Another one of the many great things I've discovered from this program is that I really only need to do 20 minutes of cardio, 3 times a week, to get incredible results. And believe me, I no longer do a second more than I have to. The key here again is intensity. If you can increase the intensity of your aerobic training, you have no need to go any longer. There's a section in the book that talks about the "High Point" technique. Learn it, live it, know it. Now, here are some of the variations I do for my aerobic training:
I use a Life Cycle and always do the "Hill" program. I like the hill because it's easier to visualize a real bike ride, and it's not as monotonous. I like using the highest level because I get a bit of a resistance workout at the same time as my cardio. I tend to use this workout on the days that I do legs. The important thing is to push yourself each ride. Try to either increase the RPM's or the level each time you get on the bike.
Get yourself a jump rope (I prefer the ones with the beads on the rope). Then do 1 minute of regular jump rope, 1 minute of alternating lifting your foot up and pressing your heel down, 1 minute of jumping on 1 foot at a time in 10 second intervals, one minute of alternating knee lifts, and then one minute of doing 15 seconds worth of the 4 exercises I just described. That makes 5 minutes. Now repeat it for another 5 minutes. Then once you can do that, try doing doubles for the 5th and 10th minute. Start at 15 seconds worth and work up from there.
Then grab a couple 2-5 lb weights, and take off for a slow jog. Your shoulders will start to catch on fire after a minute or so, so use light weights. I usually run on a track, and will do 5 laps with the weights, followed by 5 without, followed by 10 with, for a total of 10 minutes (keep increasing until you can go 10 minutes with the weights). I like this workout before doing upper body. You can also substitute the weighted jog for weighted bike. In this variation I take a set of 10 lb weights to the bike with me. I do the hill program again, this time for only 10 minutes on the highest level. As I'm pedaling away, I do shoulder shrugs, shoulder raises, and a variety of rotator cuff exercises. I always do the weighted bike before doing a heavy chest workout so that my shoulders are warmed up properly.
This section is titled "running" which is what you want to work up to to hit the 10's, but starting out at a jog or walking is how you get there. So go at your own pace here, but don't be afraid to push yourself to hit the 10's. Some tips on running: First, try to keep your hips from going all over the place. You want to keep them still, and use your legs like pistons. This will also keep the stress off your lower back. Secondly, if you've got a dog, taking him/her with you is the best way to experience running, or any form of cardio as far as that goes. Your dog will love you for it, and you can use him/her as a partner to talk to as you go and to keep pushing yourself. If you don't have a dog, I'd recommend getting one. There's no way to express how much love a dog gives with nothing asked in return except to be played with. Check out your local human society for possible future companions.
Do a slow 1-2 lap jog between sprints. And another piece of advice is to get a partner. This is a tough workout and is way more fun enjoying it with someone else. This workout takes about 45 minutes and I'd only use it once every 1-2 weeks.
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You can really take any cardio exercises and tailor them to your liking. Usually, I prefer to break it up into two, ten minute workouts instead of one 20 minute workout. It just seems to go faster and allows me to keep my concentration better. I don't recommend reading or watching TV for intense cardio until you are really tuned in. But, in reality, if watching the soaps gets you on the bike for 20 minutes 3 times a week, then by all means do it.