Use of induced acceleration to quantify the (de)stabilization effect of external and internal forces on postural responses

Due to the mechanical coupling between the body segments, it is impossible to see with the naked eye the causes of body movements and understand the interaction between movements of different body parts. The goal of this paper is to investigate the use of induced acceleration analysis to reveal the causes of body movements. We derive the analytical equations to calculate induced accelerations and evaluate its potential to study human postural responses to support-surface translations. We measured the kinematic and kinetic responses of a subject to sudden forward and backward translations of a moving platform. The kinematic and kinetics served as input to the induced acceleration analyses. The induced accelerations showed explicitly that the platform acceleration and deceleration contributed to the destabilization and restabilization of standing balance, respectively. Furthermore, the joint torques, coriolis and centrifugal forces caused by swinging of the arms, contributed positively to stabilization of the center of mass. It is concluded that induced acceleration analyses is a valuable tool in understanding balance responses to different kinds of perturbations and may help to identify the causes of movement in different pathologies

Wearing a safety harness during treadmill walking influences lower extremity kinematics mainly through changes in ankle regularity and local stability

Background: Wearing a harness during treadmill walking ensures the subject’s safety and is common practice in biomedical engineering research. However, the extent to which such practice influences gait is unknown. This study investigated harness-related changes in gait patterns, as evaluated from lower extremity kinematics during treadmill walking. Findings: Healthy subjects (n = 10) walked on a treadmill at their preferred speed for 3 minutes with and without wearing a harness (LiteGait®, Mobility Research, Inc.). In the former condition, no weight support was provided to the subjects. Lower extremity kinematics was assessed in the sagittal plane from the mean (meanRoM), standard deviation (SDRoM) and coefficient of variation (CoVRoM) of the hip, knee, and ankle ranges of motion (RoM), as well as from the sample entropy (SampEn) and the largest Lyapunov exponent (LyE) of the joints’ angles. Wearing the harness increased the meanRoM of the hip, the SDRoM and the CoVRoM of the knee, and the SampEn and the LyE of the ankle. In particular, the harness effect sizes for both the SampEn and the LyE of the ankle were large, likely reflecting a meaningful decline in the neuromuscular stabilizing control of this joint. Conclusions: Wearing a harness during treadmill walking marginally influences lower extremity kinematics, resulting in more or less subtle changes in certain kinematic variables. However, in cases where differences in gait patterns would be expressed through modifications in these variables, having subjects walk with a harness may mask or reinforce such differences

