Vital Capacity

1) My vital capacity turned out to be 2.4 on my second try; on my first attempt it was 1.8 however that many have happened because I was kind of confused as to what to do. While comparing my vital capacity to the people close to me I noticed that people that were taller tended to have a higher vital capacity. For example Monica who is much taller then me had a vital capacity of 3.2 while Brianna who is very close to my height had a vital capacity of 2.4, which is the same as mine. I also realized that the boys had a much higher vital capacity all together when compared to the girls. Therefore I think that a human's vital capacity depends on age, sex, height, and weight. The highest and lowest vital capacities are they way they are because it varies person to person and depends on how much air they can exhale in one breath. 

2) In an average usual breath there is 500 ml or half a litre of air. Our breaths are the volume that they are because of how healthy our lungs are and because our lungs tend to adapt to to how much air we need on a daily basis.

3) The mechanisms of forcefully exhaling is different from usual exhalation because it uses more muscle while blowing the air of our bodies. During forced exhalation, as when blowing out a candle, expiratory muscles including the abdominal muscles and internal intercostal muscles generate abdominal and thoracic pressure, which forces air out of the lungs. Practice at this via exercise/instrument playing/singing because you can manage and control your breathing more.