Hello shara, I'm with Zero vis and others and will say that a good day of Diving will always zonk me out physically. But so will a good day of surfing, swimming, hiking, bike riding, skateboarding etc, that's what exercising is all about.
As far as what others are saying about nitrox, I think that addresses another issue. After a good day of deep diving, I also feel fairly "Narced" in addition to being physically tired. The good nitrox advice given here will prevent that "Narced" feeling. Being narced most likely intensifies the physical exhaustion, but I think most people separate these two feelings into separate issues.
Someone may correct me, but I believe that a good amount of physical exertion always brings on a level of exhaustion, narced or not.