There are around 2.7 million people diagnosed with diabetes in England, 90% of who have Type 2 diabetes (UK Health and Social Care Information Centre 2013); a chronic disease characterised by the body’s inability to regulate blood glucose concentrations. Incidence rate has been strongly associated with physical inactivity. (National Institute for Clinical Excellence 2012), which poses challenges for the design of physical activity interventions that both promote physical activity participation and encourage long term subscription to a physically active lifestyle.
Transtheoretical Model (TTM)
The Transtheoretical Model of change (TTM; Prochaska & DiClemente 1982) has dominated empirical evidence about the making of behavioural change. TTM stipulates behaviour change, ie, physical activity, is cyclical and involves progression through five stages. Those reporting no current or future intention to change current activity levels are categorised as being in a precontemplative stage. Those thinking about making changes but not acting on thought are categorised as contemplative. Those making small changes on an irregular basis are categorised as being in a stage of preparation. The action stage represents people who have recently increased activity levels on a regular basis and the final maintenance stage represents those performing regular physical activity for more than 6 months. The aim is to encourage people to progress through stages via goal setting, decisional balance (weighing up pros and cons of activity) and self-monitoring (Avery, Flynn, Van Wersh, Sniehotta & Trenell 2012).
Strengths and limitations of TTM
Empirical evidence has associated TTM based intervention with short term improvement in glycaemic control in diabetic populations (Zanuso et al 2010). However, there are limitations to this model’s utility for such populations. Firstly, although broadly categorising people into distinct stages and timescales can aid understanding about facilitators/barriers to change, broad categorisation into a stage does not take into account fluctuating health difficulties associated with Type 2 diabetes that may result in a person moving back and forth between stages for reasons outwith perceived control, ie cardiovascular complications. Thus people may be categorised in a particular stage but unlikely to “progress” due to ill health. Secondly, the TTM model proposes people can move back and forth between stages, which may strengthen likelihood of behaviour change as people learn from mistakes (Prochaska & DiClemente 1982). However, within Type 2 diabetes populations it may be difficult to assess whether people move across stages in response to a trigger or consequence. More specifically, engaging with regular physical activity might be “triggered” by a fear of developing diabetes related health complications, and/ or social triggers such as concerns from significant others and/or medical teams about one’s health. Alternatively, engaging with regular physical activity may be a “consequence” of reward gained from activity, improved glycaemic control and psychological well-being. Thus the TTM doesn’t help to fully understand the variables that explain stage transition.
Evidence for long term efficacy
Evidence from applied studies suggest that a stage based activity programme based on TTM philosophy is effective in supporting people with diabetes to make short term changes in activity, however activity frequency returns to baseline levels over the long term (Krug, Haire-Joshu & Heady 1991). The heterogeneous nature of interventions (ie group versus individual format), cross sectional designs, and a lack of details about intervention content also limit generalisation and replicability of findings.
In light of the above, it is suggested alternative psychological models are worthy of further exploration to help develop empirically coherent and robust formulations about physical activity and adults with long term conditions such as diabetes. Further work to understand the complexity of factors contributing to long term enthusiasm for physical activity particularly amongst adults with Type 2 diabetes is also suggested.