Validation of Three Physical Activity Monitors for Assessment of Energy Expenditure in Older Women

Abstract

Doubly labelled water (DLW) is considered the criterion method for assessment of total energy expenditure (TEE) and physical activity energy expenditure (PAEE) under free-living conditions; however, it is costly and requires significant technical expertise. Body-worn physical activity monitors are a good proxy for estimating TEE and PAEE, but their accuracy compared to DLW remains uncertain in older women. PURPOSE: This study sought to i) validate three physical activity (PA) monitors for TEE assessment in free-living older women using DLW as the criterion method and ii) determine the accuracy of the PAEE estimates obtained by these monitors. METHODS: Thirty three women (age 60.7 ± 7.1 y; mean BMI 26.9 ± 5.0 kg·m-2) were recruited for this study. TEE and PAEE were measured over a 14-day period using a standardised protocol for DLW (2H2O and H218O). Women also wore SenseWear® armband (SAB), ActiHeart™ (AH) and ActiGraph GT3X (AG) PA monitors continuously, and at the same time, during their waking hours over 7 d, except for water-based activities such as bathing or swimming. RESULTS: Paired t-tests revealed mean differences of -163 ± 307 kcal·d-1 between TEEDLW and TEESAB; -134 ± 279 kcal·d-1 between TEEDLW and TEEAH; and -143 ± 242 kcal·d-1 between TEEDLW and TEEAG (all p<0.05). Measurements from PA monitors underestimated TEE derived from the criterion DLW by 6%-7%. The agreement between the criterion and PA devices for TEE demonstrated concordance (ρc) from 0.51 to 0.75. TEEDLW was strongly correlated with TEEAG (r=0.80; p<0.05). PAEE derived from PA monitors significantly underestimated the criterion PAEE by 18%-68%, with mean differences of -332 ± 333 kcal·d-1 between PAEEDLW and PAEESAB, -124 ± 250 kcal·d-1 between PAEEDLW and PAEEAH and -130 ± 217 kcal·d-1 between PAEEDLW and PAEEAG (all p<0.05). There was a moderate correlation between PAEEDLW and PAEEAG (r=0.61; p<0.05), but ρc was non-existent to moderate, ranging from 0.00 to 0.53. CONCLUSION: There were good levels of agreement between body-worn physical activity monitors and a criterion measurement of TEE in older women under free-living conditions. Physical activity monitors consistently underestimated daily levels of energy expenditure, although agreement with a criterion method was better for estimating TEE, than for PAEE. More work is needed to improve the ability of these PA monitors to accurately measure energy expenditure during daily physical activities.