Analysis and modelling of muscles motion during whole body vibration

The aim of the study is to characterize the local muscles motion in individuals undergoing whole body mechanical stimulation. In this study we aim also to evaluate how subject positioning modifies vibration dumping, altering local mechanical stimulus. Vibrations were delivered to subjects by the use of a vibrating platform, while stimulation frequency was increased linearly from 15 to 60Hz. Two different subject postures were here analysed. Platform and muscles motion were monitored using tiny MEMS accelerometers; a contra lateral analysis was also presented. Muscle motion analysis revealed typical displacement trajectories: motion components were found not to be purely sinusoidal neither in phase to each other. Results also revealed a mechanical resonant-like behaviour at some muscles, similar to a second-order system response. Resonance frequencies and dumping factors depended on subject and his positioning. Proper mechanical stimulation can maximize muscle spindle solicitation, which may produce a more effective muscle activation

A human body model for dynamic response analysis of an integrated human-seat-controller-high speed marine craft interaction system

Small boats are increasingly being operated at high speed in rough weather by organisations carrying out essential missions such as the military and rescue services. Crew and passengers on these boats are exposed to continuous vibration and impacts leading to reduced crew effectiveness, fatigue and the possibility of injury. In addition to this marine craft will soon fall under the jurisdiction of the European Union Directive 2002/44/EC on the protection of workers from vibration.To assess the possibility of injury and mitigate it at the design stage of a vessel a design tool is needed to assess the vibration levels on/in the human body while the boat operates in dynamic environments. A review of current human body models is presented and a new human body model, which allows for estimates of muscle activity, is proposed. This model is supplemented by a numerical approach using finite element methods to assess the dynamic response of the integrated human-seat-controller-boat interaction system excited by wave loads or boat motions measured in full scale boat operation tests. The vibration control actuators are arranged between the seat and boat to reduce vibrations transmitted to the human body from the boat to obtain a comfortable ride condition

A human body model for dynamic response analysis of an integrated human-seat-controller-high speed marine craft interaction system

Small boats are increasingly being operated at high speed in rough weather by organisations carrying out essential missions such as the military and rescue services. Crew and passengers on these boats are exposed to continuous vibration and impacts leading to reduced crew effectiveness, fatigue and the possibility of injury. In addition to this marine craft will soon fall under the jurisdiction of the European Union Directive 2002/44/EC on the protection of workers from vibration.To assess the possibility of injury and mitigate it at the design stage of a vessel a design tool is needed to assess the vibration levels on/in the human body while the boat operates in dynamic environments. A review of current human body models is presented and a new human body model, which allows for estimates of muscle activity, is proposed. This model is supplemented by a numerical approach using finite element methods to assess the dynamic response of the integrated human-seat-controller-boat interaction system excited by wave loads or boat motions measured in full scale boat operation tests. The vibration control actuators are arranged between the seat and boat to reduce vibrations transmitted to the human body from the boat to obtain a comfortable ride condition

Aerospace Medicine and Biology: A continuing supplement 180, May 1978

This special bibliography lists 201 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1978

Whole body modelling of musculoskeletal interactions during whole body vibration to inform rehabilitation intervention design

