Occupational Strain Models

Occupational stress or strain models are used to understand how aspects of work or its environmental demands affect an individual’s psychology and physiology, and thus explain or predict the stressors and onset of strain. Some of the main components of these theories include workplace- demands, physical and mental control, rewards, and support. As discussed in the previous section, stress stimuli or stressors are commonly divided into factors outside the individual (organizational or environmental characteristics) and those within the individual (e.g. personal attributes, demographics, capacity for adaptation). There are many interactive models of occupational stress or strain, however this study will focus on the Demand-Control model (Karasek, 1979). This model integrates the person and environment fit to occupational characteristics and to strain symptoms.

The Work Strain Model

One theoretical framework of this study is based in the original demands-control- (DC) (Karasek, 1979) or more recently developed demand-control-supports model (DCS Model) or

predict the accumulated effects of stressors and coping on the individual, specifically in the workplace. In their model, they propose that strain symptoms develop from a perceived lack of fit between the person and the job environment (Blau, 1980; Karasek, 1979). The lack of fit is between the psychological demands and the amount of personal control or decisional latitude one has on the job. Karasek, Russell, and Theorell (1982) initially found in several studies that when psychological work demands were high, and the decisional latitude was low, more individuals developed health problems. The ability to use one’s skills, and authority to decide which job skills or strategies to use are the two components ofjob control or decisional latitude (Karasek & Theorell, 1990).

The DCS Model was chosen for this study because of several key features it possesses. The model is 1) multidimensional, 2) proposes that active learning is a stress coping mechanism, that perceived behavioral control (defined as decisional latitude) is the primary determinant of occupational strain development under conditions of high psychological demand and 3) it uses physical, emotional or behavioral problems as “hard evidence” of strain manifestations (Karasek, 1981; Karasek & Theorell, 1990). Figure 3 shows interrelationships between the Work Strain Model and the model used in this study. Coping mechanisms such as exercise, self-efficacy, or social support may act to both reduce the initial perception of stress as well as buffer against stress leading to strain symptoms. The dashed arrows that intersect the horizontal arrow between the boxes represent “buffering” effects. This study will not measure the buffering effects of the variables. Any differences in correlations will be attributed to both direct and indirect effects.

Figure 3: How Demand Control Theory fits in. Interactions between the three independent variables and job demands or job decisional control and the subsequent expression of strain in poor health or mental burnout.

Social support is part of the current model and the DCS model and decisional latitude or Job Control is very similar to self-efficacy in the central concepts. However, exercise behaviors are unique, in that the particular combination of exercise with self-efficacy and social support has not been examined. Many studies have examined exercise behaviors affect on attenuating strain symptoms and burnout. Some studies have even examined exercise and social support on strain or exercise and self-efficacy on strain (Manning& Fusiler, 1999).

Stress Resistance or Coping Skills

As previously mentioned, strain occurs when the chronic stress stimuli from work exceed the stress resistance or coping skills within that individual and this results in an actual negative physical or mental change. In the Demands-Control-Supports (DCS) Model or Work Strain Model, an individual has an active role in determining the effects of stressors. Stress resistance

refers to those characteristics within an individual that counter or decrease the expression of a “negative outcome.” Rewards, support, active learning, and physical action are commonly recognized stress resistance or coping mechanisms. Karasek and Theorell (1990) found that both social support and certain types of physical activity have significant moderating or buffering

Demands vs. Control Interactions/Perceptions

(Stress)

Social Support _{Self-Efficacy}

Strain- Burnout & Health

Exercise

effects on occupational strain development. Their current model associates physical problems, including health status and incidence of cardiovascular disease to psychological work demands, decisional latitude, and social support experienced or perceived by the worker.

Weaknesses in the Model

Although the DCS theory is widely used and was substantiated in early studies on large heterogeneous populations (Karasek, 1979, 1981, Theorell, 2001), several studies have been performed where it did not predict strain symptoms very well and support for it was inconclusive (Jones & Fletcher, 1996; Pieper, LaCroix & Karasek, 1989). Several studies have been

performed to improve upon certain factors in the DCS that were not well controlled

(Schaubroeck & Merritt, 1997; deRijk, LeBlanc, Schaufeli & deJonge, 1998). Recently, Kuper and Marmot (2003) studied a very large population across a mean follow-up period of 11 years. They found that people who were in the high strain condition (high job demands, and low decision latitude) were at the highest risk for heart disease. They did not find social support to affect this relationship and low decisional latitude was less consistent. In contrast, another very large and recent study in China found psychological job demands were not correlated to strain scores (Cheng, Luh & Guo, 2003). Cheng et al. concluded that their test closely corresponded to the Job Content Questionnaire and the lowest job satisfaction was found in high demand, low control, and low social support conditions. These many studies not supporting the model suggest the need for further research.

Another study closely related to this observed what would influence the acquisition of new knowledge or facilitate active learning. The study was testing the demand control model’s theory on high demand and high control leading to active learning. The results showed high training motivation was associated with low task constraints and this was associated with

supervisor social support and positive self-efficacy beliefs (Carter, 2003). A previous study to Carter found self-efficacy moderated the effect between training method and anxiety. Tutorial method training was negatively related to anxiety in new comers with high self-efficacy and positively associated with anxiety in those with low efficacy (Gist, 1989).

A different study testing the active learning hypothesis found that the low strain condition or low demands and high control actually facilitated learning and self-efficacy better than the proposed high-demand and high-control. The longitudinal study also found that when jobs were transitioned from a low strain to a high strain condition, a strong deterioration of learning and self-efficacy occurred (Taris, Kompier, Delange, Schaufeli, & Schreurs, 2003). Thus, regardless of what demand and control condition maximized learning, self-efficacy was closely associated with learning and reduced strain. These authors concluded, “it seems fair to conclude that the evidence for Karasek and Theorell’s (1990) active learning hypothesis is actually quite weak (p.6)”. Another study by Kirkcaldy and Cooper (1993) found that exercise did not serve as a buffer in the stress-health linkage in British and German managers.