Aerobic Exercise Part 7

If you accept the fact that cardiovascular training is essential for keeping your heart going strong, it’s not far-fetched to believe that determining specific aspects of this form of training could be a matter of life or death! After all, there are many diverse theories regarding the best way to train the cardiovascular system and they all can’t be right. Therefore, it’s important to forget the hearsay and look to the experts for guidance. However, you might be surprised to learn that even with all the research that has been done in the field of exercise physiology, there is still considerable debate regarding the most important variable that defines a cardiovascular training program.

Once you have determined what you’re going to do to work your heart (i.e., the mode of training; for example, treadmill walking/jogging, elliptical stepping or stationary cycling), how often you’re going to do it (frequency) and for how long (duration), there’s only one training variable left to determine. Figuring out how hard to work when you’re training your heart is, by far, the most challenging aspect of cardiovascular exercise prescription and also the most misunderstood. And this isn’t surprising considering that the experts in the field still haven’t been able to resolve this issue.

One popular theory that has even been espoused by the American College of Sports Medicine in its 1998 position stand suggests that energetic outlay is the critical determinant of the cardiovascular training stimulus. All physical activities we do require energy expenditure and discounting relatively small inter-individual differences in efficiency, the energy cost of a given quantity of work is the same for everyone. That means it costs the same amount of calories for you or I to cover 26 miles as it does a world-class marathon runner. The difference is, of course, how long it would take each of us to complete the task. For example, in my case, we might be talking days! But the key issue is how hard I should be working when I cover that distance. After all, jogging six miles-per-hour might be every bit as hard for me as running 13 is for someone who is successful in that sport.

If the ACSM position stand was correct and the quantity of energy expended was all that mattered for determining whether your heart will stand up and take notice due to exercise, cardiovascular training objectives would be easy to determine. For example, let’s assume that an expenditure of 2000 calories per week was deemed to be the required amount for honing cardiovascular function. Exercisers would then have the option to accumulate this total through any combination of frequency, duration and intensity that they might choose. For example, in mid-summer when the weather is your ally, you could opt for a nice relaxing walk on the beach at sunset each night and as long as you covered enough distance (for example, approximately 25 miles over the course of the week for a 160-pound person), you’d be good to go. Conversely, if your time was tight and you wanted to get the job done as quickly as possible, you could run on a treadmill and cover what would amount to the same distance (that is, if you were moving instead of the belt) in a fraction of that amount of time.

Energy expenditure as the end-all-and-be-all of cardiovascular training is an attractive proposition because it makes the prospect of cardiovascular training extremely user-friendly. For example, if sweating isn’t your thing and your idea of heavy exertion is reaching for the channel changer, you could increase frequency and duration to compensate for lowered intensity and get every bit as much benefit as those crazy people killing themselves in the gym every day. Now, the guidelines did state that this was only the case once a minimal intensity threshold was exceeded, which means that twiddling your thumbs for 16 hours each day wouldn’t cut it, even if the energy expended for that amount of work added up to the requisite amount. However, the minimal threshold they recommended (55% of the maximal heart rate) was relatively low. Furthermore, they suggested that the required expenditure could be accumulated through the day in bouts of 10-minute duration. In other words, “formal” exercise sessions weren’t even required!

It is important to encourage inactive people to get off the couch and move, so if the ACSM’s “sugar-coating” of exercise requirements in its 1998 position stand accomplished that objective, it served a purpose. However, for every person who increased their activity level by working in their garden every day, taking the stairs instead of the elevator and parking at the far end of the parking lot, there might have been another who was willing to do more to satisfy their “exercise” requirements, but decided against it after learning that changes in cardiovascular health could be derived without going to that level of exertion. Furthermore, the ACSM went so far as to actually discourage higher intensity exercise, suggesting that vigorous activity is associated with increased risk of injury and dropout. Therefore, their message was clear: Be moderately active frequently throughout your day and that is enough. But is it?

This article was originally published in New Living Magazine, which can be accessed on-line at





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