Description of Lifetime Physical Activity by Time, Energy and Joint Force in a Canadian Sample

Statement of Purpose. The purpose of this population-based study was to characterize lifetime physical activity (PA) patterns in a sample of Canadians, in all PA domains (sport, occupational and domestic) using hours per week, metabolic equivalents (MET) and joint force at the hip and knee.

Methods. Data was drawn from the baseline survey of the Physical Activity and Joint Health cohort, a Canada-wide population Internet study. Participants completed a validated computer adaptive online survey on lifetime PA, joint health and other factors. Lifetime PA was measured by collecting data on specific types, frequencies, durations and intensities of PA broken down by domain (sport, occupation, domestic) and movement type (e.g., walk, run, squat, kneel). Hours per week of PA were determined by multiplying years participated in a given activity by the frequency (per week, month or year) and duration (average time per occasion) of participation. Energy expenditure was estimated by multiplying the number of hours spent in an activity by the average intensity of that activity, using standardized metabolic equivalents. Hip and knee joint (tibiofemoral and patellofemoral) forces were estimated by multiplying the duration of physical movements by multiples of bodyweight assigned to each movement, derived from a comprehensive review of the biomechanical literature. A lifetime bodyweight trajectory was derived for this purpose using current weight, weight at age 20, maximum weight, and interpolated using a lowess (non parametric smooth) curve. Mean values for 5-year intervals over a person's lifetime, averaged over all subjects, were calculated for each lifetime PA metric.
Results. Complete baseline data was collected on 4,269 subjects. The sample was 63% female with a mean age of 61.5 years. At the time of the survey, the mean weight of males was 193 lb (sd=41) and females 165 lb (sd=38). Mean lifetime PA across all domains (sport, occupational and domestic) was 41.7 in average hours per week (3.1 sport, 19.8 work, 18.8 domestic) and 119.11 in MET-hours per week. Time spent in sport activity was highest prior to the age of 20 and plateaued by 25 for the remainder of the life trajectory. Occupational and domestic activity consumed many more hours than sport. Both increased rapidly after age 20 and peaked in the mid-40’s. Hip and tibiofemoral joint forces were higher than patellofemoral joint force. Joint forces increased from age 20 to a peak at 45, and steadily declined thereafter.
Conclusion: The use of different metrics for lifetime physical activity presents opportunities for investigating the effect of activity on health. Separately analyzing time, energy and joint force over the lifetime may clarify the relationship between the numerous benefits of physical activity and the possible risks related to hip and knee joint health.

 C. Ratzlaff, None; P. Doerfling, None; J. Kopec, None; G. Steininger, None; J. Cibere, None; M. Liang, None; D. McIntyre, None; D. Wilson, None; J. Esdaile, None.