CRITICAL-EVALUATION OF THE FACTORIAL AND HEART-RATE RECORDING METHODSFOR THE DETERMINATION OF ENERGY-EXPENDITURE OF FREE-LIVING ELDERLY PEOPLE

The aim of the present study was to validate against the doubly-labell ed water (DLW) technique the factorial method and the heart rate (HR) recording method for determining daily energy expenditure (DEE) of eld erly people in free-living conditions. The two methods were first cali brated and validated in twelve healthy subjects (six males and six fem ales; 70.1 (SD 2.7) years) from open-circuit whole-body indirect calor imetry measurements during three consecutive days and during Id respec tively. Mean energy costs of the various usual activities were determi ned for each subject using the factorial method, and individual relati onships were set up between HR and energy expenditure for the HR recor ding method. In free-living conditions, DEE was determined over the sa me period of time by the DLW, the factorial and the HR recording metho ds during 17, 14 and 4 d respectively. Mean free-living DEE values for men estimated using the DLW, the factorial and the HR recording metho ds were 12.8 (SD 3.1), 12.7 (SD 2.2) and 13.5 (SD 2.7) MJ/d respective ly. 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 we re found between the three methods for either sex, using the Bland & A ltman (1986) test. Mean differences in DEE of men were -0.9 (SD 11.8)% between the factorial and DLW methods, and +47 (SD 16.1)% between the HR recording and DLW methods. Similarly, in women, mean differences w ere -7.7 (SD 12.7)% between the factorial and DLW methods, and +5.9 (S D 8.8)% between the HR recording and DLW methods. It was concluded tha t the factorial and the HR recording methods are satisfactory alternat ives to the DLW method when considering the mean DEE of a group of sub jects. 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 valu e (i.e. sleeping metabolic rate) is accurately measured.