Is lactic acid bad for you?

[andydude]

I thought this article from http://www.cyclingnews.com/features/training-is-lactic-acid-bad-for-you was quite interesting, especially the part about the "burn" in your legs not actually caused from the build up of lactate, but the build up of acidity in the blood.

 

Training: Is lactic acid bad for you?

By: Kate Hodgins, Cycling

 

The common enemy questioned

Lactic acid causes muscle fatigue and the burning sensation when the going gets tough. Right? Wrong. Although it's seen as the athlete's enemy, lactic acid – or lactate – isn't quite the villain it's been made out to be.

 

The bad press came from Meyerhoff and Hill's 1920 study. "They observed an increase in lactate and also observed fatigue, and presumed one caused the other," says English Institute of Sport senior physiologist Jamie Pringle.

 

Recent research has shown that rather than causing muscle fatigue, lactic acid is actually a key muscle fuel. "Although people are keen to point the finger and blame something for fatigue, in reality the main cause of fatigue is the lack of energy and fuel, or specifically the inability to provide those things at the rate that's needed to keep up with the muscle contraction," says Pringle.

 

In fact, lactate can be oxidised and used to fuel the Krebs Cycle, to release chemical energy, or it can be converted to glycogen in the liver in a process called the Cori Cycle. "When metabolised successfully, the use of lactate as fuel means muscle glycogen stores are actually preserved for longer," says Pringle. "Muscle lactate concentration does not start to increase until the production rate exceeds the rate of removal."

 

This is why working just below this level, known as the lactate turnpoint, can be sustained for so much longer. "This turnpoint, which is around 70-90 percent of V02 max, is where you have the right balance between lactate production and the rate your muscles can consume it," says Pringle. "The reason your muscles quickly fatigue above this point is because excess lactate causes your carbohydrate stores to be used up at a much faster rate."

 

Jargon buster

 

Lactate threshold: The lactate threshold is a lot lower than most people think, occurring at about 50-70 percent of V02 max. It marks the first increment of lactate concentration in the blood from 'moderate' to 'heavy'.

 

Lactate turnpoint: The lactate turnpoint happens at 70-90 percent of V02 max and represents a blood lactate concentration shift from 'heavy' to 'severe'. After this point muscles will fatigue significantly. "To identify your own lactate turnpoint, perform a time trial of about 60 minutes," advises Pringle. "As long as you ride at an evenly-paced effort, the average power or heart rate of that will be on or about your lactate turnpoint."

 

To increase your lactate turnpoint you should aim to work at the point just below it for three 20- to 30-minute sessions each week. "By doing this you're pushing the limit up from below," says Pringle, "and although it's possible to 'pull up' from above by using all-out interval training, this will cause much greater muscle fatigue and will be less effective in the long term."

 

Krebs Cycle: This is part of the process of aerobic cell metabolism which can be fuelled by lactate, in which glycogen is broken down to produce the basic muscle energy source adenosine triphosphate (ATP).

 

Acidosis or 'The Burn': 'The burn' occurs as a result of a build up of acidity in the blood that causes muscles to contract. Severe pain was previously believed to be caused by the build up of lactate. However, the acidity actually comes from hydrogen ions released by the breakdown of ATP.

 

If exercise is too intense, the metabolism can't get rid of these hydrogen ions quickly enough, and this is what causes acidosis. Lactate itself helps buffer and neutralise the acidic hydrogen ions, delaying acidosis.

[aungiers]

A relative and somewhat widely accepted theory on fatigue is the theory of the central governor developed by Tim Noakes. It is a very interesting concept based upon that the brain (central governor) induces fatigue to prevent damage occurring to the body through over-strenuous exertion of the body.

[andydude]

I guess that is the same principle where if you put your hand on a hot stove plate a sprinter/messenger runs to your brain which in turn tells the messenger that "IT BURNS!" and from there you only feel the burn. That is why there is a slight delay between the hand on plate and the burn feeling.

 

But on the other hand [Darren], I also look at my body like a car where if you have no fuel you can't go on... fatigue.

[fandacious]

But on the other hand [Darren], I also look at my body like a car where if you have no fuel you can't go on... fatigue.

