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In search for the criteria of evaluation of aerobic work capacity for the Korean young male adult, 104 healthy male college students who volunteered were subjected on treadmill walking at a speed of 2, 4, 6 and 8 km/hr with a 0, 5, 10, 15 and 20% grade of inclination. The heart rate, oxygen uptake and energy cost were measured during the exercise and then regression analysis was done on all three. Heart rate was recorded automatically every 5 seconds during the exercise by a telemeter(108 system. Senoh Co. Japna). The expired air during the exercise was collected into a Douglas bag and analysed for oxygen uptake and carbon dioxide output for calculation of respiratory quotient and energy cost with Orzat gas analyzer. The following results were obtained from the study. 1. Mean values of heart rate, oxygen uptake and energy cost at resting state were 77±8.5 beats/min, 3.65±1.23ml/kg/min and 1.08±0.36kcal/kg/hr, respectively. 2. One met was defined as an unit value of oxygen uptake or energy cost for the resting state. When the subjects walked on a treadmill at a speed of 2, 4, 6 and 8 km/hr with a 0, 5, 10, 15 and 20% grade of inclination, oxygen uptake and energy cost increased in proportion with the load of exercise from minimum 2.7 to maximum 15.5 Mets. 3. There were statistically significant correlation among the three parameters-heart rate, oxygen uptake and energy cost, and simple linear regression equations were derived. 4. In estimating of oxygen uptake and energy cost from heart rate during exercise, the better correlation was obtained when they were calculated in terms of unit body weight than in terms of gross amount or unit body surface area. 5. The linear regression equation of oxygen uptake(Yc : ml/kg/min) on heart rate(X: beat/min) was expressed as Yc=0.363X-24.0(S_y/x=5.35ml/kg/min) and that of energy cost(Y_c : kcal/kg/hr) on heart rate(X) as Yc=0.110X-7.27(S_y/x=1.55kcl/kg/hr) . Although the deviations of these predicted values were relatively large, standard errors of the means of theses predicted values were very small. 6. It was concluded, therefore, that oxygen uptake and energy cost could be estimated very precisely from the heart rate as a group but not so precisely as an individual basis. In evaluation of aerobic work capacity we could say that a man was of normal physical fitness if the measured values of oxygen uptake and energy cost were within the range of Yc±1S_y/x, a man of good physical fitness if the measured values were smaller than Yc-1S_y/x and a man of poor physical fitness if the measured values were larger than Yc+1Sy/x.
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