High-intensity interval training—also known as HIIT—is another kind of extreme effort you can use to hone your fitness.
Think sprinting away from a hungry lion—it may sound odd, but that’s exactly how your body interprets those heart-rate-jacking workouts.
You’ve heard of fight-or-flight, the reaction forged by evolution that kicks in to save your butt in stressful situations. When you do HIIT, that response fires up—your brain has no idea whether you’re sprinting on a treadmill in Planet Fitness or running from rhinos on a savanna.
That’s stressful, so you release stress hormones.
In the short term, these hormones burn fat and help you build muscle. They build up during HIIT and slowly decrease as you recover. They can also mitigate inflammation, guarding against heart disease and diabetes.
But there’s a catch. As with wine and women, too much of a good thing can be bad.
Your body can deal with only so much stress at once, whether it’s from HIIT, work, poor sleep, or your other workouts. Overdoing HIIT floods your body with stress hormones, so they stay elevated 24/7 and have no time to recede.
Combining too much HIIT with other training and a stressful lifestyle may have an additive effect.
In that overstressed environment, your body releases chronically high levels of cortisol, a hormone that causes you to lose muscle, retain fat, and lower your guard against illness and injury.
The fix: Do just one HIIT session a week. That’s enough for most guys, especially if you’re already lifting weights.
And do what you can to de-stress your life—through any means you want. That’ll make all your workouts more effective.