Background
Research has shown that physical activity is important for healthy aging. At the same time, physical activity and different age factors (chronological and subjective age measures) are interrelated. The present study investigated whether subjective physical age and chronological age are significantly correlated with physical activity over time.

Participants and procedure
A study design with baseline assessment and a 4-week follow-up period was conducted with an online sample (N = 541), aged 25-78 years (M = 39.62, SD = 10.74). Regression analysis with the enter method was used to predict subsequent physical activity by baseline predictors.

Results
Subjective physical age correlates with chronological age (r = –.34, p < .001). Subjective physical age predicted subsequent physical activity when controlling for baseline variables (B = –.12, t = –2.43, p = .015) until past physical activity was entered (B = –.06, t = –1.44, p = .150). The final model explained 33% of variance in subsequent physical activity.

Conclusions
Subjective physical age seems to be more important for physical activity than chronological age. This is an important finding as subjective physical age might be a target for interventions, to enable individuals to become more physically active. Future studies should investigate non-linear relationships between subjective physical age, social-cognitive predictors of physical activity and physical activity behavior.