Twenty women were asked to generate forces using a dynamometer that were consistent with one of three different work-rest schedules (a low-, medium-, and high-force schedule). Each work-rest schedule consisted of 6 identical blocks of 10 work-rest cycles. Each of the 10 work-rest cycles lasted 1 min. The first work-rest cycle in each block consisted of a 6--s maximal voluntary contraction and a 54--s rest. The remaining 9 work-rest cycles in each block consisted of a submaximal contraction and a rest period. The desired force of the submaximal contraction, the length of this contraction, and the duration of the rest period remained constant within schedules but varied across schedules. The amount of physiological work was kept constant among schedules. The fatigue that developed in the medium-force schedule was significantly lower than that developed in either the low- or high-force schedule. A model was developed that predicted the amount of fatiguable strength at the beginning and end of each contraction of a work-rest cycle. When fit to the results from the experiment, the model explained 94% of the variance. The model can be used to predict the work-rest schedule that minimizes fatigue in a given repetitive job, thereby potentially increasing productivity and reducing the incidence of cumulative trauma disorders.
Get full access to this article
View all access options for this article.
References
1.
Armstrong, T. J., Foulke, J. A., Joseph, B. S., & Goldstein, S. A. (1982, February) Investigation of cumulative trauma disorders in a poultry processing plant. American Industrial Hygiene Association Journal, 43, 103–116.
2.
Barnes, R. M. (1968). Motion and time study.New York: Wiley.
3.
Bechtold, S. E., Janaro, R. E., & Sumners, D. L. (1984) Maximization of labor productivity through optimal rest-break schedules. Management Science, 30, 1442–1458.
4.
Borg, G. A. V. (1982) Psychophysical bases of perceived exertion. Medicine and Science in Sports and Exercise, 14, 377–381.
5.
Byström, S., & Fransson-Hall, C. (1994) Acceptability of intermittent handgrip contractions based on physiological response. Human Factors, 36, 158–171.
6.
Chaffin, D. B. (1975, July) Ergonomics guide for the assessment of human static strength. American Industrial Hygiene Association Journal, 36, 505–511.
7.
Clarke, D. H. (1962) Strength recovery from static and dynamic muscular fatigue. Research Quarterly, 33, 349–355.
8.
Deeb, J. M., Drury, C. G., & Pendergast, D. R. (1992) An exponential model of isometric muscular fatigue as a function of age and muscle group. Ergonomics, 35, 899–918.
9.
Fisher, D. L., Andres, R. O., Airth, D., & Smith, S. S. (1993) Repetitive motion disorders: The design of optimal raterest profiles. Human Factors, 35, 283–328.
10.
Gilbert, O. (1968). A manager's guide to work study. London: Wiley.
11.
Gilbreth, F. B., & Gilbreth, L. M. (1953). Fatigue study. In W. R. Spriegel & C. E. Myers (Eds.), The writings of Gilbreths (pp. 303–340). Homewood, IL: Irwin.
12.
Greenhouse, S. W., & Geisser, S. (1959) On methods in the analysis of profile data. Psychometrika, 55, 431–433.
13.
Grose, J. E. (1958) Depression of muscle fatigue curves by heat and cold. Research Quarterly, 29, 19–31.
14.
Huynh, H., & Feldt, L. S. (1976) Estimation of the Box correction for degrees of freedom from sample data in randomized block and split-plot designs. Journal of Educational Statistics, 1, 69–82.
15.
Janaro, R. E., & Bechtold, S. E. (1985) A study of the reduction of fatigue impact on productivity through optimal rest break scheduling. Human Factors, 27, 459–466.
16.
Johnson, S., & Ogilvie, G. (1972). Work analysis. London: Butterworth.
17.
Jones, L. A., & Hunter, I. W. (1983) Force and EMG correlates of constant effort contractions. European Journal of Applied Physiology, 51, 75–83.
18.
