Approximately 2 million deaths every year are attributable to physical inactivity; and preliminary findings from a WHO study on risk factors suggest that sedentary lifestyle is one of the ten leading causes of death and disability in the world. Physical inactivity increases all causes mortality, doubles the risk of cardiovascular disease, type II diabetes, and obesity. It also increases the risks of colon and breast cancer, high blood pressure, lipid disorders, osteoporosis, depression and anxiety." (World Health Organization 2002)
The transtheoretical model (TTM) of behaviour change, developed in the late 1970s and early 1980s, is a model of intentional behaviour change which focuses on the decision making of the individual. Originally designed to describe changes in addictive behaviour, the TTM has expanded to include the adoption of preventive health behaviours and the use of medical services (Burkholder & Evers, 2002).
In the early 1990s, Marcus and others applied the TTM to exercise behaviour (Marcus, Selby et al., 1992). Since then, several researchers have used the TTM to develop exercise interventions. The TTM suggests that people do not change all at once, rather they move through a series of five stages toward behaviour change. There are three pre-action stages and two action stages, each defined by a temporal component related to the behaviour change. People in the first stage of pre-contemplation are not exercising and have no intention to exercise. In contemplation, people intend to exercise in the distant future, beginning sometime in the next 6 months.
Preparation is the third stage where people intend to begin to exercise sometime in the next 30 days. The next stage, action, occurs when the person begins to exercise for at least 1 day to 6 months. In the stage of maintenance, the person has been exercising consistently for at least 6 months. The transtheoretical model proposes a set of constructs that are thought to influence movement through stages of change. These constructs include self-efficacy, decisional balance, and the processes of change. Self-efficacy is the belief in one's capability to engage successfully in a specific behaviour. Decisional balance is the evaluation of the pros and cons of engaging in the target behaviour. The processes of change are the cognitive and behavioural strategies used for changing behaviour and moving through the five identified stages: consciousness raising; dramatic relief; environmental re-evaluation; self re-evaluation and social liberation.
Decisional balance, an analysis of the pros and cons of the behaviour change, is believed to influence exercise behaviour. Based on the work of Janis and Mann (1977), perceived costs and benefits to oneself and significant others influence behaviour change. Pros tend to increase to action and level off, while cons decrease with movement to each subsequent stage. Most of the evidence for exercise indicates that the crossover occurs during the preparation stage, which is consistent with several other behaviours. Prochaska and DiClemente identified 10 basic processes or strategies people