Reduces oxygen levels in your blood – You need oxygen in your muscles when you exercise. The more you exercise, the faster the oxygen is used up. Cigarettes contain carbon monoxide, which reduces the amount of oxygen available in your body as it binds to the haemoglobin in your red blood cells, preventing oxygen from doing so.
Decreases your lung capacity – which can cause a smaller volume of oxygen to reach the bloodstream, resulting in less oxygen getting to the blood.
Take your breath away – causes chronic swelling of the mucous membranes of the airways, which adds to resistance.