Updated August 18, 2020. Since I play sports, I have been told about lactic acid. At school, I remember our trainers suggesting that we stretch to eliminate lactic acid in our legs, which would prevent muscle soreness the next day. It must be said that at the time I did not yet know aches, so lactic acid was not part of my concerns!
What we have known for a long time is that the isolated muscles which contract until fatigue accumulate become acidic ( Fletcher & Hopkins (1907), Meyerhof (1920) et AV Hill (1932). What we also know is that if we allow the muscle to recover and provide it with oxygen, the amount of acid in the muscle decreases rapidly. It was therefore concluded at the time that the lack of oxygen in the muscles, increased fatigue and increased acid level in the body were related phenomena (Brooks, 1991; Wasserman & McIlroy, 1964).
Lactic acid or lactate?
More recently, the name lactic acid has come into question. Lactate production would therefore not be more responsible for the acidification of the muscle. Acid production would occur later in the energy production chain. Lactate production and muscle acidification are therefore two correlated phenomena, but one does not lead to the other.
It is true, it is that the more we increase the intensity of the effort, the more the quantity of lactate in the blood increases. Lactate is an organic molecule produced by human muscles when they have to exert themselves and there is not enough oxygen to produce energy in a "normal" way. Lactate is produced from glycogen in the absence of oxygen, which is why this process is called: anaerobic glycolysis (degradation of glucose without oxygen).
Lactate and fatigue
disturbance of the acid-base balance of skeletal muscle is not as crucial a factor in fatigue as is often suggested (RA Robergs et al).
There may be very great muscle fatigue, without the presence of a high concentration of lactate. For example, people with McArdle's disease are not able to produce lactate. However, if they make a prolonged effort, they will indeed feel tired.
It is therefore not lactate which is the main cause of fatigue. In fact, in order to perform well, it is good to be able to produce more lactate. The more anaerobic capacity an athlete has in running, the more they will be able to produce lactate in large quantities (and generally release it quickly) and the faster they will be.
Lactate and muscle aches
Lactate does not cause muscle soreness. Body aches are caused by micro-tears that occur in the muscles. Here are 2 proofs:
- After which race are you the most sore? A marathon or a 5km race? For me, it's definitely the marathon. However, during a marathon, the lactatemia is much lower than during a 5km race.
- The day after a race, you are sore. However, 2 hours after your run, your lactatemia has generally returned to its normal level. How do you explain that there is no lactate left and that you are stiff?
Lactate and cramps
Yes, it happens that we have cramps when we have a high level of lactate in the blood. On the other hand, it is also possible not to have cramps with a high rate of lactate. Often, muscle cramps occur during long periods of time when there is not much more lactate in the muscles than at rest.
In summary, lactate does not have all the wrongs we give it. It is not because 2 factors are correlated that there is a cause and effect link between them. On the other hand, since lactate is correlated with other metabolic products, studying its accumulation and training at different lactate production rates can be beneficial, which is what we will see in a future post.
Very interesting!
I have often been told that we have to do the little recovery runs. the day after long outings precisely to circulate lactic acid. If, 2 hours after the race, the lactatemia has generally returned to its normal level, what am I circulating? … Well, my blood, that I know… but why these small runs make me feel better then?
The thank you box
One thing's for sure, you don't feel better because you circulate lactate 😉 Maybe you feel better because you feel better after a race anyway? My personal opinion would say that you circulate oxygen and help circulate the little bits of muscle torn from exertion. Not yet an expert on the subject 🙂
Hello !
You cite RA Robergs et al, but is it possible to have the full reference (title of the book or article etc.) please?
I am preparing a thesis which deals in (very small) part on muscle recovery and I collect all the references that can help me 🙂
Thank you!
Hello,
Book: Cardio training, endurance sports and performance by Guy Thibault. P. 197
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