Am I Doing Cardiovascular Exercise at the Right Intensity?

People often go about exercise haphazardly, assuming just doing it is enough to achieve results. Wrong! Exercise intelligently, and you will get results. Far too often, I see people having conversations on their cell phone or reading during their workout. Then there are those who insist on jogging for hours on end or churning their elliptical into the ground for 90 minutes. Trust me, if you can hop on an elliptical for 90 minutes, you can’t be working that hard! If you want serious results, you have got to be serious about your exercise. Put the US Weekly away! A very smart person (I don’t know who) once said you can work hard, and you can work long, but you cannot do both. This is SO applicable when it comes to exercise, and the truth is, hard work beats prolonged work every time.

In kinesiology, long-duration cardio is termed steady-state exercise. Typically, steady-state exercise is of a low intensity and is always below an individual’s VO2max, or the capacity of the body to get oxygen to working muscles for exercise. Once exercise surpasses your VO2max, the exercise becomes anaerobic. Anaerobic exercise is paramount to excess postexercise oxygen consumption, also known as “EPOC”. This phenomenon is the “oxygen uptake above resting values used to restore the body to the preexercise condition” (Baechle and Earle 35).

Why is this important? EPOC is a critical factor in burning calories after you’re done exercising. That’s right, you can burn calories for up to 24 to 48 hours after exercise, when you’re relaxing! That’s huge, and any exercise that’s anaerobic creates EPOC. How do you know if an exercise is anaerobic? Well, generally if you cannot maintain your current intensity after 90 seconds with an exercise, it is anaerobic. The oxidative system takes over after 90 seconds, and the exercise becomes aerobic.

The best way to include an anaerobic portion to your cardio bouts is through interval training. Put simply, intervals are bouts of high-intensity exercise interspersed with lower intensity periods. Intervals can be done with several ratios. As a general rule, the shorter and more intense your high-intensity bout is, the longer your low-intensity period should be, relatively speaking. For example, if you want to do 10-second sprints, your low-intensity periods should be at least a minute, or a 1:6 ratio. If you want to run at a fast pace for 2 minutes, then typically you can then slow down to a fast walk or jog for 2 minutes. This ratio, of course, is 1:1. The rest periods will allow your body to recover for the next high-intensity bout.

Intervals will mobilize fat stores more efficiently than steady-state exercise. This is because high-intensity exercise will rapidly deplete your glycogen stores (the storage form of carbs in your liver and muscles). Once you deplete your glycogen levels, your body uses fat for energy. A sample protocol would look like this:

2-3 days/week

20-25 minutes total

1 minute fast (RPE = 7-9) : 2 minutes slow (RPE = 3-5)

RPE is the Rate of Perceived Exertion, using a 1-10 scale. Ten would be impossible, and one is way too easy.

Intervals are intense, so doing them without at least a base of steady-state cardio for six to eight weeks is ill advised. Also, you shouldn’t need more than 25 or 30 minutes to complete an interval session; sometimes less will suffice. Doing more than three days a week for 30 minutes can lead to overreaching and overuse injuries. When it comes to very short high-intensity training like 10 and 20-second sprints, use caution. These intervals are very intense and can lead to extreme fatigue the next day. Build up slowly.

The treadmill and bike as well as outside running are the best choices for interval training. Switch it up often to prevent overtraining and boredom. If you’re feeling extra tired one week, listen to your body and back off the intervals. A good rule of thumb is to do two interval sessions per week mixed with one steady-state session.

Next time you want to go for a run, remember this: steady-state, low-intensity exercise only burns calories during exercise. The advantages of doing intervals are clear. Even though they may burn fewer calories during the actual exercise, in the end they will burn more calories through EPOC. The harder you work, the more EPOC you create. Intervals take less time than steady-state sessions. They mobilize body fat by depleting glycogen stores. As if that wasn’t enough, intervals will increase your VO2max and therefore your overall fitness level. You get out what you put in, and the hard work is clearly worth it!


Baechle, T., & Earle, T. (2008). Essentials of Strength Training and Conditioning. Champaign, IL: Human Kinetics.

Kurt Rawlins is a fitness professional, Certified Strength and Conditioning Specialist, and author. He specializes in helping professional women in Chicago shape and tone their muscles into fat-burning machines so they can wear whatever they want, and feel healthy and confident doing it. Visit his website at to sign up for his free e-newsletter with valuable fitness and nutrition tips.