Traditionally, people have tried to answer the question, “how much exercise can I stand?” whereas a better question is “how little is actually required?” The degree of effort or intensity is the critical factor in stimulating our body to improve, rather than volume or frequency, and if the intensity is sufficiently high, your body needs sleep, proper nutrition and especially time to adapt before it is ready to benefit from further stimulus. Anything beyond the minimum needed is counterproductive at best, and at worst has been shown to actually be harmful. More is not better.