What's missing here - and which you can't really test with mice - is the emotional side of things. Exercising because you've been placed on a treadmill, as was

What's missing here - and which you can't really test with mice - is the emotional side of things. Exercising because you've been placed on a treadmill, as was the case with the mice, is akin to people exercising because they "have to", or get a trainer to "stay motivated". When you actually do it because you "want" to and it feels good it's a different story because the feelgood chemicals have a lot to do with your immune system. For many years during my late teens and early twenties I went to the gym so that I could get buff and be fit. I hated exercise, but forced myself to do it and pushed through the pain. Yes I even got a personal trainer at one stage. The results? I either got sick, injured myself, or just plain depressed (at the lack of results), only to repeat the cycle over and over again. Back to this article - what I'm trying to say is that stress, anxiety, happiness all play a HUGE part in your immune system (and fitness).