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Limited data is available on accuracy and validity of video-based, GPS and electronic tracking systems, particularly with reference to curved courses and short high intensity running activities. The main goal of this study was to assess soccer-specific accuracy and validity of the radio-frequency based local position measurement (LPM) system (1000 Hz) for measuring distance and speed during walking and sprinting. Three males walked and sprinted 4 soccer-specific courses 10 times each. Distance and speed recorded by LPM were compared to actual distance and speed measured by measuring tape and timing gates. In addition, accuracy was assessed. The static accuracy (SD of the mean) is 1 cm for devices put on the pitch and 2–3 cm when worn by participants. LPM underestimates actual distance (mean difference at most −1.6%). Coefficient of variation becomes larger at higher speed and increased turning angle. With regard to speed, validity correlations are high (range: 0.71–0.97). The LPM speed is significantly and systematically lower, although absolute and relative differences are small, between −0.1 km h −1 (−1.3%) and −0.6 km h −1 (−3.9%). The typical error of the estimate increases with increased speed, but does not increase with increased turning angle. Because the reported differences are small, we conclude that the LPM-system produces highly accurate position and speed data in static and dynamic conditions and is a valid tool for player tracking in soccer and ball team sports in general. © 2010 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Restrictions of field-of-view are known to impair human performance for a range of different tasks. However, such effects on human locomotion through a complex environment are still not clear. Effects of both horizontal (30 degrees, 75 degrees, 112 degrees, 120 degrees, 140 degrees, 160 degrees, and 180 degrees) and vertical (18 degrees and 48 degrees) field-of-view restrictions on the walking speed and head movements of participants maneuvering through an obstacle course were investigated. All field-of-view restrictions tested significantly increased time to complete the entire course, compared to the unrestricted condition. The time to traverse the course was significantly longer for a vertical field-of-view of 18 degrees than for a vertical field-of-view of 48 degrees. For a fixed vertical field-of-view size, the traversal time was constant for horizontal field-of-view sizes ranging between 75 degrees and 180 degrees and increased significantly for the 30 degrees horizontal field-of-view condition. In the restricted viewing conditions, the angular velocity of head movements made while stepping over an obstacle increased significantly over that for the unrestricted field-of-view condition, but no difference was found between the different field-of-view sizes. Implications of the current findings for the development of devices with field-of-view restrictions are discussed.

Field-of-view (FOV) restrictions are known to affect human behaviour and to degrade performance for a range of different tasks. However, the relationship between human locomotion performance in complex environments and FOV size is currently not fully known. This paper examined the effects of FOV restrictions on the performance of participants manoeuvring through an obstacle course with horizontal and vertical barriers. All FOV restrictions tested (the horizontal FOV was either 30 degrees , 75 degrees or 120 degrees , while the vertical FOV was always 48 degrees ) significantly reduced performance compared to the unrestricted condition. Both the time and the number of footsteps needed to traverse the entire obstacle course increased with a decreasing FOV size. The relationship between FOV restriction and manoeuvring performance that was determined can be used to formulate requirements for FOV restricting devices that are deployed to perform time-limited human locomotion tasks in complex structured environments, such as night-vision goggles and head-mounted displays used in training and entertainment systems.

This study investigated the effects of ship motion on peak spinal loading during lifting. All measurements were done on a ship at sea. In 1-min trials, which were repeated over a wide range of sailing conditions, subjects lifted an 18 kg box five times. Ship motion, whole body kinematics, ground reaction forces and electromyography were measured and the effect of ship motion on peak spinal moments and compression forces was investigated. To investigate whether people time their lifts in order to reduce the effect of ship motion on back loading, trials were performed at a free and at a constrained (lifting every 10s) work pace. With increase of the (local) vertical ship acceleration, increased moments and compression forces were found. Furthermore, lifting at a free work pace did not result in smaller effects of ship motion on spinal moments and compression forces than working at a constrained work pace.

Effects of field-of-view restrictions on the speed and accuracy of participants performing a real-world manoeuvring task through an obstacled environment were investigated. Although field-of-view restrictions are known to affect human behaviour and to degrade performance for a range of different tasks, the relationship between human manoeuvring performance and field-of-view size is not known. This knowledge is essential to evaluate a trade-off between human performance, cost, and ergonomic aspects of field-of-view limiting devises like head-mounted displays and night vision goggles which are frequently deployed for tasks involving human motion through environments with obstacles. In this study the speed and accuracy of movement were measured in 15 participants (8 men, 7 women, 22.9 ± 2.8 yr. of age) traversing a course formed by three wall segments for different field-of-view restrictions. Analysis showed speed decreased linearly with decreasing field-of-view extent, while accuracy was consistently reduced for all restricted field-of-view conditions. Present results may be used to evaluate cost and performance trade-offs for field-of-view restricting devices deployed to perform time-limited human-locomotion tasks in complex structured environments, such as night-vision goggles and head-mounted displays.

