Lay it on lactic acid: Fact or Fiction? Massage flushes out lactic acid
Post-event massage rids the body of lactic acid to alleviate muscle ache and stiffness and to improve overall athletic performance. That is the reason why a lot of coaches and personal trainers advise sports persons to include massage in their training plans. It is also one of the main benefits that therapists often cite to promote their professional services to athletes. True or false? Does massage eliminate lactic acid from a body that has been heavily exercised or is it another of those massage myths based on out-dated information?
Indeed the latter seems to be the case. Although the true role of lactic acid in the human physiology has been understood by scientists for a good few years now, it is still considered a waste product that causes a burning sensation in the muscles during training, muscle soreness afterwards and something that ultimately impedes performance.
The lactic burn and lactic acid build-up myths are further fuelled by the media (even websites and magazines aimed at runners and cyclists) as well as by an alarming number of body workers including massage therapists who perpetuate these untruths. Erika Kruger takes a closer look at the role of this colourless organic acid produced in the muscles during strenuous exercise and as well as the effect of post-training massage has on this biochemical process.
What is lactic acid?
Lactic acid, also known as milk acid is a product of carbohydrate metabolism that is continually in the human body.1 The body has two ways to use the energy produced through glucose metabolism namely aerobic glycolysis and anaerobic glycolysis.
During aerobic glycolysis, each glucose molecule is
divided into two pyruvic acid molecules, and energy is released to form
adenosine triphosphate (ATP). The electrons that are released from
glucose are transferred to oxygen molecules and enter the mitochondria.
As the rate of activity increases, as a result of a lack of oxygen (or in some cases as a result of too few enzymes or muscle cell mitochondria),3 the muscles require more oxygen than the blood circulatory system can supply. As a result pyruvic acid transforms into lactic acid that starts building up. (In fact the half-truths in the lactic acid theory start at this point as this colourless, organic chemical compound does not exist in the body as an acid but splits into lactate ion and hydrogen ion.)
In order to maintain its energy levels, the body has to initiate another way of liberating the energy from the glucose. This process is called anaerobic glycolysis as it does not require oxygen to provide the required energy. Without effort the lactate diffuses out of the muscle cell into the blood producing energy without using oxygen.
This is known as the lactate threshold or also by the inaccurate phrase lactic acid threshold. Blood lactate levels rise quickly and the build-up acidifies the blood (lowers pH), overwhelming the natural pH buffers in the blood and eventually blocking the rate of glycolysis. 4
Lactic acid or lactate threshold training originated from this concept and is based on the idea of riding just below the intensity at which lactic acid is supposed to overwhelm the muscles with pain. Although the underlying principle is incorrect, the training programme consisting of short, hard repeats or steady-state intervals, does help cyclists to ride longer at harder intensity as it develops more mitochondria and so processes the lactate more efficiently. (It is also said to assist with weight loss!5)
Fact or Fiction? Massage flushes out lactic acid
Myth: Lactic acid is a waste product of glucose metabolism for energy.
Fact: Rather than a mere by-product of glycolysis, lactic acid is now considered another important fuel source to be used by working muscles for energy. The lactic acid is taken up and used as a fuel by mitochondria. 7 Mitochondria even have a special transporter protein to move the substance into them. 8 As journalist Gina Kataro puts it in The New York Times, lactic acid is food, not foe. 9
Myth: Lactic acid is responsible for acidifying the blood, thereby causing a burning sensation in the muscles and fatigue during training.
