Smartphone-app-delivered Interval Walking Training In Denmark: User Characteristics And Predictors Of Adherence.

PURPOSE: To describe user characteristics and adherence to interval walking training (IWT) in Denmark, using the smartphone app InterWalk. METHODS: The InterWalk app for smartphones was developed aiming at implementing IWT in type 2 diabetes patients in Denmark. Interval walking training consists of repetitive 3-minutes cycles of slow and fast walking with individualized audio guided feedback. The intensities during walking are determined based on a short initial self-conducted audio guided fitness test. Training data (acceleration, GPS, exercise duration, height, weight, and the civil personal registration number) are uploaded by users and can be used for later data-linkage to Danish nationwide medical databases and administrative registries. RESULTS: The InterWalk app has been downloaded by >27,000 persons, including 9,466 persons providing personal user information. Of the latter users, 29% were men and 71% women, median age (quartiles) was 55.6 (46.4-63.6). Eighty percent of the men and 62% women were overweight or obese (BMI≥ 25). The risk of overweight among InterWalk app downloaders was higher compared to the Danish population of similar age (ages 45-74 years) with prevalence odds ratio (95% confidence intervals) of 2.1 (1.9; 2.3) for men and 1.8 (1.7; 1.9) for women. A total of 14,333 valid training sessions (defined as >6 min training duration) were uploaded 86 weeks post release. At least one valid session was uploaded from 2,932 unique users. People downloading the InterWalk app were more likely to be characterized as adherent users, defined as uploading >10 sessions of > 6 minutes duration (N=320) if they performed the audio-guided fitness test; odds ratio (95% confidence intervals) 6.28 (4.82 to 8.18). Men were more likely to be adherent users compared to women; odds ratio (95% confidence intervals) 1.34 (1.03 to 1.72). CONCLUSIONS: The increased risk of overweight in the InterWalk cohort compared to the Danish reference population suggests that the app is in fact of interest for the at-risk (overweight) individuals. The nationwide implementation suffers from a general lack of adherence, and efforts should be made to increase usage of the app. Our data suggest that promoting completion of the audio guided fitness test might improve adherence to interval walking training.