Background: This study aimed to identify accelerometer measured daily physical activity patterns, and to examine how they associate with health-related physical fitness among aging workers.

Methods: The study population consisted of 263 participants (mean age 62.4 years, SD 1.0) from the Finnish Retirement and Aging Study, who used wrist-worn ActiGraph accelerometer for at least one week including both workdays and days off. Health-related physical fitness measures included body composition (waist circumference, bioimpedance), cardiorespiratory fitness (CRF) (bicycle ergometer test) and muscular fitness (push-up and chair rise tests).

Results: Based on the latent class trajectory analysis, six trajectories were identified for workdays showing variation in activity level on working hours and on evening hours. Moderate activity during working hours and increase of activity level in the evening was associated with the most favorable health-related fitness in comparison to low activity throughout the workday: waist circumference 90.0 cm (95% CI 85.5-94.5) vs. 99.5 cm (95% CI 96.8-102.3), fat mass 13.9 kg (9.3-18.5) vs. 23.8 kg (20.2-27.4), CRF 33.4 ml/kg/min (95% CI 31.4-35.3) vs. 29.1 ml/kg/min (95% CI 27.8-30.3) (adjusted for age, sex, days off activity, smoking and alcohol). For the days off, two different trajectories were identified, but they differed only in terms of level and not by timing of physical activity.

Conclusions: A large variation in the workday physical activity patterns was observed among aging workers. Independent of worktime activity, people who were more active in the evenings had more favorable health-related physical fitness than those who were less active throughout the day.