Purpose: The longitudinal influence of parental leisure-time physical activity (LTPA) on their offspring's LTPA is poorly understood. This study examined the longitudinal associations between parental LTPA and offspring's LTPA at two-time intervals.

Method: Child (offspring) participants (N = 3596) were enrolled from the Cardiovascular Risk in Young Finns Study in 1980. Their LTPA was self-rated through nine phases from baseline to 2018 and categorized by year into youth (1980-1986) and adult (1992-2018) LTPA. Parental LTPA was assessed with a single self-reported question at three phases from 1980 to 1986. Latent growth curve modeling stratified by gender was fitted to estimate the potential pathways between parental LTPA and offspring's youth and adult LTPA.

Results: Higher initial levels of paternal and maternal LTPA were independently associated with greater initial levels of youth and adult LTPA of offspring in both genders, respectively, except maternal LTPA, which did not associate with male offspring's adult LTPA. The initial levels of paternal LTPA were directly related to changes in male offspring's youth LTPA after adjusting for age, residential place, paternal education and occupation, having siblings, and offspring's body mass index.

Conclusion: Our study demonstrates that the initial levels of parental LTPA are directly linked to the initial levels of offspring's LTPA during youth and adulthood, while changes in parental LTPA are unrelated to changes in offspring's youth and adult LTPA for either gender over time. These results imply that higher initial levels of LTPA in parents may serve as a predictor of offspring's LTPA across life stages.