SIMULTANEOUS MONITORING OF HEART-RATE AND MOTION TO ASSESS ENERGY-EXPENDITURE

Measurement of energy expenditure in free-living individuals represent s a methodologic challenge in epidemiologic research. Heart rate monit ors, while closely tied to energy expenditure at high levels of energy output, provide much less predictive power at low levels; however, me asurement of motion may improve the predictive ability. This study was undertaken to determine the usefulness of simultaneously monitoring h eart rate and motion for the estimation of energy expenditure. Ten sub jects were studied during simulated activities of daily living (ADLC) and submaximal treadmill tests. Compared to direct measurement, the mo tion sensor predicted oxygen consumption poorly (r(2) = 0.53) for both tests. Heart rate measured simultaneously yielded an r(2) of 0.81 for ADLC and 0.90 for the treadmill. Addition of motion data increased th e r(2) value for the ADLC for all but one individual and increased the group mean for 0.81 to 0.86. This improvement was not observed for th e treadmill, confirming the hypothesis that the principle value of mon itoring motion occurs at lower heart rates.