They don't run at the same speed in the same direction. You will have people passing each other, and who knows how long it will stay afloat in the air over the

They don't run at the same speed in the same direction. You will have people passing each other, and who knows how long it will stay afloat in the air over the trail. Two runners 100ft apart same direction same speed (6mph) is only 11 seconds before the runner in the rear passes through the exhaled breath of the runner in front.