 The workout does not directly cause any improvements. The workout is just a messenger. It's a stimulus. It's a way of telling your body the environment is placing a demand on it that if it does not respond to, if it does not improve its ability to handle, eventually is going to kill it. And again, back to the evolutionary standpoint, your body has no idea you're lifting a barbell or a machine that thinks you're trying to kill something else, which is essential if you're going to obtain food, or it thinks something else is trying to kill you. Now, it's the time in between. It's the rest. It's the recovery. It's where your body is producing those improvements. And you're better off having more clean workouts for your body to fully recover and produce the improvements than to workout too often and not have that happen. And again, with the suntan, suppose that after a bit of experimentation, you found that if you were to lay out about 12 minutes per side, and get out of the sun, that that's about as much as you can tolerate before you start to burn, and you tanned a pretty good pace after that. You wouldn't go out, lay out 12 minutes, flip over 12 minutes, come back inside, and then go out 5 minutes later and do it all over again. If you were to attempt to do that, you would, even though you only did it for 12 minutes on each side at a time, you would still end up being burned because you wouldn't have allowed your body adequate time to recover from that stress and produce an adaptation to it. Now, if you work out, you're producing microtrauma, damage, tears in the muscle, and without getting a hold on to the physiology of it, these are what start the adaptive response. But as part of that process, your body has to repair that damage. That requires a certain amount of time. As a result of that damage, you have inflammation. The inflammation has an effect on your immune system, actually involves immune system. That has an effect on your nervous system, and all of these things are things that it takes your body a certain amount of time to recover from. If you work out, and then say your body needs 2 or 3 days, but you work out again a day later, your body is still trying to recover from all those effects of the previous workout, it hasn't even gotten to the point where it's fully produced any kind of improvement. You are digging a hole deeper and deeper, placing more and more of a stress on your body for it to recover from, and never letting it get to the point where it's able to produce the adaptations that you're trying to stimulate in the first place. Again, if you're training as hard as possible, you have to be careful about the amount, because if you're training hard enough, it's placing a significant stress on your body that it has to recover from. If you do not allow your body to recover from that stress, then you're spinning your wheels. You're not going to see any improvement, and worst case scenario, too much too often, you could actually make yourself weaker over time.