Normalised step targets in fitness apps affect users’ autonomy need satisfaction, motivation and physical activity – a six-week RCT

Fitness apps are promising digital tools to support self-tracking and physical activity. Specific app functions such as normalised step targets represent controlling conditions that can affect controlled vs. autonomous motivation and thus motivated physical activity. It was the aim of this study to examine the effects of self-tracking via a fitness app and a normalised step target on aspects of motivation and physical activity by using Self-Determination Theory. In a six-week RCT (N = 152; age M = 24.43, SD = 4.61), participants in two groups were provided with Fitbit Flex 2 to track their physical activity. Participants in the experimental target group (ET) had a normalised step target of 10,000 whereas the experimental no target group (ENT) had no target. Participants in a third control group tracked their physical activity without fitness app support. Self-reported physical activity, basic needs satisfaction, and motivation regulation were assessed via the LTEQ, PNSEG, and SKK scales. Medium increases in overall and light physical activity increased were found in the fitness tracker groups compared to the control group (η2 = 0.062, η2 = 0.094). Small increases in autonomy need satisfaction were found in the ENT group (η2 = 0.012). Conclusively, self-tracking via fitness apps can support physical activity, and normalised step targets can undermine motivation in young adults during a six-week intervention. Lack of normalised targets can support autonomy need satisfaction and physical activity but can also foster amotivation. Thus, it is advised to support autonomous goal setting in fitness app users.Trial registration: German Clinical Trials Register identifier: DRKS00014835.