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A month to change your heart: Day 18

    by David Becker, M.D., FOR THE INQUIRER
    Published 

We are well into week three of the program, and hopefully starting to get into better shape.  Some questions may come to mind when it comes to your exercising.  How long? How far? How often? How do I stay motivated?

That is where the acronym F.I.T comes in: Frequency, Intensity and Time (or duration) of activity.

Frequency:  Of the three components, frequency is most important.  To get the optimal training effect, which is the degree that your workout will help your heart, doing aerobic activity at least four times per week is key.

Intensity:  Your intensity can be partly determined by your target heart rate.  This is how fast your heart should beat during exercise to get the best training effect.  Here is a simple way to figure out your target heart rate.

For a moderate intensity workout, use the following formula: 220 - your age = maximum heart rate/min.  Then, multiply this by 50-70% (use the low end when first getting started). This is your target heart rate, which you should try to sustain over 30-45 minutes.  It is usually around 110-120 beats per minute when you are getting started.  Keeping your heart rate up to that level for a longer period of time is much better than getting it higher for a short period of time (interval workouts) from a cardiac point of view.  Interval workouts are great for younger people (under 40 years old) trying to get into shape, but not as good for us as we age.  When you are in better shape, a vigorous workout target would be 220-age x 80-85%- usually around 135-140 beats per minute. If your heart rate is higher than these targets when you first start, do not stop, just slow down a bit.

If you are on certain medication such as beta blockers that slow down your heart rate, you cannot use this method.  Your heart rate will be much lower, and will not increase with exercise.  In that case,  using a perceived exertion scale, called the Borg scale,  is best.  Use a scale between 6 and 20 to rate how you are feeling when you exercise.  Six is equivalent to how you feel when lying down, doing nothing at all.  19 is very hard exercise.  Ideally, you should be 11-15 on the scale, which is light to hard perceived exertion.

As you become increasingly fit, you can gradually increase your aerobic exercise intensity.  When someone is deconditioned, (a nice way of saying that you are out of shape) the heart rate may increase despite low levels of activity. Excess weight can also accentuate this.  If your heart rate quickly increases with activity, then slow down and be patient.  It may take a while to become reconditioned.  For example, a teenager can do little exercise all winter, and then get into shape within two or three weeks when it is time to play a sport.  As we get older, we have a harder time bouncing back so take it slow to start.

Time:  Although 30-45 minutes is optimal, when you are getting started, 10-15 minutes is perfect.  Two shorter sessions a day works too.  Find something that fits into your schedule, and remember to plan ahead every day.

Hint:  Exercising in the heat and cold presents another set of problems.  But if you love being outside in extreme weather here are a few rules to follow:

Hot weather:

  1. Wear a hat to shade your face

  2. Do not wear elastic or rubber suits.  They are potentially dangerous and do not help you sweat out fat.

  3. Monitor your heart rate

  4. Allow more time to warm up and cool down

  5. Drink plenty of water

Cold weather:

  1. When it is really cold outside, especially less than 15-20 degrees, it is just as important to take precautions when you exercise.

  2. Very cold weather can make your arteries spasm, and increase the chance that plaque can rupture.

  3. Dress in layers, and remove extra clothes as you get warm.  Wear a scarf or mask over your mouth to help warm the air that you breathe.

  4. Drink plenty of fluids since cold air is drier than the air in your lungs, and draws moisture from your body as you breathe

Tips of the day:

  1. Exercising frequently is more important than how intensely you exercise

  2. Prolonged exercise is better for the heart than interval training, especially as you get older

  3. An elevated heart rate when you first start exercising can be a sign of deconditioning

  4. Take precautions if you like to exercise in extreme weather, but indoors is always safer when it is really hot or cold.

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