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12 Days of Fitness 2015: Day 9 – The Truth About Lactic Acid

December 17, 2015 0 Comments

(This is Part 9 of a 12 part series to provide you with some helpful blurbs and tips to keep your fitness in focus over the holiday season)

download (2)In a previous post I discussed side stitches – possible causes and treatments; a thorn in the side (no pun intended) of physically active individuals. Like many things in fitness, side stitches can be lumped into the bag of fitness maladies and myths. Another one that comes to mind as it is often completely misunderstood and generally has a negative connotation to it is lactic acid. Let’s take a better look at this often misinterpreted and misconstrued bodily chemical.

A Bad Rap

Lactic acid and its negatively-charged ionic form lactate have had a long association with fatigue during exercise. During the course of a prolonged and intense effort, muscles lose power. The growing fatigue with exercise can be resisted for a while through great concentration and mental effort, but eventually everyone succumbs to fatigue. Exercise physiologists for the greater part of the twentieth century studied the theorized reason for muscular fatigue during exercise is accumulation of a compound called lactic acid. Once more research and understanding the metabolism of exercise was done it was found that the body does not actually produce lactic acid, just the negatively charged ion lactate. In the 2000s, a prominent biochemist and researcher in the field, Roger Robergs, took a hard look at each step in the metabolic process that turns sugars (glucose in the blood and glycogen in the muscles) into energy when you exercise to better understand and clear the air and bad reputation of lactic acid.

A Little Physiology

Energy is created in the body by one of two pathways; aerobically and anaerobically. Aerobic respiration turns sugars into fuel using oxygen, and doesn’t have any harmful byproducts. Anaerobic respiration, which doesn’t kick in until you’re operating past your aerobic limit, can generate energy from sugar without using oxygen, but results in waste products—lactate and acid. Robergs discovered however that anaerobic respiration functions all the time, turning sugar into a compound called pyruvate, releasing some hydrogen ions at the same time. Aerobic respiration works to clean up the pyruvate, using oxygen to burn the pyruvate into carbon dioxide and water, which can be exhaled. The aerobic process also consumes acid (hydrogen ions), which slows down the buildup of acid in the muscles. The generation of lactate is actually a side reaction: when excess pyruvate and acid start to accumulate (when the rate of anaerobic respiration overtakes the aerobic system’s ability to remove the waste), the body uses a pyruvate molecule and a hydrogen ion to create lactate, another way in which it can slow down the buildup of acid. The lactate can also be shuttled out of the muscles, into the blood, and burned in other areas of the body for more energy. Phew! Now while all that science may or not mean anything to you, here are the practical implications.

  • A better understanding of the biology of fatigue only reinforces the concept that your aerobic strength is a huge factor in your physical performance. While your body has various mechanisms to buffer the acid produced during high-intensity efforts, all of these are limited. Only increasing your aerobic fitness will allow you to substantially increase how far and how hard you can go.
  • Additionally, recognizing that lactate has a greater role than simply causing fatigue allows you to better understand the place of high-intensity workouts at or faster than the “lactate threshold.” These workouts aren’t just working hard for the sake of working hard—they train your body to produce, process, and burn lactate (as a fuel!) at a greater rate.
  • There is still the inescapable fatigue that comes with acid overload. There really is no getting around it the harder you work. You can include high intensity interval workouts to improve your ability to buffer the acid produced when training or competing at high intensities, but everyone is ultimately limited by the accumulating acidity in their muscles and blood.
  • Your body certainly produces acid during exercise, and it produces lactate as well. But it’s the former, not the latter, that’s the main culprit for fatigue.

See you tomorrow for Day 10 of the 12 Days of Fitness.


Til next time, train smart, eat well, and be better.

Day 1 – Chew Your Food
Day 2 – Fitness for the Road
Day 3 – The Many Names of Sugar
Day 4 – Side Stitches: Causes and Treatments
Day 5 – The 5 Reasons Why You Should Never Feel Hungry When Trying to Lose Weight
Day 6 – 10 Rules of Fitness
Day 7 – Which Are You – A Chronic Dieter or A Healthy Eater?
Day 8 – What Happens When You Skip Your Workout

About the Author:

Jeff Harrison is a fitness coach based in Pottstown, PA. He received a BS in Exercise and Sport Science from Penn State University and is an NSCA Certified Strength and Conditioning Specialist (CSCS), NSCA Certified Personal Trainer (NSCA-CPT) and ACE Advanced Health and Fitness Specialist (ACE-AHFS). Jeff's articles have been published in peer-reviewed journals as well as consumer oriented websites and magazines.

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