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Overexertion injuries comprise the largest category of nonfatal injuries among construction workers. These injuries typically occur when the biomechanical stresses associated with tasks such as lifting, carrying, pushing, etc., exceed the worker’s strength capacity. Two studies were conducted to measure the whole-body isometric strength capability of 56 construction workers. The first study examined the effect of four typical postures (2 symmetric lifts and 2 asymmetric lifts) associated with scaffold end frame disassembly. The effect of posture on isometric strength capability was significant; the strength capability ranged from 366 N to 676 N. The second study evaluated the effect of hand separation distance (46 cm, 86.4 cm, and 116.8 cm) and vertical hand placement (knuckle, elbow, and acromial heights) on isometric force during symmetric lifting postures. The interaction effect of hand separation distance - vertical hand placement on isometric strength capability was significant.

A stereoradiographic technique is described in which two simultaneous x-ray exposures of an instrumented subject are prepared and analysed, yielding a complete six-parameter statement of the position and orientation of the instrument package relative to a coordinate system fixed in the subjects bony anatomy. A description of the radiologic equipment is included as well as details of those devices developed especially for stereoradiographic exposure and system calibration. The analytical aspects of the technique are discussed in qualitative terms in the body of the paper leaving more rigorous treatments to appendices. A statement of the inherent errors of this technique is also included.

A six-accelerometer inertial tracking package currently in intensive use in measuring living human and human surrogate response to impact acceleration is presented and discussed. The discussion includes an enumeration of the various requirements imposed upon the package as well as its design and fabrication. The on-site calibration facility is described, including a discussion of the procedures for routine calibration of the packages. Accounts of the data acquisition link from the packages through the sled borne amplifiers to the hybrid computer are also included. Particular attention is devoted to the theoretical aspects of this system. A statement of errors is developed and compared to the various precision parameters of this system and to a general estimation of the dynamic response envelope demonstrating the overall feasibility of this approach.

In preparation of an analog of human head and neck, the reports by R. G. Snyder and others were noted which stated that initial position of the head and neck had a definite effect upon resulting response. An investigation was undertaken to attempt to quantitate this effect, as a part of a much larger study underway for several years. Thirteen human volunteer subjects ranging from the 5th to the 97th percentile in sitting height were exposed to -Gx impact acceleration at peak sled accelerations of 6G and 10G. Two angles of the neck relative to chair and two angles of the head relative to the neck for a total of four conditions were tested for each subject for the 2 peak acceleration levels giving a total of 104 experiments. Instrumentation consisted of 6 accelerometers and two-axis rate gyro at the posterior spinous process of the first thoracic vertebral body, 6 accelerometers at the mouth, and a two-axis rate gyro at the top of the head.