Year

2001

Degree Name

Doctor of Philosophy

Department

University of Wollongong. Dept. of Biomedical Science

Abstract

Physical activity was once an obligatory part of daily life but in recent decadescustomary physical activity has been replaced with inactive occupational, domesticand recreational pursuits making people more sedentary in the process. Decreased physical activity levels preceded the rapid onset of many modern lifestyle diseasesincluding cardiovascular disease, hypertension, obesity and Type II diabetes and assuch physical activity is now recognised as not only a major risk factor for these diseases but an effective means of preventing illness and enhancing quality of life.

Unfortunately, the accumulating scientific evidence surrounding the benefits ofphysical activity has not translated into increased participation levels. Insomuch, ithas been estimated that at least 20% to 30% of industrialised countries areinadequately active for health and, certainly within Australia, more needs to be doneto promote physical activity to the 50% of the NSW population aged over 18-years of age who were reportedly inadequately active for health in 1994.

Clearly there is a need to develop, implement and evaluate interventions thatencourage people to increase their level of physical activity. It is important to targetinterventions towards people who are insufficiently active, where the greatest gain inpublic health may be expected. One behaviour change theory, the Transtheoreticalmodel has recently been applied to the promotion of physical activity. The keyconstruct of the Transtheoretical Model is the Stages of Change, which may be used to determine individuals' readiness for change. The Stages of Change also enableindividualised approaches to physical activity promotion to be established within amass-distributed intervention.

The main aim of this thesis was to examine whether a low-cost, self-help printintervention based on the Stages of Change delivered through the mail couldeffectively promote moderate intensity physical activity to a large sample of adultsrandomly selected from the community. To achieve these aims, it was first necessaryto develop the low-cost, self-help, stage based print intervention. The print intervention was developed after a thorough review of existing materials and wasevaluated in focus groups before being produced on mass for the proposed randomised controlled evaluation trials.

To evaluate the effectiveness of the self-help print intervention on self-reportedphysical activity participation in the short (2-months) and medium term (6-months),two randomised controlled trials were conducted. Study I, the Illawarra RCT , wasconducted using a sample (n= 462) of adults aged between 40- and 60-years selected from residents of the Illawarra, (a regional community located in the State of New South Wales (NSW)). Study II, the NSW RCT , replicated Study I but was conductedusing a larger sample (n=719) selected from residents aged between 18- and 75-yearsof age living in the State of N S W . All data were collected using self-report telephone interviews. Approximately 1-week post baseline, participants in both trials werestratified by Stage of Change and randomly allocated to either an intervention orcontrol group. The randomly allocated intervention group participants were then sent the self-help print intervention through the mail. Thereafter, all study participantswere followed-up at 2 and 6/8-months post baseline. Process evaluation of receiptand use of the self-help print intervention was conducted 4- to 6-weeks post baselinein the Illawarra RCT and at 2-months in both trials.

Data were analysed by Intention to Treat (ITT) and as well as Treatment Received(TR) and Treatment Received and Read (TR&R), using descriptive, bivariate,repeated measure ANOVAs and logistic regression analyses. Various definitions of adequate physical activity were applied to the data to determine the effects of theself-help print intervention, including reported time spent being physically active, theactive Stages of Change and estimates of adequate energy expenditure. Furthermore,criterion estimates of adequate physical activity were also applied to the data,including accumulating at least 150-minutes of physical activity per week and anincrease of at least 1-hour per week more physical activity between follow-up periods.

Both studies sustained high follow-up response rates, as well as good recognition andusage rates of the intervention materials. Significant positive results were observedin the Illawarra RCT where in comparison to the control group, the intervention group reported significant increases in time spent walking and in total physicalactivity per week at the 2-month follow-up. It also appeared that the intervention wasparticularly effective for those participants classified as inadequately active at baseline. The intervention group participants who were inadequately active at baseline were 1.88 (95% CI = 1.13-3.13) times more likely to report at least a 1-hour increase in total physical activity between baseline and 2-months when compared tothe inadequately active control group participants at baseline. In addition those participants who were least educated in the sample (< 10-years formal education)were also 1,75 (95% CI = 1.05-2.94) times more likely to report the 1-hour increase between baseline and 2-months than the more educated participants in the sample.Significant progression through the Stages of Change was also observed in the Illawarra RCT between baseline and 2-months. The significance of the results wasimproved as the analyses focused on actual receipt (TR) and use (TR&R) of the self help print intervention materials. These positive effects were not maintained at the 6-month follow-up assessment. However, there was a significant number of the intervention group participants who had taken the first step to increase their total physical activity by at least 1-hour at 2-months, who actually maintained that increase up to 6 months. However, the long-term effectiveness of the self-help print intervention remains questionable for those participants who do not take action in the first 2-months. Similar results were observed regardless of the analytic strategy oroutcome measures used.

Unlike the Illawarra RCT, the results of the State-wide NSW RCT did not support the short-term effectiveness of the self-help print intervention. There were nosignificant differences between the two study groups (inadequately active participants at baseline), in terms of changes in reported physical activity, Stage of Change progression or 1-hour increases in total physical activity in the between baseline and 2-months. One interesting finding was that there was a significant number of the inadequately active intervention group participants who reported at least a 1-hour increase in total physical activity between baseline and 8-months. However, in the TR and TR&R analyses the significance of the results diminished as the analyses became more focused in terms of actual receipt and use of the intervention materials. Therefore, it appeared unlikely that the self-help print intervention was responsiblefor the effects observed in the ITT analyses between baseline and 8-months. Other variables such as being single, being male and reporting some intention to be moreactive in the future appeared to be more significant in the NSW RCT logistic regression analyses. Again these findings were consistent across analytic strategies and no intervention effect was apparent.

Both trials experienced some of the usual challenges associated with community based research, and some of the contextual differences between the two trials may help to explain the difference observed in the main findings. For example, the seasonal effects of administering the intervention and the diversity of the sample (Regional verses State-based) that incorporated a variety of different environmental situations and conditions, may partially account for the different results between the two studies. Whilst the increases in reported physical activity in the Illawarra RCT were clinically modest, they may go some way in addressing the public health problem of inactivity in whole communities. The main findings also suggest there were some short-term benefits of implementing the intervention at a regional level,but not at the state level. Regardless, neither trial supported the role of the self-helpprint intervention as the sole method of promoting increased physical activity in themedium term.

The results of the present thesis are consistent with previous research, insomuch thata mass distributed self-help print intervention may be an effective strategy to promote increases in self-reported physical activity in the short-term. However, more specific ongoing support and training may be required in order to maintain actual behaviour change. To this end, the value of self-help print interventions, which have been designed, using the Stages of Change, should not be underestimated in terms their usefulness in designing individualised intervention programs.

Therefore, further research is recommended on the use of self-help print intervention materials as a method to promote physical activity in population settings, including investigation of appropriate supplementary strategies (like booster telephone calls, links to services and the potential of the World Wide Web ) which may enhance the longer term effectiveness of the intervention.

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