Actually, cell’s potential is the one thing he might be right about. You probably know that mitochondria are at the heart of our health etc with the atp production etc etc. So anything that improves mitochondrial health and increases atp, is actually very good for you. However, the fucker is wrong about how to do it. Hard labour is, in fact, not good on your body. Neither is extreme weather, particularly cold weather or direct heat. Some exhaustion is good but not too much. It all comes down to inflammation, son. Look it up