<s>[INST] My ten year old active son is complaining of discomfort in the chest area when he runs or jumps on the trampoline. It doesn t happen when he cycles or walks. he did have growing pains in the knees but x-rays found nothinuntoward; he has no fever or othe pains. [/INST] Dear, Welcome to ChatDoctorWe understand your concerns went through your details. Jumping in trampoline is stomach churning exercise and while doing that it is natural to have chest discomfort due to digestive tract churning fluids. Many child Chat Doctor.  Your son is not experiencing any chest discomfort while cycling or walking or during other periods. That itself is a relief. Don't worry. Experience will settle the discomfort. If you require more of my help in this aspect, please use this URL. http://goo.gl/aYW2pR. Make sure that you include every minute detail possible. Hope this answers your query.  Further clarifications are welcome. Good luck. Happy New Year. Take care. </s>