Too much high intensity cardio?

When you do your cardio, do you find yourself completely breathless at some point during your workout?

If you've ever taken a Spinning class you've heard all about heart rate zones. If you're anything like I used to be you probably ignored it and worked as hard as you could during that class because the harder you work, the more calories you burn, right? Yes, but.

High Intensity Cardio

High intensity cardio is any activity that gets your heart rate above 75% of your maximum heart rate. (Calculate yours here.) If your idea of cardio is an all-out run as hard as you can for as long as you can endure it, you're probably doing high intensity cardio.

HiiT (High Intensity Interval Training) is cardio exercise that brings your heart both above and below that 75% mark in specifically timed intervals. HiiT drills are done using only your bodyweight; jumping jacks, sprints, burpees, mountain climbers and anything else that uses major muscle groups to raise your heart rate above 75%. HiiT is very challenging and taxing on the body, and in small doses can greatly improve your health and burn fat.

High intensity (HiiT) vs. Low intensity (endurance)

Your weekly cardio plan should include a mix of both high and low intensity cardio days. We'll talk about exactly how much in a little bit.

Low/moderate level aerobic exercise (below 75%) boosts your metabolism, burns fat, reduces your risk of disease and health problems, strengthens your heart, keeps your arteries clear, cholesterol low, and even boosts your mood.

I refer to cardio at a level lower than 75% of your maximum heart rate as "endurance cardio". It's the kind of cardio that you can sustain for at least 20 minutes and doesn't cause you to be completely breathless. While you need 150 mins of endurance cardio a week, thats not all you should be doing. If all of your cardio is below or hovers around that 75% mark, you're not getting the most out of your cardio program and you're going to plateau if you haven't already.

HiiT is efficient, since you're not required to do it for long periods of time.  It's challenging, it boosts your metabolism and your aerobic capacity, lowers insulin resistance, and you burn more calories both during and after a HiiT session than you do during a low intensity cardio session, thanks to something called EPOC (your excess post-exercise oxygen consumption).You don't need any equipment to do HiiT, it causes you to build muscle and lose fat, and you can do it basically anywhere.

HiiT drills can be structured however you choose. 

examples:

20 seconds: Work interval (burpees)

10 seconds: Recovery interval (marches)

or

4 minutes: 75%+ max heart rate run

2 minutes: recovery slow jog below 75% max heart rate

Too much high intensity?

The most important part of this post!

I don't have to tell you too much of any good thing can be bad.

Just like you don't want all of your cardio to be low intensity, you don't want it all to be high intensity either.

Exercising for extended periods of time at a heart rate above 75% of your maximum heart rate causes your body to burn glycogen rather than fat. This isn't a bad thing, but too much High Intensity cardio will cause your body to crave carbs and sugar to replenish its lost glycogen stores, which will cause a cycle of glycoogen-burning and glycogen-replenishing within your body that prevents fat loss, been though you're exercising super hard. Too much HiiT also causes burnout, overtraining syndrome (inability to make strength and fitness gains, fatigue), weight gain and muscle loss. Even worse, it causes your body to release more cortisol, which is the stress hormone that causes belly fat, a weakened immune system, and decreased insulin sensitivity, which puts you at a higher risk for developing type 2 diabetes (source). If you do cardio on most days (as you should) but you're reaching or exceeding 75% of your maximum each time, you're probably getting too much.

How much of each?

High intensity cardio should always be a part of your fitness regimen, and it should always be kept under control. Depending on your current fitness level I suggest doing HiiT 1-3 times a week for 15-30 minutes each time. You'll find a ton of different opinions out in the internet world regarding heart rate zone training and HiiT, but this is what I suggest to my clients and it's in compliance with what's recommended by the American Council on Exercise, and they know their stuff. You seriously don't need any more than that, and if you think you do, maybe you're trying to out-train a bad diet? (Not possible!)

Train Smart!

Do you guys do HiiT drills?? What are your favorites??

 Cited
photo courtesy of mensfitness.com