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WHAT
TYPE(S) OF ACTIVITY PROVIDE THESE BENEFITS?
The only type of physical activity for which there is very convincing evidence
of the above benefits is “aerobic” exercise. This doesn’t mean that you need to
run out and buy nasty 1970’s leg warmers cast-off from an old 20 Minute Workout
show. “Aerobic” activity is anything that gets your heart beating fast, at a
rate that you can sustain for more than a few minutes. If you push too hard,
such that you need to stop for a breather after a minute or two, then you have
exceeded your “threshold”, and crossed into what is called “anaerobic” activity.
There is much less evidence about the health benefits of this sort of anaerobic,
maximal intensity exercise.
One easy rule of thumb gives an easy guide to whether what you are doing is
“aerobic”. The Goode-Merton “breath test” is this: when you reach a level
of exercise at which you can easily hear yourself breathing, you are crossing
the threshold into anaerobic activity.
So, aerobic activities can include just about anything (walking, cycling,
swimming, jogging, skating, rowing… the list is endless), so long as you perform
whatever it is at an appropriate intensity. Make your heart beat faster than
normal, but such that you are not breathing very hard, and such that you can
keep it up for more than a few minutes consecutively.
HOW
MUCH PHYSICAL ACTIVITY IS NECESSARY?
Some thirty years ago, fitness experts at the Cooper Institute in Dallas came up
with the “FIT Principle” as a guide: Frequency = 3 times weekly, Intensity = 70%
of maximum heart rate, Time = 30 minutes. Since then, we have learned a lot
more.
We now know that the health benefits listed above begin to appear with just a
little exercise (500 kcal/week). This amount can be accomplished just by
choosing to walk or ride your bike to work or stores instead of driving; taking
the stairs instead of an elevator; and so on. We call this “active living” as
opposed to “prescriptive exercise” as seen in a “prescription” like the FIT
Principle.
Having said that, it appears that more is better. 1000 kcal/week (3 half-hour
activities at moderate intensity) of exercise reduces death rates by 30%. 2,000
kcal/week (daily half-hour activities at moderate intensity) goes even further.
At some point, too much of a good thing is bad. There is some evidence that more
than a couple of hours of exercise daily starts causing problems, particularly
if it is too intense, (not to mention if it is violent in nature).
GETTING STARTED
Living in a more active way (getting rid of that car, or leaving it in the
garage; buying and using a bike at low intensity; choosing to walk) is something
anyone can do. If you plan to start a more vigourous program, particularly
if you have any existing health issues or concerns, it is advisable to consult a
health professional to make sure what you are planning is safe.
Whatever it is you choose to do, be it walk up more stairs or join the
Team
Healthy Butcher cycling team, have fun!
Doug Richards, MD, Dip Sport Med
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Medical Director,
David L. MacIntosh Sport Medicine Clinic, University of Toronto
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Assistant
Professor, Faculty of Physical Education and Health, University of Toronto
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Current Team
Physician of National Women’s Basketball Team, National Volleyball Beach
Teams, and Varsity Blues Intercollegiate Teams
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Former Team
Physician of the Toronto Raptors Basketball Club, 1995-2004
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Regular Customer,
The Healthy Butcher, 2005-present
To
learn more about your Maximum Heart Rate and determine your target heart
rate for aerobic activity visit:
http://www.brianmac.demon.co.uk/hrm1.htm or
http://www.briancalkins.com/HeartRate.htm
While it’s beyond our scope in this newsletter to cite all of the relevant
scientific literature on the topic of physical activity and health, readers
interested in exploring the evidence for themselves are directed to the two
largest published reviews on the topic, considered the current authoritative
summary statements in the scholarly community: the Report of the Surgeon
General in 1996 (U.S. Department of Health and Human Services1996), and the
consensus statement of an international symposium held on the topic in
Hockley Valley, Ontario in 2001 (Kesaniemi 2001).
To access past issues of live to eat? Click
here.
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