4,260 research outputs found
A new muscle fatigue and recovery model and its ergonomics application in human simulation
Although automatic techniques have been employed in manufacturing industries
to increase productivity and efficiency, there are still lots of manual
handling jobs, especially for assembly and maintenance jobs. In these jobs,
musculoskeletal disorders (MSDs) are one of the major health problems due to
overload and cumulative physical fatigue. With combination of conventional
posture analysis techniques, digital human modelling and simulation (DHM)
techniques have been developed and commercialized to evaluate the potential
physical exposures. However, those ergonomics analysis tools are mainly based
on posture analysis techniques, and until now there is still no fatigue index
available in the commercial software to evaluate the physical fatigue easily
and quickly. In this paper, a new muscle fatigue and recovery model is proposed
and extended to evaluate joint fatigue level in manual handling jobs. A special
application case is described and analyzed by digital human simulation
technique.Comment: IDMME - Virtual Concept, Beijing : Chine (2008
Fatigue evaluation in maintenance and assembly operations by digital human simulation
Virtual human techniques have been used a lot in industrial design in order
to consider human factors and ergonomics as early as possible. The physical
status (the physical capacity of virtual human) has been mostly treated as
invariable in the current available human simulation tools, while indeed the
physical capacity varies along time in an operation and the change of the
physical capacity depends on the history of the work as well. Virtual Human
Status is proposed in this paper in order to assess the difficulty of manual
handling operations, especially from the physical perspective. The decrease of
the physical capacity before and after an operation is used as an index to
indicate the work difficulty. The reduction of physical strength is simulated
in a theoretical approach on the basis of a fatigue model in which fatigue
resistances of different muscle groups were regressed from 24 existing maximum
endurance time (MET) models. A framework based on digital human modeling
technique is established to realize the comparison of physical status. An
assembly case in airplane assembly is simulated and analyzed under the
framework. The endurance time and the decrease of the joint moment strengths
are simulated. The experimental result in simulated operations under laboratory
conditions confirms the feasibility of the theoretical approach
Muscle Fatigue Analysis Using OpenSim
In this research, attempts are made to conduct concrete muscle fatigue
analysis of arbitrary motions on OpenSim, a digital human modeling platform. A
plug-in is written on the base of a muscle fatigue model, which makes it
possible to calculate the decline of force-output capability of each muscle
along time. The plug-in is tested on a three-dimensional, 29 degree-of-freedom
human model. Motion data is obtained by motion capturing during an arbitrary
running at a speed of 3.96 m/s. Ten muscles are selected for concrete analysis.
As a result, the force-output capability of these muscles reduced to 60%-70%
after 10 minutes' running, on a general basis. Erector spinae, which loses
39.2% of its maximal capability, is found to be more fatigue-exposed than the
others. The influence of subject attributes (fatigability) is evaluated and
discussed
A novel approach for determining fatigue resistances of different muscle groups in static cases
In ergonomics and biomechanics, muscle fatigue models based on maximum
endurance time (MET) models are often used to integrate fatigue effect into
ergonomic and biomechanical application. However, due to the empirical
principle of those MET models, the disadvantages of this method are: 1) the MET
models cannot reveal the muscle physiology background very well; 2) there is no
general formation for those MET models to predict MET. In this paper, a
theoretical MET model is extended from a simple muscle fatigue model with
consideration of the external load and maximum voluntary contraction in passive
static exertion cases. The universal availability of the extended MET model is
analyzed in comparison to 24 existing empirical MET models. Using mathematical
regression method, 21 of the 24 MET models have intraclass correlations over
0.9, which means the extended MET model could replace the existing MET models
in a general and computationally efficient way. In addition, an important
parameter, fatigability (or fatigue resistance) of different muscle groups,
could be calculated via the mathematical regression approach. Its mean value
and its standard deviation are useful for predicting MET values of a given
population during static operations. The possible reasons influencing the
fatigue resistance were classified and discussed, and it is still a very
challenging work to find out the quantitative relationship between the fatigue
resistance and the influencing factors
Framework for Dynamic Evaluation of Muscle Fatigue in Manual Handling Work
Muscle fatigue is defined as the point at which the muscle is no longer able
to sustain the required force or work output level. The overexertion of muscle
force and muscle fatigue can induce acute pain and chronic pain in human body.
