Strength Modeling Report

Strength modeling is a complex and multi-dimensional issue. There are numerous parameters to the problem of characterizing human strength, most notably: (1) position and orientation of body joints; (2) isometric versus dynamic strength; (3) effector force versus joint torque; (4) instantaneous versus steady force; (5) active force versus reactive force; (6) presence or absence of gravity; (7) body somatotype and composition; (8) body (segment) masses; (9) muscle group envolvement; (10) muscle size; (11) fatigue; and (12) practice (training) or familiarity. In surveying the available literature on strength measurement and modeling an attempt was made to examine as many of these parameters as possible. The conclusions reached at this point toward the feasibility of implementing computationally reasonable human strength models. The assessment of accuracy of any model against a specific individual, however, will probably not be possible on any realistic scale. Taken statistically, strength modeling may be an effective tool for general questions of task feasibility and strength requirements

Influence of 70 days of bed rest and the NASA Sprint exercise countermeasures program on skeletal muscle health

Plans for extensive manual labor in future translunar and interplanetary space missions justify the development of a fully effective countermeasure program to prevent the rampant skeletal muscle deconditioning seen in crew members during spaceflight. The current investigation: 1) reviewed all existing literature on skeletal muscle responses to real and simulated microgravity with and without an exercise countermeasure, and 2) examined the efficacy of the next generation exercise countermeasures program designed for the International Space Station (SPRINT) on lower limb skeletal muscle health during 70 days of simulated microgravity (6° head-down-tilt bedrest). Review of the literature revealed the need for further optimization of the exercise countermeasure programs for skeletal muscle in real and simulated microgravity. These data are presented in 2 supplementary files (Ground Muscle Tables.xlsx and Spaceflight Muscle Tables.xlsx), each containing 6 supplementary tables. To test the efficacy of the SPRINT protocol, individuals underwent 6° head-down-tilt bedrest (BR, n=9), bedrest with resistance and aerobic exercise (BRE, n=9), or bedrest with exercise and low-dose testosterone (BRE+T, n=8). Quadriceps and calf (triceps surae) muscle volumes were measured via MRI before and after bed rest, and strength was assessed via maximal isokinetic contractions of the two muscle groups. Vastus lateralis (VL) and soleus (SOL) muscle biopsies were performed pre- and post-bedrest for the measurement of myosin heavy chain (MHC) single muscle fiber type distribution, MHC I and IIa muscle fiber size, metabolic enzyme activities (glycogen phosphorylase, citrate synthase, β-hydroxyacyl- CoA dehydrogenase), and capillarization. Exercise decreased the number of hybrid muscle fibers in the VL and blunted the bed rest-induced increase in the SOL. BR decreased MHC I fiber size in the VL (-7%) and SOL (-12%) (p < .05), while MHC IIa fiber size was maintained in both muscles (p > .05). In BRE, MHC I and IIa fiber size was maintained in VL and SOL (p > .05). In BRE+T, MHC I and IIa fiber size was maintained in the VL (p > .05), while MHC I fiber size decreased (-12%) (p < .05) and MHC IIa fiber size was maintained (p > .05) in the SOL. Metabolic enzyme activities and capillarity were unchanged (p > .05) in all three groups across both muscles, suggesting these muscle health components were regulated proportionally with muscle volume changes (Quadriceps: BR: -10%, BRE: +3%, BRE+T: +5%; Calf: BR: -22%, BRE: -7%, BRE+T: - 6%). SPRINT, without testosterone, showed better effectiveness than previous microgravity exercise countermeasures programs regarding quadriceps and calf skeletal muscle health. The SPRINT exercise program appears viable for thigh skeletal muscle health, but refinement is needed to completely protect the calf at the myocellular and whole muscle levels.Thesis (Ph. D.

Muscular activity and its relationship to biomechanics and human performance

The purpose of this manuscript is to address the issue of muscular activity, human motion, fitness, and exercise. Human activity is reviewed from the historical perspective as well as from the basics of muscular contraction, nervous system controls, mechanics, and biomechanical considerations. In addition, attention has been given to some of the principles involved in developing muscular adaptations through strength development. Brief descriptions and findings from a few studies are included. These experiments were conducted in order to investigate muscular adaptation to various exercise regimens. Different theories of strength development were studied and correlated to daily human movements. All measurement tools used represent state of the art exercise equipment and movement analysis. The information presented here is only a small attempt to understand the effects of exercise and conditioning on Earth with the objective of leading to greater knowledge concerning human responses during spaceflight. What makes life from nonliving objects is movement which is generated and controlled by biochemical substances. In mammals. the controlled activators are skeletal muscles and this muscular action is an integral process composed of mechanical, chemical, and neurological processes resulting in voluntary and involuntary motions. The scope of this discussion is limited to voluntary motion

