The GREEN curve shows the fat combustion in kcal/h as a function of speed/power. The apex of the curve +/- 5% is marked with the green area. You may well find that in the area of the apex of the curve, there isn’t a significant difference in fat combustion rates. Often a decrease of intensity (power/speed) by 10% doesn’t make any difference in practical application in training.
The RED curve shows the actual carbohydrate combustion rate. As can be seen, this curve doesn’t display an apex: the higher the intensity, the higher the combustion rate is. In addition to the kcal/h unit, the carbohydrate combustion is also shown in g/h on the right y-axis. The known and maximum exogenous uptake rate of 60-90 g of carbohydrates per hour is marked with an orange bar.
Fat and carbohydrate combustion data are used to specify zones for low-intensity endurance training and for prescribe fueling recommendations for training and racing.