sentences:  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.