... from my results. The results should have showed that people who exercise were fitter than the subjects who smoke or who take no exercise. One reason why I thought this is because if a person exercises regularly it causes enlargement of the heart muscle, the blood flow to the lungs increases which slightly stretches the elastic tissue in the lungs which allows more air to enter them. I expected smokers to show a larger difference in respiratory inefficiency because smoking usually causes a person to be short of breath even if they take moderate exercise as well. Nicotine constricts terminal bronchioles, which decreases airflow into and out of the lungs. With time, smoking leads to destruction of the elastic fibres in the lungs and is the prime cause of emphysema. These changes cause collapse of the small bronchioles and trapping of air in alveoli at the end of exhalation. The result ...

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