After six months of weight training using a customized schedule of Chalene Johnson’s ChaLEAN Extreme, next week we will be changing over to the latest Beachbody product, Shawn T.’s Insanity. Reviews will follow once we have had a chance to properly evaluate it. As we prepare to update our own personal exercise routines, it seems like a good time to address workout intensity.

Just like in the children’s story, exercise routines can be too soft, too hard, or just right.

If you select a regimen that is too soft, too easy, you won’t get the results you hope for. You won’t slim down, tone up, help your heart as much as you think, or burn as many calories as you think. In short, you will be cheating yourself by pretending to work out when you are merely playing around.

On the other hand, selecting too hard a workout has more serious implications. Launching into too hard a workout (or working out too vigorously) can have bad effects ranging from demotivation to death. Seriously. That’s why programs like P90X and Insanity have self-evaluations before you get started. That’s why personal trainers spend a lot of time on the first visit evaluating your current condition, and why most workout DVDs start with a disclaimer about consulting your doctor before starting.

The ideal is to exercise with an intensity that is “just right.” While there are fancy ways to determine this level with great precision, most people don’t have the patience or equipment for such things. There are, however, several tests you can run on yourself, while working out, to make sure you are “in the zone.”

The first is very simple: “the talk test.” The idea is that you should be able to carry on a conversation (with your workout partner, coach, or yourself) while working out. Certainly it won’t be a long or complicated conversation, but you should be able to communicate. This will certainly keep you from working too hard, but it doesn’t keep you from being too easy on yourself.

The second is almost as simple: the “Rating of Perceived Exertion,” or RPE for short. RPE asks you to rate how hard you are working on a scale of 0-10 (it used to be 6-20, and corresponded very roughly to 1/10 of heart rate). 0 would be no effort — sitting on the sofa with a bag of Doritos and the TV remote — and 10 would be maximum effort. Ideally, most people would want to be working out at an RPE of 4-6. Because it is subjective, it is easy to over- or under-estimate your intensity level.

“Check your heart rate. What’s your zone?”

More precise are workout targets based on heart rate. While seriously out-of-shape people can see benefits from working out at as little as 55% of maximum heart rate, most people should be working out at 65-85% of maximum heart rate. Since it can be difficult to determine maximum heart rate without expensive supervised medical tests, most people will have to estimate it using the formula:

220 – Age in years = Estimated maximum heart rate

This formula isn’t as accurate as many people would like, so there is a more precise way to estimate your target zone called the Karvonen formula:

(Estimated maximum heart rate – actual resting heart rate) X desired intensity [55-85%, just like above] + actual resting heart rate

This brings up an interesting problem:  what is resting heart rate? Is it first thing in the morning after your alarm clock has jolted you out of a sound sleep and your heart is pounding? Since it can change over time, how do you accurately measure it at all? How do you know whether it has changed because you are in better shape, because you have been working too hard, or because you are coming down with something?

Whichever method you use, you don’t need anything more than the ability to take your own pulse and some scratch paper (or a calculator).  Since there will be a discrepancy between the two, double check during cardio workouts using the talk test and RPE.

As important as regular physical activity is, it is even more important to make sure that the level of activity is appropriate. A workout that is tailored to your fitness levels and goals is one you are more likely to keep doing regularly, and one more likely to help you achieve positive results.