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How Much Intensity Is Enough?

When you work out, you need to try your hardest. At least, some of the time.

For most people, this means an all-out effort twice per week.

But the rest of the time, training at your maximum capacity can actually be counterproductive. While those crazy workouts with your buddies can feel like you’ve accomplished something, always going hard for hard’s sake probably won’t get you the results you want.

Look, I’m guilty of overdoing the intensity. When we found CrossFit, I wanted to do it every day…even though the original prescription for CrossFit was 3 days on, 1 day off. I’d often go Monday to Friday and squeak in a Saturday “partner” workout on top if possible.

HIIT workouts train your body to burn muscle glycogen better. The reports of people actually reversing diabetes and losing fat are true, especially in their first year of training with high intensity. There are thousands of stories out there.

Over time, however, you can actually train your body to preferentially burn glycogen instead of fat. This makes sense: your body is wonderfully adaptive, and if you’re constantly doing high intensity work, your body will get better at producing energy to match the work.

Unfortunately, your body can’t break down fat stores very quickly. To burn fat as fuel during a workout–or even for a few hours afterward–you need to take things a bit slower.

How hard should you go? How slow do you have to go to burn fat?

Your heart will tell you.

At different heart rates, your body will shift its metabolism of fats and carbohydrates. When your heart is beating harder, you need energy fast to meet that demand. Your body will kick glycogen out of your muscles and burn that for fuel. When your heart rate is slightly elevated but not excessively so, your body will start to slowly burn fat for fuel.

Want a hot really hot fire? Burn dry kindling–sugars. Want a slow-burning but consistent flame? Burn a big block of maple–fats.

You can count the number of times your heart beats while exercising, and group different levels of intensity into “heart rate zones”. We published a video on the topic here:

For most people, exercising with high intensity is essential. They should do two workouts per week where they’re putting out as much work as possible. This is heart rate Zone 4 or 5, and it’s really important for increasing your work capacity and ability to withstand cardiovascular shock.

But most people should also exercise with a lower intensity – zone 2 – to burn fat as their preferential fuel source.

Zone 3 is also really important, because it helps them regulate (or pace out) their glycogen utilization. This is where the big gains are made against diabetes and insulin insensitivity.

What’s the best mix for you? Your coach can tell you. At Catalyst, our coaches program a variety of exercise intensity in our group workouts, and make specific programs for our private clients to follow.

But if you’re doing this on your own, get a heart rate monitor; do at least two Zone 2 workouts per week; do 1-2 high intensity workouts per week; and try to get a half-hour of Zone 3 in the mix, too.

I’ll be straight with you: most people don’t exercise hard enough. But if you’ve been working out for awhile with high intensity and you’re still not burning fat, try shifting two workouts per week to Zone 2.

And if you’re hammering a sports drink while you exercise, think about cutting that out–the fructose is undoing most of your high-intensity work anyway. More on that tomorrow!