 

Actually, its more a case of there is no more oxygen, so you cant go on. There's plenty of fuel, but you need oxygen to convert the glycogen into ATP (adenosine triphospate). When you go past LT, pyruvate is produced. Some of this pyruvate can be converted into energy, but the rest becomes lactic acid and sits in your muscles

[andydude]

Actually, its more a case of there is no more oxygen, so you cant go on. There's plenty of fuel, but you need oxygen to convert the glycogen into ATP (adenosine triphospate). When you go past LT, pyruvate is produced. Some of this pyruvate can be converted into energy, but the rest becomes lactic acid and sits in your muscles

 

But according to the article its not the lactace that causes the burning feeling: "result of a build up of acidity in the blood that causes muscles to contract"; "however, the acidity actually comes from hydrogen ions released by the breakdown of ATP."

[Guest agteros]

And another thing that peeves me re lactic acid, is the notion that people believe that it stays in their muscles/system for up to (and sometimes over) a day.

It actually gets flushed out in 30 mins(or just over, don't have reference material at work) after exercise. The stiffness that people experience after exercise seems to be actual damage to the muscle fibres... not a lactic acid build up.

[Purnjap]

And another thing that peeves me re lactic acid, is the notion that people believe that it stays in their muscles/system for up to (and sometimes over) a day.

It actually gets flushed out in 30 mins(or just over, don't have reference material at work) after exercise. The stiffness that people experience after exercise seems to be actual damage to the muscle fibres... not a lactic acid build up.

So all that beer I religiously consume after a race to flush out the lactic acid is for nothing?? Dont worry, I'll invent a new reason...

[Face Plant]

wasnt the theory that you should cool down after exercise to flush the lactic acid out your muscles or else the lactic acid casues stiffness and pain the following day?

[aungiers]

@andydude: the example of the hot-plate is very different; that is down to a reflex. When you place your hand on the plate the stimulus causes the response in nervous system which sends the stimulus through the reflex arc. The action of pulling your hand away from the stove is created by motor neurons that send a "message" to your muscles which pull away. It does not make use of the brain but just the reflex arc where processing is done in the spinal cord and as a result is know as a spinal reflex. The central governor theory is a theory with regards to long-term and prolonged activity. Asd the body exercises it produces heat; one part of the central governor is related to protecting the body from overheating. The body needs to run at very specific conditions to function and if these conditions change i.e an increase in temperature the effects could be fatal. The central governor's role is to prevent this overheating from happening via exercise by inducing fatigue to ensure that no further activity can occur and heat produced. using your car analogy; imagine your engine had the processing ability to cut out at a certain temperature to prevent any damage occurring to your engine. This is only one aspect of the central governor theory.

 

The pain the next day is DOMS (Delayed Onset of Muscle Soreness) and as agteros says it is from micro-tears of the muscle fibres(this is a necessary response for adaptation of the muscle). The theory with regards to "flushing" the lactic acid is active recovery and it does speed up the reduction of blood-lactate

['Dale]

wasnt the theory that you should cool down after exercise to flush the lactic acid out your muscles or else the lactic acid casues stiffness and pain the following day?

Yah, that is what I do with my 20 minute cool-down after racing/training or my next-day recovery ride... active recovery.

Hmmm...

Edited January 9, 2011 by AirBender

[Guest agteros]

Yah, that is what I do with my 20 minute cool-down after racing/training or my next-day recovery ride... active recovery.

Hmmm...

 

next day recovery ride is too late ...

 

I'll quote from the 4th edition of Lore of running by Prof. Tim Noakes: (pg 163-164)

"Lactate Removal After Exercise

A frequent question is whether the stiffness that athletes feel after a hard training session or, in particular, after a marathon race is caused by the presence of lactate in those stiff muscles. One old theory even proposed that the lactate caused needlelike crystals to form in the muscles and that it was these needles that caused the pain we feel.

 

Within an hour of an intensive interval training session during which blood lactate levels reach the highest achievable values (15mmol per liter), muscle lactate levels will return to normal (Peters-Futre et al. 1987). Futhermore, the worst muscle is always evident after long races that are run at speeds below the lactate turnpoint and that do not, therefore, elevate either blood or muscle lactate levels. For both these reasons, lactate cannot be a cause of the muscle soreness or stiffness felt after exercise (Schwane, Johnson, et al. 1983), In chapter 7 I argue that this stiffness is almost certainly due to racing-induced muscle cell damage, especially to the elastic elements in the skeletal muscles."