Physiological Responses to Work Load: An Exploratory Field Study. Robert D. Cnplan and John R. P. French, Jr.

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1 Physiological Responses to Work Load: An Exploratory Field Study Robert D. Cnplan and John R. P. French, Jr. Research Center for Group Dynamics, University of Michigan This study is part of a program of research on the effects of stresses in the social environment on health particularly on coronary heart disease.^ I t focuses on the ubiquitous stress of work overload, both objective and perceived, and the psychological and physiological strains which may ensue. Our earlier studies have demonstrated that work overload is associated with low job satisfaction, high job-related tension, dissatisfaction with the boss, and symptoms of physical anxiety (Kahn, Wolfe, Quinn, Snook, & Rosenthal, 1964; Kraut, 1965). More recently we found that the work load of university professors was associated with cholesterol level, a well-known risk factor in coronary heart disease (French, Tuppe.r, & Mueller, 1965; -Brooks & Mueller, 1966). ' The correlation was low but significant (r=.25, p<.01). Others have! reported that tax accountants show increased cholesterol as the tax deadline approaches (Friedman, Rosenman, & Carroll, 1958); and several - I studies have found that students show similar increases' at examination, time. v The main purpose, of the present study is to test the hypothesis that objective and perceived overload w i l l increase both the level of i cholesterol and the heart rate (IIR). A secondary methodological purpose ; is to explore whether the use of telemetry to record the HR of men performing their normal work can give us 'a more detailed knowledge of those stresses in the environment which are producing physiological strain and eventually disease. _j.

2 2 Method Design The Headquarters of NASA in Washington, D. C. was chosen as a f i e l d site because i t had high work loads with severe deadline pressures. Between May and September 1967, 22 white-collar males, ages 22 to 54, were observed on three separate days selected for maximal variation in work load. During each two-to three-hour observation period, the Ss were observed by a two-person research team and monitored for heart rate. After each period,, the Ss.were interviewed with regard.to work load pressures, and bled to obtain serum for biochemical analyses. Tn addition, the Ss f i l l e d out a questionnaire on job overload. Variables and Measures Our measure of the independent variable, objective.overload, was based on an index obtained from observer records. This index was defined as the total number of phone calls and office visitors.encountered by each S_ per 100 minutes of observation. The measure of subjective overload which was obtained on day three is a six-item factor from the previously cited study'of university professors (French et a l., 1965). The measure requires that subjects rate, on a four-point scale, the extent to which they feel certain aspects of their jobs constitute a source of pressure for them. The following are examples of items making up this measure: 1. Overwhelming work load. Too many things need to be done. 2. Being torn by conflicting demands. 3. The feeling of never having any time. Cholesterol, one of the two dependent variables, was measured at

3 3 the Institute for Social Research's biochemical laboratory using an automated version of the method of Zak. Our second dependent variable, HR, was monitored using a pocketsized telemetry unit which the- S_ could wear inconspicuously over his belt. The telemetered heart beats were picked up by an FM receiver and transformed into a beats-per-minute measure. This measure was then transcribed onto a paper chart recorder as a continuous record. HR and cholesterol were unrelated on a l l three days (r=.33,.05,,07) indicating that they.are mutually independent response measures. Results Between-individual Analyses of HR and Cholesterol The results presented are based on data obtained during each of the three days. We want "to note, howeverthat only data from the third day were used in analyzing the factor score on subjective overload, because this measure was only administered on day three. A l l p_ values presented are for one-tailed tests of significance. The relationships obtained on the third day are outlined in Figure 1. Insert Figure 1 here Although the.first-order, correlation between mean HR and objective overload is non-significant, the three correlation coefficients representing the three days suggest a positive trend (r=.19,.14,,39). Mean HR, however, is strongly and significantly related to subjective overload (r=.68, p<.001). Subjective and objective overload arc correlated.64. Some Insight into these relationships is gained when one obtains the correlation between objective overload and IIR with subjective

4 4 overload par tin led oul. The correlation drops from.39 (p<.05) to a non-significant.08. This suggests that IJK is primarily determined by the way a person perceives the environment and only indirectly by the objective overload. Supporting this Interpretation, we find that the multiple correlation of both objective and subjective overload with I1R is only.68, which i s the same as the f i r s t-o r d e r c o r r e l a t i o n with subjective overload alone. Cholesterol level, like HR, is positively related to both objective and subjective overload. The correlations with objective overload for the three days arc.40,.33, and.33 (p<.05, p<.10, p<.10) respectively. The correlation between cholesterol and the subjective measure is.41'(p <. 05). Unlike their relationships to HR, however, both objective and subjective overload seem to independently influence cholesterol; thus, the multiple correlation is raised to.46 (p C.05). Within-individual Analyses of HR and Cholesterol. Two analyses of within-individual variation in HR'in relation to changes in objective.overload were carried out. One analysis examined variance between days while the other'analysis examined changes within any one day. Because blood samples were only taken "once per day, only between-days analysis of cholesterol was possible. The HR data comparing the highest and lowest objectively overloaded days for each S_ indicate a non-significant trend for HR. to be higher with increases in objective Overload (t=l.40, p <C. 10). The second analysis of within-day HR changes, looked at only those periods of time when the S/s environment directly changed from working alone to an office v i s i t or to a phone call. The highest 11R values from

5 5 the last 13 seconds of working alone wore compared with the. highest values from the f i r s t 15 seconds of the v i s i t or phone call. The results show that seven of the 22 Ss showed significant increases in 1IR (p <i.05) with the onset of office visits and phone conversations. Only about one out of the 22 Ss should be expected to show such an increase by chance. There were no significant reversals. Cholesterol also shows a positive but non-significant tendency to be higher for days with high objective overload (t=1.28, n-21). Discussion These results confirm Kraut's (1965) earlier finding that objective work load and subjective overload, though correlated (r=.64), have different effects; and that subjective overload sometimes, but not always accounts for a l l of the effect of objective overload. The reasons why between-individual rather than within-individual.analyses lend stronger support for a positive relationship of HR and cholesterol to objective quantitative work load and subjective overload may l i e in the discovery of relevant individual differences in personality and autonomic reactivity which interact with changes in the. environment. Further work is being carried out to explore these possibilities. Ref erenc.es Brooks, G. W., & Mueller, E. Serum urate concentrations among university professors. Journal of the American Medical Association, 1966, 195, French, J. R. P., Jr., Tupper, C. J., & Mueller, E. F. Work Load of UnIvcrsity Professors. Michigan: Cooperative Research Project No. 2171, Institute for Social Research, University of Michigan, 1965.

6 6 Friedman, M., Roscnman, R. I I., & Carroll, B. Changes in the serum cholesterol and blood clotting time in men subject to cyclic variations of occupational stress. Cijj^ul^aj^o 11, 1958, 17.* 852- Kahn, R. L., Wolfe, 1). M., Quinn, R. P., Snoek, J. D., &. Rosenthal, R. A. Qj^^l^ aaioi^j- Stress: Studios_ln Role Conflict and Ambiguity. New York: Wiley & Sons, Inc., 1964, Kraut, A. A study of role conflicts and their relationship to job satisfaction, tension, and performance. Michigan: Doctoral thesis, University of Michigan, Footnotes The authors want to. thank Margaret Child, M. D.. and Robert Toronto for their assistance in conducting this study. The study was supported by NASA grant NGR I85 and done in cooperation with their medical department, Legend for Figure 1 Figure 1. The relations.of objective overload and subjective overload to cholesterol and heart rate. J

7 Partial r=.24 ^-^\jy Cholesterol Objective Overload : > Subjective Overload Partial r=.08 ^.^Heart Rate

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