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Cardio: How Much is Too Much?


Cardiovascular exercise is a great way to burn calories, enhance your body composition and improve many overall fitness capacities. But, just like anything else, too much cardio may be counterproductive when it comes to your individual goals. For all of you “cardioholics” out there, here is a bit of science on just how much cardio can be too much.

Cardiovascular exercise is not directly intended for fat loss. When you hear this, it may not make sense but here is why: when engaging in cardiovascular activities (such as running or cycling), you are not necessarily burning a lot of fat mass WHILE you are exercising — you are burning carbohydrate (and when that is used up, you switch to protein, not fat). Fat loss comes from a calorie deficit, not from extreme amounts of cardio. Cardio is intended to improve one or more fitness capacities, not burn fat as a primary fuel source. Some (but not all) of the benefits from cardiovascular exercise include:

  • Stronger heart and cardiovascular system
  • Increased stroke volume
  • Improved circulation and improved VO2max
  • Increased energy stores
  • Lower blood pressure
  • Lower cholesterol
  • Stronger bones

The list could go on, but this blog is not intended to “knock” cardiovascular exercise, as it clearly has substantial health benefits. I am here to explain why, in healthy individuals looking to improve body composition, extreme amounts of cardio can be counterproductive.

Many individuals believe that as long as they are doing hours and hours of cardio each week, they will lose fat mass and improve their overall body fat percentage. This is not true, especially with LONG bouts (>60 mins) of low intensity cardio.

During long duration, low intensity cardio, we not only burn fewer calories compared to higher intensity, shorter duration cardio, we can also have less than desirable hormonal responses:

  • Depressed Testosterone: the function of testosterone is to spare/rebuild muscle tissue and some research suggests it acts as a lipolytic (fat burner).
  • Depressed Growth Hormone: again, this is a muscle protein sparer and plays an anabolic (muscle building) function, as well as acts as a lipolytic.
  • Reduced Epinephrine (at lower intensities – epinephrine is not released at higher levels): This is your primary exercise induced lipolytic hormone. Thus, less influence from this hormone means less fat loss.

Research also strongly suggests that the number of calories burned after longer bouts of low intensity cardiovascular exercise is far fewer than calories burned by shorter, higher intensity (interval) training.

What does this all mean? This means that if you are an individual who is looking to lose those last 5lbs of fat mass to better your overall body composition, longer bouts of low intensity cardiovascular exercise are not the answer. Not only are you suppressing essential hormonal responses required for the maintenance of lean mass, you may even run the risk of breaking down lean mass as fuel.

The Solution

Do short (30-60mins), high intensity interval training. Not only will your overall energy expenditure be much higher, but hormonal responses, responsible for burning fat and maintaining lean mass will be maximized. Limiting cardio to 3-4 days/week would also be a good idea to avoid overtraining or overuse injuries.

So if you are one of the many individuals “stuck” at a certain body fat percentage, do not get stuck in the “more is better” mentality when it comes to your cardiovascular exercise. Switch to shorter bouts of high intensity interval training to maximize your results.



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