Sunday, June 22, 2008

 

Of Potassium and Interval Training

Neither of these are directly related to the other except in relation to recent events in my life and general fitness. Yahoo Health recently ran an article on burning more calories in less time. The process they describe in interval training. Interval training is "any cardiovascular workout (e.g. stationary biking, running, rowing, etc.) that involves brief bouts at near-maximum exertion interspersed with periods of lower-intensity activity."

Having been an avid cyclist in my earlier years and still cycling now, I've been aware of interval training for over 30 years. One interval training workout on a bicycle involves sprinting between every other telephone pole and pedaling comfortably between the others. Although in the areas I've always lived, simply riding on the available roads created a natural interval training workout due to the hills. Riding up the hills provides the intense, near-maximum exertion while riding down the other side enables lower-intensity activity.

During the colder months or when too busy to get in a day ride, I've ridden my exercise bike inside. I've always noticed that it never seemed to provide the same level of workout as riding outside. The Yahoo Health article explains why. While my home exercise bike doesn't have the computerized training courses, when I've ridden computerized bikes at the YMCA and health clubs, the indoor "bikes" still don't provide the same level of workout as outdoor riding.

I attribute this to the fact that on an exercise bike you can always slow down, lower the intensity level and such. When riding outside you can't make the hills any less steep. Sure, you can go into a lower gear but once you're in the lowest gear you either pedal harder or walk. I've always found the challenge of pedaling all the way to the top irresistible which creates a more intense workout.

I also love cycling because I travel faster than when running, can feel the breeze in my face and it doesn't involve the pounding that running does.

Potassium. A few weeks ago as I lay in bed trying to fall asleep I felt my heart beating irregularly. Having recently had an angiogram and other heart tests, my heart had been declared to be "that of a ten year old." As I lay there it popped into my mind that I had read that potassium helped control the heart rate and that my potassium had been low in a recent blood test.

The next day I looked up some potassium rich foods on Web and went to the grocery store. (USDA list HERE.) The best source I found was low sodium tomato juice and low sodium vegetable juice. But there are plenty of easily available, tasty sources.

Within hours of drinking a pint of tomato juice and eating a couple of bananas, my heart rate evened out and my blood pressure dropped 20 points. It turns out that in my efforts to consume more potassium I pretty much fell into the DASH diet plan. I also feel significantly more energetic. I mentioned this to a co-worker who also has hypertension plus is a diabetic. A few days later he told me he had began eating more high potassium foods and also felt more energetic, etc.

In my searches I also came across this sobering article on the greater risk of death for heart patients with low and low normal potassium levels.
"Our findings showed that heart failure patients with low to low-normal (less than 4 mEq/L) potassium levels were more likely to die than those with higher levels (4 to 5.5 mEq/L) of potassium," said Ali Ahmed, M.D., associate professor of medicine in the Division of Gerontology, Geriatrics and Palliative Care and director, Geriatric Heart Failure Clinics, at UAB and the study's lead investigator. "These patients were not significantly more likely to be hospitalized than the higher potassium group, suggesting that most low potassium associated deaths were sudden deaths due to ventricular arrhythmias."

Additionally, Ahmed and colleagues found that what was previously considered an acceptable level of potassium may, in fact, be too low. A level of 3.5 mEq/L is often clinically considered as low potassium. However, Ahmed's group found that patients with potassium levels less than 4 mEq/L had increased risk of long-term mortality.
In my recent blood test, my potassium level was 3.1 mEq/L. Not good according to this article.

Since it was time for my annual check up I discussed my potassium level with my doctor. He seemed to think that while 3.1 was low, it wasn't that low. He did prescribe me a potassium supplement however.

I believe what happened in my case is that last fall I decided to lose some weight. I cut back drastically in drinking orange juice, an excellent source of potassium, for this reason. Before hand I would drink a gallon of orange juice every 2-3 days. I lowered that to about a gallon a month but did not add another source of potassium. Combine this with by blood pressure medication which can deplete potassium and you have trouble.

Tomato juice and vegetable juice work wonderfully as the low sodium varieties have about double the potassium per ounce as orange juice and about half the calories.

Still, I wonder if more attention shouldn't be paid to potassium levels. Most foods don't even list potassium on the nutritional labels. With so many refined foods which have depleted nutritional value, more information is invaluable. Also I wonder if doctors and researchers need to take a closer look at what is an acceptable level of potassium in the blood.

Comments:
Hey Dad -

I think potassium is very important - swimmers (my daughter swam competitively) need lots!

And while I'm here - thought I'd mention that I tagged you at my post here. Have fun!!!

-Anne
 
There is so much we don't know about nutrition. I know I have felt better when I have upped my potassium foods. Low-sodium V8, great stuff.
 
nice article about potassium...very informative and beneficial for me...thanks
 
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