If someone is stranded in a harness, but is not unconscious or injured, and has something to kick against or stand on (such as a rock ledge or caving leg-loops) it is helpful for them to use their leg muscles by pushing against it every so often, to keep the blood pumping back to the torso. If the person is stranded in mid-air or is exhausted, then keeping the legs moving can be both beneficial and rather dangerous. On the one hand, exercising the leg muscles will keep the blood returning to the torso, but on the other hand, as the movements become weaker the leg muscles will continue to demand blood yet they will become much less effective at returning it to the body, and the moment the victim ceases moving their legs, the blood will immediately start to pool. "Pedaling an imaginary bicycle" should only be used as a last-ditch effort to prolong consciousness, because as soon as the "pedaling" stops, fainting will shortly follow. If it is impossible to rescue someone immediately, then it is necessary to raise their legs to a sitting position, which can be done with a loop of rigging tape behind the knees or specialized equipment from a rescue kit.