Lactic acid has been the focus of sports massage therapists for many an athletic season. History tells us that massage 'rids' the body of that evil, muscle-ravaging, soreness-provoking chemical, leaving the body 'recovered' and ready for another exercise bout. However, it should be asked… what exactly is lactic acid? Does it really cause muscle soreness? Does it really sit in the blood stream and muscles for prolonged periods of time after exercise, and finally, the all-important question: does 'massage' make an iota of difference?
The energy systems
For muscles to contract, they require energy, which is supplied to the muscle cells as molecules of energy called ATP. There are three methods the body uses to supply energy in the form of ATP. Two of these methods, the ATP/alactic system and the glycolytic/lactate system, are both considered anaerobic systems because they do not require oxygen immediately. The third system is considered aerobic as it relies on a steady supply of oxygen to regenerate the ATP molecule.
ATP/alactic energy system — Power athletes (e.g. weightlifters, 100m sprinters). No lactic acid formed. ATP is broken down for fast, large amounts of energy and is simultaneously reformed via Creatine Phosphate. This pathway can only produce continuous energy for up to 15 seconds due to limited stores. Beyond this, the glycolysis/lactate system takes over.
Glycolytic/lactate system — Intense muscle activity beyond approximately 15 seconds and up to 3 minutes (e.g. 100m swimming, 400m running). No oxygen necessary. Glucose is converted to energy with pyruvic acid as the end product. Lactic acid is produced as a by-product if the formation of pyruvic acid is more than its removal. The fuel comes from glucose circulating in the blood or stored as glycogen, broken down via a series of ten chemical reactions into pyruvic acid. Only a small amount of ATP is resynthesised, so in endurance events the pyruvic acid must be shunted into the aerobic system.
The aerobic energy system — Prolonged muscle activity beyond approximately 3 minutes (e.g. marathon). Oxygen necessary. This virtually limitless supply provides for more than 90% of the energy required for such activities. However, the rate of maximal energy production is not as high as from the anaerobic systems.
Why is lactic acid formed?
A problem can arise if the product of glycolysis (pyruvic acid) is not being removed and funnelled into the aerobic system as fast as it is being produced. If the concentration of pyruvic acid becomes too high it will bring glycolysis to a halt. To avoid this, an enzyme called lactate dehydrogenase steps in and converts some of the pyruvic acid to lactic acid, and hence 'buys some time' to allow glycolysis to continue.
Once lactic acid has been formed, it immediately breaks down into a salt called lactate and hydrogen ions, which are transported out of the muscle cells and diffuse into the blood and surrounding tissues. The constant formation and removal means lactic acid levels can remain constant without adverse effects for long periods. Lactate can later be reconverted into pyruvate, acting as a fuel source to tissues not working as hard.
For this reason, a marathon runner will have near-resting levels of lactic acid in their blood following a race, due to a balance between release and removal.
When does lactic acid become a problem? At some point of exercise intensity between 55 and 90 percent of VO2 max, the 'lactate threshold' is passed. Up until this point the lactate is being used by the aerobic system at the same rate it is being produced. Beyond it, utilisation is overwhelmed by production. Blood lactate levels increase rapidly, acidifying the blood and eventually blocking the rate of the glycolytic/lactate system — the lactic acid 'burn'. Hence the only type of athlete that will experience excessive lactic acid levels are those competing in sports that demand high-intensity exercise for prolonged periods. These athletes tend to train this system, enabling a greater ability to withstand high levels.
What happens to these excessive levels of lactic acid?
Scientific evidence has shown that approximately 70% of the lactic acid formed during any intensity of exercise is converted back to pyruvic acid and used as a substrate by the heart and skeletal muscle. Lactic acid concentration in the blood is almost at resting levels 30–60 minutes following all intensities and durations of athletic events. It takes approximately 20–60 minutes to fully remove lactic acid produced during maximal exercise. Given this, those sore achy muscles that occur the following day can hardly be blamed on lactic acid, which is well at resting levels by this time. Muscle soreness that occurs 24–72 hours after exercise is most likely delayed onset muscle soreness, which is not affected by lactic acid levels.
Does massage help remove blood lactate?
Several studies have shown massage to be no more effective for speeding up lactic acid removal from the blood than simply resting after exercise. The failure is thought to be because massage, like passive recovery, fails to effect any significant change to the volume or rate of blood flow that enters and leaves muscles. However, it is widely acknowledged that blood lactate is removed more quickly during active recovery, because blood flow remains elevated through the active muscle.
So what does recovery massage do?
If blood lactic acid removal is unlikely to be one of the benefits of recovery massage, then what does it do? There are many possible effects, all of which need further study:
- Possibly an enhanced rate in the exchange of fluids around the cells.
- Normalising hypertonicity — decreasing metabolic rate, relaxing muscle to decrease pressure on surrounding tissues, and neurological calming effects (reducing hypersensitivity of nerve endings, alleviating pain-spasm-pain reflexes, releasing chemical messengers associated with parasympathetic responses).
Studies have demonstrated massage improving subsequent cycling duration, and decreasing muscle tone (measured by H-reflex amplitude). Various techniques have been shown to increase hip flexion range, neck extension and shoulder abduction range, and shoulder internal rotation range. One study showed massage to have an effect on positive mood state.
In conclusion
Lactic acid is not the nasty chemical we make it out to be, and even when it does create problems (when in excess) it is quickly restored to resting levels without any intervention. Our challenge as Soft Tissue Therapists is to search for the more probable effects that recovery massage no doubt has, and to support these claims — and moreover squash ill-founded beliefs — through scientific evidence.