Why do you get sick after working out?

Answer 1

One of the main reasons is lactic acid. Normally when a person is doing something their muscles use oxygen to make energy, but when you work out for an extended period of time, they cant gen enough to make the energy they need. They have the ability to make energy without oxygen, but it has a drawback. Making energy without oxygen, call anaerobic respiration, has a byproduct called lactic acid. So the more you work out, the more lactic acid your body puts out. This is what causes your muscles to get sore and can cause people to fell sick. After you stop working out and switch back to your muscles using oxygen, aerobic respiration, then your body gets rid of it and you begin to feel better.

Answer 2

That is not a typical response to exercise unless you exercise with people who are sick with a cold or the flu. These infections are caused by viruses. It could be that you are exercising in public places or gyms with shared equipment and during the cold and flu season it is easy to catch viruses such as these when in public, especially if you do not wash your hands properly and immediately after touching public items and before you touch your own face, mouth, nose or eyes to introduce the virus. It may be coincidental timing and have no real relationship to the exercise. But, to know for sure in your case, you would need to have an examination by a health care professional.