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Ep. 38 – Exercise intensity or exercise volume?

As an exercise physiologist, Dr. Chet frequently gets asked: what's more important - exercise intensity or exercise volume? His answer is always yes! To make that point a little clearer, He’s going to check out a recent study that examined that very question on this edition of Straight Talk on Health.

Welcome to Straight Talk on Health. I’m your host Dr. Chet Zelasko. Straight Talk on Health is a joint production with WGVU in Grand Rapids MI. I examine the world of health. Whether it’s research that makes the news, another miracle diet, or a new food fad, I look at the science behind them, and let you know whether it’s real or not. You can check out other things that I do on my website drchet.com and sign up for my free emails.

Exercise is my most favorite thing to talk about, not surprising for an exercise physiologist. There is no question that diet is important to our health. But if I had to focus on just one habit that people should adopt it would definitely be exercise first before anything else. Understand that I believe we should all eat more vegetables and fruits, take complementary supplements if there are gaps in our diet, and that we should all try to attain a normal body weight. But aside from quitting smoking, the most important thing that a human being can do is to be physically active. I truly believe that.

When I say exercise first, I mean all the components of exercise. Aerobic activity that stresses the cardiovascular system and every other system in the body critical to health. But it isn't just about getting in your steps or your bike ride. Maintaining and increasing muscle mass is also critical especially as we age. And we also need to keep our muscles, tendons, and ligaments, stretched on a regular basis to stay limber and loose. But for the most part, people are most concerned about being in better physical condition, protecting their hearts, and burning calories.

Before I get into the study, let me be clear. Exercise is a lousy way to burn calories for weight loss. You have to invest so much time for what seems to be so little return. If you were a professional athlete or a performer of some sort, you would invest hours a day in physical training. That's what you're getting paid to do. In that we get no more than 10 to 20% of all Americans exercising at a level that will gain them benefits, we want to try to be as efficient as possible for them to attain this goal because exercise benefits health.

Let's look at the study. The title is Physical Activity Volume, Intensity, And Incident Cardiovascular Disease. It was published in the European Heart Journal in October of 2022. The subjects in the study were a subgroup of people that were in the United Kingdom Biobank study. The data were collected from 88,412 middle-aged adults with 58% being women. Another key factor is that they did not have cardiovascular disease before the study.

Researchers started with a couple basic questions. First what was the association between device-based physical activity volume and intensity with cardiovascular disease? We'll talk about what device-based means in a moment. Second question: does physical activity energy expenditure derived from moderate to vigorous activity confer any additional benefits to incident cardiovascular disease risk? In effect what that means is that they wanted to know if adding vigorous activity to moderate activity would confer additional benefits in reducing the risk of cardiovascular disease events.

What was the device based physical activity? They gave the participants accelerometers which they wore on their wrist for seven days. So the first issue that arise would be this: is what the subjects do in seven days reflective of what they normally do? One of the things that's a standard of research is that once you interfere with a person, whether you give them a pill, whether you do a surgery, or whether you give them an accelerometer to wear, it can change their behavior. That's why placebos are so important in any type of research. However, if a person did not wear an accelerometer at all, you would have no way of collecting any actual activity levels. That would not be practical in this type of study.

The researchers broke the data into tertiles or in other words, into thirds by activity level. The mean age of the subjects in the study was 62 years and the average BMI of 27 kg/meter2. They tracked the subjects for 6.8 years. In that amount of time there were just over 4000 cardiovascular disease events. Those were things like ischemic heart disease, stroke or other CVD events.

Their findings were pretty interesting related to the question of volume versus intensity. The rate of cardiovascular disease events was 14% lower when moderate volume physical activity accounted for 20% rather than 10% per day physical activity energy expenditure. Now that may seem a little confusing so let's start at the beginning.

Movement that's slow and steady up to moderate and steady is going to reduce the risk of cardiovascular disease events. They also found that the rate of cardiovascular disease events decreased with higher physical activity energy expenditure. Put a different way, the higher the intensity, the lower the rate of cardiovascular disease events.

So going back to that 14% decrease that I mentioned earlier, if you were to exercise at a higher intensity, you would only have to exercise half the time than you would if you were doing moderate volume exercise. So instead of a 20 minute walk, a 10 minute jog could be better. What if the subjects combined exercising at a lower intensity but for a longer period of time some days, with higher intensity exercise for shorter times on other days? Would that give them additional benefits? And as you might expect, the answer to that question is absolutely.

Does this mean that everyone should be doing high intensity interval training? Not in the classic sense. What I mean by that is that you don't have to do a special workout where you're going to plus the gut for 90 seconds and then take it easy for for 5 minutes. That is intense and it overall takes less time. But these were not people who were using any type of machinery to exercise for the most part. The accelerometers track motion in three directions and so a stationary bike or even an elliptical trainer would not yeah adequate information. But everything from gardening to walking the dog to spontaneously breaking out into a run to catch a bus, those would show up as mild moderate or high intensity exercise. It also doesn't mean that all the exercise that you do has to be high intensity. Simply going for a walk is going to provide you with benefits to reduce your risk of cardiovascular disease and, while not assessed, type 2 diabetes, hypertension, and cancer as well. But investing time in higher intensity exercise may provide you with additional benefits.

That's why my latest recommendations are that people use short bursts throughout the day to stress the heart and the blood vessels if they are physically able. And let's be reasonable here. You have to be fit enough and ambulatory enough to actually do high intensity exercise. But you know something? I know of at least one physical therapist who encourages subjects to do jumping jacks while sitting in a wheelchair. Of course they can't do the leg part of it but for 60 seconds, their arms are going up and down up and down up and down at a very high rate--and that is high for them. For others of you, it may be doing a 2 minute run up a very steep hill. It is the intensity of the exercise that stresses the heart in ways that a nice easy walk does not. And for that, you get additional benefits.

So check with your doctor to find out the limitations that he's putting on you as it relates to exercise intensity and then go and get after it. Not to lose a whole bunch of weight. Not to win the next 5K. Not every day. But to make your heart stronger and fitter. Because remember health is a choice. Choose wisely today and every day. I'm Dr. Chet Zelasko

Dr. Chet Zelasko is a scientist, speaker, and author. Dr. Chet has a Ph.D. and MA in Exercise Physiology and Health Education from Michigan State University and a BS in Physical Education from Canisius College. He’s certified by the American College of Sports Medicine as a Health and Fitness Specialist, belongs to the American Society of Nutrition, and has conducted research and been published in peer-reviewed journals. You can find him online at drchet.com.
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