The first 20 minutes are where most of your results are coming from, after that your body adjusts and you go on sort of an autopilot. Hence the HIIT is a huge thing right now. And also, the elliptical and stationary bike are two of the most useless pieces of equipment in the gym. No offense to OP intended of course, but we all need to make adjustments to our routine from time to time to get it most optimal. Source: http://www.bodybuilding.com/fun/10-best-and-worst-cardio-machines.html