USING THREE DIFFERENT HEART RATE VARIABLES AS A PREDICTOR OF ENERGY EXPENDITURE

Abstract

In our earlier study (Hiilloskorpi et al. Int J Sports Med 1999;:438–443) we developed a prediction equation to estimate energy expenditure kcal*min−1 (EE) during exercise, based on the linear relationship with heart rate (HR) and EE during intensive activity. The aim of our new study was to develop a prediction equation which is applicable also for all daily activities. In our earlier study (Hiilloskorpi et al. Int J Sports Med 1999; 20:438–443) we developed a prediction equation to estimate energy expenditure (kcal*min−1 (EE) during exercise, based on the linear relationship with heart rate (HR) and EE during intensive activity. The aim of our new study was to develop a prediction equation which is applicable also for all daily activities. In this presentation we assessed possibilities to improve the EE estimation using three different HR variables as a predictors: HR alone, % of HR reserve [100*(activity HR - resting HR) / (maximal HR - resting HR)], and the difference between activity HR and resting HR. The study group consisted of 89 healthy volunteers, 42 men (mean age 36.5[sd 7.6]y., BMI 24.5 [2.4] kg*m−2, VO2 max 45.2 [6.5]ml*kg*min−1) and 47 women (37.5 [9.5]y., 23.3 [3.4] kg*m−2, 36.3 [5.4]ml*kg*min−1). The subjects performed an exercise test consisting two different parts: a low-activity part, during which the subjects moved lightweight objects while sitting and standing, during the second part the subjects did a maximal treadmill uphill-walking test (Lasset, Finland, 1986). Oxygen uptake VO2 (l*min−1) and carbon dioxide production (VCO2, l*min−1) were calculated from the gas analyses done by indirect calorimetry (SensorMedics Vmax 29 (California, USA). HR was registered by electrocardiography (Max-1, Marquette Electronics (Wisconsin, USA). Generalised linear models were used for the prediction of EE. Repeated EE values of the tests were predicted by the corresponding HR values from the same test. The other predictors were body weight, sex and the intensity of exercise. When compared to the measured EE values the standard error of estimate (SEE) was 1.41 kcal*min−1, when HR was used as a predictor in the equation. The best EE prediction was when % of HR reserve was used instead of HR, the SEE was then 1.02 kcal*min−1. The SEE was 1.09 kcal*min−1 when the difference between activity HR and resting HR was used in the prediction equation. Supported by Polar Electro Oy and The Ministry of Health, Finland.