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For our Running ABC's, we look at the letter L for Lactic Acid!
There has been some changes in the way that we view lactic acid and its effect on runners. Most people view lactic acid as a waste product that causes fatigue and muscle soreness. While lactic acid production does accompany fatigue, it does not directly cause tired muscles or as we discussed previously Delayed Onset Muscle Soreness(DOMS).
Lactic acid is an important energy source for your body both during and after a workout. As we discussed in the letter "A" for Aerobic, the body prefers to generate most of its energy using aerobic methods, meaning with oxygen. Sometimes though, we need energy production faster than our bodies can deliver with oxygen, so the muscles generate it anaerobically.
During this anaerobic exercise muscles break down carbs to provide energy, resulting in a compound called pyruvate. When oxygen is available the pyruvate is broken down further into more energy, but when sufficient oxygen is not available, the pyruvate is converted into lactic acid.
Your body can clear lactic acid by metabolizing it for energy, but when the production exceeds clearance rate, it accumulates in your muscles. The lactic acid build up is not responsible for the muscle soreness following strenuous exercise. Rather the production of lactate during extreme exertion results in the burning sensation often felt.
Where Does Lactate Threshold Training Come In
“Lactate threshold” (LT) pace describes a hard but manageable effort that forces your body to begin producing considerably more lactate. When you train at LT pace, your body conditions itself to move lactate around, and this should improve your performance at these faster paces.
In the Journal of Applied Physiology, George Brooks provided findings of research performed on both training and untrained subjects. This research showed in untrained subjects, about 75% of the lactate used is directly oxidized. In trained subjects, about 90% is directly oxidized. Trained subjects also burn significantly more lactate overall. He also wrote "these findings suggest that in trained subjects, lactate is a preferred substrate over glucose." So in other words if you train enough, you actually prefer lactate to sugar!
Links to the Journal of Applied Physiology:
http://www.physiology.org/doi/abs/10.1152/japplphysiol.00043.2013?sid=b1c444e2-70c4-4443-a51f-4521249c370b&
The liver can clear lactate from the bloodstream by converting it into glucose or amino acids. Nearly all of the lactate you produce during a workout is cleared within 30 to 60 minutes after you stop exercising. Performing an active cool down after your workout will help you clear lactic acid more quickly than simply resting.
If you missed my earlier posts, you can see them at the following link:
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