In the past few months, I had been doing 2 a day workouts back to back. I would run 1st, then either spin/bike or swim. Worked out very well, felt good. Now, for safety reasons, I have switch my routine and I am swimming or spinning first, and then running. I haven't changed times, distance or anything else, just runnung after (good training, right?) but it's kicking my butt! I feel tired and sore, and really hungry during the run much more so than when I ran 1st. So am I burning more calories or does the run, b/c of it's tougher nature on the body, just SEEM harder after a swim/spin?