Validity of muscular fitness self-assessments in the ecofit smartphone application (Preprint)

BACKGROUND Mobile health apps that promote physical activity are being developed at a rapid rate. App-based interventions have the potential for wide reach and therefore, may be a useful tool in up-scaling physical activity interventions. In larger scale interventions, face-to-face assessments are less cost effective, and researchers often rely on surveys or built-in activity trackers to assess ongoing efficacy/effectiveness of outcomes. While there are valid means of assessing aerobic activity via smartphone apps, there is limited evidence of valid muscular fitness assessments that can be self-administered within mHealth. OBJECTIVE To evaluate the concurrent validity of upper and lower body muscular fitness that have been independently assessed by participants via the ecofit app, and face-to-face assessments conducted by a trained researcher. METHODS This study compared baseline data from the ecofit two-armed randomised controlled trial and self-assessed data collected via the ecofit smartphone app. As part of baseline assessment in a larger community-based physical activity intervention ‘ecofit’, participants undertook the validated 90-degree push-up and the 60-second sit-to-stand test face-to-face with a trained researcher. Those allocated to the intervention group received access to the ecofit app and were instructed to complete the self-assessed fitness tests within 14-days of receiving access to the app. To assess the concurrent validity, the self-assessed push-up and sit-to-stand tests were correlated using Spearman’s correlation coefficient against the research-assessed results. Bland-Altman plots were also used to allow visualisation of the differences between the self- and research-assessed tests. RESULTS Fifty-four participants completed at least one of the two muscular fitness self-assessments within 14-days of receiving the app, of these 24.1% and 100% completed the push-up and the sit-to-stand test respectively. The results found a strong significant correlation for the push-up test (0.83, p <.001) and a moderate significant correlation for the sit-to-stand test (0.63, p <.001). CONCLUSIONS This study provides support for the concurrent validity of self-reported upper and lower body muscular fitness assessments (i.e., the push-up and sit-to-stand tests) in mHealth. While these tests may be a feasible option for large scale physical activity interventions, more research is needed to determine the generalisability of these results. CLINICALTRIAL The ecofit trial is registered with the Australian and New Zealand Clinical Trial Registry (ANZCTR): ACTRN12619000868189.