Effects of portable computing devices on posture,muscle activation levels and efficiency

Very little research exists on ergonomic exposures when using portable computing devices. This study quantified muscle activity (forearm and neck), posture (wrist, forearm and neck), and performance (gross typing speed and error rates) differences across three portable computing devices (laptop, netbook, and slate computer) and two work settings (desk and computer) during data entry tasks. Twelve participants completed test sessions on a single computer using a test–rest–test protocol (30 min of work at one work setting, 15 min of rest, 30 min of work at the other work setting). The slate computer resulted in significantly more non-neutral wrist, elbow and neck postures, particularly when working on the sofa. Performance on the slate computer was four times less than that of the other computers, though lower muscle activity levels were also found. Potential or injury or illness may be elevated when working on smaller, portable computers in non-traditional work settings.     

基于激光测距仪全局匹配扫描的SLAM算法研究

针对传统的SLAM(Simultaneous Localization and Mapping)算法构建地图时容易受环境因素和外界条件的的影响,在非线性系统状态下误差修正能力不足,且当机器人位姿都处于未知状态时,移动机器人位姿获取不精确,地图构建SLAM技术特征量的获取比较繁琐、不准确等问题。以电力巡检机器人为平台,研究了基于全局匹配的扫描算法,摒弃传统的栅格地图模型的插值方法,采用双线性滤波的插值方法,保证子栅格单元的精确性,估算栅格占用函数的概率和导数。最后采用此算法解决了SLAM地图构建的问题,并分别在室内室外环境进行实验。实验结果表明：基于激光测距仪的全局匹配扫描的SALM算法,在室内室外两种不同环境下,不受复杂背景的影响,准确地进行机器人位姿定位,以及环境地图的构建     

Postural support strategies of disabled drivers and the effectiveness of postural support aids

The paper discusses a series of driving trials that were conducted to investigate postural stability of disabled drivers and to assess the effectiveness of a representative sample of support aids. Twenty-three disabled drivers with varying levels of physical disability and seven non disabled drivers participated in the study. The test car was equipped with transducers to measure vehicle velocity and acceleration (longitudinal and lateral), steering wheel movement and torque, and the bracing forces exerted by the driver on the steering wheel. Video cameras were installed to record postural support strategies and displacement of the driver and to record deviation of the car from the specified path. Subjective data regarding driver attitudes and acceptance were also collected through the administration of questionnaires. Findings from the study showed that support aids significantly improved driving performance and reduced physical exertion to maintain an upright driving position for disabled drivers. However, ergonomics design aspects regarding the ease of use and acceptance of the support aids by the end users were identified as obstacles to their sustained use in everyday driving.     

Static and dynamic postural loadings during computer work in females: Sitting on an office chair versus sitting on an exercise ball

Seated computer work results in prolonged static loading, which has been associated with the development of musculoskeletal disorders. A popular alternative to sitting on an office chair while performing computer work is to sit on an exercise ball. Sitting on an exercise ball might affect static and dynamic aspects of working posture. We monitored posture, muscle activation and spinal shrinkage in 10 females performing a 1-h typing task, while sitting on an office chair with armrests and while sitting on an exercise ball. Sitting on an exercise ball resulted in 33% more trunk motion and in 66% more variation in lumbar EMG. Both of these findings can be considered to be an advantage for the exercise ball. However, the fifth percentile and average lumbar EMG were also higher when sitting on an exercise ball, with 38% and 78%, respectively. In addition, more spinal shrinkage occurred when sitting on an exercise ball than when sitting on an office chair. Arm flexion was reduced, but trapezius activation was unaffected when sitting on an exercise ball. It is concluded that the advantages with respect to physical loading of sitting on an exercise ball may not outweigh the disadvantages.     

Differences in lifting strength profiles between experienced workers and novices at various exertion heights

This study compared lifting strength patterns between experienced workers and novices at various exertion heights. Twenty-one experienced workers and 21 novices were recruited to determine their static-lifting strength under various heights (10-150 cm in increments of 10 cm) using two exertion methods (vertically upward lifting, VUL, and toward body lifting, TBL). Testing posture was also recorded by a motion analysis system for comparing with the corresponding strength values.Results showed that strength during VUL were much higher than strength during TBL at 15 height positions (p < 0.001). Strength in all 30 task combinations showed no difference between the two groups except for the VUL at heights of 100-120 cm. On the average, strength exerted by novices during VUL was 4.57-7.61 kg lower than that of workers while lifting at 100-120 cm heights (all p < 0.05). The strength during TBL consistently decreased with increased heights of lifting. When workers performed VUL, the strength surprisingly remained nearly unchanged throughout the heights of interest. The postures adopted by workers during VUL were also highly differentiated from novices while performing near-floor positions, but the strength was equivalent to each other. This study demonstrated that the static-lifting strength of novices were significantly lower than those of experienced workers while upward lifting near the participant’s elbow height. It was concluded that workers tend to adopt a safer (i.e., more flexed knees) and more skillful technique than novices to generate forces, resulting in lower spinal loads during both methods of lifting.

