The Truth About Cardio

March 2008

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Today is the day that you decide that you are going to start exercising.  You put on your shorts, slip on your running shoes, do a couple of quick stretches and you’re out the door at the start of your 5 mile run.  No doubt, this is the image of exercise that most people have when they decide that they are going to “lose weight and get in shape.” Unfortunately, if you choose this exercise method with the intention of losing bodyfat and achieving ideal body composition (low bodyfat percentage, high degree of muscle definition) you are going to be sorely disappointed.

Visualize an elite level marathon runner standing side by side with an Olympic sprinter.  Based solely on a visual survey, which one of these two athletes usually has lower bodyfat percentages and more muscle definition?  Nine times out of ten, the sprinter’s body comes closer to describing the look that most people are trying to achieve through exercise - toned shoulders/arms, shapely hips, rounded glutes, sculpted thighs, and a chiseled midsection.  On the other hand, despite his/her “skinny” appearance the marathon runner often appears flaccid, with little or no muscle tone, lacking the aforementioned superficial physical characteristics most individuals are in search of.

Of course these are broad generalizations and a visual survey of this type cannot provide the sole means of evidence to support a complex argument.  However, in providing such a comparison I’m merely trying to illustrate the point that sprinter style training, i.e. short-duration, high intensity cardiovascular exercise (“Interval Training”) is a superior method of training for achieving ideal body composition when compared to long-duration, low-moderate intensity cardiovascular exercise (“Aerobic Endurance Training”), i.e. jogging/running.

Aerobic Endurance Training

I apologize if you are now regretting all of those hours spent jogging along on the treadmill and, as a result, are secretly cursing me under your breath for making all of that hard work seem worthless.  If that’s the case, please allow me to calm you down by letting you know that your adherence to this faulty methodology was not totally fruitless and certainly not your fault. 

The good news is that Aerobic Endurance Training offers numerous benefits to your heart, namely that as a result of this form of training your heart becomes stronger and more efficient at supplying blood and oxygen to the rest of your body.  Additionally, low-moderate intensity, long duration cardiorespiratory training does provide calorie burning benefits, which is where its connection to weight loss/bodyfat reduction comes in.  However, this is also where the problem begins.

Suffice to say that if you run long enough and far enough you are going to burn a significant number of calories during any one training session.  This would appear to be a good thing in terms of creating a caloric deficit for the purposes of moving closer towards your ideal body composition, right?  Well, yes and no.  “Yes,” in thatresearch suggests that Aerobic Endurance Training can lead to bodyfat loss, but “no,” in that this type of training has “little or no significant effect on fat-free mass.”[1]  Additionally, “studies have also shown decreases in muscle fiber size in humans with aerobic endurance training…such changes would compromise muscle size and strength adaptations.”[2]

I emphasized these important bits of information to illustrate Aerobic Endurance Training’s effect on muscle.  Muscle (one component of fat-free mass) matters in terms of lowering your bodyfat levels because muscle is metabolically active tissue that requires energy (calories) for preservation.  The more muscle you have, the more calories and fat you will burn daily. Therefore, it is in your calorie burning interest to avoid any type of training that “compromises muscle size,” and limits your body’s overall ability to burn fat.

Another important factor to consider is, “Aerobic endurance training, especially running, is often associated with protein sloughing from muscle…In the case of running, catabolic effects predominate and can lead to muscle degradation and reduction in power.”[3]  Further, “Excessive training might lead to a predominance of catabolic activity in the body and cause muscle metabolism not to be able to keep up with the needed amount of protein synthesis.”[4] 

Unfortunately, this scientific evidence suggests that Aerobic Endurance Training essentially reduces your body’s overall fat-burning efficiency because it catabolizes, or in other words, eats away at muscle.  This matters greatly because, as we know, anything that eats away at muscle ultimately limits your ability to burn fat and maintain low bodyfat levels over the long-term.

Interval Training

I’m sure that you are now ready to throw away your running sneakers, short shorts, and headband and head for the couch to watch Judge Judy because, “Andrew said that I shouldn’t do cardio.”  Well, my friend, that’s not the message you need to be taking away.  Cardiovascular training is a necessary component of a healthy and fit lifestyle, but there is a new, more beneficial approach.  Current exercise science research now suggests that short duration, higher intensity bouts of cardiorespiratory training (“Interval Training”) can deliver the same heart strengthening benefits of Aerobic Endurance Training minus the muscle catabolizing effects.  However, most importantly, Interval Training has been shown to increase calorie burning by raising your metabolism long after your workout has ended.

