Louhevaara V. 28 Dec 2014
Ergonomics (human factors) is the scientific discipline focused on the understanding of interactions among humans and other elements of a system in order to optimize human well-being and performance and output of the system. Ergonomics is a multidisciplinary field having contributions from psychology, engineering, biomechanics, industrial design, physiology, and anthropometry. Ergonomics can be divided into physical, cognitive and organizational fields which can be implemented to human systems related to work and leisure time. Ergonomics at work considers the interaction between a worker and work at aiming to improve health, workability and well-being as well as productivity and quality of work.
In physical ergonomics at work it important to understand physical capacities and limitations of individual workers who differ in terms of cardiorespiratory, muscular and skill related abilities. They are strongly affected by many factors such gender, age, lifestyle and living environment. According to this knowledge the practitioners of physical ergonomics design work processes, workplaces, machines and equipment which are friendly and easy for the users, and guide to apply correct work techniques, and cause no over or under strain. The ultimate goal of the practitioners is adequate harmonization between a worker, work demands and work environment. The harmonization is very dynamic in nature and it needs to evaluate or when possible to measure regularly.
Physical work can be categorized as heavy dynamic work, manual materials handling, static postural work and repetitive work. Heavy dynamic work mainly affects the cardiorespiratory system producing overall strain responses which quantify energy expenditure and heat balance. Responses to manual materials handling are both cardiorespiratory and musculoskeletal in nature. The local strain responses of muscles, bones, joints, tendons, and membranes of the musculoskeletal system are primarily due to static postural work and repetitive work. The strain responses are similar in static, static-repetitive and repetitive muscular work employing small muscle masses which are typically used in sedentary work tasks within fingers and hands. In each category of work, it is essential to perform work tasks efficiently but producing as low output of force as possible. This requires to maximize the amount of active muscle mass, to optimize the length of active muscles depending on joint angles and the use of ergonomically sound work techniques including work pace and equipment with a good usability.
The only method available for measuring neuromuscular functions in static, static-repetitive and repetitive contractions in actual work is surface electromyography (EMG). Surface EMG measures the electrical activity of voluntary muscle functions steered by the brains via the kinetic chain and helps to determine the output of force and the level of fatigue. The main parameters of EMG are amplitude and frequency. EMG is a highly individual bio-signal affected by muscular characteristics and fitness, fatigue, injuries, some drugs and a number of neurological disorders and diseases. EMG reveals abnormal muscle contractions in standardized and temperate activities and tests particularly when a healthy baseline is available. EMG is the most suitable to follow-up individual changes based on repetitive and regular measurements. Some changes in EMG may be used for early detection of overstrain and injuries of the muscles.
Myontec Ltd has developed and patented the wireless sensory technology including wearable EMG electrodes embedded into clothing, modules and computer programs which provide multiple and new information on activity and functions of main muscles. The technology allows monitoring and recording EMG from functional muscle groups i.e., agonist and synergistic muscles. The technology of Myontec has obvious applications in the field of sports, rehabilitation and medicine, and in physical ergonomics at work.
Myontec Ltd has a product “ErgoSleeve” which has developed and patented in Finland (FI 124550 B). At the moment ErgoSleeve has no competition in the market. ErgoSleeve measures EMG of extensors and flexors of fingers and hand. It has been specifically designed to measure EMG in tasks requiring the use of computers, tabs, smartphones or play consoles. In this kind of tasks, EMG is quite weak due to low level static, static-repetitive and repetitive contractions of fingers (under 5% of the force in the maximal voluntary contraction). The output of finger force is markedly affected by the joint angle of the wrist. There is no consensus on the acceptable EMG level which results in no negative health consequences in long-term static and/or repetitive tasks.
Long-term static and/or repetitive contractions of the fingers and hands in a poor work environment cause almost without exception various symptoms ranging from mild feelings of discomfort to heavy pains. Over time the symptoms may lead to various permanent and serious musculoskeletal disorders, disabilities, sickness leaves and occupational diseases. One of the most common work-related disorder or disease is a repetitive strain injury (RSI) which is a global and growing problem due to increasing exposure to various devices requiring the repetitive use of fingers. The increase of the total exposure is caused by larger amount of high-tech devices available and their continuous use from the early childhood. It has been estimated in the US that the annual number of work-related injuries is far over 1 000 000, and about 50% of them can be classified as RSI. The RSI cases are very costly as the expenses of workers compensation are over $20 billion in a year.
ErgoSleeve is designated for the measurements of muscle activity, functions, and fatigue and for the early detection of overstrain which may lead to far more serious health problems such RSI. It is very probable that with the proper adjustment of load and early detection of muscular problems prevent serious health consequences. This requires carefully targeted ergonomic measures and training of correct ergonomic work methods after the detection of overstrain by ErgoSleeve.
Some market validation studies both in Finland and the US suggest that about 50% of end users ranked ErgoSleeve as the top of potential solutions for reducing the risk of RSI. Also, the practitioners of the occupational health services were very interested in ErgoSleeve as an additional method for the field assessments. The end users also considered the proper price of ErgoSleeve. The average value estimation was $75 per pair and $20 for replacement sleeves.
It can be estimated globally that every second individual exposure to the constant use of high-tech devices requiring the use of fingers force. Over 50% of them have some short- or long-term symptoms and disorders due to the exposure. The market would be huge (over $100) if is just a fraction of potential end users would get ErgoSleeve for preventing and alleviating negative exposure and health consequences.
In addition to sports and rehabilitation, the basic parameters of ErgoSleeve have been used in studies on muscle load in various jobs and tasks such tram driving, shoveling of snow and ladling in the industrial kitchen. Also, the assessments of usability of manual tools (pruners, axes) have been completed successfully in the collaboration with the Fiskars Group.
Alizadeh BN. Market validation report. ErgoSleeve: Ergonomic injury rehabilitation and re-injury prevention via a sensory-textile-enabled muscle performance monitor. InBac-International Business Accelerator. Santa Clara, CA 2010.
Louhevaara V, Järvelin S. Electromyography of the shoulder muscles, heart rate and heart rate variability on tram drivers. Proceedings of Nordic Ergonomics Association Conference 2011, Oulu, Finland, 80-84.
Tolvanen P, Kähkönen J, Louhevaara V. Menetelmä käsillä tapahtuvan työskentelyn ergonomian ja kuormituksen määrittämiseksi ja laite menetelmän soveltamiseksi. Patenttijulkaisu FI 124550 B. Patentti- ja rekisterihallitus. Suomi-Finland 2014.