Relevance to Industry

Many studies have established the human strength data based on student participants who do not have experience in manual materials handling. The present findings clearly suggest that lifting strength data collected on novices (e.g., on students) should be carefully applied in the task (re)design at the workplace as their strength profiles and the postures adopted during lifting differ from workers.     

The model-based human body motion analysis system

In this paper, we propose a model-based method to analyze the human walking motion. This system consists of three phases: the preprocessing phase, the model construction phase, and the motion analysis phase. In the experimental results, we show that our system not only analyzes the motion characteristics of the human body, but also recognizes the motion type of the input image sequences. Finally, the synthesized motion sequences are illustrated for verification. The major contributions of this research are: (1) developing a skeleton-based method to analyze the human motion; (2) using Hidden Markov Model (HMM) and posture patterns to describe the motion type.     

Upper quadrant postural changes of school children in response to interaction with different information technologies

The objective of this study was to quantitatively analyse the sitting posture of school children interacting with both old (book) and new (laptop and desktop computers) information technologies to test the hypothesis that posture is effected by the type of information technology (IT) used. A mixed model design was used to test the effect of IT type (within subjects) and age and gender (between subjects). The sitting posture of 32 children aged 4?–?17 years was measured whilst they read from a book, laptop, and desktop computer at a standard school chair and desk. Video images were captured and then digitized to calculate mean angles for head tilt, neck flexion, trunk flexion, and gaze angle. Posture was found to be influenced by IT type (p?<?0.001), age (p?<?0.001) and gender (p?=?0.024) and significantly correlated to the stature of the participants. Measurement of resting posture and the maximal range of motion of the upper and lower cervical spines in the sagittal plane was also undertaken. The biophysical impact and the suitability of the three different information technologies are discussed.     

Simultaneous measurements of posture and movements of head and trunk by continuous three-dimensional registration

The postures of three groups of employees were measured: straddle carrier drivers, crane operators and office employees. This type of sedentary work can be characterized as being highly static. Using a continuous three-dimensional registration device, the postures and movements of head and trunk were recorded simultaneously. The results show that the adopted postures and patterns of movement were predominantly imposed by the workplace. The posture of the crane operators was the most static compared to the other occupations. The most adopted posture in the sagittal plane for crane operators was trunk flexion of 5° and head flexion of 60°. Typically, a straddle carrier driver rotated his head more than 45° to the left or right for 28% of the day, which far exceeded that of the other groups. The measuring device provides accurate and reproducible data that can subsequently be used for calculating the postural load and for ergonomic analysis.     

A medical hand tool physical interaction evaluation approach for prototype testing using patient care simulators

The purpose of this study was to develop and test a physical ergonomics assessment approach for medical device handles. The method assesses wrist posture and force of exertion simultaneously by task element. Electrogoniometers and EMG sensors were connected through a data acquisition module for synchronization with video recordings of trials. Task analysis of video recordings were performed offline with Observer XT software. Average posture and force data across several repetitions of individual task elements were calculated and presented in a format suitable for informing product designers of specific issues during a test trial. A handle comfort questionnaire is proposed to survey subjective responses. The evaluation approach was applied to an endoscope needle in sampling a biopsy from the stomach wall using a gastrointestinal track simulator with ten physician surrogates. The results showed that for all task elements the wrist was in extension (33(°)-45(°)). Peak muscle forces ranged from 28% to 68% MVC across the three muscles studied. Muscle peak forces were above ACGIH HAL maximum threshold limits for four of the seven task elements, and above the action limit for all seven task elements for two muscles. The handle comfort questionnaire data also supported the high muscle force findings, and also on force distribution on the handle due to contact stresses. This combined approach could be used to collect and report detailed early stage ergonomics data from user trials on patient care simulators. The approach is proposed for use by medical device designers at the design stage of new products using prototypes, but it could also be used on existing products with real patients.     

The effect of aging on muscle activation and postural control pattern for young and older computer users

A lot of older adults try to learn to use computers and might use different ways to perform a computer task compared to younger people. Fifteen healthy young and 15 healthy older adults participated in this study and all performed a series of mouse tasks. A three dimensional motion capture system and electromyographic analysis were used to obtain kinematic and kinetic data during performing the computer tasks. Three-way analysis of variance with repeated measures on task and time factors was used to analyze all dependent measurements. Older adults had higher RMS of forearm muscles compared to the young adults. The RMS of the finger extensor was highest when performing a dragging task. Compared with young adults, the older adults had greater cranial-cervical angle and neck flexion, but smaller head flexion, shoulder angle, elbow angle and ulnar deviation. Consequently, the older adults might have a greater risk of developing musculoskeletal disorder.