Kirkendall, D. T. (1990). Mechanisms of peripheral fatigue. Medicine and Science in Sports and Exercise, 22, 444–449.
19.
Laurie, N. (1992). Validation of the Gripmaster TM as an ergonomic tool for evaluating grip forces and wrist angles in real time (unpublished master's thesis). Amherst: University of Massachusetts, Department of Exercise Science.
20.
Lee, F. S. (1974). The human machine and industrial efficiency Easton, PA: Hive.
21.
MacLaren, D. P. M., Gibson, H., Parry-Billings, M., & Edwards, R. H. T. (1989). A review of metabolic and physiological factors in fatigue. In K. B. Pandolf (Ed.), Exercise and sports science reviews (pp. 29–67). Baltimore, MD: Williams & Wilkins.
22.
McFarland, R. A. (1971). Understanding fatigue in modem life. Ergonomics, 4, 1–10.
23.
Monod, H., & Scherrer, J. (1957) Capacite de travail statique d'un groupe musculaire synergique chez l'home [Capacity for static work in a synergistic muscle group in man]. Comptes Rendus des Seances de la Societe de Biologie et de Ses Filiales (Paris), 151, 1358–1362.
24.
Petrofsky, J. S. (1981) Quantification through the surface EMG of muscle fatigue and recovery during successive isometric contractions. Aviation, Space and Environmental Medicine, 52, 545–550.
25.
Price, D. D., McGrath, P. A., Ram, A., & Buckingham, B. (1983) The validation of visual analogue scales as ratio scale measures for chronic and experimental pain. Pain, 17, 45–56.
26.
Rich, G. Q. (1960) Muscular fatigue curves for boys and girls. Research Quarterly, 31, 485–498.
27.
Rohmert, W. (1960) Ermittlung von Erholungspausen für statische Arbeit des Menschen [Determiniation of rest breaks for static work in humans]. Internationale Zeitschrift fur Angewandte Physiologie Einschliesslich Arheitsphysiologie, 18, 123–164.
28.
Royce, J. (1958) Isometric fatigue curves in human muscle with normal and occluded circulation. Research Quarterly, 29, 204–212.
29.
Sahlin, K. (1992) Metabolic factors in fatigue. Sports Medicine, 2, 99–107.
30.
Schoenmarklin, R. W., & Marras, W. S. (1989) Effects of handle angle and work orientation on hammering: II. Muscle fatigue and subjective rating of discomfort. Human Factors, 31, 413–420.
31.
Silverstein, B. A., Fine, L. J., & Armstrong, T. J. (1987) Occupational factors and carpal tunnel syndrome. American Journal of Industrial Medicine, 11, 343–358.
32.
Sjogaard, G., Savard, G., & Juel, C. (1988). Muscle blood flow during isometric activity and its relation to muscle fatigue. European Journal of Applied Psychology, 57, 327–335.
33.
Streimer, I. (1971). Considerations of energy investments as determinants of behavior. In W. T. Singleton, J. G. Fox, & D. Whitfield (Eds.), Measurement of man at work (pp. 35–59). London: Taylor & Francis.
34.
Taylor, F. W. (1967). The principles of scientific management.New York: W. W. Norton.
35.
Ulin, S. S., Ways, C. M., Armstrong, T. J., & Snook, S. H. (1990). Perceived exertion and discomfort versus work height with a pistol-shaped screwdriver. American Industrial Hygiene Association Journa1, 51, 588–594.
36.
Wood, D. D., & Andres, R. O. (1992). Validation of grip force measured by force-sensitive resistors through comparison with prediction from EMGs. In S. Kumar (Ed.), Advances in industrial ergonomics and safety IV (pp. 789–796). London: Taylor & Frances.
37.
Wrosz, T. J., Deeb, J. M., & Drury, C. G. (1990) The effects of strength-testing schedules on muscle strength recovery following static work. International Journal of Industrial Ergonomics, 6, 249–253.
