Have you ever wondered how hard you should be exercising?

There are many ways to determine how hard someone is working out. Elite athletes like to gain their information very scientifically, using anything from a heart-rate monitor, at the simplest end of the spectrum, to more invasive methods including blood analysis and even muscular biopsies. (I had eight of those in my Aussie Rules days and, frankly, they rate just above colonic irrigation and full-body waxing on my list of things to avoid for the rest of my life.)

For the average gymgoer, the heart monitor works just fine. However, if you don't have one and are unsure how to calculate it yourself, you can also use a technique called RPE (rate of perceived exertion), originally developed for coaches to measure an athlete's level of intensity during training.

It's a simple technique: you assess the level you're working at against a scale of 1–10 (Level 1 being at rest and Level 10 very, very hard) and match your level of exertion to the requirements of the training you're doing. Essentially, it's a sort of sliding scale, with the key markers set like this:
0. Nothing at all
3. Light exercise
5. You're working at a level you can easily sustain for 30 minutes or so
7. Challenging
10. About to pass out

Below I've listed some activities along with the average levels you should be working at for each.
Warm up — Level 5
Stretching pre or post-exercise — Level 6
Running — Level 7
Pilates class — Level 7
Spin class — Level 7-8
Tennis — Level 6-9
Intense cardio workout — Level 8-9

Whatever you're doing, I probably don't need to point out that unless you are a professional athlete, or you know your body very, very well, if you reach level 10, it's probably best to back off a little.

David Higgins is co-founder of Tenpilates.com