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That was pretty much the modus operandi when I was in the Marines, running composed probably 70% of our fitness program. Short runs, long runs, runs with boots and packs, runs on the beach, runs uphill, sprinting, fartlek, you name it. Whenever you see commercials for gym memberships they always show lots of people running, biking, swimming, doing tae bo, and other forms of cardiovascular exercise. So the question is, what does cardio do for you, is that an appropriate part of a proper fat loss program, and if so how much and what kind should you do?

Cardiovascular exercise, otherwise known as Aerobic exercise, meaning “with oxygen” is generally lower in intensity, and longer in duration. Examples include running, swimming, biking, cross-country skiing, aerobics, and any other activity that involves repeated low intensity effort. Adaptations to training include:

1) Strengthening of the muscles involved with respiration

2) Improved heart pumping action and lowered resting heart rate

3) Increased number of red blood cells, enabling greater oxygen transport

4) Increased intramuscular energy storage

5) Neovascularization of the muscle sarcomeres to increase blood flow through the muscles

6) Greater Mitochondrial density

7) Increased speed at which the aerobic metabolism is activated in the musculature

Overall gains in performance are often measured by an increase in VO2 max, the total amount of oxygen consumed during the exercise period. All of those things are good for your HEALTH, but do they really mean much in terms of weight loss? As it turns out, the answer is no, not really. We left out two major benefits however:

A) Cardio burns calories both during the event, and post exercise due to temporarily elevated metabolism

B) Cardio lowers your blood sugar level, making you more carb tolerant for a short while after finishing

Creating a significant daily calorie deficit can be difficult, especially when you’re trying to avoid hunger. Cardio can be effectively utilized to help you reach that goal by raising your daily energy requirement. The meters on most treadmills and stationary bikes have a calories burned setting, but most tend to be highly inflated, you can generally expect that your actual results were about half of whatever they say they were. Bodybuilding.com has an excellent calculator to show how much you can burn for each type of activity, it’s located here:

Calorie Calculator

Here are a few examples for a 200lb individual for 30 minutes worth of exercise:

Low Impact Aerobics - 238
Stationary Bike - 333
Running 10 Min Mile - 476
Swimming Moderate Freestyle - 333
Walking 3 Mph - 157

As you can see, burning 200-400 calories worth of energy in thirty minutes in a pretty attainable goal. Since for most people on calorie restriction this will represent a 10%-20% increase in daily energy expenditure, it’s easy to see the benefit in terms of faster weight loss. So the next question is what kind of cardio should you be doing?

Since the main benefit of cardio is calories burned (at least in terms of what we care about which is fat loss) then the energy expended is one way of deciding what to do. In that case the fartlek (a combination of jogging and sprinting) is probably the highest in terms of energy per unit time. For me however there are two other considerations that usually overshadow the calorie issue. The first is impact, I find running fairly hard on my knees, and prefer something a bit less jarring. The second is compliance, many cardio activities are basically boring, and for me, something I can do while watching television is the best way to ensure that I do it every time regardless of weather or other distractions.

My personal choice of cardio activities is stationary bike, not the most efficient choice perhaps, but one that seems to solve most of my requirements. An elliptical machine would probably also be a good choice. I put mine in the living room, and plug away till the counter reads 400 calories (which I figure is probably actually 200) while watching shows or music videos. Compliance is high, impact is low, efficiency is medium.

How much cardio should you do every week? Well, generally you want to aim for about 2-4 hours per week. Anything less than two and you’re really not going to see much in terms of results. Anything more than 4 and you’re starting to create too much strain, this will tend to steal adaptive energy from your weightlifting routine and sabotage your attempts to retain lean body mass. I do approximately 30 minutes after each weightlifting session, so on my current 3 on 1 off, 3 on 2 off schedule that makes for about 3.1 hours of cardio per week, which seems to work out just about right.

Generally you should not do cardio on your off days, as it tends to slow your recovery. Cardio sessions should be a minimum of 20 minutes in length since it takes 10-15 minutes to really get into the fat burning zone, and no more than about an hour or so maximum, otherwise your system starts producing large amounts of cortisol, a muscle wasting stress hormone. Aerobic exercise can be performed on its own, or directly after lifting weights (though you should limit it to 30 minutes if you’re going to be doing it at that time). Never do your cardio before lifting weights, as that will negatively affect your performance. If you’re a morning person, doing your cardio first thing after waking is about 5% more effective than at other times due to the fact that your glycogen reserves are already low and you’ll go into fat burning mode faster. In general if you’re not sweating or breathing fast you’re not working hard enough to produce results.