For years now, I have been seeing magazines and newspaper articles make reference to the fact that if you do aerobic activity multiple times a day, but for short amounts of time, it is equally as effective as one bout of longer exercise. For example, if you walk for 10 minutes in the morning, 10 minutes at lunch, and 10 minutes after work that would be considered the same as if you exercised for 30 minutes at the end of the day. This notion, however, is incorrect.
As I have seen this theory in numerous places, I have often wondered where it comes from. Scientifically, it doesn't make sense, so why would sources be making such a claim? The only response I have to my own question is, it must be a tactic to just get people moving. With the majority of our population sedentary, maybe it seems overwhelming to many to consider adding 30 to 60 minutes of aerobic activity each day. So if we tell people they can break up their aerobic activity throughout the day, it seems less intimidating and more realistic.
The problem with this, however, is that it makes people think all they need to do is walk a little bit here and there and they can be in great shape, which is not true.
Here's the problem; if I asked most people "why is aerobic activity so important?", I would get many responses such as decreased risk of heart disease, lower cholesterol, lower blood pressure, reduced body fat, and better fitness levels. But these benefits of aerobic exercise occur only because of the endurance factor of aerobic activity.
The purpose of aerobic exercise is to train our heart and lungs (both cardiovascular and respiratory systems) to be more efficient; pump blood more efficiently, deliver nutrients to the body cells quicker, and to pump more blood, per beat, making the heart work less (thus helping it to last longer). This training, if you will, comes from endurance activity. Cardiorespiratory (aerobic) exercise is meant to help us improve endurance, overall, so telling people they only need to exercise for a few minutes at a time could not possibly help someone improve their endurance. Ample time is needed to truly condition the heart and the lungs to be more efficient.
Now focusing on reducing body fat, one must exercise for a minimum of twenty minutes to efficiently "burn" body fat. For the first twenty minutes of aerobic exercise, we primarily use glucose (sugar) for energy. After twenty minutes, we begin to use more fat for energy. So if you only exercise for 10 minutes at a time, you are using more sugar than fat for energy, which is not nearly as effective for body fat loss.
All that being said, if you are new to exercise and desire to incorporate regular aerobic activity into your life, it is perfectly acceptable to start out slow, even for just 10 minutes a day. This can help you build the habit of exercise without feeling overwhelmed. You would set progressive goals to increase the time spent doing aerobic activity, eventually bringing you to a total of 30-60 minutes each session.
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