Friday, April 6, 2012

Sugar Fix

You know the feeling when you're pushing really hard, maybe running up a long hill or kicking it in for the last quarter mile of a race? The muscles in your legs slowly turn to stone. It takes several minutes post-hill or post-race for them to feel normal again.

This stone-like sensation is caused by a buildup of lactic acid in your muscles. Lactic acid is a byproduct of the chemical reaction that pulls sugar (glucose = fuel) from your blood and burns it for energy. The amount of lactic acid produced depends on how hard your muscles are working.

There are several "zones" that your body will normally go through during a workout: aerobic and anaerobic. These zones correlate to your heart rate, which increases as your muscles work harder. Each of us have a maximum heart rate, MHR, which is the maximum number of times your heart can beat per minute (generally, this number does not increase or decrease with fitness level, but may change with age). If your heart rate is 70% of your MHR, or less, you are in the aerobic zone.  Conversely, if your heart rate is above 70%, you are in the anaerobic zone.

The aerobic zone is also called the "fat-burning" zone because your body is using oxygen to turn stored fat into energy. There are many positives to training and running in the aerobic zone: energy production does not produce large amounts of lactic acid, so your muscles do not tire as quickly; energy production from fat is very efficient; and the more you train in the aerobic zone, the better your body will become at converting fat to energy!

When you are in the anaerobic zone, your body is demanding energy now! It burns the sugars in your bloodstream in the absence of oxygen, creating lactic acid. If you are in the lower end of the anaerobic zone, the amount of lactic acid produced is small enough that it can be dissipated by your bloodstream.  However, when your legs are pumping, propelling you up that hill, the lactic acid builds up in your muscles quicker than it can be removed, hence the stonelike feeling.  As your body works to dissipate the lactic acid, your legs will feel better, but you'll be left with much less energy for the rest of your run, and for that next hill!

So what can you do? Refuel! Getting that glucose in your blood back up to a reasonable level as quickly as possible is very important, especially if you are part-way through a long race. So eat some sugar!

Of course there are many practical options available, from GU energy gels that contain caffeine for that extra kick to Clif Shot Bloks which taste like delicious fruit chews.  But what about something a little more fun? Maybe a handfull of Starburst(R) Jelly Beans or Candy Corn? After all, what could have more sugar than Candy Corn! If you compare the nutrition facts and look at the top ingredients, candy does provide a large amount of sugars, but specifically formulated energy gels and chews contain slightly more complex carbohydrates which will fuel your body for longer and may actually be easier to digest; they also contain amounts of potassium and sodium - other essentials that your body desperately needs during a tough run. My recommendation? Indulge sweet treats once in a while, but for general training needs, and especially on race day, stick to the products specifically formulated for athletes.

Happy running, and happy refueling!

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