One frustrating aspect of aerobics (of any exercise, really) is how everybody has an ax to grind... or a program to sell. One bunch, typically very muscular and energetic, tells you that you need to do this much of this exercise to get in shape. Another bunch, typically clad in white doctor's garb and looking all solemn and knowledgeable, tells you to avoid that exercise and only do this much of a second exercise.
Of course, the first group stays in shape for a living and the second group doesn't look like they've been in shape for years. It sounds like Goldilocks and the Three Bears -- this program is not enough, and that program is too much.
How am I supposed to know when I find one that's just right? With apologies to Jeff Foxworthy, I'm going to try and answer that question right now.
- If you fall asleep during your workout, you just might be slacking off. If your pulse sounds like Keith Moon during a drum solo, you just might be working out a bit too hard. Ideally, the proper level of exercise gets your pulse rate up, but you shouldn't hear or feel it pounding in your temples.
- Start by subtracting your age from 220. This gives you your maximum heart rate in beats per minute (bpm), and it's your starting point. DANGER, WILL ROBINSON! DANGER! You don't want to get anywhere near this during a workout, even if you are in shape.
- Multiply your maximum heart rate times .6. This tells you the bottom of your target heart rate zone. It's 60% of your maximum heart rate.
- Multiply your maximum heart rate times .8. This tells you the top of your target heart rate zone. It's 80% of your maximum heart rate.
- During your workout, keep your heart rate between these two numbers. If your pulse rate goes up too much, slow down; if it drops below the bottom number, pick up the pace.
A couple more thoughts. If I'm out of shape, or I just haven't been working out for a while, I'll be better off if I keep my workouts down around that 101 figure, maybe in the 101 to 110 area. And even if I'm in shape, I probably don't want to push it right up to that 135 top; I'd probably shoot for the 70-75% range. That's 118-127 bpm.
You can get more info about target heart rates at many sites on the Web, like this page at The Walking Site. By the way, they recommend beginners stay in the 50-60% target range. I don't see any problem with that; it's just that I learned to use 60% as the bottom when I started out. Remember: It's always better to go a bit slower rather than too fast.