149-a : VO2 max AND HEART RATE

VO2 max is the maximum oxygen consumption by the body during maximum exertion that lasts longer than two minutes and shorter than 5 minutes. The VO₂ max is expressed in liters per minute. During efforts, at the level of VO2 max, the energy supply is both aerobic and anaerobic. Because the maximal anaerobic energy supply has only a limited capacity, the test persons are forced to slow down, after a short time.

Under the influence of training VO2 max increases.  But much more important is the shifting of the anaerobic threshold under the influence of training. After a training period of a few months, the anaerobic threshold may rise from 40% of the VO₂ max   to, for instance, 60% of the VO₂ max. This means that, after a training period, lactic acid is formed at a load corresponding to a higher percentage of the VO₂ max. The effort that previously could be sustained only briefly, due to acidification of the muscles, now delivers, with the same intensity, no problems in terms of persevering time. The intensity of the exercise can thus be increased, from 40% to 60% of VO2 max, without being accompanied by an accumulation of lactic acid.

Training creates an increase in the VO₂ max, but also a more significant increase in the percentage of the VO₂ max where an effort can be sustained over a long period. In the ‘graph HR max and VO₂ max’ the right vertical axis shows the shift from the deflection point after a training period.

In the graph, the HR is at the deflection point, for an untrained person is 130 beats per minute. After a training period of several months in the example the deflection point shifts to 180 beats per minute.

The left vertical axis in the ‘HR-max and VO₂ max ” graph shows the increase in VO₂ max, but mostly the increase in the percentage of the VO₂ max where the effort can be sustained during a long time. This means that the deflection point is shifted to a higher level. The VO₂ max can improve through training up to 10 to maximally 30 percent. Well-trained marathon runners run the marathon with an intensity of 93 percent of their VO2 max.

149-1
Schematic representation of changes that occur after a training period of several months. Percentage of VO2 max increases more clearly than the VO2 max itself
149-2
The linear relationship between the HR and the oxygen uptake.
Percentage of HR-max Percentage of VO2-max
50 30
60 44
70 58
80 72
90 86
100 100

Efforts at the level of the VO₂ max only can be sustained only for a few minutes. Therefore, the VO₂ max is not a good measure of the performance of the athlete. A better measure for this is the anaerobic threshold or lactate threshold. The anaerobic threshold corresponds to the maximum load intensity an athlete can sustain during a long period of time without a progressive increase in lactic acid levels in the blood.