At a press workstation eight industrial workers processed light-weight objects at six different combined adjustments of reach distance and working height. Working posture, workers' perceptions, and task performance were measured. Two recommendations were formulated in order to minimize the load on the musculoskeletal system: (1) the maximum reach distance is not exceeded if the object can be placed in the stamp on the press as well as be removed without bending the trunk forward, and (2) the working height should be adjusted between 5 and 10 cm above elbow height. © 2002/2003 - IOS Press. All rights reserved.

Manual materials handling on a moving platform, like a ship, might be a risk factor for the development of low back pain due to the influence of accelerations on low back loading. In the current simulation study, 3-D accelerations, measured on a frigate were applied to the kinematics of symmetrical and asymmetrical lifting movements and to a pulling task that had been performed under stable conditions. The aim was to find out to what extent low back loading is increased when the task execution is not adapted to the ship accelerations. Unfavorable timing, analyzed using the 99th percentile of predicted low back moments, resulted in only a moderate (up to 15%) increase of extending and total low back moments, and in a substantial increase of the twisting moment (up to 67%) during asymmetrical lifting. Moments in the pulling task were low and were relatively unaffected by ship accelerations, but adaptation of the movement pattern to prevent falling would be needed more often than during lifting. It furthermore appeared that a substantial reduction of low back loading by favorable timing is not a realistic option. Designing tasks in such a way that they are located midship would reduce the 99th percentile of predicted low back moments. During lifting, orienting the task in such a way that the feet are pointing sideward relative to the ship reduces the predicted peak twisting moment at the low back compared to pointing the feet forward or backward. Relevance to industry: Accelerations on a ship may influence safety and loading of workers during manual materials handling. This study investigates potential effects of moderate accelerations on low back loading during lifting and pulling tasks. It is shown that working midship reduces the risk of low back overloading, compared to working at the front deck.

At a VDU workstation professional touch-typing operators worked at eight different combined adjustments of visual target height and chair backrest inclination. Working posture, workers' perceptions and work performance were measured. Two conclusions were drawn. First, in order to minimize the load on the musculoskeletal system for touch-typing VDU operators, the gaze inclination to a visual target (screen, document) should be 6-9 degrees (range 0-15 degrees ) below the horizontal and, second, the gaze inclination recommended is independent of sitting posture (that is with the backrest between upright and 15 degrees inclined backwards).

At a traditional sewing machine workstation professional operators worked at ten different combined adjustments of table height, desk slope, and pedal position. Working posture and workers’ perceptions were measured. Two recommendations were formulated in order to minimize the load on the musculoskeletal system during operation, i.e. (1) the table desk should be adjusted between 5 and 15 cm above elbow height in a seated posture, (2) the table desk should be given a slope (indication: 10°) and the pedal should be positioned as far under the table as considered comfortable (indication: pedal axis behind the needle).

This paper describes the literature and two experiments on the evaluation of head and neck postures. It is concluded that health and safety professionals and ergonomists during posture evaluation should consider neck flexion/extension (head vs. trunk), besides the traditionally used inclination of the head and/or neck segment (head/neck vs. gravity).

The evaluation of working postures in relation to machinery was described. The health risk was analyzed together with contributing risk factors. The recommendations were based on current ergonomic knowledge and were subjected to changes according to future research. The recommendations were intended to reduce the risks for all healthy adults.

This paper describes the current status, general content, and application of the standards EN 1005, ISO 11226, and ISO 11228-3 concerning upper limb risk assessment. The upper limb risk assessment according to International Organization for Standardization (ISO)/CEN standards is discussed. Risk factors in repetitive work include primarily the level, frequency and duration of postures/movements and force exertion. Aggravating factors mentioned are for instance contact forces, vibration, adverse temperatures, lack of job control, monotony and a low level of training/skill. Application in this field led to a promising result for health and safety professionals and ergonomists, etc.

In the study maintenance workers were involved in pneumatic wrenching, oxy-gas cutting, and grinding at 5 different heights. Working posture and workers' perceptions were measured. Guidelines on working height were formulated in order to minimize the load on the musculoskeletal system. Data from the present experiment as well as from literature were studied in depth in order to disclose generic mechanisms behind the adoption of working postures during visual-manual operations in relation to workstation adjustment. It was found, for instance, that the working posture was constrained by a strictly followed relationship between gaze inclination and head inclination for-/backwards. Also, the study provided insight into the role of visual interference, viewing distance, manipulation distance, hand grip of the tool, and body support for stability. Concerning evaluation criteria for working postures, it was concluded that neck flexion/extension (i.e., head inclination for-/backwards versus trunk inclination for-/backwards) seems to be the dominant determinant of neck load, as compared to head inclination for-/backwards. Furthermore, the position of the upper arm with respect to the trunk, that is, shoulder flexion/retroflexion in particular, seemed to be a dominant determinant of shoulder and shoulder girdle load, as compared to upper arm elevation.

