Development and assessment of the Canadian personal load carriage system using objective biomechanical measures

The Defence Research and Development Canada--Toronto managed a collaborative team of designers, biomechanists, ergonomists and military stakeholders in the development of a new personal load carriage (LC) system for the Canadian Forces. Ergonomics design principles using objective measurement tools and user-centred feedback from soldiers were considered essential to system development. The purpose of this study was to provide a detailed report of contributions by biomechanical testing to the final design of the final Canadian LC system. The Load Carriage Simulator and Compliance Tester were used to test design iterations of: three fragmentation vests, seven tactical vests and three iterations of the backpack. Test data were compared to a data pool of seventeen previously tested systems. Results indicated that the objective measures helped the design team by: (1) quantifying and understanding the consequences of various design changes; (2) predicting soldiers' responses to design changes in skin contact pressure, force and relative motion; (3) objectively comparing design iterations to other systems; and (4) providing information quickly so that ideas and recommendations could be incorporated into the next design iteration. It was concluded that objective assessments added valuable information not easily interpreted from human trials. However, objective assessments cannot replace human trials for feedback on functionality and features.     

Development and assessment of the Canadian personal load carriage system using objective biomechanical measures

The Defence Research and Development Canada—Toronto managed a collaborative team of designers, biomechanists, ergonomists and military stakeholders in the development of a new personal load carriage (LC) system for the Canadian Forces. Ergonomics design principles using objective measurement tools and user-centred feedback from soldiers were considered essential to system development. The purpose of this study was to provide a detailed report of contributions by biomechanical testing to the final design of the final Canadian LC system. The Load Carriage Simulator and Compliance Tester were used to test design iterations of: three fragmentation vests, seven tactical vests and three iterations of the backpack. Test data were compared to a data pool of seventeen previously tested systems. Results indicated that the objective measures helped the design team by: (1) quantifying and understanding the consequences of various design changes; (2) predicting soldiers' responses to design changes in skin contact pressure, force and relative motion; (3) objectively comparing design iterations to other systems; and (4) providing information quickly so that ideas and recommendations could be incorporated into the next design iteration. It was concluded that objective assessments added valuable information not easily interpreted from human trials. However, objective assessments cannot replace human trials for feedback on functionality and features.     

Load carriage for fun: a survey of New Zealand trampers, their activities and injuries

Much of the published research investigating the physiological, biomechanical and psychological impact of load carriage by backpack has studied young, fit males carrying loads for an hour or less. The resultant body of knowledge may not be appropriate to the increasing numbers of middle-aged and older men and women who are taking up or returning to tramping as a recreational activity. In this study, members of 11 tramping clubs throughout New Zealand were surveyed to discover their personal characteristics, characteristics of tramping trips undertaken and injuries sustained. Significant numbers of men and women over 30, 40 and 50 years of age and with generally sedentary lifestyles reported occasional tramping during which they carried backpacks weighing up to 29% of their body weight for more than five hours over 11–15 km/day. Injuries were reported by 74%, with sprains being the most common injury type and knees, ankles and feet the most frequent location of injury. These findings may have implications for route planning and the design of interventions to reduce injuries, health care, training, tracks, equipment and footwear, and demonstrate the need for further research to investigate the risks and requirements of recreational trampers.     

Evaluation of the effect of backpack load and position during standing and walking using biomechanical,physiological and subjective measures

Recommendations on backpack loading advice restricting the load to 10% of body weight and carrying the load high on the spine. The effects of increasing load (0%–5%–10%–15% of body weight) and changing the placement of the load on the spine, thoracic vs. lumbar placement, during standing and gait were analysed in 20 college-aged students by studying physiological, biomechanical and subjective data. Significant changes were: (1) increased thorax flexion; (2) reduced activity of M. erector spinae vs. increased activation of abdominals; (3) increased heart rate and Borg scores for the heaviest loads. A trend towards increased spinal flexion, reduced pelvic anteversion and rectus abdominis muscle activity was observed for the lumbar placement. The subjective scores indicate a preference for the lumbar placement. These findings suggest that carrying loads of 10% of body weight and above should be avoided, since these loads induce significant changes in electromyography, kinematics and subjective scores. Conclusions on the benefits of the thoracic placement for backpack loads could not be drawn based on the parameter set studied.     

