Information on maximal oxygen uptake

According to tortora (2000)"Maximal oxygen uptake can be defined as the maximal amount of oxygen that can be taken in, transported and consumed by the working muscles during maximal exercise. Those who are more fit have higher VO2 max values and can exercise more intensely than those who are not as well conditioned". (p211) When exercise commences the uptake of oxygen rises rapidly during the first few minutes of exercise. If you are doing steady-rate …

…greater the contribution of fat catabolism. Whereas, the greater the carbon dioxide production relative to oxygen consumption, the greater the contribution of carbohydrate. However, as there is a limit to the amount of carbohydrate that can be stored in the muscles, high intensity work can only be sustained for short periods. After that the increased levels of carbon dioxide causes increased anaerobic glycolysis for energy generation, yielding lactate as a metabolic byproduct, causing fatigue. (Tortora,2003