Background: A major secondary complication which can arise in individuals with spinal cord injury (SCI) is disuse-related bone loss as a result of long-term paralysis and immobilisation. An emerging rehabilitation technique used to treat this musculoskeletal degeneration is whole body vibration (WBV). This can be applied to patients in different body positions on a WBV platform in order to stimulate different muscle groups and in turn apply muscle forces to target bones. To treat the disuse-related bone loss, the hypothesis is that WBV intervention can stimulate bone formation indirectly via targeted muscle action, and/or directly if vibration acts as a mechanostimulus on the bone. Aim & Objectives: The aim of this study was to develop whole body computational models of WBV intervention, to inform the design of intervention protocols in SCI patients. Effects of muscle loss were simulated, and activation and forces of different muscles analysed for a number of proposed configurations on the WBV platform. Methods: WBV intervention was simulated using the AnyBody Technology Modelling software by implementing and adapting the currently available standing model. Different body positions (standing, knee flexed standing, squatting) and parameters of WBV such as frequency and amplitude were modelled and analysed, and the muscle actions simulated. Results: Realistic muscle activities compared to the literature were found in all body position configurations without the WBV simulation. When modelling the WBV intervention, only the squatting body position and side-alternating WBV plate were found to give accurate results. The activities of several muscles were recorded in this configuration under a variety of frequencies and amplitudes. Finally muscle forces were analysed with changes in frequency and amplitude and found to cause a corresponding change in the loading of regions the bones of the ilium, tibia, femur, ischium, fibula, sacrum and coccyx. The aim is for the results of this model to be used in the future to inform WBV protocol development for musculoskeletal rehabilitation in SCI and other target patient groups.Background: A major secondary complication which can arise in individuals with spinal cord injury (SCI) is disuse-related bone loss as a result of long-term paralysis and immobilisation. An emerging rehabilitation technique used to treat this musculoskeletal degeneration is whole body vibration (WBV). This can be applied to patients in different body positions on a WBV platform in order to stimulate different muscle groups and in turn apply muscle forces to target bones. To treat the disuse-related bone loss, the hypothesis is that WBV intervention can stimulate bone formation indirectly via targeted muscle action, and/or directly if vibration acts as a mechanostimulus on the bone. Aim & Objectives: The aim of this study was to develop whole body computational models of WBV intervention, to inform the design of intervention protocols in SCI patients. Effects of muscle loss were simulated, and activation and forces of different muscles analysed for a number of proposed configurations on the WBV platform. Methods: WBV intervention was simulated using the AnyBody Technology Modelling software by implementing and adapting the currently available standing model. Different body positions (standing, knee flexed standing, squatting) and parameters of WBV such as frequency and amplitude were modelled and analysed, and the muscle actions simulated. Results: Realistic muscle activities compared to the literature were found in all body position configurations without the WBV simulation. When modelling the WBV intervention, only the squatting body position and side-alternating WBV plate were found to give accurate results. The activities of several muscles were recorded in this configuration under a variety of frequencies and amplitudes. Finally muscle forces were analysed with changes in frequency and amplitude and found to cause a corresponding change in the loading of regions the bones of the ilium, tibia, femur, ischium, fibula, sacrum and coccyx. The aim is for the results of this model to be used in the future to inform WBV protocol development for musculoskeletal rehabilitation in SCI and other target patient groups

Evaluation of motion comfort using advanced active human body models and efficient simplified models

Active muscles are crucial for maintaining postural stability when seated in a moving vehicle. Advanced active 3D non-linear full body models have been developed for impact and comfort simulation, including large numbers of individual muscle elements, and detailed non-linear models of the joint structures. While such models have an apparent potential to provide insight into postural stabilization, they are computationally demanding, making them less practical in particular for driving comfort where long time periods are to be studied. In vibrational comfort and in general biomechanical research, linearized models are effectively used. This paper evaluates the effectiveness of simplified 3D full-body human models to capture comfort provoked by whole-body vibrations. An efficient seated human body model is developed and validated using experimental data. We evaluate the required complexity in terms of joints and degrees of freedom for the spine, and explore how well linear spring-damper models can approximate reflexive postural stabilization. Results indicate that linear stiffness and damping models can well capture the human response. The results are improved by adding proportional integral derivative (PID) and head-in-space (HIS) controllers to maintain the defined initial body posture. The integrator is shown to be essential to prevent drift from the defined posture. The joint angular relative displacement is used as the input reference to each PID controller. With this model, a faster than real-time solution is obtained when used with a simple seat model. The paper also discusses the advantages and disadvantages of various models and provides insight into which models are more appropriate for motion comfort analysis

Computer simulation of one-handed backhand groundstrokes in tennis

A subject-specific, torque-driven, 3D computer simulation model with eight segments was developed to investigate the effects of different variables belonging to the racket and player on the wrist and elbow loadings in one-handed tennis backhand groundstrokes. Wobbling masses were included to represent soft tissue movement. The string-bed was represented by nine-point masses connected to each other and the racket frame with elastic springs. There were twelve rotational degrees of freedom: three at the shoulder, two at the elbow, two at the wrist, three at the grip and two between the racket handle and racket head. Seven pairs of torque generators were used to control (via activation profiles) the joint angle changes in the model. An elite player was chosen to perform consistent and high standard backhand topspin strokes and a Vicon System was used to record the performances. [Continues.

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 171

This bibliography lists 186 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1977