How Does Lactic Acid Affect Muscles?

Lactic acid buildup is often blamed for post workout muscle fatigue and pain, but just how true are these claims, and how exactly does lactic acid affect muscles, fitness and performance?

First of all, let’s get familiar with the basics of the chemical process of energy production in muscle.

In aerobic metabolism, the oxygen that is required by cells to create energy is obtained via respiration. The “energy” that is produced is ATP, or adenosine triphosphate, which is a molecule that is created and stored in all body cells and provides chemical energy for cellular function. ATP provides the energy required for a muscle to contract, and is also necessary for the operation of the muscle’s calcium pump, which is involved in the sliding filament mechanism responsible for muscle contraction.

When the body is no longer able to obtain oxygen from aerobic metabolism, the energy is obtained by a process known as anaerobic cellular metabolism. Activities such as weight lifting, sprinting, or prolonged maximum output activities achieve oxygen deficit quite quickly, where more oxygen is required for cellular reactions than is available. Lactic acid is a metabolic by-product of anaerobic processes.

During anaerobic activities, energy is produced in one of two ways, the first of which involves a reaction between the creatine phosphate that is stored in muscle cells, and adenosine diphosphate (ADP). The creatine phosphate gives its phosphate molecule to adenosine disphosphate, making it “triphosphate”; therefore, the by-products of this reaction are creatine and ATP. The energy produced from this reaction is enough to last about 15 to 20 seconds, or a 100 metre sprint, then it needs to be replenished.

The second process by which anaerobic metabolism occurs is known as glycolysis – the breakdown of glycogen, which is stored energy in muscle. (glycol = sugar or glucose; lysis = splitting). ATP is a by-product of glycolysis, as is pyruvic acid. If there is still not enough available oxygen to produce more ATP in conjunction with pyruvic acid, then the pyruvic acid is converted to lactic acid and is released into the blood stream.

And this is how it happens…

Maximum contraction of a muscle during quick bursts of power, or maximal sustained effort, increases lactic acid production in muscle because blood vessels are compressed and oxygen can’t be delivered to the cells – the aerobic, energy producing pathway is insufficient to allow oxygen to fuel the reaction. As a result, an anaerobic energy production is used, and ATP and pyruvic acid are produced. The pyruvic acid is then converted to lactic acid – therefore, during an oxygen deficit, lactic acid will be the primary by-product of glucose metabolism within a cell.

When lactic acid is released from the muscle cells into the bloodstream, it is taken to the liver usually within 30 minutes of cessation of activity. In the liver it is reconverted to pyruvic acid and released into the bloodstream for further use by muscles, or it is converted to glycogen or carbon dioxide via aerobic metabolism. It is important to note at this point that lactic acid is not necessarily the “bad guy” it has been made out to be, as it still plays an important role in energy production when sufficient oxygen becomes available again.

When large amounts of glucose are used in sustained anaerobic activity, lactic acid accumulates and is alleged to contribute to muscle soreness. The buildup of lactic acid increases muscle cell acidity (hence the burning feeling in muscle) and makes ATP production more difficult. ATP is also required for the sodium-potassium pump which maintains cellular homeostasis. In the absence of ATP, the sodium-potassium pump is unable to correct any ionic (sodium, potassium etc) imbalances in the cell environment, and muscle becomes unresponsive to stimuli.

And don’t forget that the calcium pump, used in muscle contraction, requires ATP to operate. When a deficit of ATP occurs, the muscle fibres are unable to release the “cross bridges” which are created during contraction.

As a result, in either one of the two above case scenarios, the muscle may not be able to relax, resulting in cramping and spasm.

How Can Massage Therapy Assist with Lactic Acid removal?

Ok, so maybe you don’t really care about how this all transpires, and that’s fine. Here is what you need to know about lactic acid if you are a fitness enthusiast:

The claim that lactic acid causes muscle pain has been disproven, as mentioned in the article Lactic Acid Does More Than Cause Fatigue , though it is known to cause fatigue. If this is the case, then my (educated) guess is that muscle pain is caused by micro-tearing and inflammation of muscle fibres due to over-exertion.

