My son played baseball and basketball in high school and continues to play on adult softball leagues now. His HCM cardiologist had him wear a heart monitor while playing softball, to see how his heart was reacting to the sprinting between bases. While his heart rate increased, it did not increase to a dangerous level, so for now, he is cleared to play softball. There are certain sports that are potentially more threatening than other sports. Any sport that requires a sprint (soccer, basketball, baseball, football) are the sports they say to take it easy with or not play at all. My son is doing well and his HCM is not yet at a super dangerous spot (his thickening isn't severe). His ventricle will continue to enlarge as he gets old, but at what rate is unknown. He has to have a heart MRI once per year to measure the thickening progress and each year they will re-evaluate whether or not he can continue to play sports. He has decided to quit playing his pick up basketball games, just a precaution, since he loves baseball and only likes basketball 😉 My sister is having open heart surgery in a month for HCM. Her case is much worse, as is a first cousin who should have the surgery, but is too anxious about it to commit. Each person in the same family can have different intensities of the defect. So, even with confirmed HCM, it doesn't mean that anything may ever have to be done. Just depends on the growth rate. I would really recommend a heart MRI, which could clear him entirely, like it did me. That would answer a lot of questions for you. Also, your son should be going to a HCM specialty office. A lot of the "regular" cardiologists are not super up to date with HCM. You will get much better information and direction from a HCM cardiologist.