A multitude of things CAN go wrong with any system in the body, but seldom DO. Take the heart/circulatory system for example. Heart disease is the leading cause of death in the US. 873 per 100,000 die of heart disease (CDC). (Remember, natural birth is between 6 and 14 per 100,000 in the US, depending on the population.) Some of arteries on the verge of clogging. Some of heart defects they are unaware of. Some have damage they don't know about. Something could go wrong at any minute and immediately available surgery can undoubtedly save lives.--
Using the logic of obstetrics, all health clubs should be in hospitals and all fitness trainers should be cardiac surgeons. Any independent health club with 'lay' trainers would be 'practicing medicine without a license,' subject to prosecution. It's for your own good.
In fact, in order to know if a problem is developing, close monitoring and 'management' is required. We will need to place straps on the muscles to measure the intensity of the workout. of course, it will be restrictive, but we need to know how hard the muscles are working to know if the heart can take it. We'll need to monitor heart rate, blood pressure, fluid output. We'll need to give an IV because with sweat excreted, you could dehydrate, and of course, we simply can't take the risk of letting you drink anything lest you need emergency surgery....