The association of physical activity and perceived physical fatigability on gait speed: the long life family study

The purpose of this paper was to determine if greater physical activity and lower perceived physical fatigability are independently associated with a faster gait speed, and thus a lower likelihood of having an activity limitation. The study population was two generations (proband and offspring) of adults enrolled in the Long Life Family Study, a study of exceptional longevity in families. Gait speed was assessed with a usual-paced 4 meter walk as an indicator of activity limitation. Physical activity, measured with the Framingham Physical Activity Index (total metabolic equivalents of a task per day) and perceived physical fatigability, assessed with the 10-item Pittsburgh Fatigability Scale were independent variables to examine their association on gait speed adjusted for age, gender, family structure, field center and health conditions. In both generations, greater physical activity was inversely associated with a lower perceived physical fatigability (proband: Q2=-2.1, Q3=-5.5, Q4=-7.5, p<0.001)(offspring: Q2=-1.7, Q3=-2.8, Q4=-4.0, p<0.001). Lower perceived physical fatigability was inversely associated with a faster gait speed (proband: beta=-0.013, p=0.03)(offspring: beta=-0.005, p<0.001). Physical activity and gait speed shared a strong dose response relationship (proband: Q2=0.1, Q3=0.28, Q4=0.21, p<0.001)(offspring: Q2=0.020, Q3=0.024, Q4=0.022, p=0.08). When both physical activity and perceived physical fatigability were included in the model with gait speed as the outcome, physical activity was independently associated with gait speed in the proband generation (Q2=0.095, Q3=0.26, Q4=0.17, p<0.001) but not in the offspring (Q2=0.015, Q3=0.017, Q4=0.01, p=0.4). Conversely, perceived physical fatigability was strongly associated with gait speed in the offspring generation (beta=-0.0057, p