Regular exercise boosts the immune system………unless you overdo it.
In moderate amounts, physical activity reduces the risk of upper respiratory tract infection.
It works in opposite if you go to extremes. Marathon runners have higher risk of colds after a race, because immune function goes down after a prolonged intense exercise.
It is similar with inflammation, which can be a sign of weakened immune system. Regular exercise decreases inflammation. On the other hand, playing a hard game of soccer or basketball only once in a month or once in 2 weeks can boost inflammation if that’s all you do.
The weekend athlete who does something strenuous once in a while can do more harm than good to a lot of systems. You should perform vigorous activity at least two or three times a week to avoid making things worst.
Build up to it with regular exercise – weight training, cardio workout, flexibility training for at least 6 weeks before you start doing vigorous activity like playing soccer. And than, when you start, don’t stop and do it at least 2 times per week. Your body will get use to a work load and you can push it even further without any harm.