From a bit more of a physiological point of view, what happened to you was that your lungs couldn't keep up and your muscles kicked over from aerobic to anaerobic activity. Aerobic exercise burns both fat and sugars together in an efficient and fairly clean process. When your muscles need more oxygen than your lungs can provide the muscles start kicking into anaerobic mode. The muscles switch to burning mostly sugars and generate lactate which causes your muscles to burn and can cause some nausea. The longer you stay in anaerobic mode the more lactate the muscles generate and the greater the discomfort. Fortunately, in a fit person, the body can clear excessive lactate fairly rapidly when the activity level falls back to the place where the respiratory system can provide enough oxygen to keep up.