Time to Elicit Physiological and Exertional Vigorous Responses from Daily Living Activities: Setting Foundations of an Empirical Definition of VILPA

Purpose Vigorous intermittent lifestyle physical activity (VILPA) are bursts of incidental vigorous activity that occur during day-to-day activities outside of the exercise-domain. Vigorous intermittent lifestyle physical activity has shown promise in lowering risk of mortality and chronic disease. However, there is an absence of an empirically derived definition. Using physiological and effort-based metrics commonly used to define vigorous intensity, we investigated the minimum time needed to elicit physiological and perceived exertion responses to standardized activities of daily living. Methods Seventy adults (age = 58.0 ± 9.6 yr; 35 female) completed 9 VILPA activities of daily living in a randomized order, which included fast walking, fast incline walking, stair climbing, stationary cycling, and carrying external weight equal to 5% and 10% of body weight. Metabolic rate (by continuous indirect calorimetry), heart rate (telemetry) and perceived effort (Borg Scale) were measured during exercise. Time to reach VILPA was assessed using %VO _2max, %HRmax, and rating of perceived exertion thresholds. Results The mean time to elicit VILPA ranged from 65 to 95 s (mean ± sd = 76.7 ± 3.8 s) for %VO _2max, 68 to 105 s (mean ± sd = 82.8 ± 6.8 s) for %HRmax, and 20 to 60 s (mean ± sd = 44.6 ± 6.7 s) for rating of perceived exertion. For each of the three indices, there was no difference in the time to elicit VILPA responses by sex or age (P > 0.08), and times were also consistent between activities of daily living tasks. For example, for females and males, the average time to elicit vigorous responses while walking on a flat surface was 85.8 s (±16.9 s) and 80 s (±13.9 s), respectively, and for stair climbing while carrying 10% of body weight the duration was 78.4 s (±17.6 s) and 76.9 (±17.7 s). Conclusions When participants undertook activities of daily living, VILPA elicited a physiological response at an average of 77 to 83 s for %VO _2max and %HRmax, and 45 s for perceived exertion. The absence of a difference in the time to reach VILPA between sex and age suggests that a consistent behavioral VILPA translation can be used in interventions and population-based studies designed to assess the health effects of incidental physical activity.