Abstract Body: Introduction:
Physical activity (PA) is an important component of healthy aging, playing a key role in preserving mobility, preventing falls, and mitigating the risks of conditions like sarcopenia, osteoporosis, and cognitive impairment. Despite its importance, engagement in PA, particularly higher intensity exercise, tends to diminish as individuals age, yet there is limited understanding of the specific patterns and factors influencing this decline across diverse populations. The purpose of this study was to quantify patterns of PA change from midlife to older adulthood, by domain and intensity.

Methods:
Data are from 6,814 MESA participants (53% women, 39% White persons) who attended at least one exam. Participation in ten PA types or categories was measured by the MESA Typical Week PA Survey at each exam. To characterize the life-course, participant data from Exams 1-7 were grouped based on age categories (5-year age increments from <50 to ≥90 years). Participants reporting 0 min/week within the PA category determined non-participation in the respective category. Participation in PA categories was assessed for each intensity category (light, moderate, vigorous) for all activity categories, where appropriate. Findings are presented as heat maps.

Results:
Marked reductions in the endorsement of most PA types across increasing age groups was found, particularly in categories reflecting higher intensity sports and occupational activity categories (Figure). PA categories reflecting everyday lower intensity lifestyle activities, including television viewing, non-active commuting, and household chores, had a more stable endorsement over time. Walking, for both exercise and transportation, was common regardless of age.

Conclusions:
These findings present valuable insights into patterns of PA across an important life-course transition. Opportunities to further support the promotion of walking is needed to ensure adequate PA accumulation for health benefits in older adults.