Hi,
Actually, now that I went back to the site and looked, set 21 is all walking intervals, so you may want to do a different one that has walking, jogging and running. If you can jog for 30 minutes, you can do any of the I-Trains that have these 3 levels. What they do is keep all 3 paces going at the same time. Sometimes the walking pace is too fast for me, so I go down a percentage or 2, then keep at that level. What is great about these is that you can work at your own pace, the pace that they give is "only a guideline" as they explain on most of them. It also depends on whether you want a flat walk/jog, or inclines for interval training. I love the inclines because I don;t jog for very long. Set 20 has a 30 minute interval workout that takes your pace up .1% every minute, but is all done on flat surface. Did you see how you can read the descriptions and actually hear a little bit of the workout? do this with a couple then just go for it! :7 I am headed off to the basement right now to do theSet 5, 40 minute one.
Deb