5 Common Myths about Lactic Acid and Running

There are 5 common myths about Lactic Acid and that still persists today among coaches and athletes.

1. “The burn” felt in the leg muscles during fast running is caused by a buildup of lactic acid

2. Lactic Acid provides soreness experienced the day after an especially tough workout

3. Lactic Acid is a metabolic waste product formed in muscles during vigorous exercise

4. Lactic Acid shows up in the muscles when athletes run to a point of oxygen debt

5. Lactic Acid is fatigue during intense running

Science tells us that all 5 of these assertions about Lactic Acid are untrue.

Author Owen Andreson dispels these myths in quick order in his book Running Science:

Lactic acid doesn’t produce burning sensations, it doesn’t induce soreness, and it’s not a form of metabolic garbage that must be eliminated from muscle cells as quickly as possible.

The burn experienced during high-speed running is probably a protective mechanism created by the nervous system in order to stop runners from damaging their muscles with too much high-speed effort.

The soreness experienced 24 to 48 hours after a tough workout is most likely the result of an inflammatory process occurring in muscle cells that have been partially damaged by very strenuous running; lactic acid is not involved.

In addition, oxygen shortfalls are not required in order to make lactic acid appear in the muscles and blood, and lactic acid does not induce fatigue. The truth is that lactic acid is produced in the body all the time, even when athletes are at rest, because it’s a natural byproduct of the key energy-producing process of glycolysis. Furthermore, running velocity at lactate threshold occurs at 60 to 88 percent of VO₂ Max, that is, at an exercise intensity at which oxygen is not yet limiting since VO₂ Max has not been reached.

The concentration of lactic acid in the muscles and blood can rise significantly whenever a carbohydrate-containing meal is consumed; many of the ingested carbs are broken down glycolytically to pyruvic acid, which is then converted to lactic acid. If lactic acid really caused muscle soreness and fatigue, runners would experience muscle pain and tiredness every time they wolfed down their favorite carbohydrate-rich meals!

Anderson goes on to define Lactic Acid’s, or more accurately, lactate’s, real role in the body as follows:

Instead of being a dangerous compound that wreaks havoc inside muscle cells, lactic acid (or, more accurately, lactate, which is just lactic acid without a hydrogen ion) plays a paramount role in carbohydrate processing throughout a runner’s body. Lactate can move out of the muscles and travel through the bloodstream to the liver; the liver can then use lactate to produce glucose, a runner’s most important source of carbohydrate fuel. This is an incredibly significant role for lactate because the liver relies on glucose to maintain normal blood sugar levels.

In addition, up to 50% of the lactate produced during a very tough workout or race may be used eventually to synthesize glycogen in the muscles. Glycogen is the key storage form of carbohydrate in the body. This is important because the muscles use carbohydrates as the major energy source during high-quality workouts and competitive endurance performances. Far from damaging tissues or inducing soreness, the glycogen that comes from lactate provides the energy needed to carry out subsequent, high-quality workouts; the glycogen can be broken down into countless molecules of glucose, which then undergo glycolysis. During exercise, lactate is also an irreplaceable source of immediate energy for muscles and other tissues because lactate can be converted back to pyruvate, which can then quickly enter the energy-producing Krebs cycle. cycle. Enhancing the ability to use lactate can improve a runner’s race times rather dramatically. Thus, lactate can go two ways in muscles: (1) into glycogen formation, or energy storage, or (2) into energy creation via pyruvate’s entry into the Krebs cycle. Developing the ability to process lactate effectively helps athletes run faster and longer.

Source: Running Science, Anderson, Chapter 10.

Lactate Threshold vs. Lactate Tolerance Training

When training runners, it is important to understand the difference between Lactate Threshold and Lactate (acidosis) Tolerance.

Improving both a runner’s Threshold and Tolerance to lactate are important physiological variables that significantly influence running performance, albeit in different ways.

Lactate Threshold training is aimed at delaying acidosis.

Lactate Tolerance training is aimed at coping with acidosis.

Lactate Threshold training does not help with acidosis tolerance. And Lactate Tolerance training does not improve Lactate Threshold.

This is why it is important to understand the specific training designed to improve both of these lactate variables and the degree what runners will benefit most from each type of training.

As a general rule of thumb, the shorter the race distance the more important Lactate Tolerance becomes. As race distance increases the more important Lactate Threshold becomes.

Lactate Threshold training is important for all runners, especially for runners competing in 10,000m and longer races. In contests lasting 30 minutes or more, the import of using lactate as fuel is a key determinate to performance success. Therefore, a significant percentage of training should be focused on enhancing one’s Lactate Threshold so race speeds can be sustained without slow down due to the presence of acidosis in the bloodstream.

Classic high-quality aerobic running, such as high volumes of sustained periods of steady running, like tempo runs or cruise miles at Lactate Threshold, works best at upgrading Lactate Threshold.

For races 800m to 8,000m in distance the presence of acidosis is inescapable due to the fast speeds (forces) at which these races are contested. Therefore, it is important to compliment Lactate Threshold training with Lactate (Acidosis) Tolerance training to improve the muscles’ alkaline reserves, allowing the muscles’ ability to work in the presence of increased acidosis.

Training at, or slightly above, the intensity where acidosis occurs improves an athlete’s tolerance to the presence of acidosis allowing them to maintain a relatively higher force output despite the increasing presence of acidosis.

For example, for the 5,000m runner typically the last 1,000m of an honest pace race will be contested in an increased internally acidic environment. A workout such as repeat sets of 3-4 x 600m at 3K speed with 1:1/2 work:rest ratio will adequately train the body to continue running fast in the presence of increasing acidosis.

For the miler, a session such as sets of 3-5 x 300m at 800m speeds with a 1:1 work:rest ratio will teach this as well.

A word of caution: effective Lactate Tolerance sessions are very taxing and the recovery from these sessions can be slow, about 2 - 4 days in even highly trained runners. This makes Lactate Tolerance sessions less frequent training sessions, about once every 7 - 12 days.

On the other hand, Lactate Threshold training is easier on the body because the exposure to corrosive metabolic waste products is little to nonexistent, so recovery takes only about 1 - 2 day, or less for highly trained runners, making it a more frequent training session in a runner’s program, up to 2 - 3 times per week.