Determination of optimal location for parachute ripcord handle in a suspended position.

A number of parachuting fatalities are attributed every year to the inability of the parachutist to pull the ripcord. The purpose of this study was to determine a location for the ripcord handle in parachutes, which would be most compatible with human capabilities. Eight different ripcord handle locations were selected for this investigation. Eighteen male and 18 female subjects participated in the study. The subjects were tested while being suspended 5 cm above floor level wearing a parachute harness. Maximum voluntary force exertions were measured with the subjects pulling the ripcord handle using their left, right and both hands at all locations. The results indicate that the thigh locations are superior in regard to pull forces for all hand applications (left, right, and both). Also, two-handed pulls yield the largest forces at all locations.

Effect of handle height on lower-back loading in cart pushing and pulling.

This paper presents results of a study conducted to estimate lower back loadings in cart pushing and pulling. Experiments were conducted in the laboratory using a cart. Six subjects with different weights (ranging from 50 to 80 kg) were tested for three different pushing and pulling forces (98, 196 and 294 newtons), three different heights of exertion (660, 1090 and 1520 mm high) and two different moving speeds (1.8 and 3.6 km/h). It was found that, in general, pushing a cart results in lesser lower-back loading than pulling. Subject body weight affected the lower-back loadings more significantly in pulling (50% increase as body weight increased from 50 kg to 80 kg) than in pushing (25% increase). Handle height of 1090 mm was found to be better than other handle heights in pushing while 1520 mm handle height was better for pulling in reducing lower-back loadings.

A review of physical exercises recommended for VDT operators.

This paper presents an evaluation of exercises that have been recommended for the prevention of musculoskeletal discomfort among VDT/office workers. 127 individual exercises were analysed for their suitability for performance in VDT workplaces. Additionally, each exercise was judged in terms of its safety and its compliance with principles of physiotherapy. Results showed that, in the majority of cases, the prepared instructions for the exercises were satisfactory and the exercises could be readily performed at the workstation. However, over a third of the exercises were conspicuous and potentially embarrassing to perform, and half would significantly disrupt the work routine. Additionally, a number of the exercises posed potential safety hazards, exacerbated biomechanical stresses common to VDT work, or were contraindicated for persons with certain health problems. These findings suggest a need for greater attention to both the practical and the therapeutic aspects of exercises promoted for VDT users.

Types of activities and body parts affected in the recommended exercises for VDT operators.

This paper presents results of an analysis of recommended exercises proposed for the reduction of musculoskeletal stress in VDT operation and similar types of work. Fifteen exercise programs consisting of 123 individual exercises were reviewed. Most of the programs exhibited some redeeming features from a practical and a professional standpoint. It was found that recommendations concerning exercises have been directed primarily to muscle stretching and relaxation. The body parts targeted by various exercises were back, leg, neck, shoulder, side and upper extremities. Maximum number of exercises were available for shoulder (35.8%) and upper extremities (17.9%). The exercises reviewed consisted of combinations of thirteen different activities. It was found that rotation (26.8%), stretching (20.3%), and flexing or bending (18.7%) were the most frequently employed activities.

Level of knowledge and misconceptions about cholesterol: gender and race differences.

This study highlights the differences in knowledge and misconceptions about cholesterol according to gender and race in the United States. Data were obtained from a randomly selected national sample of 1,068 adults. Respondents were asked a series of true-false questions covering such topics as recommended cholesterol levels, how cholesterol is reduced, the effect of diet, smoking habits, and exercise on cholesterol levels, etc. The results indicated that the knowledge level differed according to gender and race.

Maximum acceptable weight of lift for side and back lifting.

