Don't have a heart monitor, and looking for a way to tell when you're working hard enough on your cardio, without working too hard?
The new issue of Muscle & Fitness describes the "Talk Test," which was recently validated by researchers at the University of Wisconsin at La Crosse.
As you're doing cardio, recite something simple to yourself on occasion, like the Pledge of Allegiance or nursery rhymes.
For aerobic training, you want to get the point where you're having a little bit of trouble talking, but you can still do it.
For interval, anaerobic training, you want to have intervals of maybe 30 seconds where you pass a bit beyond that point, so you can't really speak. Come down for a minute or two and then go harder for another 30 seconds.
Not only does this give you a good basis for measuring yourself, but it also dispels a myth a lot of people believe about cardio. When people think about cardio, they imagine running like fugitives for fifteen miles in the hot sun, and even the thought of that is too exhausting to deal with.
The fact is, you only have to work as hard it takes you to get your heart rate to a certain point. Fortunately (or unfortunately, depending on how you look at it), if you haven't exercised much in a while, you may not have to work very hard to get to that point.
After a while, it will get easier and you'll have to do more work to reach the same heart rate, but you'll still basically be exerting the same amount of effort--and, when you hit that point, you'll be burning more calories in a shorter amount of time.
But hopefully the idea of walking or jogging at a speed that you're just able to carry on a conversation seems a little less daunting than trying to do a Carl Lewis impression.