Influence of heavy weight carrying on the cardiorespiratory system during exercise.

To study the influence of weight carrying on the cardiorespiratory system during dynamic exercise (walking) four conditions, i.e., rest, and treadmill exercise at 25, 50, and 75% of the individual VO2max, were combined with weight carrying of 10, 20, and 30 kg. In all experiments oxygen uptake, heart rate and pulmonary ventilation were measured. For each dynamic exercise condition and for the rest condition regression lines are calculated showing the relation between weight load an oxygen uptake, heart rate and pulmonary ventilation. From the slopes of these regression lines it can be seen that in rest (standing position) weight carrying does not influence oxygen uptake, heart rate and pulmonary ventilation. In dynamic exercise oxygen uptake, heart rate and pulmonary ventilation increase linearly with the amount of weight carried. To a large extent this increase is independent of the dynamic work load. In this study it was found that each kilogram extra weight increases oxygen uptake with 33.5 ml/min, heart rate with 1.1 beats/min and pulmonary ventilation with 0.6 1/min. In dyanmic work for loads higher than 50% of VO2max the relationship between weight carried and pulmonary ventilation is no longer a linear one. For the subjects studied it is assumed that oxygen consumption per kilogram weight is not different for body weight or extra weight carried.