The expression lactic acid, or lactate, is used most commonly to describe the intense
pain felt during exhaustive exercise, especially short events like the 400 metres and 800 metres. To explain what it is we first have to look briefly into how the working muscles use energy (ATP). Actively contracting muscles obtain Adenosine Triphosphate (ATP) from glucose stored in the blood stream and the breakdown of glycogen stored in the muscles. Initially pyruvic acid and small amounts of ATP are generated from the breakdown of glucose. The pyruvic acid mixed with oxygen is converted to carbon dioxide, water and ATP. When muscles contract vigorously for long periods the circulatory system begins to lose ground in delivery of oxygen. In these conditions most of the pyruvic acid produced in the breakdown of glucose is converted to lactic acid (LA). As the lactate is produced in the muscles it leaks out into the blood and is carried around the body. If this condition continues the functioning of the body will become impaired and the muscles will fatigue very quickly. When oxygen becomes available the lactic acid is converted to pyruvic acid and then into carbon dioxide, water and ATP.
Lactic acid - friend or foe?
Lactic acid (lactate) is not:
responsible for the burn in the leg muscles when exercising very fast
responsible for the soreness you experience in the 48 hours following a hard session
is not a waste product
Lactate is produced by the body all day long and is a key chemical which is used to dispose of dietary carbohydrate and, you will like this, also helps you from getting fat. During a hard session 50% of the lactate produced is used by the muscles to form glycogen which provides you with more energy. Sounds like a friend to me.
The lactate shuttle involves the following series of events:
As we exercise pyruvate is formed
When insufficient oxygen is available to breakdown the pyruvate then lactate is produced
Lactate enters the surrounding muscle cells, tissue and blood
The muscle cells and tissues receiving the lactate either breakdown the lactate to fuel (ATP) for immediate use or use it in the creation of glycogen
The glycogen then remains in the cells until energy is required
The breakdown of glucose or glycogen produces lactate and hydrogen ions - for each lactate molecule, one hydrogen ion is formed. The presence of hydrogen ions, not lactate, makes the muscle acidic which will eventually halt muscle function. As hydrogen ion concentrations increase the blood and muscle become acidic. This acidic environment will slow down enzyme activity and ultimately the breakdown of glucose itself. Acidic muscles will aggravate associated nerve endings causing pain and increase irritation of the central nervous system. The athlete may become disorientated and feel nauseous.
Given that high levels of lactate/hydrogen ions will be detrimental to performance, one of the key reasons for endurance
training is to enable the body to perform
at a greater pace with a minimal amount of lactate. This can be done by long steady runs, which will develop the aerobic capacity by means of capillarisation (formation of more small blood vessels, thus enhancing oxygen transport to the muscles) and by creating greater efficiency in the heart and lungs. If the aerobic capacity is greater, it means there will be more oxygen available to the working muscles and this should delay the onset of lactic acid at a given work intensity.
Lactic acid starts to accumulate in the muscles once you start operating above your anaerobic threshold. This is normally somewhere between 85% and 90% of your maximum heart rate (MHR).
What a low Lactate Threshold means
If your lactate threshold (LT) is reached at a low exercise intensity, it often means that the "oxidative energy systems" in your muscles are not working very well. If they were performing at a high level they would use oxygen to break lactate down to carbon dioxide and water, preventing lactate from pouring into the blood. If your LT is low it may mean that :
you are not getting enough oxygen inside your muscle cells
you do not have adequate concentrations of the enzymes necessary to oxidize pyruvate at high rates
you do not have enough mitochondria in your muscle cells
your muscles, heart, and other tissues are not very good at extracting lactate from the blood
Improving your Lactate Threshold
The aim is to saturate the muscles in lactic acid which will educate the body's buffering mechanism (alkaline) to deal with it more effectively. The accumulation of lactate in working skeletal muscles is associated with fatigue of this system after 50 to 60 seconds of maximal effort. Sessions should comprise of one to five reps (depends on the athlete's ability) with near to full recovery.
Training continuously at about 85-90% of your maximum heart rate for 20-25 minutes will improve your LT.
A session should be conducted once a week and commence eight weeks before a major competition. This will help the muscle cells retain their alkaline buffering ability. Improving your LT will also improve your tlimvVO2max.
Lactate Tolerance Training Sessions
The following table identifies some possible training sessions that can be used to improve your lactate tolerance:
Distance Pace Recovery Reps
150m 400m 90 secs 3 * 3
300m 800m 2 mins 6
150m 800m 45 secs 12
150m 800m 20 secs 2 * 4
300m 1k 90 secs 9
Research indicates that sodium phosphate ingestion can improve your lactate threshold. Richard Kreider (University of Memphis) conducted a six day trial with a sodium phosphate supplement where 4 grams/day were consumed. At the end of this period VO2max was improved by 9%, LT raised by 12% and blood-haemoglobin levels by 5%.
There are potential side effects to taking higher than normal levels of phosphate so consult with your doctor first.
The following Sports Coach pages should be read in conjunction with this page:
Delayed Onset Muscle Soreness - (DOMS)
Associated Web Sites
The following web sites contain more information on this topic:
None at present
Associated Journals and Books
The following journals and books contain more information on this topic:
Advanced PE for Edexcel - F Galligan et al - page 385 Essentials
of Exercise Physiology (2nd Edition) - W.D. McArdle, F.I. Katch & V.L. Katch - Page 108 & 256 & 452
Principals of Anatomy and Physiology (6th Edition) - G. J. Tortora & N. P. Anagnostakos - pages 241 & 793
Disposal of Lactate during and after Strenuous Exercise in Humans, Journal of Applied Physiology, Vol 61(1), pp338-343, 1986
Peak Performance - Issue 41, 72, 73, 100 & 101,
Peak Performance - Issue 112
Peak Performance - Issue 113 (Rugby)
Peak Performance - Issue 121 pages 3 & 10
Peak Performance - Issue 130 page 1
Peak Performance - Issue 151, page 11
Peak Performance - Issue 162, page 6
Peak Performance - Issue 173, page 7
The Coach - Issue 3 page 29
BMC News - Volume 3 Issue 12 - page 10