Measuring the time costs of exercise : a proposed measuring method and a pilot study

Background: The cost of time spent on exercise is an important factor in societal-perspective health economic analyses of interventions aimed at promoting physical activity. However, there are no existing measuring methods for estimating time costs. The aim of this article is to describe a way to measure the costs of time spent on physical activity. We propose a model for measuring these time costs, and present the results of a pilot study applying this model to different groups of exercisers. Methods: We began this investigation by developing a model for measuring the time spent on exercise, based on the most important theoretical frameworks for valuing time. In the model, the value of utility in anticipation (expected health benefits) of performing exercise is expressed in terms of health-related quality of life. With this approach, the cost of the time spent on exercise is defined as the value of utility in use of leisure activity forgone minus the value of utility in use of exercise. Utility in use for exercise is valued in comparison with utility in use for leisure activity forgone and utility in use for work. To put the model into practice, we developed a questionnaire with the aim of investigating the valuations made by exercisers, and applied this questionnaire among more experienced and less experienced exercisers. Results: Less experienced exercisers valued the time spent on exercise as being equal to 26% of net wages, while more experienced exercisers valued this time at 7% of net wages (p < 0.001). The higher time costs seen among the less experienced exercisers correlated to a less positive experience of exercise and a more positive experience of the lost leisure activity. There was a significant inverse correlation between the costs of time spent on exercise, and the frequency and duration of regular exercise. Conclusion: The time spent on exercise is an important factor in interventions aimed at promoting physical activity, and should be taken into consideration in cost-effectiveness analyses. The proposed model for measuring the costs of the time spent on exercise seems to be a better method than the previously-used assumptions of time costs