Discover how to use your wearable fitness watch to track your health and live a longer life.

Apple sells 40 million Apple Watches per year, with about 90% of the wearers using the exercise-tracking technology the watch affords. But many don't fully understand the health data our wearables provide.

I am Maillard Howell, former head of fitness at Reebok HQ and owner of Dean Crossfit gym in Brooklyn, NY. I've received a decade of feedback from hundreds of clients about their fitness habits and wearables like the Apple Watch, and their understanding of the data outputs provided.

I have realized that other than step-counting, most have no clue what the data means, including resting heart rate, HRV, and VO2 max, and how these apply to their long-term health and longevity.

I'm going to make it easy for you to understand what this data means and why you should be aware of these figures as you age.