The Effect of a Physical Activity Program Using WhatsApp on Adolescents’ Exercise Behavior

This study aims to demonstrate the effect of a transtheoretical model (TTM)-based physical activity program on the exercise behavior of adolescents using WhatsApp. The study was conducted with high school students ( N = 185) in a pre-/posttest, quasi-experimental design. TTM-based text messages were sent to the intervention group ( n = 95) over WhatsApp every day for 8 weeks. The intervention group demonstrated more statistically significant progression in the exercising stages of change compared to the control group ( n = 90) (χ 2 = 20.10; p = .00). It was also found that this group had a higher exercising self-efficacy score ( t = 2.647; p = .009) and a higher physical activity total metabolic equivalent of task score ( Z = −3.521; p = .000). There was no significant difference in BMI and perception of pros and cons ( p > .05). The program was found to be effective in terms of recording progress in the exercising stages of change, increasing exercising self-efficacy, and maintaining a physical activity program.