@Animandel - I had a friend in high school who had asthma. This breathing problem made it more dangerous for him than the rest of us when we were playing sports. After years of wanting to play on the school football teams in grade school, his parents and his doctor finally gave him permission to play on the school team when we reached high school.
One of the conditions for him being on the team was that there had to be oxygen on the sidelines during every game and during all practices. During games he would use the portable oxygen therapy tanks two or three times on average.
There are plenty of people with breathing disorders playing high school, college and professional sports every day. These people may be in great shape, but this doesn't mean they can't have asthma or some other kind of respiratory illness that makes breathing more of a challenge for them when they are active.