A pilot study was conducted regarding the effects of working posture, handling frequency, and task duration on musculoskeletal discomfort. Participants rated their discomfort perceived while perform-ing a repetitive task at 8 different combinations of manipulations. Pauses between the work periods lasted 15 min. Discomfort was rated according to Borg's category-ratio scale CR-10 and postures were recorded by an optoelectronic movement registration system. From linear multiple regression analysis equations for predicting discomfort at various body regions were obtained. Coefficients of determination especially point to trunk inclination and handling frequency as major determinants of musculoskeletal discomfort.

There is a need for a collective variable that captures the dynamics of team sports like soccer at match level. The centroid positions and surface areas of two soccer teams potentially describe the coordinated flow of attacking and defending in small-sided soccer games at team level. The aim of the present study was to identify an overall game pattern by establishing whether the proposed variables were linearly related between teams over the course of the game. In addition, we tried to identify patterns in the build-up of goals. A positive linear relation and a negative linear relation were hypothesized for the centroid positions and surface areas respectively. Finally, we hypothesized that deviations from these patterns are present in the build-up of goals. Ten young male elite soccer players (mean age 17.3, s = 0.7) played three small-sided soccer games (4-a-side) of 8 minutes as part of their regular training routine. An innovative player tracking system, local position measurement (LPM), was used for obtaining player positions at 45 Hz per player. Pearson correlation coefficients were calculated to investigate the proposed linear relation of the key variables. Correlation coefficients indicate a strong positive linear relation during a whole game for the centroid position in all three games, with the strongest relation for the forwardbackward direction (r > 0.94). For 10 out of 19 goals a crossing of the centroids in this direction can be seen. No negative linear relation was found for surface area (-0.01

The objective of this study was to establish the best prediction for endurance time of combat soldiers marching with extremely heavy loads. It was hypothesized that loads relative to individual characteristics (% maximal load carry capacity [MLCC], % body mass, % lean body mass) would better predict endurance time than load itself. Twenty-three male combat soldiers participated. MLCC was determined by increasing the load by 7.5 kg every 4 minutes until exhaustion. The marching velocity and gradient were 3 km.h(-1) and 5%, respectively. Endurance time was determined carrying 70, 80, and 90% of MLCC. MLCC was on average 102.6 kg +/- 11.6. Load expressed as % MLCC was the best predictor for endurance time (R2 = 0.45). Load expressed as % body mass, as % lean body mass, and absolute load predicted endurance time less well (R2 = 0.30, R2 = 0.24, and R2 = 0.23, respectively). On the basis of these results, it is recommended to assess the MLCC of individual combat soldiers.

In a design process major decisions are often taken at an early phase, i.e. at the CAD screen. In order to consider ergonomics in a proper way, a designer then needs a valid human model (digital manikin). The paper describes several experiments that were done to improve human models.

This paper reports 2 baseline studies and one experiment performed in a confined-space military vehicle concerning the effects on fitness and performance of time in a sitting posture and workstation characteristics. On average physical fitness decreased by slightly more than 10% per hour, the observation performance decreased by 30% per hour, and the technical performance (of gunners) showed a relatively small decrease, i.e., less than 5% per hour. So-called active breaks (changing sitting into standing and walking) led to a significant reduction in the decrease of physical fitness, almost reducing it to zero. Furthermore, the level of confinement was shown to affect physical fitness.

The strategy for approaching a manual work position is an important reference for describing a goal-directed task. However, knowledge on this aspect of human behavior is scarce. The objectives of this study are twofold: (1) to describe and understand the strategy people tend to adopt for approaching a manual work position from different directions when their initial standing position is three meters away, and (2) to describe the working posture they tend to adopt when operating a pistol-grip hand tool at different heights. An experiment involving eight participants was conducted to measure the whole-body position and orientation when approaching a work position from five directions. The working posture adopted when operating a pistol-grip hand tool at six working heights was examined. The results indicate that the final whole-body position and orientation (while performing the operation) was affected significantly by the approach direction. A linear relationship between the approach direction and the final whole-body orientation was obtained. The participants adopted a strategy combining the work efficiency and comfort strategies. They deviated from the least-distance (straight line) walking path and re-oriented their whole body for the operation when approaching the work position. The working posture was significantly affected by the working height. The working postures at six working heights were established. The participants adopted a standing posture when the working height was between eye and hip height, and a stooping or squatting posture when operating at knee and ankle height. The results of this study can be used to enhance digital human modeling motion generated for human movement simulation.

