This week I was reminded of one more. On monday my stomach felt slightly uncomfortable. Back from the gym, I felt rather faint. It was time to go home and throw a sofa at the problem.
I stayed home and cross trained on the sofa all next day. By early afternoon, my hands no longer needed to stay under blankets to be warmer than a frozen haddock.
Quite simply, there you have it. A higher level of energy that helps with the everyday, including being channeled into a powerful immune response more potent than a sedentary person could ever hope to muster (as witnessed by my sofa).