Fact: The general consensus is that lactic acid cannot be blamed for the dreaded lactic acid burn that athletes experience when they go anaerobic. As explained, a rise in blood lactate levels does lower the pH balance of blood thus acidifying it. 10 When the body stops exercising, both lactate and pH return rapidly to their normal levels. 11 La Porte refers to a study in which subjects who were given high levels of sodium lactate did not suffer any of the symptoms ascribed to being anaerobic. He argues that these symptoms are caused by the drop in the blood pH. “You’d get the same symptoms from anything that produced acidosis.” he states. 12
Lactic acid is also not responsible for muscle fatigue during exercise it seems. Scientists internationally agree on this point but a plethora of studies are being conducted on what exactly it is that causes an athlete to experience fatigue during strenuous exercise. Some look at the possibility that hypoglycaemia makes the athlete feel weak and fatigued. 13
A combined investigation between Swedish and Australian scientists looks at inorganic phosphate, which increases during fatigue due to breakdown of creatine phosphate, and appears to be a major cause of muscle fatigue. It could be that rather than acidification, some other consequence of anaerobic metabolism is the actual cause of impaired muscle function, and increased levels of inorganic phosphate is a strong candidate in this respect.14
An Australian study has concluded that muscle fatigue is an exercise-induced reduction in maximal voluntary muscle force caused not only by changes in the muscle but also occurs as a result of changes that occur in the relaying of impulses from the fatiguing muscles to the central nervous system due to the altered input from muscle spindle, tendon organ, and group III and IV muscle afferents innervating the fatiguing muscle. This affects, for example, proprioception, tremor, and postural control. The researchers conclude that human muscle fatigue does not simply reside in the muscle.15 This relates to an article that appeared in the British Journal of Sports Medicine. The American scientists conclude that a variety of peripheral factors other than lactic acid are known to compromise muscle force and power including the subconscious brain’s ability to regulate power output by adjusting motor unit recruitment to prevent ‘burn-out’ by maintaining whole body homoeostasis, 16
According to scientists at La Trobe University in Melbourne and at the University of Aarhus in it is in fact the acidity that helps prevent muscle fatigue. In an article that appeared in the American Association for the Advancement of Science, they explain that muscles use acidosis to help ensure that they keep responding properly to nerve signals and so avoid the fatigue that would otherwise occur. The acidosis counteracts the depressing effects of potassium and chloride to help the muscle membranes stay excitable, enabling the impulses to keep exciting the muscle when they would otherwise fail. This they say counteracts fatigue muscles. 17
Thus although we don’t understand the mechanism that causes muscle fatigue during exercising in its entirety yet, it is clear that lactic acid build-up is not the culprit.
Myth: Lactic acid causes delayed onset muscle soreness (DOMS)
Fact: Stiffness and DOMS are not the result of an accumulation or continued production of lactic acid in the tissue after cessation of exercise. 18 It is due mostly to microscopic tears and trauma to the muscle myofibrils and inflammation during eccentric or lengthening contractions. Lactic acid levels in fact return to pre-exercise levels within 30 minutes to an hour following exercise and can therefore not contribute to delayed pain experienced 24 to 48 hours after exercise. 19
According to Dr Andrew Bosch of the Sports Science Institute who writes on the Time-to-Run website, a blood sample taken from a runner the day after a marathon or ultra-marathon indicate very high levels of an enzyme called creatine kinase. This is an indication of muscle damage as this particular enzyme “leaks” from tears or ruptures of the muscle fibres. It is also possible that the connective tissue in and around the muscles has also been disrupted.
Bosch states that the erroneous thinking behind the lactic acid theory can be demonstrated by runners experiencing more severe muscle soreness after a long or hard downhill run than after running over flat terrain.
“Comrades runners, particularly, will have noticed that the post-race stiffness is worse after a down run than an up run.” he says. “(I)t is this very phenomenon that begins to exclude a build-up of lactic acid as a cause of the pain. In downhill running the concentration of lactate in the blood and muscle is very low compared to running at the same speed on the flat. Thus, the most painful post-race stiffness occurs when the lactate concentration is lowest”. 20
Downhill running, according to Bosch, is particularly damaging because of the greater eccentric muscle contractions that occur. “When your foot contacts the ground after the air-borne phase of the gait cycle, the muscles in the thigh contract to support you,” he explains. “But the nature of the running action is such that although the muscle is contracting, it is forced to lengthen at the same time.” It is this simultaneous contracting while lengthening or eccentric contraction that is most damaging to muscle fibres. Running fast or running downhill places greater strain on the muscle fibres and connective tissue compared with running over a flat route.” 21 (See also Box)
Where did it all start?
According to George Brooks, professor of integrative biology at Berkley University, lactic acid was cast in the role of the villain early in the previous century when Nobel laureate, Otto Meyerhoff cut a frog in half and put its bottom half in a jar.6 The frog’s muscles had no circulation and therefore no source of oxygen or energy. Meyerhoff gave the frog’s leg electric shocks to make the muscles contract, but after a few twitches, the muscles stopped moving. When he examined the muscles, he discovered that they were bathed in lactic acid. This is where the theory that a lack of oxygen to muscles leads to lactic acid, leads to fatigue originated and eventually from that the myth that post-exercise massage can it flush out to prevent muscle soreness.
Lactic acid and muscle contraction
Muscle contraction is classified as either isometric or isotonic. Isometric contraction is considered static as it does not result in changes in joint angle or length of the muscle. Isotonic contractions are dynamic contractions as tension develops in the muscle while it either shortens or lengthens.
If the muscle shortens during contraction it is called concentric contraction. The muscle causes movement against gravity or resistance as its attachments and the structures it is attached to move closer together.
Eccentric contractions take place when the muscle lengthens as it contracts. The attachments separate during eccentric contractions. It is the body’s way of controlling movement with gravity or resistance.