“How does it work?”  The concept is quite simple.  Your body is lazy.  It wants to expend as little energy as possible.  The way it does that is by utilizing oxygen to allow fat and glucose to be used as energy sources.  Thus, when you increase the oxygen demands on your body during and after exercise the harder your body will have to work in order to return to its resting state.

This theory applies to Interval Training because when you perform short duration cardiovascular exercise at high intensities (upwards of 85% Heart Rate Max), your body will require more oxygen during the exercise as well as during the recovery from the exercise.  In order to meet the increased post-exercise oxygen demands, your body’s metabolism elevates for several hours (some research suggests even into the next day) following cessation of your training session, resulting in significantly more post-workout calorie and fat burning than with Aerobic Endurance Training.  Further, the prevalent body of research on this subject concludes that the greater the intensity of the exercise, the greater the boost to your post-exercise metabolism.[5]

Another reason to favor Interval Training is that due to the shorter duration of the workout, unlike Aerobic Endurance Training, Interval Training is less likely to result in the release of muscle-destroying hormones such as the villainous cortisol. And finally, my personal favorite reason for touting the benefits of Interval Training is, assuming proper posture and gait, it saves your joints and muscles from the wear and tear associated with long-distance runs.  In my experience, the clients that have put in the most running mileage over the years are the ones that come to me from the start with the greatest number of ankle, knee, hip, and spinal pain issues. 

Is Interval Training for you?

That depends on your current fitness level.  First, one needs to consider that in order to obtain the full benefit of Interval Training, one needs to work at intensities equal to or greater than 85% of your Maximum Heart Rate (MHR).  Therefore, before commencing this form of training you should have a physical exam that includes a cardio stress test in order to determine whether or not your heart can handle this level of activity. 

Regardless, even with a clean bill of health anyone who hasn’t exercised in the last 6 months ought to lay off the Interval Training until establishing a base level of conditioning.  It is potentially dangerous for any deconditioned individual to exercise at 85% above their Maximum Heart Rate.  It is much safer and healthier to slowly work up to higher intensity training by first establishing your fitness at lower intensities. 

However, if you are a person that has been doing the same old cardio routine for years (Yes, you. The one who stays on the treadmill for 45 minutes, jogging along at 4.5 speed) and are in otherwise good physical condition with a physical exam and stress test to show for it, then Interval Training might give you that fat-burning boost that you have yet to experience with Aerobic Endurance Training.

Interval Training Protocols

I know, you want to know how to utilize this new and exciting form of training.  At this point, exact protocols for Interval Training have not been uniformly established, but there are some basic guidelines to follow:[6]

1. Warm-up for 5-10 minutes at 65-75% of your Maximum Heart Rate (220-age x .65 or .75);
2. Increase the intensity (speed and/or incline) until you reach 86-90% of your MHR (220-age x .86-.90) and stay there for 10-60 seconds.  It may take one or two minutes to reach this HR, so don’t start counting until you’ve reached at least 86% of your MHR;
3. After you’ve timed out, decrease the intensity to warm-up levels and stay there until the HR drops to 65-75% of MHR;
4. Repeat the process 2-5 times to start, adding one cycle every time, but never going longer than 40 minutes during one session (not including warm-up/cool down) in order to prevent the catabolic effects of overtraining.

You can adjust your intervals, but if your high intensity intervals last more than 1-minute, chances are you are not working hard enough.  To measure your heart rate you can always take your radial (wrist) or carotid (neck) pulse, or use the scale of perceived exertion (rate your level of effort based on a scale of 1-10), but it may be useful and more accurate to purchase a heart rate monitor for about $35-$40 online or from your local sporting goods store. 

As you progress, you can increase the intensity and shorten the duration of the intervals.  However, please keep in mind that safety always comes first and when in doubt always err on the side of caution.  Therefore, if you feel dizzy, nauseous, or out of sorts in any way, that is a sign to cut back on the intensity.  Further, if you continue to experience the aforementioned effects while Interval Training you should stop immediately and consult your doctor before resuming this type of training.  However, if all is well you can begin to incorporate Interval Training into your regimen as a powerful bodyfat loss tool and an effective means of realizing your ideal body composition.

©Andrew Kass, 2008.

This information is not intended to diagnose or treat any specific or general condition or to replace your own judgment or that of your physician, medical, or health professional.  Please always consult your physician and/or health/medical professional before making any diet, exercise, or lifestyle changes in connection with the information contained in these newsletters. 

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