The health belief model, grounded in John Atkinson’s expectancy–value theory of achievement motivation, proposes that people are rational decision makers who, during decision making, take into consideration advantages and disadvantages associated with physical activity. The theory also posits that motivation is unidimensional and that the construct of intentions, which represents motivation, is one of the most immediate determinants of physical activity. Therefore, the health belief model is a motivational theory that explains intention formation. It does not explain the processes by which people carry out their previously formed intentions.
The health belief model proposes that an individual’s readiness (intention) to engage in physical activities is a function of the perceived vulnerability to a health condition and the probable severity of that condition. Consistent with the expectancy– value model, the model posits that readiness is determined by a person’s beliefs about the benefits to be gained by a particular behavior such as exercise weighted by one’s perceived barriers associated with physical activity. Finally, the model predicts that readiness to action may not result in physical activity unless some instigating event occurred to set the action process in motion. Irwin M. Rosenstock termed such instigating events as cues to action.
Overall, the health belief model predicts that strong intentions emerge when individuals feel vulnerable to an illness, the illness is perceived to be severe, and individuals believe that physical activity will reduce the health threat associated with the illness. For example, individuals may feel susceptible to cardiovascular disease because they have a poor diet and had been told by their physician that they have hypertension. They may also believe that regular exercise may reduce the threat of cardiovascular disease. According to the model, these perceptions are likely to motivate the individual to participate in physical activity.
Thus far research has shown that perceived severity and beliefs about the benefits of physical activity exert strong influences on readiness to engage in that behavior, while perceived severity and barriers have lesser impact. In addition, evidence suggests that the direct effects of perceived vulnerability, severity, susceptibility, benefits, and barriers on physical activity are small and are mediated by readiness. Further, there is evidence to suggest that the health belief model does not sufficiently capture all of the psychological determinants of physical activity and that the model may benefit from considering effects of other constructs such as self-efficacy on intentions and behavior.
One limitation of the health belief model is that it does not define perceived vulnerability clearly, nor does it specify how different variables combine in influencing readiness and physical activity. For example, it is unclear what type of vulnerability to disease should be measured. Shall we measure vulnerability to cardiovascular disease or vulnerability to back pain? In addition, vulnerability to cardiovascular disease may not predict the physical activity behavior of young individuals, given that getting a heart attack is a remote prospect for youth. Moreover, the model does not explicitly state whether perceived vulnerability would facilitate exercise or healthy dieting given that both behaviors would be effective in ameliorating cardiovascular disease risk. Hence, the model does not address behavioral choice. As a result, empirical evidence related to health belief model varies greatly across studies because different studies have used different operational definitions for psychological constructs or populations.
An important function of research is to provide information about the content of interventions. Generally speaking, the greater the relative importance of a factor in predicting physical activity intentions, the more likely it is that changing that factor will influence intentions and ultimately physical activity behavior. Given that studies adopting the health belief model have shown that appraisals related to perceived vulnerability and perceived severity, and appraisals related to benefits and barriers influence intentions to exercise, it can be suggested that attempts to change exercise behavior should try manipulate threat appraisals alongside perceived benefits and barriers. An important question, therefore, is how health appraisals can be influenced.
Threat appraisals can be manipulated through fear-arousing communications that highlight (a) the painful and debilitating effects of an illness (perceived severity) and (b) that people who do not exercise regularly are vulnerable to heart disease (perceived vulnerability). Physical activity benefits can be manipulated by exposing people to information that explains the effectiveness of exercise in preventing disease. The negative impact of perceived barriers on exercise can be circumvented by asking people to engage in types of physical activities that are relatively easy to perform or by prompting people to invent coping strategies that help them cope with barriers.
One caveat of interventions based on the health belief model is that although they may be successful in strengthening intentions, they may not always bring substantial changes in exercise behavior. Therefore, it cannot be expected verbatim that application of this model will produce strong effects on exercise behavior. Instead, the effectiveness of the health belief model in changing exercise behavior may be enhanced through the implementation of volitional techniques that can help people translate intentions into actions. Another limitation of the health belief model is that the threatening messages can sometimes undermine rather than enhance intentions. Generally speaking, people have a desire to protect or enhance sense of self. As a consequence, they may not easily accept and endorse health-threatening messages. Therefore, fear-arousing communications should be designed and applied with caution. Health messages should not be too threatening because otherwise interventions will elicit a maladaptive coping response. For example, telling individuals that exercise reduces the risk of cardiovascular disease may be more easily accepted than telling individuals that they will have a heart attack if they do not exercise on a regular basis. It is therefore always desirable to pilot intervention strategies in a small group of people before conducting largescale interventions.
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