Many people believe that lactic acid is responsible for muscle pain and limits athletic performances.  Is that true?

Lactic acid, which can be found in our blood stream, is produced by our muscles when exercising. That’s the lactate.  For a long time, we have been operating under the belief that the lactate was responsible for muscular fatigue and muscular cramps.  However, several recent studies have concluded that lactic acid has little to do with muscular fatigue.

Indeed, it has been observed that muscular fatigue still occurs when lactic acid levels are at a minimum. In addition, recent studies have also concluded that high levels of lactic acid can be attained without the “expected” generation of muscular fatigue.  By way of example:

<!--[if !supportLists]-->·         <!--[endif]-->At the end of a century or even longer ride, lactate level in the blood stream may be only slightly higher than at rest, though muscular fatigue at the end of such a long workout is very significant.

<!--[if !supportLists]-->·         <!--[endif]-->People with McArdle disease are incapable of producing and accumulating lactic acid. However, they often experience muscular fatigue.

<!--[if !supportLists]-->·         <!--[endif]-->Wall seating exercises generate high levels of lactate and extreme muscular fatigue after only 2 minutes. However, after a 2 minute rest, one could perform the same exercise again, with the same level of performance, while lactate level is still very high from the first repetition.

It has also been established that starting a time trial race with lactate in the blood stream leads to better performances. In support of this conclusion, British researchers conducted the following study:  Riders had to hold an intensity level equivalent to 100%, 110%, and 120% of their Vo2Max for as long as possible. Two test groups were observed:

<!--[if !supportLists]-->·         <!--[endif]-->Without any significant warm-up; and

<!--[if !supportLists]-->·         <!--[endif]-->After a 10 minute warm-up at a high, but sub-maximal intensity.

While those in the group that included the warm-up phase generated a significant level of lactate prior to the start of the real test, researchers observed much better results, as seen in the table below:

Source: Jones AM and coll. (2003) Med Sci Sports Exerc 35; 2085-92.

This improvement in performance is why, among other reasons as well, we see professional cyclists go through a rigorous and intense warm-up before a Time Trial race.

Similar conclusions can be reached when reviewing the performance of Track bike racers.  Specifically, these bike riders reach very high lactate concentration levels - which can exceed 20 times higher than resting levels.  However, post-riding interviews suggest that these riders very rarely experience muscle cramps.  Conversely, some people experience cramps during their sleep while other athletes experience cramps after steady, long efforts, such as a long bike workout; however, while in such cases the lactate concentration may be higher than the level observed at rest, it is still significantly lower than the maximal levels observed after short, but extremely intense efforts.

Let’s be clear: Despite misinformed common belief, recent scientific studies combined with tracking of individual athletic performances have concluded that muscular cramps have little, if anything, to do with the level of lactate concentration.  Simply put: To conclude otherwise is old-school thinking. 

The truth is that at the present time we do not know exactly what causes muscle cramping.  Between the brain neuron-transmitters – that are responsible for sending information to the muscles - and the muscle myofilaments themselves, we must all recognize that the information transmission chain is complex and relies on multiple links and steps.  At any point in time these vital cogs supporting individual performance capabilities can “misfire” and prevent or alter the proper transmission of information - causing muscle contraction to stop working properly, generating muscle cramps.  Among the multiple possible origins and potential culprits, the mere presence of lactic acid might be a contributing factor, but it is certainly not the primary and unique culprit and, equally important, the actual level of lactic acid does not correlate to the generation or intensity of muscle cramping!

Eric G.