Walking towards health: Does size matter?

Physical activity is recommended for health, wellbeing, and to assist with weight management. Walking is the most popular leisure-time physical activity. National and international guidelines for the prescription of physical activity advise that adults should undertake 150 minutes each week of moderate intensity physical activity. This guideline is based on the duration of walking required for healthy-weight men to expend 1,000 kilocalories. The aim of this thesis was to investigate the prescription of brisk walking for obese adults. Methods This thesis involved four processes, the development of the research focus, an observational study, a mixed-methods study, and a validation study. In the development process, a systematic review and meta-analysis identified the evidence base for the prescription of brisk walking for obese adults and identified the parameters for a personalised, clinically effective, dose of brisk walking. This was followed by an observational study (N = 62) explored the influence of obesity on energy expenditure during brisk walking. These data were used to generate a predictive algorithm to estimate energy expenditure during brisk walking. The mixed methods study (N=346) tested whether the public found an online calculator, based on the energy expenditure algorithm for walking prescription to be acceptable and usable. The validation process was a second observational study (N=20) that compared the energy expenditure algorithm with gold-standard indirect calorimetry, and two wearable activity trackers. Results The systematic review and meta-analysis provided evidence suggesting that the effectiveness of brisk walking is dependent on individual characteristics and dose. However, significant heterogeneity in participant characteristics and intervention design amongst individual studies included in the review precludes evaluation of dosage effects. The first observational study provided strong correlations between energy expenditure and body weight, waist circumference and body composition. The results of the first observational study informed the development of the online walking prescription calculator. The feasibility study demonstrated that there was a high level of acceptability and usability of an online calculator for walking prescription. The second observational study confirmed that the energy expenditure algorithm was strongly correlated with indirect calorimetry. The algorithm was superior to both wearable activity trackers and to other predicative equations for energy expenditure. Conclusions The thesis has provided evidence that the current national and international physical activity guidelines may not be suitable for obese adults. The thesis has proposed a novel method for prescribing a personalised dose of brisk walking for all adults. An algorithm integrated into a simple online calculator has proven to be acceptable, usable, and has good validity. A future main trial could assess whether personalised prescription could improve safety, effectiveness, and compliance of brisk walking amongst obese adults