In general manufacturing consists of a sequence of actions on different spots. Depending on the sequence, workers may have to approach a spot from varying angles. The purpose of the study conducted was to describe the whole-body orientation and position when approaching a spot for a manufacturing action from five different angles, starting several meters away. Eight subjects were instructed to perform three different actions (knob rotating, pneumatic wrenching, and button pressing) at six working height s (between ankle height and eye height). The actions were selected for their varying level of constraint at the subject-environment interface. Amongst others, it was disclosed that there is a linear relationship between the final whole-body orientation (while performing the action) and the initial approach angle (while being on the starting position, directed to the manufacturing spot). Furthermore, a translation effect was found, showing that, when approaching from the right side, right-handed subjects position themselves more to the left of the straight line between their initial position and the spot for the manufacturing action. The results of the study may be used for proactive ergonomic assessments of manufacturing environments, allowing the user of a digital human model to accurately and efficiently be able to simulate realistic human motions and action sequences.

Standards organizations have given considerable attention to the problem of work-related musculoskeletal disorders. The publication of international standards for evaluating working postures and movements, ISO 11,226 in 2000 and EN 1,005-4 in 2005, may be considered as a support for those involved in preventing and controlling these disorders. The first one is a tool for evaluation of existing work situations, whereas the latter one is a tool for evaluation during a design/engineering process. Key publications and considerations that led to the content of the standards are presented, followed by examples of application.

This paper is about the use of avatars and maneuvering in virtual environments for simulation-based design ergonomics. An avatar is a digital human model driven by an instrumented human who is immersed in a virtual environment. A presentation on locomotion devices is followed by descriptions of various studies on maneuvering in a virtual environment by means of hand-held controls and body-mounted sensors, and a brief discussion on further studies and future technology such as I3VR - Intuitive Interactive Immersive Virtual Reality - a technology for interaction of two or more subjects in a wide space through the use of full body avatars and wireless data transmission. Copyright © 2006 SAE International.

The paper describes two studies. In the first study the most comfortable position of headgear centre-of-mass is determined for three masses. The positions are described in a head-fixed co-ordinate system based on skull geometry and eye position, considering that these are essential to all headgear, and anticipating the growing use of 3D scan data in headgear design. In the second study the results were applied to a helicopter pilot helmet to improve comfort when using night vision goggles.

This paper describes postural behaviour in static reaching sidewards, and the role of the trunk in particular. It turned out that the trunk (chest, pelvis) is not involved when reaching sidewards up to roughly 40-50°(depending on the reach distance). At greater angles the arm, the chest, and the pelvis each contribute at a particular rate to get the index finger onto target. These rates are reasonably similar to the average contributions of the arm, chest, and pelvis to the total of the range of motions of the arm, chest, and pelvis, suggesting that these segments share the musculoskeletal load equally. Copyright © 2003 SAE International.

This paper describes ISO/FDIS 11226, the international standard on evaluation of static working postures. The scope, the evaluation procedure, and the current status are described. The impact of static working postures on the musculoskeletal system was evaluated. The evaluation procedure considered various body segments and joints independently. It is stressed that the measures meant to induce variations of posture should not lead to monotonous repetitive work. It is stated that the work tasks and operations should provide sufficient physical and mental variation.

We studied the influence of dopaminergic medication on the duration of standing up, static posture and gait in five patients with parkinson's disease (Hoehn and Yahr stage 1.5 to 3) and four healthy controls, using an optoelectronic camera system. Duration of standing up was prolonged in patients, while static posture and gait were largely unaffected. The prolonged duration of standing up was corrected by dopaminergic medication. These results suggest that an increased duration of standing up is a relatively early and dopa-sensitive abnormality in Parkinson's disease.

In den meisten Industriestaaten stellen Schaden am Bewegungsapparat* ein umfangreiches Problem dar. Diese Problematik geht in erster Linie die Gesundheit und das Wohlbefinden von Arbeitnehmer an. Auserdem trifft es die Gesellschaft sowie einzelne Firmen.

INTRODUCTION Performing heavy work (such as lifting) on a ship is associated with a high prevalence of musculoskeletal problems [1,2]. Lifting results in high low back loading [3], thereby affecting low back pain risk. Ship motion may have an additional effect on low back loading during lifting [4]. Depending on the timing of a lifting movement, ship motion can either increase (for example when a ship accelerates upwards) or decrease (for example when a ship accelerates downwards) low back loading. The aim of the present study was to find out to what extent ship motion affects the peak low back moment at the L5S1 joint during manual lifting on a ship at sea. Furthermore, it was investigated whether people are able to time their lifting movements in such a way that the effect of ship motion reduces peak low back moments.