Subject: Which has a greater effect on lung capacity: age, gender or physical finess

For the last three weeks I have been working on a science fair experiment about 
lung capacity. So far, 23 people of different ages, gender, physical fitness 
and sizes have completed the test.  In looking at my results, I noticed that of 
all 22, the top five scores are men all in the 20-40 age group. The other two 
men, in the 65+ age group, scored lower than the women in the 20-40 age group. 
I am thinking that maybe at a certain age our lungs stop working as well. 

Re: Which has a greater effect on lung capacity: age, gender or physical finess