What is anaerobic exercise?

One of the nice things about stepping out of nature is that most of us no longer need to kill to eat or worry about being killed. But when we did, we had an extra gear to call on -- ten seconds of raw power for what wildlife biologists call “escape or capture” moments.

You can push the glucose pace all the way up to about 85% of your maximum heart rate, where you hit the limit of your high aerobic capacity. That’s the fastest pace you can sustain, but for a few seconds you can go faster still. In a burst of youthful enthusiasm at the beach, you can sprint 100 yards to the top of a dune. You double your power output for those last 300 feet. Your heart is putting out 400% of its resting capacity, and still you go way beyond its ability to deliver blood and oxygen. You kick in the afterburners for that burst of power, dumping energy into your muscles in a controlled chemical explosion. You have gone anaerobic, your third metabolic gear, the realm beyond oxygen.

That’s not aerobic exercise, it’s not endurance training and it’s not something you should do every day, but it’s fun to play with. It’s anaerobic exercise, where there’s no oxygen in your muscles. It’s also your oldest metabolic pathway, dating back to the days when there was no oxygen on earth, before the bacteria invented mitochondria. It’s more primitive than aerobic metabolism: less efficient and less biochemically elegant, but far more powerful over short distances and a critical gear to have in the evolutionary transmission. It saved your ancestors’ lives, or let them end someone else’s, countless times over the past few billion years.