This number's at the heart of the matter

The complementary goal to working hard is recovering quickly from it.

There are lots of numbers to track when it comes to fitness. But here's the one you're probably overlooking, according to Matt Berenc, director of the Equinox Fitness Training Institute. For the other numbers to keep in mind, click here.

A performance-based measure that I feel would be beneficial for most people to track on a daily basis, and is often taken for granted, is heart rate recovery. It's easy to measure by anyone and provides a great deal of insight into a person's fitness level.

Simply use a heart rate monitor to track how much your heart rate recovers within 60 seconds after completing an exercise or performance. In short, the more the better. An average target to shoot for is 20 to 40 beats per minute. [Meaning that you complete an exercise and immediately get your heart rate, then wait one minute and check again. You'll want that number to have dropped 20 to 40 bpm.] This shows a good level of fitness and is an easy range to keep in mind. Once your recovery gets over 40 bpm, you can consider yourself to be in a high level of fitness.

An added benefit of this measure, if you do it daily, is that is can help you to determine how you should train for a given day. If, for instance, you normally have a recovery of 30 bpm in 60 seconds, but today, for the same intensity or exercise, it is only 15 bpm, it may be an indicator that you haven’t fully recovered from your previous training, or that you are particularly stressed out. In either case, that wouldn’t be the day to hit it hard.