Although concentric contractions do not produce the damage that eccentric contractions do, concentric contractions produce more lactic acid. 22 23
Myth: Massage helps to remove lactic acid and alleviate DOMS
Fact: As the discussion so far has indicated, the re-uptake of lactate happens rapidly and spontaneously after cessation of training. Unless the athlete is massaged immediately after an event, the re-absorption process will have been completed anyway. Furthermore no evidence exists that massage either promotes the re-uptake or flushing out of lactic acid.24
This is confirmed by a study done at the University of Northern Iowa in Cedar Falls that compared the effects of massage, passive recovery, and mild bicycle riding (about 40% of max oxygen uptake) on lactate metabolism after an exhaustive treadmill run. Researchers sampled the subjects’ blood lactate for up to 20 minutes after exercise and found that passive recovery (lying down supine) and massage had no effect on blood lactate levels, while mild bicycle riding caused a better removal of blood lactate 15–20 minutes after exhaustive exercise. They conclude that the result doesn’t suggest that “massage is useless for athletes; all it means is that the benefits of massage have nothing to do with the removal of lactic acid.” 25
Benefits of massage after strenuous exercise or post-event
If not applied to flush out lactic acid, does post-event massage serve any purpose? The answer seems to be a resounding yes when you speak to sports massage therapists and participants. Benefits include: 26
- Dealing with the mechanical damage to muscle fibres and the subsequent inflammation.
- Normalising residual hypertonicity in fatigued muscles by decreasing the metabolic rate of the muscles. This leads to reduced fuel usage and reduced metabolic waste production.
- Improving local circulation and lymphatic drainage.
- Possibly reducing hypersensitivity of nerve endings
- Alleviating pain-spasm-pain reflexes
- Inducing para-sympathetic dominance.
Grant concludes that in synergy, these effects allow the body to “more effectively perform the recovery miracle it was designed to do. In short, what is being affected by massage post-exercise is not a static state of chemical dysfunction but the dynamic metabolic and neuro-chemical balance.” 27
The last word on the subject goes to Whitney Lowe, owner and director of Orthopedic Massage Education and Research Institute in the : “This lactic acid concept illustrates the perpetuation of misinformation that can happen if (therapeutic massage therapists) don’t have the research base. When we are looking for credibility with others in health care, they want to know on what we base our opinions. A lot is passed along on hearsay, not on scientific information. What we need to keep our eyes on is how to reduce that as much as possible so we do have accurate information.” 28
For a complete list of references, contact the author at firstname.lastname@example.org
1. Bosch, A. Time-to-Run http://www.time-to-run.com/theabc/lactic.htm
2. Chaitow, L & Walker Delaney, J. (2000). Clinical application of neuromuscular techniques Vol 1. P20
3. Gandevia, S.C. (2001). Spinal and Supraspinal Factors in Human Muscle Fatigue. In Physiol. Rev. 81: 1725-1789, 2001. hxxp://physrev.physiology.org/cgi/content/abstract/81/4/1725.
4. Grant, K.E. (2000). General Concepts of Lactic Acid Physiology. http://www.mckinnonmassage.com
5. Inner West Mobile Massage http:// www. innerwestmassage.com
6. Kolata, G. (2006). Lactic acid is not muscles’ foe, it’s fuel. In The New York Times 16 May 2006.http;//www,nytimes,com
7. Jordaan, D.P. (2004). Traumeel S: The sportsman’s answer to enhanced exercise performance and the overtraining syndrome?. Unpublished masters thesis Department of Biokinetics, Sport and Leisure Sciences, University of Pretoria . http://upetd.up.ac.za.
8. Kravitz, L & Dalleck, L (2005). Lactate Threshold Training. In Network, the official magazine of Australian Fitness Network. Autumn, pp 27-30. Downloaded from http://www.unm.edu
9. LaPorte, D.C. Lactic acid.http://mckinnonmassage.com
10. Quin, E. Lactic acid and performance. About.com. Sports medicine http:// www.sportsmedicine.about.com
11. Thompson, C W & Floyd, R T (1994). Manual of structural kinesiology. St Lois, : Mosby.P11.
12. Vanderbilt, S (2001). Sports Massage & Recovery Time Re-examining the Role of Lactic Acid. In Massage & Bodywork http://www.massagetherapy.com
13. Weir, J P, Beck, T W, Cramer, J T & Housh, T J. (2006). Is fatigue all in your head? A critical review of the central governor model. In British Journal of Sports Medicine 2006;40:573-586 http://bjsm.bmj.com/cgi/content/abstract/40/7/573
14. Westerblad, H, David G. Allen, D.G.2 and Jan Lännergren, J. (2002) Muscle Fatigue: Lactic Acid or Inorganic Phosphate the Major Cause? In News Physiol Sci 17: 17-21, 2002 http://physiologyonline.physiology.org.