Felt great until about 1/2 way through when my heart felt like it was going to leap out of my throat. I stopped and walked a bit and then started running again, then it happened again shortly afterwards. I had to run/walk the whole way home. Walking seemed to bring my heart rate back under control, but it was definitely high on the running intervals. I was a little under dressed so hopefully that was the cause... otherwise a beautiful afternoon for a run! (note I accidentally hit stop instead of lap once).