Ekonomicky dostupný aktivní exoskeleton pro dolní končetiny pro paraplegiky

After a broad introduction to the medical and biomechanical background and detailed review of orthotic devices, two newly developed lower limbs exoskeletons for paraplegics are presented in this study. There was found out the main challenges of designing devices for paraplegic walking can be summarized into three groups, stability and comfort, high efficiency or low energy consumption, dimensions and weight. These all attributes have to be moreover considered and maintained during manufacturing of affordable device while setting a reasonable price of the final product. A new economical device for people with paraplegia which tackles all problems of the three groups is introduced in this work. The main idea of this device is based on HALO mechanism. HALO is a compact passive medial hip joint orthosis with contralateral hip and ankle linkage, which keeps the feet always parallel to the ground and assists swinging the leg. The medial hip joint is equipped with one actuator in the new design and the new active exoskeleton is called @halo. Due to this update, we can achieve more stable and smoother walking patterns with decreased energy consumption of the users, yet maintain its compact and lightweight features. It was proven by the results from preliminary experiments with able-bodied subjects during which the same device with and without actuator was evaluated. Waddling and excessive vertical elevation of the centre of gravity were decreased by 40% with significantly smaller standard deviations in case of the powered exoskeleton. There was 52% less energy spent by the user wearing @halo which was calculated from the vertical excursion difference. There was measured 38.5% bigger impulse in crutches while using passive orthosis, which produced bigger loads in upper extremities musculature. The inverse dynamics approach was chosen to calculate and investigate the loads applied to the upper extremities. The result of this calculation has proven that all main muscle groups are engaged more aggressively and indicate more energy consumption during passive walking. The new @halo device is the first powered exoskeleton for lower limbs with just one actuated degree of freedom for users with paraplegia.První část práce je věnována obsáhlému úvodu do zdravotnické a biomechanické terminologie a detailnímu souhrnnému představení ortopedických pomůcek. Následně jsou představeny dva nově vyvinuté exoskelety aplikovatelné na dolní končetiny paraplegiků. Bylo zjištěno, že hlavní úskalí konstrukčního návrhu asistenčních zařízení pro paraplegiky lze shrnout do tří hlavních skupin, jako první je stabilita a komfort, druhá je vysoká účinnost a nízká energetická náročnost uživatele a do třetí lze zahrnout rozměry a hmotnost zařízení. Toto všechno je navíc podmíněno přijatelnou výslednou cenou produktu. Nový ekonomicky dostupný exoskelet pro paraplegiky, který řeší problematiku všech tří zmíněných skupin je představen v této práci. Hlavní myšlenka tohoto zařízení je postavena na mechanismu HALO ortézy. HALO je kompaktní pasivní ortéza s mediálním kyčelním kloubem umístěným uprostřed mezi dolními končetinami. Speciální mediální kyčelní kloub je kontralaterálně propojen s kotníkem soustavou ocelových lanek což zajištuje paralelní polohu chodidla se zemí v každém okamžiku chůze a navíc asistuje zhoupnutí končetiny. Tento mediální kyčelní kloub je redesignován a v novém provedení je vybaven jedním aktuátorem, nové řešení aktivního exoskeletu dostalo název @halo. Díky tomuto vylepšení lze dosáhnout stabilnější a plynulejší chůze s výrazně redukovanou energetickou náročností uživatele přičemž dochází k zachování nízké hmotnosti a kompaktnosti zařízení. Toto bylo dokázáno během předběžných experimentů se zdravými subjekty, během kterých byla testována aktivní chůze se zařízením vybaveným odnímatelnou pohonnou jednotkou a pasivní chůze se stejným zařízením bez této aktivní jednotky. Nadměrné naklánění se během chůze ze strany na stranu a nadměrná výchylka pohybu těžiště těla ve vertikálním směru byly sníženy o necelých 40% s velmi významně menšími standardními odchylkami v případě chůze s pohonem. Z rozdílu výchylky pohybu těžiště těla ve vertikální poloze bylo vypočítáno snížení energetické náročnosti uživatele o 52% při chůzi s aktivní konfiguraci @halo. Při pohybu s pasivní ortézou byl naměřen o 38,5% větší reakční silový impuls v berlích, což znamená nárůst zátěže pro svalový aparát horních končetin. Pro podrobné vyšetření zátěže ramenních kloubů byl aplikován model inverzní dynamiky. Výsledek tohoto výpočtu jednoznačně indikuje agresivnější a hlubší zapojení všech svalových skupin ramenního kloubu a tím vyšší spotřebu energie uživatelem během pasivní chůze. Nové asistenční zařízení @halo je prvním exoskeletem svého druhu pro paraplegiky s jediným poháněným stupněm volnosti.354 - Katedra robotikyvyhově

Upper Extremity Kinetics during Lofstrand Crutch-Assisted Gait in Children

Complete biomechanical analysis helps evaluate the motion during various gait patterns for the upper and lower extremities. Extensive studies have been performed to evaluate unassisted gait patterns, but very little has been accomplished for studying assisted motion. Children with pathologies such as osteogenesis imperfecta, spinal cord injury, and cerebral palsy use assistive devices such as anterior and posterior walkers, canes, Lofstrand and axillary crutches for ambulation purposes. Statistics show that there are currently about 566,000 crutch users in the United States. The long-term crutch users in this population can suffer various upper limb pathologies associated with extensive upper extremity (UE) loading. Better knowledge of UE dynamics in crutch users may ultimately help to prevent injuries due to excessive loading or inappropriate gait patterns. These evaluations may ultimately assist in pre-treatment planning and post-treatment rehabilitation. Currently, there is no validated system for the assessment of UE joint kinetics during Lofstrand crutch-assisted gait in children. To address these needs two aims will be accomplished: 1. A novel crutch system will be designed and validated to accurately evaluate the UE joint kinetics in children and young adults. 2. A kinetic model will be demonstrated for the newly developed crutch system during Lofstrand crutch-assisted gait in children with spinal cord injury, cerebral palsy and osteogenesis imperfecta

Neuromuscular Control Strategy during Object Transport while Walking: Adaptive Integration of Upper and Lower Limb Movements

