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Exercise – How Much; How Often?

By Professor Gordon S. Lynch

Can exercising for just a few days a week give the same health benefits as exercising more often?

Exercise targets for good health

To keep reasonably fit and reduce the risk of chronic diseases like diabetes, heart disease and some cancers, most health authorities recommend we undertake at least 30 minutes of moderate-intensity exercise on most days in order to reach a basic weekly target of 150 minutes. And recent dietary guidelines suggest we may need to do even more than that if we're to keep our weight under control.

But what if we were to cram our weekly exercise target into just a couple of days per week? Would that still produce similar health benefits?

That was the question posed by Canadian researchers who studied whether the frequency of exercise was associated with health markers associated with metabolic syndrome.

Metabolic syndrome describes a group of factors that increases risk for diabetes, heart disease and stroke. These factors usually cluster and include having a large waistline; high triglycerides; low HDL (good) cholesterol; high blood pressure; and high fasting blood glucose.

Regular exercise and a healthy diet are the first steps to tackling metabolic syndrome. This study investigated the impact of exercise frequency (how often someone exercised) – rather than just the total amount of exercise they performed each week – on risk for metabolic syndrome.

The study examined health information and exercise habits of 2,324 Canadian adults aged from 18 to 64 years old. The participants were interviewed, completed questionnaires and attended a mobile clinic for physical measurements and blood tests.

All participants were provided with an accelerometer which they wore on a belt around their waist for one week to record the intensity of their movements and to calculate energy expenditure.

The participants were divided into physically active and inactive groups based on how much moderate to vigorous exercise they performed during that week.

Those who met the physical activity guidelines of more than 150 minutes per week of aerobic exercise were divided into two groups: frequently active (active five to seven days of the week); or infrequently active (active on one to four days of the week).

What did the study find?

Not surprisingly, the researchers found that physically inactive adults had more than four times greater risk for metabolic syndrome than active adults. Yes, being sedentary is bad for your health!

The more surprising finding was there was no difference in the risk of metabolic syndrome between the frequently active and infrequently active groups. As long as participants accumulated 150 minutes of exercise throughout the week, their risk for metabolic syndrome did not differ.

That means longer sessions of exercise only a few days a week could keep you as healthy as exercising five or more days a week, provided that total of 150 minutes was achieved. Doing no exercise from Monday to Friday then 150 minutes of activity over the weekend could potentially achieve the same health benefits as 20-25 minutes of daily exercise.

The researchers concluded that adults should aim to accumulate at least 150 minutes of weekly physical activity in whatever pattern that works for their schedule.

Is this the right exercise and health message?

While reaching the basic target of 150 minutes in whatever pattern suits sounds like a good message, it isn’t the best message. That’s because many of us aren’t just inactive for most of the day, we’re completely sedentary – sitting or lying down.

Research over the last five years has shown that regularly sitting for hours at a desk or in front of a computer screen is linked to poor health outcomes and increases risk for inactivity-related conditions like diabetes and heart disease.

That’s because the large muscle groups like those of the legs are essentially not doing anything, and so the body’s metabolism slows and blood flow becomes sluggish. People who sit more tend to have worse results when it comes to their blood cholesterol, triglycerides, and blood sugar, and their waist size tends to be bigger – all factors linked with an increased risk of diabetes, heart disease and other inactivity-related diseases.

Perhaps the most disconcerting aspect is that even being physically active may not cancel all of the undesirable effects of sitting for long periods, which is why a better health message is to try to be active at every opportunity. Things like taking the stairs instead of the elevator, taking regular breaks to get up and walk around, and standing instead of sitting during meetings and phone calls can all help.

A recent study from the same group also concluded that, for children and adolescents at least, more frequent physical activity is associated with lower risk of insulin resistance – a condition which leads to diabetes. This may also be the case in adults, as the Exercise and Sports Science Australia (ESSA) clinical guidelines for exercise in people with type 2 diabetes and pre-diabetes note the benefits of exercise in reducing insulin resistance tend to wear off after around 48 hours. Consequently, these guidelines recommend no more than two consecutive days without physical activity.

Based on the above, it seems the best approach is to stick with at least 30 minutes of moderate intensity physical activity on most, preferably all, days of the week.

Reaching and exceeding the target

Instead of advocating shortcuts and minimums we need to recognise that when it comes to physical activity and health, more is usually better. Activities like brisk walking are good ways to reach the target of 150 minutes of exercise. You can do less exercise overall if you’re engaging in more vigorous activities like running, but not everyone can exercise at that higher intensity.

It is also true that not everyone can perform exercise for long periods to reach a 150-minute target in just a couple of sessions. Most will need to accumulate the benefits of exercise from activities they perform every day. In fact, current Australian physical activity guidelines encourage us to think of movement as an opportunity, not an inconvenience, and to be active every day in as many ways as we can. So incorporating incidental daily activities – such as walking or cycling to or from work, taking the stairs instead of the lift and getting up and moving around during the television commercial breaks – can make your daily activity target more achievable.

Additional health benefits can be achieved by exercising more often and by performing activities at a higher intensity. After you’ve reached the basic 150 minute target, slowly increase the total duration to 300 minutes a week of moderate exercise or perform 150 minutes of more vigorous exercise.

If you have not exercised in the past 6 months, have medical conditions or are taking prescribed medications, it is best to obtain medical clearance from your GP before starting any moderate to vigorous activity. An exception to this is brisk walking, at a pace that makes you slightly short of breath but still able to talk comfortably. Walking at this pace is very safe for most people and is a great way to start being more active.

Reference:

Australian Government Department of Health & Ageing (2005) Physical Activity Guidelines. http://www.health.gov.au/internet/main/publishing.nsf/content/health-pubhlth-strateg-phys-act-guidelines

Clarke J, Janssen I (2013) Is the frequency of weekly moderate-to-vigorous physical activity associated with the metabolic syndrome in Canadian adults? Applied Physiology, Nutrition, and Metabolism 38: 773–778.

Hordern MD, Dunstan DW, Prins JB, Baker MK, Singh MAF, Coombes JS (2012) Exercise prescription for patients with type 2 diabetes and pre-diabetes: a position statement from Exercise and Sport Science Australia. Journal of Science and Medicine in Sport 15: 25–31.

Janssen I, Wong SL, Colley R, Tremblay MS (2013) The fractionalization of physical activity throughout the week is associated with the cardiometabolic health of children and youth. BMC Public Health 13: 554.

National Health and Medical Research Council (2013) Australian Dietary Guidelines. NHMRC. www.eatforhealth.gov.au

Van der Ploeg HP, Chey T, Korda RJ, Banks E, Bauman A (2012) Sitting time and all-cause mortality risk in 222 497 Australian adults. Archives of Internal Medicine 172: 494–500.

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