Effect of including fitness testing in preventive health checks on cardiorespiratory fitness and motivation: study protocol of a randomized controlled trial

Background: Preventive health checks may identify individuals with an unhealthy lifestyle and motivate them to change behaviour. However, knowledge about the impact of the different components included in preventive health checks is deficient. The aim of this trial is to evaluate whether including cardiorespiratory fitness testing in preventive health checks 1) increases cardiorespiratory fitness level and motivation to change physical activity behaviour and 2) reduces physical inactivity prevalence and improves self-rated health compared with preventive health checks without fitness testing. Methods/Design: An open-label, household-cluster, randomized controlled trial with a two-group parallel design is used. The trial is embedded in a population-based health promotion program, "Check your Health Preventive Program", in which all 30-49 year-old citizens in a Danish municipality are offered a preventive health check. In each arm of the trial, 750 citizens will be recruited (1,500 in total). The primary outcome is cardiorespiratory fitness level assessed by submaximal cycle ergometer testing after one year. An intermediate outcome is the percentage of participants increasing motivation for physical activity behaviour change between baseline and two-weeks follow-up assessed using the Transtheoretical Model's stages of change. Secondary outcomes include changes from baseline to one-year follow-up in physical inactivity prevalence measured by a modified version of the questions developed by Saltin and Grimby, and in self-rated health measures using the Short-Form 12, Health Survey, version 2. Discussion: This trial will contribute to a critical appraisal of the value of fitness testing as part of preventive health checks. The conduction in real-life community and general practice structures makes the trial findings applicable and transferable to other municipalities providing support to decision-makers in the development of approaches to increase levels of physical activity and improve health.