Prospective cohort studies of odds ratio of lower functional performance or functional limitations in "higher" level functions (such as walking a distance or climbing stairs) in relation to physical activity level. The odds ratio (OR) for each level (1,2,3) of physical activity are compared with the lowest physical activity group assigned as the referent (physical activity group = 0, OR = 1). The odds ratios are those reported for analyses statistically adjusted for confounder variables. The OR is an approximation as the actual data may have been separated into men versus women, or other groupings and thus in assembling the data these values have been combined. The level of physical activity was determined from analysis of types of activities that were reported for each activity level in each study; for example, in a number of studies there were only two activity groups but to be in the higher group there had to be report of vigorous activities or walking of 1 hour per day. Thus the physical activity groups were determined to require: 3 - vigorous activities and/or high volume of systematic activity (walking for exercise); 2 - moderate level of activity from participation in normal walking or gardening with a volume of 3-5 days/week and 30 min per day; 1 - participation mainly in light activities of daily living with only occasional walking or gardening; and some physical activity groups were scored as 2.5 as they included vigorous activity (not included in group 2) or exercise walking but at a lower volume than group 3. Dashed lines indicate study data where only two activity groups were categorized, whereas solid lines join the data points for studies in which more than two activity groups were formed.
Paterson and Warburton International Journal of Behavioral Nutrition and Physical Activity 2010 7:38 doi:10.1186/1479-5868-7-38