There is also some debate concerning the degree of assistance that massage therapy can lend to the removal of lactic acid from muscle. However, as mentioned in my previous article, Massage Therapy, Fitness and Optimal Performance , massage therapy has both a mechanical and chemical effect on the body, and I believe for these reasons, it can have a positive influence on the removal of lactic acid from muscle tissue.

Mechanically, the stretching, manipulation and kneading of tissue will assist in “unhooking” the cross bridge created during contraction and relieve some cramping and spasm. Increasing circulation by this mechanical effect will assist in oxygen delivery and waste removal to and from muscle respectively. In addition, the chemical effects of massage, causing increased blood vessel permeability, will also assist in the process. And, also, don’t forget about the release of endorphins as a benefit of massage, which can help alleviate pain.

To learn more about the physiology behind this topic, please refer to my source noted below:

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Massage Therapy, Fitness and Optimal Performance

Massage therapy is often used as an adjunct to a fitness routine to assist in achieving peak athletic performance. There are a variety of ways in which massage therapy is used to promote optimal fitness – massage therapy is not all just about spas and “fluff”. Massage can be used to increase the suppleness of muscle, aid in recovery after exertion, assist in fluid removal in the presence of injury or inflammation (from non-infectious origins) or control pain through the release of endorphins.

Massage therapy affects muscles in 2 ways: mechanically and chemically. Mechanically, it is the kneading, stretching and compression of the tissue which stimulates the smooth muscle of the blood vessels and increases blood flow to and from the area. (due to an increase in histamine – see below). Manual manipulation of the tissue will also literally break adhesions and scar tissue, regardless of whether techniques are applied with or against the muscle fibre. This decrease in inelastic scar tissue will allow muscles to contract and elongate as they should, and will increase muscle performance.

At a chemical level, massage therapy can cause the release of “endorphins”, neurotransmitters that reduce the perception of pain, and increase a feeling of wellbeing. Increased permeability of the blood vessels is caused by release of histamine in response to mechanical stimulation – this increase in blood flow leads to “hyperemia”, redness which is often visible after a massage.

The application of therapeutic massage plays a role in event preparation as well as recovery and maintenance, though the goals and application will be different depending on the timing of the treatment in relation to the activity.

Pre-event, the purpose of massage is to “wake-up” and warm-up the muscles, ensuring that they are ready for physical demands to be placed on them. During a pre-event treatment, the movements of the therapist are quick, stimulating the nerves in the area and increasing the ability of a muscle to react to stimuli. Circulation to the muscle is also increased and with it oxygen delivery to the muscle cells, causing a subsequent increase in cellular metabolism and improved functionality. Increased blood flow also warms up the muscle, allowing for greater pre-event stretching, imperative to optimizing performance and reducing injury due to muscle strain.

Post-event massage is much slower, encouraging the body to relax after exertion. Massage therapy at this stage is utilized to assist the body in removing metabolic waste, relaxing and stretching the fatigued muscle. This is done by increasing the circulation and pliability of the muscle tissue. The increased removal of metabolic waste such as lactic acid will decrease recovery time and soreness in the days following an event.

Massage therapy used as a maintenance tool will assist an athlete in maintaining optimal muscle health. During maintenance treatments, the therapist will assess the condition of tissue and establish a treatment plan in conjunction with the goals and condition of the client. It is during these treatments that muscle imbalances are often identified; adhesions and scar tissue are broken down (thus increasing muscle functionality) via manipulation, stretching and breaking down of tissue. Circulation is increased, assisting in oxygen delivery and metabolic waste removal.

Regardless of fitness level, massage therapy can help a fitness enthusiast or athlete achieve his or her performance goals by promoting and maintaining muscle health.

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Jodi Forsythe
www.whymassagetherapy.com
All Rights Reserved.