[A simple method of determining the intensity and duration of physical exertion]

Determination of the intensity and duration of physical activity with respect to the individual condition of the organism is essential for the effective control of physical training. One of the possible methods of establishing those quantities is making use of the dependence of intensity on the duration of physical exercise. Using semi-logarithmic coordinates (the intensity of exercise is given in the decomal system, the period of time in logarithms) this dependence is of the linear type. The straight line constructed from the limit (highest) intensities of exertion and the relevant times of exercise in any given individual, which must take into account that individual's state of health and fitness, cuts the plane of all conceivable combination of intensity-duration, into two semi-planes. All the actual combinations of those variables exploitable for training purposes are found in the semi-plane situated to the left of this line. With regard to the purpose of physical training it is then possible simply to choose the required intensity of exercise and to find the respective zone of the duration of this exercise, or it is possible to choose the duration of physical exercise and to read from the graph the respective zone of intensity. This intensity can be put either in terms of the speed of movement or, indirectly, in terms of the heart rate. This method of determining the intensity and duration of physical exercise can be used for all activities of the cyclic type, e.g. running, cycling, swimming and so on.