When muscle fatigue is accumulated, the functional disability can be resulted
as musculoskeletal disorders (MSD). There are several posture exposure analysis
methods useful for rating the MSD risks, but they are mainly based on static
postures. Even in some fatigue evaluation methods, muscle fatigue evaluation is
only available for static postures, but not suitable for dynamic working
process. Meanwhile, some existing muscle fatigue models based on physiological
models cannot be easily used in industrial ergonomic evaluations. The external
dynamic load is definitely the most important factor resulting muscle fatigue,
thus we propose a new fatigue model under a framework for evaluating fatigue in
dynamic working processes. Under this framework, virtual reality system is
taken to generate virtual working environment, which can be interacted with the
work with haptic interfaces and optical motion capture system. The motion
information and load information are collected and further processed to
evaluate the overall work load of the worker based on dynamic muscle fatigue
models and other work evaluation criterions and to give new information to
characterize the penibility of the task in design process.Comment: International Conference On Industrial Technology, Chengdu : Chine
(2008
Predictive model of the human muscle fatigue: application to repetitive push-pull tasks with light external load
Repetitive tasks in industrial works may contribute to health problems among
operators, such as musculo-skeletal disorders, in part due to insufficient
control of muscle fatigue. In this paper, a predictive model of fatigue is
proposed for repetitive push/pull operations. Assumptions generally accepted in
the literature are first explicitly set in this framework. Then, an earlier
static fatigue model is recalled and extended to quasi-static situations.
Specifically, the maximal torque that can be generated at a joint is not
considered as constant, but instead varies over time accordingly to the
operator's changing posture. The fatigue model is implemented with this new
consideration and evaluated in a simulation of push/pull operation. Reference
to this paper should be made as follows: Sakka, S., Chablat, D., Ma, R. and
Bennis, F. (2015) 'Predictive model of the human muscle fatigue: application to
repetitive push-pull tasks with light external load', Int
Oral application of L-menthol in the heat: From pleasure to performance
When menthol is applied to the oral cavity it presents with a familiar refreshing sensation and cooling mint flavour. This may be deemed hedonic in some individuals, but may cause irritation in others. This variation in response is likely dependent upon trigeminal sensitivity toward cold stimuli, suggesting a need for a menthol solution that can be easily personalised. Menthol’s characteristics can also be enhanced by matching colour to qualitative outcomes; a factor which can easily be manipulated by practitioners working in athletic or occupational settings to potentially enhance intervention efficacy.
This presentation will outline the efficacy of oral menthol application for improving time trial performance to date, either via swilling or via co-ingestion with other cooling strategies, with an emphasis upon how menthol can be applied in ecologically valid scenarios. Situations in which performance is not expected to be enhanced will also be discussed. An updated model by which menthol may prove hedonic, satiate thirst and affect ventilation will also be presented, with the potential performance implications of these findings discussed and modelled. Qualitative reflections from athletes that have implemented menthol mouth swilling in competition, training and maximal exercise will also be included
Multi-Objective Optimisation Method for Posture Prediction and Analysis with Consideration of Fatigue Effect and its Application Case
Automation technique has been widely used in manufacturing industry, but
there are still manual handling operations required in assembly and maintenance
work in industry. Inappropriate posture and physical fatigue might result in
musculoskeletal disorders (MSDs) in such physical jobs. In ergonomics and
occupational biomechanics, virtual human modelling techniques have been
employed to design and optimize the manual operations in design stage so as to
avoid or decrease potential MSD risks. In these methods, physical fatigue is
only considered as minimizing the muscle or joint stress, and the fatigue
effect along time for the posture is not considered enough. In this study,
based on the existing methods and multiple objective optimisation method (MOO),
a new posture prediction and analysis method is proposed for predicting the
optimal posture and evaluating the physical fatigue in the manual handling
operation. The posture prediction and analysis problem is mathematically
described and a special application case is demonstrated for analyzing a
drilling assembly operation in European Aeronautic Defence & Space Company
(EADS) in this paper
A review of contemporary techniques for measuring ergonomic wear comfort of protective and sport clothing
Protective and sport clothing is governed by protection requirements, performance, and comfort of the user. The comfort and impact performance of protective and sport clothing are typically subjectively measured, and this is a multifactorial and dynamic process. The aim of this review paper is to review the contemporary methodologies and approaches for measuring ergonomic wear comfort, including objective and subjective techniques. Special emphasis is given to the discussion of different methods, such as objective techniques, subjective techniques, and a combination of techniques, as well as a new biomechanical approach called modeling of skin. Literature indicates that there are four main techniques to measure wear comfort: subjective evaluation, objective measurements, a combination of subjective and objective techniques, and computer modeling of human–textile interaction. In objective measurement methods, the repeatability of results is excellent, and quantified results are obtained, but in some cases, such quantified results are quite different from the real perception of human comfort. Studies indicate that subjective analysis of comfort is less reliable than objective analysis because human subjects vary among themselves. Therefore, it can be concluded that a combination of objective and subjective measuring techniques could be the valid approach to model the comfort of textile materials
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