There’s Cardio in My CrossFit?

Nicole flies over the bar in CrossFit Open 14.5.

Nicole flies over the bar in CrossFit Open 14.5.

Friday morning I slogged through CrossFit Open workout 14.5, a descending ladder of thrusters and burpees. I never left my little corner of the gym for nearly 17 minutes and when I was done my lungs felt like they’d been pushed through a hard 5k. Sunday morning’s 10k was a breeze by comparison.

So there you are in the gym getting all out of breath and choking for oxygen as you plug away at a 12:00 AMRAP of burpees, wall balls and thrusters. “I can’t catch my breath,” you say or “I need more cardio.” Really? Are you breathing hard? Wait, don’t answer yet. Let me explain what “cardio” is.

Cardiovascular or aerobic exercise is any type of activity where oxygen is used to provide fuel for your workout. As far as your body is concerned any exercise lasting three minutes or longer is considered “cardio.” Three minutes!

The aerobic system is just one way to create energy for working muscles. The anaerobic system is another. When you are performing a one rep max your body uses ATP (adenosine triphosphate). This energy system is good for a whole 10 seconds. If you are working through a five rep set of deadlifts you will use up the ATP first and then your body will switch gears and use glycogen, another anaerobic form of energy. The problem with glycogen is that it is only good for 11 seconds to three minutes. Now you’re back to using trusty, always available oxygen. In case you’re not paying attention, that would be “cardio.”

Maybe you’re confusing “cardio” with “aerobic capacity.” Aerobic capacity is the ability of the heart and lungs to get oxygen to the muscles. Maximum oxygen consumption (VO2 Max) reflects aerobic fitness. The higher the VO2 max, the higher the anaerobic threshold and the faster you can perform in endurance events. Did you catch the key word in that last sentence? Read it again. In order to improve your “cardio” you need to work anaerobically. That means short, hard workouts. These workouts build overall strength and increase your endurance because your muscles have the ability to withstand fatigue. You also give your metabolism a big boost.

Defining workouts as “strength training” or “cardio” is an exercise science and fitness industry thing. It has no basis in nature. With CrossFit our goal is to blur the lines between strength training and cardio. Let’s go back to that question I asked earlier. You’re in the middle of a 12 minute AMRAP of burpees, wall balls and thrusters. Your heart rate is elevated, your breathing is laboured and your body is doing its best to keep up with the oxygen demand. Are you breathing hard? You better be! Do you still think you need cardio? I don’t think so.


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