Implementation of Analytical Fatigue Models Into Opensim to Predict the Effects of Fatigue on Anterior Cruciate Ligament Loading

The anterior cruciate ligament (ACL) provides stability to the knee joint while performing activities such as a side step cut. Neuromuscular fatigue, a reduction in muscle force producing capabilities, alters lower extremity mechanics while performing a side step cut and may increase the risk of ACL injury, particularly in females. Musculoskeletal modeling allows for the measurement of muscle forces, which are difficult to measure in-vivo. Therefore, musculoskeletal modeling, may improve our understanding of the effects of neuromuscular fatigue on muscle force production and loading of the ACL. Therefore, the purpose of this study was to develop a musculoskeletal model which incorporated two analytical fatigue models by Tang et al. (2005) and Xia et al. (2008). These fatigue models were used to determine the effects of neuromuscular fatigue on muscle force production and ACL loading at various levels of fatigue (i.e. 10%, 25%, 50%, 75% and 90%) and were validated by comparing these results with experimental data. Six recreationally active females performed five anticipated side step cuts both before and after an isolated hamstrings fatigue protocol using the right lower extremity. Root mean square (RMS) differences were calculated between both fatigue models and the experimental hamstrings muscle force 1.91 N·kg-1 and 1.88 N·kg-1, for RMSTang and RMSXia, respectively. Despite similar RMS differences, the Xia et al. (2008) model was selected for analysis of fatigue as this model utilized general input parameters. The total quadriceps and hamstrings muscle forces demonstrated significant decreases (p0.05) due to fatigue. The limited number of participants in this study suggested an underpowered study and may help explain the lack of significance in various dependent variables including peak ACL loading. Using the model developed in this study can aid researchers in understanding the effects of fatigue on risk of ACL injury in order to develop better training programs in order to reduce the risk of injury

Neuromuscular Reflex Control for Prostheses and Exoskeletons

Recent powered lower-limb prosthetic and orthotic (P/O) devices aim to restore legged mobility for persons with an amputation or spinal cord injury. Though various control strategies have been proposed for these devices, specifically finite-state impedance controllers, natural gait mechanics are not usually achieved. The goal of this project was to invent a biologically-inspired controller for powered P/O devices. We hypothesize that a more muscle-like actuation system, including spinal reflexes and vestibular feedback, can achieve able-bodied walking and also respond to outside perturbations. The outputs of the Virtual Muscle Reflex (VMR) controller are joint torque commands, sent to the electric motors of a P/O device. We identified the controller parameters through optimizations using human experimental data of perturbed walking, in which we minimized the error between the torque produced by our controller and the standard torque trajectories observed in the able-bodied experiments. In simulations, we then compare the VMR controller to a four-phase impedance controller. For both controllers the coefficient of determination R^2 and root-mean-square (RMS) error were calculated as a function of the gait cycle. When simulating the hip, knee, and ankle joints, the RMS error and R^2 across all joints and all trials is 15.65 Nm and 0.28 for the impedance controller, respectively, and for the VMR controller, these values are 15.15 Nm and 0.29, respectively. With similar performance, it was concluded that the VMR controller can reproduce characteristics of human walking in response to perturbations as effectively as an impedance controller. We then implemented the VMR controller on the Parker Hannifin powered exoskeleton and performed standard isokinetic and isometric knee rehabilitation exercises to observe the behavior of the virtual muscle model. In the isometric results, RMS error between the measured and commanded extension and flexion torques are 3.28 Nm and 1.25 Nm, respectively. In the isokinetic trials, we receive RMS error between the measured and commanded extension and flexion torques of 0.73 Nm and 0.24 Nm. Since the onboard virtual muscles demonstrate similar muscle force-length and force-velocity relationships observed in humans, we conclude the model is capable of the same stabilizing capabilities as observed in an impedance controller

