Longer legs are associated with better vo2 and lower risk of respitatory disease. Why?
Your link doesn't say that. They say that they found no relationship between asthma and final height in the study population.
But height is used to produce predicted lung volumes, and the explanation is as follows:
In normal humans, lung size is a function of height, sex, race and age.2-4 Each lung fills a pyramidal box with a height and radius. Height is the distance from base (diaphragm) to apex of the box. Because of racial differences in limb:trunk length ratios, there is a racial correction for height. A 6-foot tall Caucasian has shorter legs (and therefore a longer trunk) than a 6-foot tall African American. A 6-foot tall North American Indian or Hispanic has even shorter legs (and therefore a longer trunk), than a Caucasian. So for the same height, different races have different lung volumes (lung sizes). African Americans have 10% less TLC than Caucasians for the same height, and Hispanics about 10% more.