An investigation into perception of change in the foot-floor interface during repeated stretch-shortening cycles

Proprioceptive input is critical for normal and safe movement. There exists a gap in the literature regarding the assessment of proprioceptive function during dynamic tasks of the lower limb. To fill this gap, the present thesis has investigated perception of change in the foot-floor interface during repeated stretch-shortening cycles. This doctoral research serves as a foundation for considering proprioception as it pertains to dynamic function at the ankle

Stretch hyperreflexia in children with cerebral palsy:Assessment - Contextualization - Modulation

Cerebral palsy (CP) is a neurological disorder and the most frequent cause of motor impairment in children in Europe. Around 85% of children with CP experience stretch hyperreflexia, also known as “spasticity”. Stretch hyperreflexia is an excessive response to muscle stretch, leading to increased joint resistance. The joint hyper-resistance causes limitations in activities such as walking. Multiple methods have been developed to measure stretch hyperreflexia, but evidence supporting the use of these methods for diagnostics and treatment evaluation in children with CP is insufficient. Furthermore, most methods are designed to assess stretch reflexes in passive conditions, which might not translate to the limitations encountered due to stretch reflexes during activities. Furthermore, while a broad range of stretch hyperreflexia treatments is available, many are invasive, non-specific, or temporary and might have adverse side effects. Training methods to reduce stretch reflexes using biofeedback are promising non-invasive methods with potential long-term sustained effects. Still, clinical feasibility needs to be improved before implementation in clinical rehabilitation of children with CP. This thesis aimed to develop methods to assess stretch hyperreflexia of the calf muscles during passive conditions, as well as in the context of walking. Additionally, this thesis aimed to develop clinically feasible methods to modulate stretch hyperreflexia in the calf muscle of children with CP. The outcomes are described in eight different studies presented in this thesis. All in all, the work presented in this thesis shows that sagittal plane clinical gait analysis can be performed using the human body model and can be complemented with ultrasound imaging of the calf muscle. Motorized methods to assess stretch hyperreflexia in passive conditions might be useful for evaluation in adults after SCI/Stroke. Still, limitations regarding feasibility and validity limit clinical application for children with CP. Furthermore, this thesis provides additional evidence that the deviating muscle activation patterns during walking, particularly the increased activation around initial contact, are caused by stretch hyper-reflexes in children with CP. The deviating muscle activation patterns, with increased activation during early stance and reduced activation around push-off, can be modulated within one session by several children with CP. Therefore, the next step is to develop a training program to modulate the activation pattern and potentially decrease stretch hyper-reflexes in children with CP to improve the gait patter

Development and Biomechanical Analysis toward a Mechanically Passive Wearable Shoulder Exoskeleton

Shoulder disability is a prevalent health issue associated with various orthopedic and neurological conditions, like rotator cuff tear and peripheral nerve injury. Many individuals with shoulder disability experience mild to moderate impairment and struggle with elevating the shoulder or holding the arm against gravity. To address this clinical need, I have focused my research on developing wearable passive exoskeletons that provide continuous at-home movement assistance. Through a combination of experiments and computational tools, I aim to optimize the design of these exoskeletons. In pursuit of this goal, I have designed, fabricated, and preliminarily evaluated a wearable, passive, cam-driven shoulder exoskeleton prototype. Notably, the exoskeleton features a modular spring-cam-wheel module, allowing customizable assistive force to compensate for different proportions of the shoulder elevation moment due to gravity. The results of my research demonstrated that this exoskeleton, providing modest one-fourth gravity moment compensation at the shoulder, can effectively reduce muscle activity, including deltoid and rotator cuff muscles. One crucial aspect of passive shoulder exoskeleton design is determining the optimal anti-gravity assistance level. I have addressed this challenge using computational tools and found that an assistance level within the range of 20-30% of the maximum gravity torque at the shoulder joint yields superior performance for specific shoulder functional tasks. When facing a new task dynamic, such as wearing a passive shoulder exoskeleton, the human neuro-musculoskeletal system adapts and modulates limb impedance at the end-limb (i.e., hand) to enhance task stability. I have presented development and validation of a realistic neuromusculoskeletal model of the upper limb that can predict stiffness modulation and motor adaptation in response to newly introduced environments and force fields. Future studies will explore the model\u27s applicability in predicting stiffness modulation for 3D movements in novel environments, such as passive assistive devices\u27 force fields

Physical diagnostics of cartilage degeneration

Thesis (Ph.D.)--Harvard--Massachusetts Institute of Technology Division of Health Sciences and Technology, February 1999."January 1999."Includes bibliographical references (leaves 219-239).by Steven Treppo.Ph.D

Down-Conditioning of Soleus Reflex Activity using Mechanical Stimuli and EMG Biofeedback

Spasticity is a common syndrome caused by various brain and neural injuries, which can severely impair walking ability and functional independence. To improve functional independence, conditioning protocols are available aimed at reducing spasticity by facilitating spinal neuroplasticity. This down-conditioning can be performed using different types of stimuli, electrical or mechanical, and reflex activity measures, EMG or impedance, used as biofeedback variable. Still, current results on effectiveness of these conditioning protocols are incomplete, making comparisons difficult. We aimed to show the within-session task- dependent and across-session long-term adaptation of a conditioning protocol based on mechanical stimuli and EMG biofeedback. However, in contrast to literature, preliminary results show that subjects were unable to successfully obtain task-dependent modulation of their soleus short-latency stretch reflex magnitude