Neuromuscular Reflex Control for Prostheses and Exoskeletons

Recent powered lower-limb prosthetic and orthotic (P/O) devices aim to restore legged mobility for persons with an amputation or spinal cord injury. Though various control strategies have been proposed for these devices, specifically finite-state impedance controllers, natural gait mechanics are not usually achieved. The goal of this project was to invent a biologically-inspired controller for powered P/O devices. We hypothesize that a more muscle-like actuation system, including spinal reflexes and vestibular feedback, can achieve able-bodied walking and also respond to outside perturbations. The outputs of the Virtual Muscle Reflex (VMR) controller are joint torque commands, sent to the electric motors of a P/O device. We identified the controller parameters through optimizations using human experimental data of perturbed walking, in which we minimized the error between the torque produced by our controller and the standard torque trajectories observed in the able-bodied experiments. In simulations, we then compare the VMR controller to a four-phase impedance controller. For both controllers the coefficient of determination R^2 and root-mean-square (RMS) error were calculated as a function of the gait cycle. When simulating the hip, knee, and ankle joints, the RMS error and R^2 across all joints and all trials is 15.65 Nm and 0.28 for the impedance controller, respectively, and for the VMR controller, these values are 15.15 Nm and 0.29, respectively. With similar performance, it was concluded that the VMR controller can reproduce characteristics of human walking in response to perturbations as effectively as an impedance controller. We then implemented the VMR controller on the Parker Hannifin powered exoskeleton and performed standard isokinetic and isometric knee rehabilitation exercises to observe the behavior of the virtual muscle model. In the isometric results, RMS error between the measured and commanded extension and flexion torques are 3.28 Nm and 1.25 Nm, respectively. In the isokinetic trials, we receive RMS error between the measured and commanded extension and flexion torques of 0.73 Nm and 0.24 Nm. Since the onboard virtual muscles demonstrate similar muscle force-length and force-velocity relationships observed in humans, we conclude the model is capable of the same stabilizing capabilities as observed in an impedance controller

Workshop on Countering Space Adaptation with Exercise: Current Issues

The proceedings represent an update to the problems associated with living and working in space and the possible impact exercise would have on helping reduce risk. The meeting provided a forum for discussions and debates on contemporary issues in exercise science and medicine as they relate to manned space flight with outside investigators. This meeting also afforded an opportunity to introduce the current status of the Exercise Countermeasures Project (ECP) science investigations and inflight hardware and software development. In addition, techniques for physiological monitoring and the development of various microgravity countermeasures were discussed

Neuromuscular Reflex Control for Prostheses and Exoskeletons

Recent powered lower-limb prosthetic and orthotic (P/O) devices aim to restore legged mobility for persons with an amputation or spinal cord injury. Though various control strategies have been proposed for these devices, specifically finite-state impedance controllers, natural gait mechanics are not usually achieved. The goal of this project was to invent a biologically-inspired controller for powered P/O devices. We hypothesize that a more muscle-like actuation system, including spinal reflexes and vestibular feedback, can achieve able-bodied walking and also respond to outside perturbations. The outputs of the Virtual Muscle Reflex (VMR) controller are joint torque commands, sent to the electric motors of a P/O device. We identified the controller parameters through optimizations using human experimental data of perturbed walking, in which we minimized the error between the torque produced by our controller and the standard torque trajectories observed in the able-bodied experiments. In simulations, we then compare the VMR controller to a four-phase impedance controller. For both controllers the coefficient of determination R^2 and root-mean-square (RMS) error were calculated as a function of the gait cycle. When simulating the hip, knee, and ankle joints, the RMS error and R^2 across all joints and all trials is 15.65 Nm and 0.28 for the impedance controller, respectively, and for the VMR controller, these values are 15.15 Nm and 0.29, respectively. With similar performance, it was concluded that the VMR controller can reproduce characteristics of human walking in response to perturbations as effectively as an impedance controller. We then implemented the VMR controller on the Parker Hannifin powered exoskeleton and performed standard isokinetic and isometric knee rehabilitation exercises to observe the behavior of the virtual muscle model. In the isometric results, RMS error between the measured and commanded extension and flexion torques are 3.28 Nm and 1.25 Nm, respectively. In the isokinetic trials, we receive RMS error between the measured and commanded extension and flexion torques of 0.73 Nm and 0.24 Nm. Since the onboard virtual muscles demonstrate similar muscle force-length and force-velocity relationships observed in humans, we conclude the model is capable of the same stabilizing capabilities as observed in an impedance controller

Rehabilitation Engineering

Population ageing has major consequences and implications in all areas of our daily life as well as other important aspects, such as economic growth, savings, investment and consumption, labour markets, pensions, property and care from one generation to another. Additionally, health and related care, family composition and life-style, housing and migration are also affected. Given the rapid increase in the aging of the population and the further increase that is expected in the coming years, an important problem that has to be faced is the corresponding increase in chronic illness, disabilities, and loss of functional independence endemic to the elderly (WHO 2008). For this reason, novel methods of rehabilitation and care management are urgently needed. This book covers many rehabilitation support systems and robots developed for upper limbs, lower limbs as well as visually impaired condition. Other than upper limbs, the lower limb research works are also discussed like motorized foot rest for electric powered wheelchair and standing assistance device