Evaluation of the effect of backpack load and position during standing and walking using biomechanical, physiological and subjective measures

Recommendations on backpack loading advice restricting the load to 10% of body weight and carrying the load high on the spine. The effects of increasing load (0%-5%-10%-15% of body weight) and changing the placement of the load on the spine, thoracic vs. lumbar placement, during standing and gait were analysed in 20 college-aged students by studying physiological, biomechanical and subjective data. Significant changes were: (1) increased thorax flexion; (2) reduced activity of M. erector spinae vs. increased activation of abdominals; (3) increased heart rate and Borg scores for the heaviest loads. A trend towards increased spinal flexion, reduced pelvic anteversion and rectus abdominis muscle activity was observed for the lumbar placement. The subjective scores indicate a preference for the lumbar placement. These findings suggest that carrying loads of 10% of body weight and above should be avoided, since these loads induce significant changes in electromyography, kinematics and subjective scores. Conclusions on the benefits of the thoracic placement for backpack loads could not be drawn based on the parameter set studied.     

The reliability of the Extra Load Index as a measure of relative load carriage economy

Abstract

The aim of this study was to measure the reliability of the extra load index (ELI) as a method for assessing relative load carriage economy. Seventeen volunteers (12 males, 5 females) performed walking trials at 3 km·h^?1, 6 km·h^?1 and a self-selected speed. Trial conditions were repeated 7 days later to assess test–retest reliability. Trials involved four 4-minute periods of walking, each separated by 5 min of rest. The initial stage was performed unloaded followed in a randomised order by a second unloaded period and walking with backpacks of 7 and 20 kg. Results show ELI values did not differ significantly between trials for any of the speeds (p = 0.46) with either of the additional loads (p = 0.297). The systematic bias, limits of agreement and coefficients of variation were small in all trial conditions. We conclude the ELI appears to be a reliable measure of relative load carriage economy.

Practitioner Summary: This paper demonstrates that the ELI is a reliable measure of load carriage economy at a range of walking speeds with both a light and heavy load. The ELI, therefore, represents a useful tool for comparing the relative economy associated with different load carriage systems.     

Lifting in four restricted lifting conditions: psychophysical, physiological and biomechanical effects of lifting in stooped and kneeling postures

Many underground coal mines are less than 1.2 m in height, and require that manual lifting tasks be performed in restricted postures (usually stooped or kneeling). Unfortunately, little is known about how these postures affect the underground coal miner's capabilities to perform such work. A previous Bureau of Mines study indicated that lifting capacity is greater when stooped than kneeling when lifting under a 1.2 m roof height (Gallagher et al, 1988). However, many low-seam coal mines present even more restricted headroom than 1.2 m. Therefore, a study was conducted to: (1) examine the psychophysical lifting capacity of low-seam coal miners under four restricted lifting conditions, (2) investigate the associated metabolic costs, and (3) analyse the electromyography (EMG) of trunk muscles when lifting in these restricted positions. Subjects were 12 coal miners accustomed to handling materials in restricted postures (mean age = 35.9 yrs +/- 6.4 SD). Results of this study indicated that lifting capacity was greater when the subjects could assume a stooped posture than when kneeling (p < 0.01). Furthermore, the metabolic cost was greater in the kneeling posture for heart rate (p < 0.001), oxygen consumption (p < 0.001), minute ventilation (p < 0.05] ), and respiratory exchange ratio (p < 0.05), despite the fact that miners lifted less weight in this posture. Analysis of the EMG data indicated increased activity of the electores spinae when kneeling (p < 0.001), but higher latissimus dorsi activity when stopped (p < 0.001). The findings of this study indicate that the weight of supply items should be reduced approximately 14-18% when the kneeling posture must be used for lifting.     

Ergonomic and physiological aspects of military operations in a cold wet climate

Military operations provide a unique set of circumstances from which lessons can be drawn of general application to those engaged in arduous activity in adverse cold wet weather -conditions. The opportunity arose to collect information from a large number of troops who had been engaged in military operations in the South Atlantic. The results of that survey are presented and discussed, with particular reference to the use of cold weather clothing, the requirements for physical fitness and the limitations of human load carriage.     