When carrying an object while walking, a significant challenge for the central nervous system (CNS) is to preserve the object’s stability against the inter-segmental interaction torques and ground reaction forces. Studies documented several strategies used by the CNS: modulation of grip force (GF), alterations in upper limb kinematics, and gait adaptations. However, the question of how the CNS organizes the multi-segmental joint and muscle coordination patterns to deal with gait-induced perturbations remains poorly understood. This dissertation aimed to explore the neuromuscular control strategy utilized by the CNS to transport an object during walking successfully. Study 1 examined the inter-limb coordination patterns of the upper limbs when carrying a cylinder-shaped object while walking on a treadmill. It was predicted that transporting an object in one hand would affect the movement pattern of the contralateral arm to maintain the overall angular momentum. The results showed that transporting an object caused a decreased anti-phase coordination, but it did not induce significant kinematic and muscle activation changes in the unconstrained arm. Study 2 examined muscle synergy patterns for upper limb damping behavior by using non-negative matrix factorization (NNMF) method. Four synergies were identified, showing a proximal-to-distal pattern of activation preceding heel contacts. Study 3 examined the effect of different precision demands (carrying a cup with or without a ball) and altered visual information (looking forward vs. looking at an object) on the upper limb damping behavior and muscle synergies. Increasing precision demand induced stronger damping behavior and increased the electromyography (EMG) activation of wrist/hand flexors and extensors. The NNMF results replicated Study 2 in that the stabilization of proximal joints occurred before the distal joints. The results indicated that the damping incorporates tonic and phasic muscle activation to ensure object stabilization. Overall, three experiments showed that the CNS adopts a similar synergy pattern regardless of task constraint or altered gaze direction while modulating the amount of muscle activation for object stabilization. Kinematic changes can differ depending on the different levels of constraint, as shown in the smaller movement amplitude of the shoulder joint in the transverse plane during the task with higher precision demand

Work Related Diurnal Changes in Trunk Mechanical Behavior

The objectives of this study were to analyze effects of day-long exposure to LBP risk factors on lumbo-pelvic coordination (LPC) in nursing occupations and to verify if physical activity level affects diurnal work-related changes in LPC. Thirty-three nurses were recruited into three groups based on workplace physical demands and each completed two data collection sessions, one before and one after their 8-12 hour work shift. Participants completed several stationary trunk forward-bending/backward-return exercises at self-selected “fast” and “slow” rotational speeds, and while holding a 15 lbs. load. Kinematic data collected during these exercises were then used to characterize the timing and magnitude aspects of LPC during each exercise. We did not find any work-related changes in our measures of LPC, however, significant differences among groups were seen in thoracic rotation for all exercises (F\u3e 13.39, p\u3c .03) and pelvic rotation during the slow exercise (F= 3.678, p= .037). Considering earlier reports of changes in LPC following a short period of exposure to a single LBP risk factor, our results suggest that such changes when exposed to multiple risk factors and over the course of work day do not accumulate and likely recover by the end of work day

Characterizing the Effects of High-intensity Exercise on Balance and Gait under Dual-task Conditions in Parkinson’s Disease

Parkinson’s disease (PD) is a neurodegenerative disorder, characterized by four cardinal motor symptoms including bradykinesia, tremor, rigidity, and postural instability, and non-motor symptoms including cognitive impairment. Daily activities, such as walking and maintaining balance, are impacted due to impairments in motor function, and are further exacerbated with the addition of cognitive loading, or dual-tasking (DT). High-intensity exercise has demonstrated centrally-mediated improvements of PD symptoms, with additional positive effects on overall health. The goal of this project was to identify changes in dynamic balance recovery and gait function under conditions with and without increased cognitive load after a high-intensity exercise intervention in a PD population. Participants included people with PD who completed an eight-week cycling intervention (PDE), people with Parkinson’s disease who did not complete the intervention (PDC), and healthy age-matched controls (HC), with 14 subjects per group. In Aim 1, while participants underwent a series of destabilizing balance tests, the time taken to regain balance and the center of pressure movement during balance recovery were measured. The PDE group demonstrated greater improvement in balance recovery after exercise compared with the PDC group. In Aim 2, participants completed a series of gait and cognitive tasks, both separately and concurrently. Outcome measures included spatiotemporal and kinematic gait parameters of the lower and upper extremities. The PDE group demonstrated significant improvement in gait measures and DT abilities compared to PDC, while no changes were found in cognitive function for any group. The standard clinical methods of measuring motor function can be subjective, and may not capture subtle motor characteristics. Force plate and motion-capture technologies can provide detailed, objective outcome data, therefore improving the understanding of how exercise affects motor symptoms of Parkinson’s disease. The Motek Computer Assisted Rehabilitation Environment (CAREN) system at the Cleveland Clinic was used to create the testing environment and for data collection. These results of this project suggest global changes in motor function demonstrated by changes in balance recovery and lower and upper extremity gait function. Quantitative gait analysis has shown to be an important metric in assessing effectiveness of an exercise intervention in PD

