You get very tired, and there was a certain amount of pain and you slow up. Your legs are so tired that you are in fact slowing. If you don't keep running, keep your blood circulating, the muscles stop pumping the blood back and you get dizzy. ↗
I am now in that happy comfortable state that I do not hesitate to indulge in any fancy in regard to diet, but watch the consequences, and do not continue any course which adds to weight or bulk and consequent discomfort. ↗