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A biomechanical model for predicting paths of motion and the associated motion characteristics for the arm articulation joints is presented. The underlying principle of the model is that the average individual follows an optimizing criterion in performing his tasks. A detailed description of the model assumptions, mechanics, and formulation is presented for three-dimensional motions. Three approaches are presented for solving the model: (1) suboptimization (linear and geometric programming); (2) dynamic programming; and (3) simulation. The accuracy and the adequacy of the model in predicting human motion under planar conditions were tested and evaluated. Future perspectives and limitations of modeling human motion are outlined and discussed.

A considerable amount of research has been done to determine the magnitudes of forces man can exert on loads. However, very little has been done to determine the optimum configurations an operator should assume in front of a load to be most effective. This paper presents the methodology and results of an investigation concerning these skeletal configurations and selects an optimum for pushing as well as pulling of loads. In addition, a biomechanical analysis of the forces and torques developed at various joints is included.

Although several photogrammetric systems are commercially available, their cost limits the application of photogrammetric human factors studies. This paper describes a relatively low cost system developed at Texas Tech University to be used in connection with biomechanics and human performance studies. A detailed description of the basic theoretical and laboratory investigations of the various parameters which influence the design, construction, and use of the system is presented. The adequacy and accuracy of the system were measured by conducting two verification tests under static and dynamic orientations. Typical acceleration and velocity curves for human hand motion, obtained by the system, are presented.

SUMMARY SUMMARY An investigation was carried out to determine the effect of the independent variables of sex, weight carried and distance moved on the following dependent variables for three-dimensional hand movements: (1) maximum acceleration, (2) maximum velocity, (3) ratio between maximum velocity and average velocity, (4) per cent time until maximum acceleration is reached, (5) per cent time until maximum velocity is reached. Additional objectives were to determine the pattern and shape of acceleration and velocity curves, and to develop mathematical relationships to evaluate the velocity and acceleration at any time during a three-dimensional hand movement.

Human performance during a low-frequency vibratory environment was investigated. The performance measures of interest were the accuracy and total time of a whole-body orientation task. A zero vibration condition as well as frequencies of 2, 5, and 8 Hz. were studied. Amplitude was held constant at 0.09 in., resulting in acceleration intensities from 0.04 to 0.58 g. Performance was studied before, during, and after exposure to the vibration environment. Twenty male subjects participated in the investigation in both sitting and standing body positions. Vibration exposure times were 20 min. for all sessions. The task used in this investigation was a body orientation task that required subjects to orient their bodies as quickly and as accurately as possible toward one of a series of colored lights located at angles of 15, 30, and 60° on either side of a zero reference plane. The results indicated that the shortest travel time was obtained under zero vibration conditions but that most accurate performance was obtained under vibrations of 2 Hz. Differences in performance were also found between the two body positions and direction of orientation.

An experiment was designed using muscle electromyography to determine if an optimum cylindrical handle size exists. The experiment had two phases. One phase was concerned with an experimental task ...

Biomechanical modelling, just as physiological systems modelling, has become quite popular. Biomechanical analysis, and models investigating man's activities while in motion, require records of mot...

This paper describes an effort to study the simultaneous motion trajectories of a large number of human body landmarks of a pilot during upper limb motions typical of those necessary to fly an aircraft. The objective is to gather engineering anthropometric data necessary, from a human engineering point of view, in the design of aircraft cockpits and other similar manned work stations. Twenty subjects participated in an experiment conducted to record the movements. A photographic procedure combining slow speed motion picture and interrupted light photography was employed to record the movements. This paper describes the procedure and also presents a set of typical paths of movement obtained through such recording. Also mentioned are some of the preliminary findings regarding the motion characteristics of parts of the human body.

In the most basic sense, a model is a representation of reality and must be regarded as a tool to be used in the analysis and/or design of a real system. If models are as complex and difficult to control as reality, there would be no advantage in their use. Fortunately, models usually can be constructed that are simpler than reality but that will predict and explain reality with a reasonable degree of accuracy. These characteristics of simplicity and accuracy provide the greatest advantage with models and the reason for their widespread use in analyzing complex systems. Unfortunately, the simplification of reality, as well as other limitations of models, generates the prime causes of erroneous interpretation of the results of model manipulation. Considerable caution must be exercised in the evaluation and application of the results obtained from models; however, when the pitfalls are avoided, advantages such as efficiency and feasibility of analysis result.

This research was conducted for the purpose of studying the performance and recovery characteristics of men when subjected to low-level, whole-body vertical sinusoidal vibration for durations of one to two hours. Several male subjects performed a vertical compensatory tracking task using a CKT display according to three work-rest schedules under both normal and vibratory environments. The vibratory environment was that of vertical sinusoidal vibration with a frequency of.5 cps and an amplitude- of 0-08 inches resulting in an acceleration intensity of approximately 0.20 g. The working period was divided into equal intervals during which performance was continuously monitored. Decrement of performance was measured using absolute error score. Results and conclusions are presented regarding performance decrement and recovery under varying work-rest schedules. Optimum work-rest schedules and implications of control tasks under a vibratory environment are discussed.

The problem of sustained efficiency in monotonous perceptual tasks is particularly pertinent to industrial inspection. The present research has extended Holland's techniques of behavioral analysis to an industrial framework by analyzing the assembly-line inspection of products. By utilizing four basic schedules of defective product (fixed ratio, variable ratio, fixed interval, and variable interval), it was demonstrated that the detection of defectives can serve as reinforcements for observing behavior. In addition, the vigilance decrement associated with the inspection task was shown to be a function of the differential reinforcement of observing responses. The fact that a rather precise control can be exerted by the environment over the operator's observing behavior has important implications for industry. Some of these implications are discussed.