Question from B. Einicke, Sangerhausen: As there is a lot of snow here in the Harz Mountains in winter, I sometimes train on the ergometer. The wattage control is great for interval training, but what do I do during long GA1 sessions? I torture myself on the machine once a week for three to four hours, but after two and a half to three hours I can no longer keep my heart rate in the basic range. I then corrected this by reducing my wattage, thus maintaining my heart rate, but sometimes pedalling 30 watts less! Is that correct? Or should I leave the wattage unchanged and train with a higher heart rate at the end?
Dr Björn Stapelfeldt: The way you do it is the right way. Basically, the following applies: In the basic endurance 1 (GA1) range, training should be controlled according to heart rate, in the GA2 range according to heart rate and/or power, at higher intensities only according to power. The heart rate is too slow to follow the rapid increase in performance during intervals or in the development area. In the basic range, however, it reflects the current overall strain on the body very well.
If your heart rate increases during long GA1 training sessions at a constant power output, this is initially due to a change in the metabolic situation: If the carbohydrate stores are increasingly depleted, the body has to ramp up the fat metabolism. However, in order to obtain the same amount of energy from fats as from carbohydrates, the muscle cells need more oxygen. This means: more oxygen for the same performance, for which the heart has to transport more blood and therefore beat faster. In addition, the body can heat up considerably in poor climatic conditions. As a result, blood is diverted from the muscles to the skin for cooling. This also means more work, which results in an increased heart rate for the same performance. This effect can be exacerbated if you do not drink enough. You sweat more indoors and therefore need more fluids than outdoors.
However, as your heart rate only increases after around two and a half hours, this is more likely to be due to the energy fatigue described above, unless you have not drunk enough. Normally, an increase in heart rate of 10 to 15 beats per minute over the course of longer basic units should not be regarded as negative. However, if the values increase further, it is right to reduce your performance in order to prevent excessive heating.
