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

Objective: 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 %V̇O 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 %V̇O 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 %V̇O 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.