Ergonomic Models of Anthropometry, Human Biomechanics and Operator-Equipment Interfaces

The Committee on Human Factors was established in October 1980 by the Commission on Behavioral and Social Sciences and Education of the National Research Council. The committee is sponsored by the Office of Naval Research, the Air Force Office of Scientific Research, the Army Research Institute for the Behavioral and Social Sciences, the National Aeronautics and Space Administration, and the National Science Foundation. The workshop discussed the following: anthropometric models; biomechanical models; human-machine interface models; and research recommendations. A 17-page bibliography is included

Examination of the effect of tool mass and work postures on perceived exertion for a screw driving task

Eighteen subjects with industrial work experience drove screws into perforated sheet metal at three vertical (64, 114 and 165 cm) locations with a pistol-shaped tool, and at two horizontal (13 and 63 cm) work locations using an in-line tool. Both air-powered tools were varied in mass (1, 2 and 3 kg). Subjects drove screws using each tool mass at all work locations. After driving 25 screws at a particular work location/tool mass combination, subjects assessed their perceived exertion for that condition using the Borg ten-point ratio rating scale and completed a body part discomfort survey. Both tool mass and work location were significant factors in determining the ratings. As tool mass increased, so did the ratings of perceived exertion (18% to 100%). The lowest ratings of perceived exertion were at 114 cm on the vertical surface and at 13 cm on the horizontal surface. For the vertical surface, the body part discomfort data revealed that the low back and the right arm were often cited as uncomfortable at 64 cm, the right arm was identified as uncomfortable at 114 cm, and the right arm and the chest were cited as uncomfortable at 165 cm. For the horizontal surface, at both 13 cm and 63 cm, the neck and the right arm were identified as uncomfortable.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30647/1/0000289.pd

A single metric for quantifying biomechanical stress in repetitive motions and exertions

The relative effects of repetition, force and posture were studied in order to investigate how continuous biomechanical measurements can be combined into a single metric corresponding to subjective discomfort. A full factorial experiment was conducted involving repetitive wrist¯exion from a neutral posture to a given angle against a controlled force. Seven subjects performed the task using two paces (20 and 4 motions/ min), two force levels (15 and 45 N) and two angles (15 and 458 ) for 1 h each. Discomfort was reported on a 10 cm visual analogue scale anchored between`no discomfort' and`very high discomfort' . Repeated measures analysis of variance showed that all main effects were statistically signi® cant (p <0× 05) and no signi® cant interactions were observed. A linear regression model was ® tted to the data and used for generating frequency weighted digital ® lters that shape continuous recordings of repetitive motions and exertions into an output proportional to relative discomfort. The resulting high-pass digital ® lter had a 22 dB/decade attenuation slope. A simulated industrial task used for validating the model involved repetitively transferring pegs across a horizontal bar and inserting them into holes against a controlled resistance. Angular wrist data were recorded using an electrogoniom eter and ® ltered. Six subjects performed the task of the three conditions consisting of (1) 158 wrist¯exion, 15 N resistance and 6 motions/min, (2) 158 wrist¯exion, 45 N resistance and 12 motions/min, and (3) 458 wrist¯exion, 45 N resistance and 15 motions/ min. Subjective discomfort was reported after performing the task for 1 h. Pearson correlations between subjective discomfort ratings and the integrated ® ltered biomechanical data for individual subjects ranged from 0× 90 to 1× 00. The pooled correlation across subjects was 0× 67. This approach may be useful for physical stress exposure assessment and for design of tasks involving repetitive motions and exertions