The Extra Load Index as a method for comparing the relative economy of load carriage systems

The Extra Load Index (ELI) has been proposed as a suitable method of assessing the relative economy of load carriage systems. The purpose of this study was to determine, based on empirical evidence, that the ELI can accommodate variations in both body composition and added load. In total, 30 women walked carrying loads of up to 70% body mass at self-selected walking speeds whilst expired air was collected. In addition, each of the women had body composition assessed via dual energy X-ray absorptiometry. Results show that the ELI is independent of body composition variables, the magnitude of additional loads and the speed of progression. Consequently, it is suggested that it represents an appropriate method of comparing load carriage systems in both scientific and commercial arenas. STATEMENT OF RELEVANCE: This paper demonstrates that ELI is independent of body composition, added load and speed and is therefore an appropriate method to generalise comparisons of load carriage systems. It has the advantage of being easily understood by manufacturers and consumers whilst retaining appropriate scientific precision.     

The Extra Load Index as a method for comparing the relative economy of load carriage systems

The Extra Load Index (ELI) has been proposed as a suitable method of assessing the relative economy of load carriage systems. The purpose of this study was to determine, based on empirical evidence, that the ELI can accommodate variations in both body composition and added load. In total, 30 women walked carrying loads of up to 70% body mass at self-selected walking speeds whilst expired air was collected. In addition, each of the women had body composition assessed via dual energy X-ray absorptiometry. Results show that the ELI is independent of body composition variables, the magnitude of additional loads and the speed of progression. Consequently, it is suggested that it represents an appropriate method of comparing load carriage systems in both scientific and commercial arenas.

Statement of Relevance:This paper demonstrates that ELI is independent of body composition, added load and speed and is therefore an appropriate method to generalise comparisons of load carriage systems. It has the advantage of being easily understood by manufacturers and consumers whilst retaining appropriate scientific precision.     

Security of medical images for telemedicine: a systematic review

Multimedia Tools and Applications - Recently, there has been a rapid growth in the utilization of medical images in telemedicine applications. The authors in this paper presented a detailed...     

Geometric and biomechanical analysis for computer-aided design of assistive medical devices

This paper presents geometric and biomechanical analysis for designing elastic braces used to restrict the motion of injured joints. Towards the ultimate goal of the brace research, which is to design custom-made braces of the stiffness prescribed by a physician, this paper presents an analysis of the relationship between the brace geometry/dimension and its stiffness. As input, physician-prescribed brace stiffness and 3D-scanned data of the injured joint are given. The 3D joint geometry determines the tentative dimension of the brace. When the joint is bent, the brace stuck onto it is accordingly deformed through an appropriately devised deformation model. As a result of the deformation, strain energy is stored in the brace material. The strain energy is calculated using strain energy density functions. For effective calculation, mesh simplification and surface parametrization techniques are innovatively applied, which have been widely investigated in the computer graphics field. The calculated strain energy leads to the brace stiffness, and the obtained relationship between the brace dimension and stiffness can be used for designing a custom-made brace that meets the stiffness prescribed by a physician. The experiment results prove that geometric and biomechanical analysis works quite well for computer-aided design of assistive medical devices.     

Ergonomic and medical aspects of vdu workplaces

VDU's are a new tool in many workplaces. They can produce complaints due to inadequate workplace design, not optimally developed technology, unadapted work organization or psychological attitudes of end-users. Many therapies are available; others must still be studied and developed though therapies are useful only if they are applied.     

Comparing the revised NIOSH lifting equation to the psychophysical,biomechanical and physiological criteria used in its development

The purpose of this study was to perform a systematic and comprehensive comparison between the recommended weights of lift (RWL) from the revised NIOSH lifting equation, and the specific biomechanical, psychophysical and physiological criteria that were stated to be used in the equation's development. A composite acceptable load (CAL) table was developed for the 216 conditions presented in the female lifting table of Snook and Ciriello (1991). Each CAL value was calculated to correspond to the most conservative load of the three design criteria. The RWLs caused lumbar compression forces close to the biomechanical limit of 3400 N for lifts below knuckle height, but resulted in compression forces that are much lower at higher lifting heights. At moderate lifting frequencies, the average RWL would be acceptable to more than 95% of female workers according to the psychophysical criterion. At the highest frequencies, the RWL was found to be an average of 63% of the CAL values based on the integration of the psychophysical and physiological criteria. It is recommended that ergonomists acknowledge the very conservative nature of the revised NIOSH lifting equation when using it to evaluate occupational lifting tasks.