Deja Vu

The only time i ever did more than 50 pushps was about 20 years ago when i was a teenager. I remember that day vividly. Even those days I had never done more than 25 consequetive pushps, But that day, while i was doing the pushups, all of a sudden, I had this rush of energy and kept doing pushups way past my previous limits. I had that same sensation yesterday although it only lasted for 3 pushups. At one point my hands were getting very tired and started shivering and I thought I was about to collapse, then out of blue, My hands stopped shivering and became steady and all the fatigue in my hands vanished. I did another 3 Pushups without any effort and then My hands started shivering again and the fatigue came back. Pretty soon I collapsed unable to do no more pushups.