Validity of Physical Activity Measures During a 23-hour Metabolic Chamber Stay in Older Adults

Abstract

PURPOSE: To compare the relative validity of various objective physical activity measures with metabolic chamber-measured energy expenditure in older adults. METHODS: Eighteen adults (15 females, 3 males; age= 76 ± 7 (mean ± SD)) wore three activity monitors (New Lifestyles pedometer, Actigraph, and a Sensewear armband) during a 23-hour stay in a metabolic chamber. Subjects had the choice to do a 30-minute exercise video of seated and standing exercises, twice, while in the chamber. Total energy expenditure (TEE) and resting metabolic rate (RMR) were measured with indirect calorimetry, and the thermic effect of food was estimated. Three estimates of physical activity energy expenditure were calculated (PAEE, kcal/d; PAI, kcal/kg/d; PAL, TEE/RMR). Mean differences in TEE and correlations between the various physical activity measures and chamber-measured energy expenditure were compared. RESULTS: TEE was 1796 ± 303 kcal/day. PAEE, PAI, and PAL were 467 ± 148 kcal/day, 3.14 ± 0.91 kcal/kg/day, and 1.57 ± 0.13 (mean ± SD), respectively. On average, 171 ± 49 and 16 ± 11 minutes/day were spent in light and moderate activity, as measured by the Actigraph using count cutpoints of 100, 760, and 5724 cts/min, and the average steps/23 hrs was 862 ± 438. There were no vigorous minutes recorded and the rest of the time was inactive. Although TEE from the chamber and armband were strongly correlated (r=0.69, p<0.01), the armband underestimated TEE by 671 kcals, (p<0.0001). Similarly PAEE from the chamber and armband were correlated (r=0.57, p=0.01), but highly underestimated by the armband (mean difference = 422 kcals). The Actigraph and pedometer did not correlate well with PAEE (r=0.24, p=0.35; r=0.13, p=0.61, respectively), but did tend to correlate with PAI (r=0.42, p=0.08; r=0.41, p=0.10). CONCLUSIONS: Under the highly accurate, but movement limiting conditions of the chamber, the Sensewear armband reasonably ranked older adults by energy expenditure, but the absolute estimates were not accurate. Neither accelerometry nor pedometry did as well as the multi-sensor device.