A comparison of energy expenditure estimates from the Actiheart and Actical physical activity monitors during low intensity activities, walking, and jogging.

Combining accelerometry with heart rate monitoring has been suggested to improve energy estimates, however, it remains unclear whether the single, currently existing commercially available device combining these data streams (Actiheart) provides improved energy estimates compared to simpler and less expensive accelerometry-only devices. The purpose of this study was to compare the validity of the heart rate (HR), accelerometry (ACC), and combined ACC/HR estimates of the Actiheart to the ACC estimates of the Actical during low and moderate intensity activities. Twenty-seven participants (mean age 26.3 ± 7.3) wore an Actical, Actiheart and indirect calorimeter (K4b(2)) while performing card playing, sweeping, lifting weights, walking and jogging activities. All estimates tended to underestimate energy, sometimes by substantial amounts. Viewed across all activities studied, there was no significant difference in the ability of the waist-mounted Actical and torso-mounted Actiheart (ACC, HR, ACC/HR) estimates to predict energy expenditure. However, the Actiheart provided significantly better estimates than the Actical for the activities in which acceleration of the pelvis is not closely related to energy expenditure (card playing, sweeping, lifting weights) and the Actical provided significantly better estimates for level walking and level jogging. Similar to a previous study, the ACC component of the Actiheart was found to be the weakest predictor of energy suggesting it may be responsible for the failure of the combined ACC/HR estimate to equal or better the estimates derived solely from a waist mounted ACC device.

Traditional physical activity indexes derived from the Harvard alumni activity survey have low construct validity in a lower income, urban population.

The purpose of this study is to investigate the construct validity of the Harvard Alumni Activity Survey (HAAS) in an urban, lower income population. Data were collected from 192 smokers enrolled in an antioxidant micronutrient trial. Activity data were compared to body mass index (BMI), diastolic, and systolic blood pressure. The traditional physical activity index (PAI), using data on stair climbing, walking, and sports, was calculated including and excluding body mass. A new scale, the total weekly activity (TWA) scale, was derived from other questions on the HAAS. The PAI scale calculated with body mass was unassociated with BMI and blood pressure. The PAI scale calculated without body mass was unassociated with BMI and systolic blood pressure but was associated with diastolic blood pressure (Beta = -0.001, p = 0.03). The TWA scale was associated with BMI (Beta = -0.01, p = 0.01), diastolic (Beta = -0.03, p = 0.01), and systolic blood pressure (Beta = -0.04, p = 0.01). A one standard deviation change in the TWA scale is predicted to be equivalent to a change of 0.99 BMI units, 2.97 mmHg of diastolic blood pressure, and 3.96 mmHg of systolic blood pressure. This work suggests that the TWA scale has greater construct validity than the traditional PAI scale in this population.