Documents physical performance 9 results

"A meta-analysis to mathematically summarize the effect of hot and cold temperature exposure on performance was completed. The results from 515 effect sizes calculated from 22 original studies suggest that hot and cold temperatures negatively impact performance on a wide range of cognitive-related tasks. More specifically, hot temperatures of 90°F (32.22°C) Web Bulb Globe Temperature Index or above and cold temperatures of 50°F (10°C) or less resulted in the greatest decrement in performance in comparison to neutral temperature conditions (14.88% decrement and 13.91% decrement, respectively). Furthermore, the duration of exposure to the experimental temperature, the duration of exposure to the experimental temperature prior to the task onset, the type of task and the duration of the task had differential effects on performance. The current results indicate that hot and cold temperature exposure have a negative impact on performance and that other variables (e.g., length of exposure to the temperature or task duration) may modify this relationship."

"This paper provides two models for males and females to assess the psychophysical maximum acceptable weight of lift. The weight guidelines generated by the models are a function of lifting frequency, height of lift, sagittal or asymmetrical lifting, task duration, container size in the sagittal plane, presence or absence of container couplings, and percentage of the working population. The developed models were generated from a knowledge base available in the published literature. A computer program was written in BASIC to assist the user in determining the safe load that could be handled by a specified working population. Model validation showed that the models developed predict the maximum acceptable weight of lift with a reasonable degree of accuracy. A comparison between the National Institute for Occupational Safety and Health recommendations and those made on the basis of the models developed in this paper is also presented."

"The biomechanics of the lower back was reviewed as a basis for establishing a load handling limit. Topics included occupational biomechanics of load lifting, biomechanical basis for back injury, compressive strength of lumbar spinal column, biomechanical models, effect of dynamic factors on spinal stress, intraabdominal pressure, asymmetric lifting, effect of task variables on stresses to spine, vertical location of load, horizontal location of load, speed of lifting, lifting straight up, and lifting technique. Studies have indicated that lifting compact objects of moderate weights close to the body can create compressive forces sufficient to cause damage to some lumbar intervertebral discs. The compressive force is directly related to the horizontal moment arm of the load and thus even light loads should be lifted close to the body through proper workplace design and education and training of the workers. Both the intradiscal pressure and compressive force increase with an increase in angle of trunk flexion. Asymmetric lifting results in significantly lower maximum voluntary muscle strength and higher compressive force, intradiscal pressure, myoelectric activity and antagonistic activity of trunk muscles."

"The review discussed various aspects of guidelines for safe manual lifting. Specific topics covered in the report included low back pain, impairment, disability and compensation; causes of low back pain; comparative analysis of risk factors, age, gender, anthropometry, physical fitness and training, lumbar mobility, strength, medical history, years of employment, smoking, psychosocial factors, and structural abnormalities; job risk factors such as heavy physical work, lifting, bending, stretching and reaching, twisting, pushing and pulling, prolonged standing, vibration, and accidents; and preventive approaches such as radiological screening, lifting techniques, preemployment screening, and ergonomic job design. Studies have indicated that low back pain is an extremely significant cause of disability and has a major socioeconomic impact. Many different personal and job factors are associated with the incidence and prevalence of low back complaints. It is concluded that prospective studies are needed so that factors contributing to the development of low back pain can be separated from factors resulting from low back pain."

"A review was conducted of the physiological factors which can be used in developing guidelines for manual lifting tasks. Local muscle strength and fatigue are affected by biomechanical factors (cross sectional area of the muscle, work posture, speed of lifting, muscle availability, and whether the lift is one handed or two handed) and physiological factors (duration of force exertion, frequency of repetition). Metabolic limits in lifting tasks were discussed under the following headings: measuring the metabolic cost of lifting activities; factors influencing the metabolic costs of lifting tasks (beginning posture and the vertical travel distance, lifting technique, workload, lifting versus lowering, special lifting situations); the relationship between psychophysically acceptable weights and the metabolic coast of lifting; oxygen consumption prediction models; and determining lifting task limits based on aerobic capacities. Assumptions made in generating frequency correction factors for the lifting guidelines including components of the frequency connection factor table, baseline aerobic capacity assumptions, workload criteria, frequency factor calculations, and determining the lifting frequency and duration were discussed."