Insufficient physical activity is now a global pandemic. Problematic social media use (PSMU) has been reported to be associated with physical activity levels, and nomophobia can be one of the co-existing psychological conditions of PSMU. Additionally, physical activity avoidance has been reported to be associated with lower physical activity levels. Therefore, the present study examined nomophobia and physical activity avoidance as underlying factors potentially explaining the association between PSMU and physical activity among Taiwanese young adults. A cross-sectional online survey comprising the Bergen Social Media Addiction Scale (BSMAS), Nomophobia Questionnaire (NMPQ), Tendency to Avoid Physical Activity and Sport Scale (TAPAS), and International Physical Activity Questionnaire – short form (IPAQ-SF) was completed by 885 participants (36% male, mean age = 28.8 ± 6.06 years) between September and December 2023. The structural equational modeling results indicated a negative direct association between PSMU and physical activity (standardized coefficient [β] = 0.040, p = 0.004). PSMU was also associated with higher nomophobia (β = 0.601, p < 0.001), which was associated with higher physical activity avoidance (β = 0.354, p < 0.001), which negatively correlated to physical activity (β = -0.114, p < 0.001). Moreover, the association between PSMU and physical activity was significantly mediated through the sequence of nomophobia and PA avoidance (β = -0.024, 95% bootstrap confidence interval = -0.071, -0.024). The results suggested that PSMU may be associated with lower physical activity through the mediation of nomophobia and physical activity avoidance. Corresponding strategies may aim to reduce PSMU and enhance physical activity engagement. Other approaches, such as motivational interviewing or cognitive behavioral therapy, can be adopted to reduce nomophobia and physical activity avoidance, thereby improving the individuals’ physical activity participation.
