In a previous blog, I wrote about Zone 2 aerobics, the steady, moderate exercise I spend much of my movement time in. Another type of aerobic activity, actually anaerobic activity, is High Intensity Interval Training (HIIT). This is hard and fast, short-duration movement that gets your heart rate up above 85% of its maximum and often closer to 100%.

I have been doing HIIT training for over 5 years. I do it once or twice a week, either in addition to Zone 2 sessions or in place of them. (Before I started, I had a thorough cardiology exam, including a stress test, which is a good idea for anyone new to HIIT.)

Doing HIIT is easy, in theory at least. I just move as hard and fast as I can until my heart rate is above 140 (87.5% of my maximum heart rate). Then I take it easy for at least as long as I was exerting myself and repeat the activity. I do this anywhere from 8 to 15 times depending on how exhausted I am in the later intervals.

The variations are infinite. HIIT activities could include a very fast walk up a hill for about a minute, then walk back down and start over. Or spend 30 seconds on a rowing machine followed by 45 seconds of rest. Or do burpees or running in place at home. (What’s a burpee? This exercise combines a jump, squat, plank, and push-up – all in one smooth movement. You can watch YouTube videos to learn how to do burpees the correct way.)

One of my very high intensity activities is working out on a Rogue Assault bike in the gym using my arms and legs as hard as I can: 15 seconds of work followed by 45 seconds of rest. I repeat this “cycle” 10-15 times. In the first intervals, my top heart rate is in the 150s and goes back down to the 120s on the resting part. In the latter intervals, my heart rate doesn’t go down as much, and I know it’s nearly time to stop. The flood of endorphins at the end of these sessions is just one of the wonderful rewards I get for the effort I’ve put in.

HIIT training gets a lot of press as an “efficient” form of exercise, that is, you get the same metabolic results in less time than if you were to spend a longer time doing the activity without pushing as hard and with no scheduled rests. This was the initial appeal of HIIT, which inspired many variations such as CrossFit and Tabata sessions.

The benefits are medically measurable: improved blood pressure, cardiovascular, VO2 max, and metabolic levels. Yet to me this is a limited analysis of this training. I believe there are less tangible – and more critical – benefits to High Intensity Interval Training.

Our human bodies evolved to operate at two distinct speeds. Our ancestors spent most of their time moving around at slower, sustainable levels. But occasionally they needed supercharged bursts for short periods of time (think hunting or danger). This anaerobic, high-octane, adrenaline-fueled energy enables us to operate differently. It is there as a resource for survival.

Every time I push myself to replicate this supercharged, adrenaline-fueled energy in a HIIT session, it not only taps into this evolutionary memory it sends a message to my body to rebuild this system and make it strongerthan it was before, because my survival depends on it. This is the ultimate secret of recovery and healing following exertion; they improve strength and health, make us stronger, and give us more endurance than before.

I believe there is still much to learn about HIIT and its effects on longevity and later life. I will continue to look for new information and report it in these pages. For me, the immediate benefits are deep and palpable. Being able to run up the stairs two at a time at 73 years old and only be slightly winded at the top makes me feel great. Or walking up a very steep hill with my teenage daughters at a fast pace, as we recently did. I kept up with them, and there was no difference in our breathing at the top. (If you read my articles on the Blue Zones, it's interesting to note that the Sardinians walk up steep hills into their 90s and beyond.)

Another HIIT benefit I’ve read about is increased stem cell production, the supercharged growth cells we lose as we get older. If this is true, it is the best natural fountain of youth we can drink from. Coming from a 73-year-old with a VO2 max of around 45, I know it certainly feels that way.