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

Abstract

Vigorous intermittent lifestyle physical activity (VILPA) are bursts of incidental vigorous activity that occur during day-to-day activities outside of the exercise-domain. VILPA 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 standardised activities of daily living. Seventy adults (Age = 58.0 ± 9.6y; 35 female) completed 9 VILPA activities of daily living in a randomised order, that 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 %VO2max, %HRmax, and rating of perceived exertion thresholds. The mean time to elicit VILPA ranged from 65-95 seconds (mean ± sd = 76.7 ± 3.8 seconds) for %VO2max, 68 to 105 seconds (mean ± sd = 82.8 ± 6.8 seconds) for %HRmax, and 20 to 60 seconds (mean ± sd = 44.6 ± 6.7 seconds) 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 (±16.9) and 80 (±13.9) seconds, respectively, and for stair climbing while carrying 10% of body weight the duration was 78.4 (±17.6) and 76.9 (±17.7) seconds. When participants undertook activities of daily living, VILPA elicited a physiological response at an average of 77-83 seconds for %VO2max and %HRmax, and 45 seconds for perceived exertion. The absence of a difference in the time to reach VILPA between sex and age suggests that a consistent behavioural VILPA translation can be used in interventions and population-based studies designed to assess the health effects of incidental physical activity.