T. George; Physical Medicine and Rehabilitation, School of Medicine
    Background and Purpose: Previous data suggest that large amounts of high intensity stepping training in variable contexts (tasks and environments) may improve locomotor function, aerobic capacity and treadmill gait kinematics in individuals post-stroke. Whether similar training strategies are tolerated and efficacious for patients with other acute-onset neurological diagnoses, such as motor incomplete spinal cord injury (iSCI) is unknown, particularly with potentially greater, bilateral impairments. This case series evaluated the feasibility and preliminary short and long-term efficacy of high intensity variable stepping practice in ambulatory participants >1 year post-iSCI. Case Series Description: Four participants with iSCI (neurological levels C5-T3) completed up to 40 1-hr sessions over 3–4 months. Stepping training in variable contexts was performed at up to 85% maximum predicted heart rate, with feasibility measures of patient tolerance, total steps/session, and intensity of training. Clinical measures of locomotor function, balance, peak metabolic capacity and gait kinematics during graded treadmill assessments were performed at baseline and post-training, with >1 year follow-up. Outcomes: Participants completed 24–40 sessions over 8–15 weeks, averaging 2222±653 steps/session, with primary adverse events of fatigue and muscle soreness. Modest improvements in locomotor capacity where observed at post-training, with variable changes in lower extremity kinematics during treadmill walking. Discussion: High intensity, variable stepping training was feasible and tolerated by participants with iSCI although only modest gains in gait function or quality were observed. The utility of this intervention in patients with more profound impairments may be limited.
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    Kinematic and Neuromuscular Adaptations in Incomplete Spinal Cord Injury after High- versus Low-Intensity Locomotor Training
    (Mary Ann Liebert, 2019-05-28) Ardestani, Marzieh M.; Henderson, Christopher E.; Salehi, Seyed H.; Mahtani, Gordhan B.; Schmit, Brian D.; Hornby, T. George; Physical Medicine and Rehabilitation, School of Medicine
    Recent data demonstrate improved locomotion with high-intensity locomotor training (LT) in individuals with incomplete spinal cord injury (iSCI), although concerns remain regarding reinforcement of abnormal motor strategies. The present study evaluated the effects of LT intensity on kinematic and neuromuscular coordination in individuals with iSCI. Using a randomized, crossover design, participants with iSCI received up to 20 sessions of high-intensity LT, with attempts to achieve 70–85% of age-predicted maximum heart rate (HRmax), or low-intensity LT (50–65% HRmax), following which the other intervention was performed. Specific measures included spatiotemporal variables, sagittal-plane gait kinematics, and neuromuscular synergies from electromyographic (EMG) recordings. Correlation analyses were conducted to evaluate associations between variables. Significant improvements in sagittal-plane joint excursions and intralimb hip-knee coordination were observed following high- but not low-intensity LT when comparing peak treadmill (TM) speed before and after LT. Neuromuscular complexity (i.e., number of synergies to explain >90% of EMG variance) was also increased following high- but not low-intensity LT. Comparison of speed-matched trials confirmed significant improvements in the knee excursion of the less impaired limb and intralimb hip-knee coordination, as well as improvements in neuromuscular complexity following high-intensity LT. These findings suggest greater neuromuscular complexity may be due to LT and not necessarily differences in speeds. Only selected kinematic changes (i.e., weak hip excursion) was correlated to improvements in treadmill speed. In conclusion, LT intensity can facilitate gains in kinematic variables and neuromuscular synergies in individuals with iSCI.
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    Task-Specific Versus Impairment-Based Training on Locomotor Performance in Individuals With Chronic Spinal Cord Injury: A Randomized Crossover Study
    (SAGE, 2020-06-01) Lotter, Jennifer K.; Henderson, Christopher E.; Plawecki, Abbey; Holthus, Molly E.; Lucas, Emily H.; Ardestani, Marzieh M.; Schmit, Brian D.; Hornby, T. George; Physical Medicine and Rehabilitation, School of Medicine
    Background: Many research studies attempting to improve locomotor function following motor incomplete spinal cord injury (iSCI) focus on providing stepping practice. However, observational studies of physical therapy strategies suggest the amount of stepping practice during clinical rehabilitation is limited; rather, many interventions focus on mitigating impairments underlying walking dysfunction. Objective: The purpose of this blinded-assessor randomized trial was to evaluate the effects of task-specific vs impairment-based interventions on walking outcomes in individuals with iSCI. Methods: Using a crossover design, ambulatory participants with iSCI > 1-year duration performed either task-specific (upright stepping) or impairment-based training for up to 20 sessions over ≤6 weeks, with interventions alternated after >4 weeks delay. Both strategies focused on achieving higher cardiovascular intensities, with training specificity manipulated by practicing only stepping practice in variable contexts or practicing impairment-based tasks targeting impairments underlying locomotor dysfunction (strengthening, balance tasks, and recumbent stepping). Results: Significantly greater increases in fastest overground and treadmill walking speeds were observed following task-specific vs impairment-based training, with moderate associations between differences in amount of practice and outcomes. Gains in balance confidence were also observed following task-specific vs impairment-based training, although incidence of falls was also increased with the former protocol. Limited gains were observed with impairment-based training except for peak power during recumbent stepping tests. Conclusion: The present study reinforces work from other patient populations that the specificity of task practice is a critical determinant of locomotor outcomes and suggest impairment-based exercises may not translate to improvements in functional tasks.
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    The Value of High Intensity Locomotor Training Applied to Patients With Acute-Onset Neurologic Injury
    (Elsevier, 2022) Fahey, Meghan; Brazg, Gabrielle; Henderson, Christopher E.; Plawecki, Abbey; Lucas, Emily; Reisman, Darcy S.; Schmit, Brian D.; Hornby, T. George; Physical Medicine and Rehabilitation, School of Medicine
    Long-standing research in animal models and humans with stroke or incomplete spinal cord injury (iSCI) indicate that specific physical training variables, such as the specificity and amount of practice, may influence neurologic recovery and locomotor function. More recent data highlight the contributions of exercise intensity, as estimated indirectly by cardiovascular exertion, as potentially more important than previously considered. The effects of exercise intensity are well described in neurologically intact individuals, although confusion regarding the definitions of intensity and safety concerns have limited its implementation during physical rehabilitation of patients with neurologic injury. The purpose of this review is to delineate some of the evidence regarding the effects of exercise intensity during locomotor training in patients with stroke and iSCI. We provide specific definitions of exercise intensity used within the literature, describe methods used to ensure appropriate levels of exertion, and discuss potential adverse events and safety concerns during its application. Further details on the effects of locomotor training intensity on clinical outcomes, and on neuromuscular and cardiovascular function will be addressed as available. Existing literature across multiple studies and meta-analyses reveals that exercise training intensity is likely a major factor that can influence locomotor function after neurologic injury. To extend these findings, we describe previous attempts to implement moderate to high intensity interventions during physical rehabilitation of patients with neurologic injury, including the utility of specific strategies to facilitate implementation, and to navigate potential barriers that may arise during implementation efforts.