The measure of success for the adventurous athlete comes in miniature digital packages

You've heard the questions before: How steep is the grade? How high is the peak? How long is the interval? But you may not be satisfied by the typical answers, since you wind up with nothing but numbers. Indeed, there's a difference between information and knowledge, and assuming you're more of an outdoor athlete than a numerologist, what you need is the latter. So it's time to ask yourself how fast can you pedal down that grade, how high are you on that peak when you get light-headed and loopy, and how far are you into that interval when lactic acid floods your limbs.

The distinction is important. To fully exploit it—whether you're running, hiking, biking, climbing, or otherwise romping outside—you'll need some technical assistance by way of an altimeter, heart-rate monitor, or cyclometer. Or perhaps all three. To that end, we've field-tested the best gadgets in each category and reviewed them on the pages that follow. These digital measuring devices crunch all the pertinent data to spell out your limits and give you a notion of how you might want to stretch them. They get you where you want to be. They help you push yourself precisely as hard as you want to go. Some of them even have the megahertz-muscle to do all of these things. Which brings us to our final question: How much do you want to know?

INSIDE:

• The perfect pack for your lower back
• An atlas you won't want to shrug off
• Books: A big-fish tale from Fred Waitzkin

Photo: Clay Ellis