How Hard Is Hard?

Outside magazine, November 1998

How Hard Is Hard?
To firm up the nebulous, get cozy with your lactate threshold

At what pace should you be working? Good question — and one you should be constantly asking yourself, says Dave Scott. The best way to monitor your training intensity, he says, is to become familiar with the index below, called the Perceived Exertion Scale. The idea is to ask yourself how you feel during exercise and answer with one of the qualitative phrases in the scale. Each exertion level corresponds to numbers that Scott will use to prescribe your workout intensity.

The terms may seem all too vague at first, but you can pin them down by assigning a heart rate to 17 on the scale: It's equal to your lactate threshold. To determine this number, warm up for 10 minutes on any aerobic machine. Then increase your speed to the highest level that you can maintain for 20 minutes; your average heart rate during the last five minutes signifies your lactate threshold. Jot that number down next to 17, and now you have a quantitative measure of going "very hard." You can also extrapolate your heart rate for the remaining levels, so if Scott has you working out at 14, which is 82 percent of 17, simply calculate 82 percent of your lactate-threshold heart rate. One caveat: Your lactate threshold will rise as your fitness improves, so you'll need to retest yourself and reassign heart rates to the index every three weeks, on Mondays.

  • Very, very light: 7, 8
  • Very light: 9, 10
  • Fairly light: 11, 12
  • Somewhat hard: 13, 14
  • Hard: 15, 16
  • Very hard: 17
  • Very, very hard: 18, 19
— P.K.

Illustration by John Hersey

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