A series of laboratory experiments were conducted to find maximum acceptable weights in front, side, and back lifting. Fifteen college students participated in the experiment. Experimental trials for each type of lifting were conducted for 10 min for each subject at a rate of 4 lifts/min. Psychophysical methodology was used to find the acceptable weight based upon their perceived feeling of stress in the lower back. It was found that subjects are willing to lift the heaviest load using back lifting (average maximum acceptable weight: 41.5 lbs). Front lifting was the close second with 39.4 lbs. Also, there was a significant difference in maximum acceptable weight of lift between side lifting (average maximum acceptable weight: 25.5 lbs) and the other two types of lifting. It was also found that leg strength was a limiting variable for maximum acceptable weight in front lifting. Composite strength and shoulder strength were found to be limiting variables in side lifting. Composite strength was the limiting variable in the back lifting.

Impact of anthropometric and personal variables on grip strength.

This paper presents the results of a study to evaluate the effects of personal and anthropometric variables on grip strength. Weight, height, frame size, and Fat-Free Cross-Sectional Area (FFCSA) were the anthropometric variables included in the study. Sex and the amount of exercise were the personal variables included. A group of 33 female and 59 male students were used as subjects. A stepwise regression analysis was performed to find a model which can be used to predict grip strength. It was found that the sex and weight are two variables which account for maximum variation in grip strength among these variables. Although, FFCSA (r2 = 0.788) correlated strongly with grip strength but was not chosen in the model, possibly because of lower correlation between FFCSA and sex. Height and weight also seem to correlate with grip strength, but to a lesser extent.

Evaluating lifting tasks using subjective and biomechanical estimates of stress at the lower back.

The objective of this study was to evaluate five different lifting tasks based on subjective and biomechanical estimates of stress at the lower back. Subjective estimates were obtained immediately after the subjects performed the lifting tasks. Rankings for different tasks were obtained according to the perceived level of stress at the lower back. A biomechanical model was used to predict the compressive force at the L5/S1 disc for the weight lifted considering link angles for the particular posture. The tasks were also ranked according to the compressive force loading at the L5/S1 disc. The weight lifted in these tasks for obtaining the subjective estimate of stress was the maximum acceptable weight of lift (MAWOL). This was determined separately for each subject using a psychophysical approach. Subjective estimates of stress were obtained for infrequent lifting, specifically for a single lift, as well as for lifting at a frequency of four lifts per min. The results showed that a lifting task acceptable from the biomechanical point of view may not be judged as a safe or acceptable task by the worker based on his subjective perception. This may result in a risk of the worker not performing the recommended task or not following the recommended method.

Improving marketability of exercise programs: implications for health promotion in the workplace.

Musculoskeletal stress due to sedentary work has been a problem in workplaces. Exercise programs are available to help alleviate such stress; however, they have been adopted by few companies. The acceptability of these problems, that is their "marketability" will be enhanced if employee preferences regarding exercise in the workplace are taken into account during their design. A questionnaire was administered to employees engaged in sedentary work to determine employees' preferences about exercise programs in the workplace. Respondents preferred exercises that are targeted for specific body parts, have easy-to-follow instructions, are somewhat difficult but more beneficial, and can be completed in a private room. Marketability of exercise programs may be improved by focusing on these characteristics.

Lower back muscle forces in pushing and pulling.

In the investigation of lower back stress, the muscle forces of the erector spinae and the rectus abdominis are often calculated using the two-dimensional biomechanical model. These muscle forces are used to estimate the compressive forces at L5/S1 disc. This paper presents a study of the muscle forces predicted by a two-dimensional biomechanical model during pushing and pulling and myoelectric activity from the corresponding muscles. The goal was to investigate whether a simple two muscle torso model would reasonably estimate the muscle actions in pushing and pulling tasks. Six subjects participated in the experiment. EMG (rms) value was used as an indicator of muscle forces. The results show high correlation between the predicted muscle forces and the measured root-mean-square EMG values in trunk pushing and pulling (r2 = 0.93) and hand pushing and pulling (r2 = 0.96) in an erect posture with hips braced but low in hand pushing and pulling using a free posture (r2 = 0.37).