With rates of obesity and obesity-related illnesses climbing in the Canadian population, it's suggested that Canadians strive to build more activity into their daily lives in order to stay healthy or improve health. Most of us know that an active lifestyle is good for our health; the problem is that our lives keep getting busier and busier. So how does one find the time to get their daily dose of physical activity?
What if you had the choice, let's say, to accumulate short bouts of activity throughout the day rather than slog it out on the treadmill for 30 minutes? Performing multiple, shorter bouts of activity over the course of the day might be a more realistic (and perhaps enjoyable) option for you, given that lack of time is a frequently reported barrier to physical activity among adults. But would health-related benefits differ according to the way in which you built activity into your day? And how long would these activity bouts need to be to confer health benefits?
A recent review of the scientific literature looked at the effects of similar amounts of exercise performed in either one continuous bout (i.e., 30 minutes), or two or more accumulated bouts (of less than 10 minutes), on a range of health outcomes in adults. After comparing results from sixteen different exercise training studies, the authors concluded that shorter bouts of accumulated activity appear to be as equally effective as longer, continuous bouts of activity at improving cardiovascular fitness and blood pressure, as long as the total duration is the same. For other health outcomes such as body fatness, there were mixed results; the authors suggested that more evidence was needed to determine whether accumulated exercise is as beneficial as the more traditional, continuous approach.
A Matter of Time
It seems that accumulated activity can bring health benefits. But do these accumulated bouts need to be at least 10 minutes long? Can even shorter bouts bring health benefits too? A recent study I conducted looked at the physical activity patterns of children living in the UK, and discovered that the association between physical activity and aspects of health (body fatness, aerobic fitness and vascular function) were similar regardless of how the child accumulated the activity (i.e., in short (less than 4 s) bursts of activity or longer (less than 5 minute) bouts). Although the research has yet to be conducted in adults, it certainly provides a rationale for looking at whether the accumulation of very short activity bouts offers adults certain health benefits too.
We know that physical activity is instrumental in maintaining healthy, functioning bodily systems. Healthy physiological systems are complex and can adapt to unpredictable stresses (for example, increasing heart rate and breathing rate during exercise, and increasing blood flow to exercising muscles). When the complexity of the body's physiological systems breaks down and the ability to adapt worsens, this signals the transition to a diseased state. Getting activity in short bouts throughout the day would force the body to frequently adapt to these physiological stresses, while one continuous bout would require adaptation at a single time point. It's therefore especially interesting that the total number of activity bouts per day was positively related to vascular health in UK children. As you increase the number of bouts of activity in a given day, what you are doing is breaking up the time you spend being sedentary and it's this behaviour that may be responsible for protecting aspects of cardiovascular health in adults. Perhaps the key message then is as simple as "spend less time sitting and spend more time moving". As the Public Health Agency of Canada suggests, think about building physical activity into your daily life at home, at school/work, through play, and on the way!
What Should We Be Aiming For?
The Public Health Agency of Canada recommends getting at least 60 minutes of light intensity activity into each and every day, and gradually progressing to activities of moderate or greater effort. As the intensity of the activity increases, the amount of time decreases. If you're performing moderate-intensity activity, then scientists recommend attaining at least 30 to 60 minutes per day. If the activity is vigorous, then aim for at least 20 to 30 minutes per day. To differentiate between these two intensities, ask yourself: How does the activity feel? How warm am I? What is my breathing like? If you're just starting to feel warm and there's a slight increase in your breathing rate, then it's a good chance you're performing an activity of a light effort (i.e., light walking/easy gardening/stretching). As you start to get warmer and your breathing rate accelerates, you're getting into moderate intensity activity (i.e., brisk walking/biking/raking leaves). You might start to perspire a little, but you should still be able to carry on a conversation. You'll know the activity is vigorous or hard when you start perspiring heavily and become more out of breath, and carrying on a conversation becomes increasingly difficult (i.e., aerobics/jogging/basketball).
Key Messages:
* As long as you're getting the same amount of exercise, you should expect to see similar improvements in aerobic fitness and blood pressure, regardless of whether you get your activity in shorter, accumulated bouts or a longer, continuous bout
* The jury is still out on whether accumulated or continuous exercise is better for reducing body fatness, but it seems likely that a given amount of exercise would induce similar changes whether it is performed in single daily bouts or one continuous bout
* Very short bouts of activity accumulated over the course of the day appear to be health beneficial in children, and there's reason to believe that breaking up sedentary time with "bursts of activity" throughout the day is critical to protecting your cardiovascular health
Some tips for getting activity into your life:
* Make yourself an example of active living
* Be the exception. Take the stairs and avoid the crowded escalators. You might actually reach the top first and you'll feel better for it! Who knows, you might even start a trend.
* Instead of surfing the net on your lunch break, throw on your coat and mittens and head outside for a walk. Grab a friend/colleague on the way – they could probably use an "active break" from work too!
Final thoughts
Building physical activity into your day might be hard to do with the Canadian winter upon us, when the temptation to hibernate like a bear seems as good an idea as any! As discussed last week, Canadians tend to be less active during the winter season. Yet the decline in physical activity is actually rather modest, which infers that many Canadians do find a way to keep moving despite the chilly temperatures. As suggested, bundle up warm and embrace the outdoors. Try your hand at a new winter activity (snowshoeing perhaps?). Go for a walk in the snow. Dig out your skates. Explore. Play. Laugh. Have fun. Feel invigorated. And be healthier!
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