Critical evaluation of the factorial and heart-rate recording methods for the determination of energy expenditure of free-living elderly people.

The aim of the present study was to validate against the doubly-labelled water (DLW) technique the factorial method and the heart rate (HR) recording method for determining daily energy expenditure (DEE) of elderly people in free-living conditions. The two methods were first calibrated and validated in twelve healthy subjects (six males and six females; 70.1 (SD 2.7) years) from open-circuit whole-body indirect calorimetry measurements during three consecutive days and during 1 d respectively. Mean energy costs of the various usual activities were determined for each subject using the factorial method, and individual relationships were set up between HR and energy expenditure for the HR recording method. In free-living conditions, DEE was determined over the same period of time by the DLW, the factorial and the HR recording methods during 17, 14 and 4 d respectively. Mean free-living DEE values for men estimated using the DLW, the factorial and the HR recording methods were 12.8 (SD 3.1), 12.7 (SD 2.2) and 13.5 (SD 2.7) MJ/d respectively. Mean free-living DEE values for women were 9.6 (SD 0.8), 8.8 (SD 1.2) and 10.2 (SD 1.5) MJ/d respectively. No significant differences were found between the three methods for either sex, using the Bland & Altman (1986) test. Mean differences in DEE of men were -0.9 (SD 11.8) % between the factorial and DLW methods, and + 4.7 (SD 16.1) % between the HR recording and DLW methods. Similarly, in women, mean differences were -7.7 (SD 12.7) % between the factorial and DLW methods, and + 5.9 (SD 8.8) % between the HR recording and DLW methods. It was concluded that the factorial and the HR recording methods are satisfactory alternatives to the DLW method when considering the mean DEE of a group of subjects. Furthermore, mean energy costs of activities calculated in the present study using the factorial method were shown to be suitable for determining free-living DEE of elderly people when the reference value (i.e. sleeping metabolic rate) is accurately measured.