Athletes who die suddenly on the playing field are most often found to have structural heart disease. At autopsy, HCM is the most common structural heart disease found. Because of these observations, it is recommended that patients with HCM should avoid competition and extremes of exertion. Exercise would not, in any case, be expected to improve the patient’s cardiac condition, which might be a patient-held misconception. This recommendation may be barely relevant in severely symptomatic patients or in the elderly who limit themselves. However, in the young, or in asymptomatic middle-aged patients, this recommendation may have profound effect. The guidelines allow recreational sports activity and specifically allow exercise to maintain muscular tone. There is inevitable ambiguity in the intensity of activity allowed. We try to clarify by pointing out that, in competition, athletes will often push beyond limiting symptoms to win and this is to be specifically avoided, whether in formal competition or in pickup games. We also recommend avoiding activities where syncope would have disastrous effect such as scuba diving or surfing. We recommend that patients not lift more than 40 lb.