Characterizing the Effects of High-intensity Exercise on Balance and Gait under Dual-task Conditions in Parkinson’s Disease

Parkinson’s disease (PD) is a neurodegenerative disorder, characterized by four cardinal motor symptoms including bradykinesia, tremor, rigidity, and postural instability, and non-motor symptoms including cognitive impairment. Daily activities, such as walking and maintaining balance, are impacted due to impairments in motor function, and are further exacerbated with the addition of cognitive loading, or dual-tasking (DT). High-intensity exercise has demonstrated centrally-mediated improvements of PD symptoms, with additional positive effects on overall health. The goal of this project was to identify changes in dynamic balance recovery and gait function under conditions with and without increased cognitive load after a high-intensity exercise intervention in a PD population. Participants included people with PD who completed an eight-week cycling intervention (PDE), people with Parkinson’s disease who did not complete the intervention (PDC), and healthy age-matched controls (HC), with 14 subjects per group. In Aim 1, while participants underwent a series of destabilizing balance tests, the time taken to regain balance and the center of pressure movement during balance recovery were measured. The PDE group demonstrated greater improvement in balance recovery after exercise compared with the PDC group. In Aim 2, participants completed a series of gait and cognitive tasks, both separately and concurrently. Outcome measures included spatiotemporal and kinematic gait parameters of the lower and upper extremities. The PDE group demonstrated significant improvement in gait measures and DT abilities compared to PDC, while no changes were found in cognitive function for any group. The standard clinical methods of measuring motor function can be subjective, and may not capture subtle motor characteristics. Force plate and motion-capture technologies can provide detailed, objective outcome data, therefore improving the understanding of how exercise affects motor symptoms of Parkinson’s disease. The Motek Computer Assisted Rehabilitation Environment (CAREN) system at the Cleveland Clinic was used to create the testing environment and for data collection. These results of this project suggest global changes in motor function demonstrated by changes in balance recovery and lower and upper extremity gait function. Quantitative gait analysis has shown to be an important metric in assessing effectiveness of an exercise intervention in PD

Prolonged treadmill walking in healthy participants with and without the use of foot orthoses to support the medial longitudinal arch

In the research setting, instrumented treadmills are often used to study prolonged periods of walking. This thesis examines the effects of in-shoe foot orthoses on walking gait during prolonged periods of treadmill walking. The two types of foot orthoses investigated were: 1) a pedorthist hand-made orthotic with medial longitudinal arch (MLA) support and 2) a proprioceptive feedback-type orthotic designed to stimulate the intrinsic foot muscles of the MLA. The three kinematic variables observed over 60 minutes of intermittent treadmill walking were toe-out angle in the transverse plane, pelvic tilt angle in the sagittal plane, and trunk lean angle in the frontal plane. Kinematic data were collected with a real-time optical motion capture system that consisted of five high resolution digital cameras which tracked the location of the reflective markers placed on the surface of skin. Static and dynamic trials were collected and analyzed to calculate the change in joint angles every 5 minutes of testing. Due to the appearance of three distinct groups for the kinematic variables, each participant was assigned into one of the following groups: Increase Group, No Change Group, or Decrease Group based on the magnitude of the change in joint angles during the 60 minutes of treadmill walking. To be assigned into either the Increase or Decrease Groups, the kinematic variable had to change by at least 1.5˚. In all three conditions, data interpreted within the three subgroups showed statistical significance. In the Control condition, statistical significance was detected in the Increase Group for pelvic tilt angle and the Decrease Group for toe-out angle. In the MLA orthotic condition, statistical significance was detected in the Increase Group for pelvic tilt angle and the Decrease Group for trunk lean angle. In the Proprioceptive orthotic condition, statistical significance was detected in the Increase Group for pelvic tilt angle and the Decrease Group for trunk lean angle. Overall, generic insoles and the two types of foot orthoses have minimal changes on the three kinematic gait variables over 60 minutes of treadmill walking