Lactic Acid Articles

Lactic Acid Is Not Muscles' Foe, It's Fuel

By GINA KOLATA

Everyone who has even thought about exercising has heard the warnings about lactic acid. It builds up in your muscles. It is what makes your muscles burn. Its buildup is what makes your muscles tire and give out.

Coaches and personal trainers tell athletes and exercisers that they have to learn to work out at just below their "lactic threshold," that point of diminishing returns when lactic acid starts to accumulate. Some athletes even have blood tests to find their personal lactic thresholds.

But that, it turns out, is all wrong. Lactic acid is actually a fuel, not a caustic waste product. Muscles make it deliberately, producing it from glucose, and they burn it to obtain energy. The reason trained athletes can perform so hard and so long is because their intense training causes their muscles to adapt so they more readily and efficiently absorb lactic acid.

The notion that lactic acid was bad took hold more than a century ago, said George A. Brooks, a professor in the department of integrative biology at the University of California, Berkeley. It stuck because it seemed to make so much sense.

"It's one of the classic mistakes in the history of science," Dr. Brooks said.

Its origins lie in a study by a Nobel laureate, Otto Meyerhof, who in the early years of the 20th century cut a frog in half and put its bottom half in a jar. The frog's muscles had no circulation — no source of oxygen or energy. Dr. Myerhoff gave the frog's leg electric shocks to make the muscles contract, but after a few twitches, the muscles stopped moving. Then, when Dr. Myerhoff examined the muscles, he discovered that they were bathed in lactic acid.

A theory was born. Lack of oxygen to muscles leads to lactic acid, leads to fatigue.

Athletes were told that they should spend most of their effort exercising aerobically, using glucose as a fuel. If they tried to spend too much time exercising harder, in the anaerobic zone, they were told, they would pay a price, that lactic acid would accumulate in the muscles, forcing them to stop.

Few scientists questioned this view, Dr. Brooks said. But, he said, he became interested in it in the 1960's, when he was running track at Queens College and his coach told him that his performance was limited by a buildup of lactic acid.

When he graduated and began working on a Ph.D. in exercise physiology, he decided to study the lactic acid hypothesis for his dissertation.

"I gave rats radioactive lactic acid, and I found that they burned it faster than anything else I could give them," Dr. Brooks said.

Dr. Brooks said he published the finding in the late 70's. Other researchers challenged him at meetings and in print.

"I had huge fights, I had terrible trouble getting my grants funded, I had my papers rejected," Dr. Brooks recalled. But he soldiered on, conducting more elaborate studies with rats and, years later, moving on to humans. Every time, with every study, his results were consistent with his radical idea.

Eventually, other researchers confirmed the work. And gradually, the thinking among exercise physiologists began to change.

"The evidence has continued to mount," said L. Bruce Gladden, a professor of health and human performance at Auburn University. "It became clear that it is not so simple as to say, Lactic acid is a bad thing and it causes fatigue."

As for the idea that lactic acid causes muscle soreness, Dr. Gladden said, that never made sense.

"Lactic acid will be gone from your muscles within an hour of exercise," he said. "You get sore one to three days later. The time frame is not consistent, and the mechanisms have not been found."

The understanding now is that muscle cells convert glucose or glycogen to lactic acid. The lactic acid is taken up and used as a fuel by mitochondria, the energy factories in muscle cells.

Mitochondria even have a special transporter protein to move the substance into them, Dr. Brooks found. Intense training makes a difference, he said, because it can make double the mitochondrial mass.

It is clear that the old lactic acid theory cannot explain what is happening to muscles, Dr. Brooks and others said. Yet, Dr. Brooks said, even though coaches often believed in the myth of the lactic acid threshold, they ended up training athletes in the best way possible to increase their mitochondria. "Coaches have understood things the scientists didn't," he said.

Through trial and error, coaches learned that athletic performance improved when athletes worked on endurance, running longer and longer distances, for example.

That, it turns out, increased the mass of their muscle mitochondria, letting them burn more lactic acid and allowing the muscles to work harder and longer.

Just before a race, coaches often tell athletes to train very hard in brief spurts.

That extra stress increases the mitochondria mass even more, Dr. Brooks said, and is the reason for improved performance.

And the scientists?

They took much longer to figure it out.

Why does lactic acid build up in muscles? And why does it cause soreness?

Scientific American, January 23, 2006

Stephen M. Roth, a professor in the department of kinesiology at the University of Maryland, explains. As our bodies perform strenuous exercise, we begin to breathe faster as we attempt to shuttle more oxygen to our working muscles. The body prefers to generate most of its energy using aerobic methods, meaning with oxygen. Some circumstances, however, --such as evading the historical saber tooth tiger or lifting heavy weights--require energy production faster than our bodies can adequately deliver oxygen. In those cases, the working muscles generate energy anaerobically. This energy comes from glucose through a process called glycolysis, in which glucose is broken down or metabolized into a substance called pyruvate through a series of steps. When the body has plenty of oxygen, pyruvate is shuttled to an aerobic pathway to be further broken down for more energy. But when oxygen is limited, the body temporarily converts pyruvate into a substance called lactate, which allows glucose breakdown--and thus energy production--to continue. The working muscle cells can continue this type of anaerobic energy production at high rates for one to three minutes, during which time lactate can accumulate to high levels.

A side effect of high lactate levels is an increase in the acidity of the muscle cells, along with disruptions of other metabolites. The same metabolic pathways that permit the breakdown of glucose to energy perform poorly in this acidic environment. On the surface, it seems counterproductive that a working muscle would produce something that would slow its capacity for more work. In reality, this is a natural defense mechanism for the body; it prevents permanent damage during extreme exertion by slowing the key systems needed to maintain muscle contraction. Once the body slows down, oxygen becomes available and lactate reverts back to pyruvate, allowing continued aerobic metabolism and energy for the body’s recovery from the strenuous event.

Contrary to popular opinion, lactate or, as it is often called, lactic acid buildup is not responsible for the muscle soreness felt in the days following strenuous exercise. Rather, the production of lactate and other metabolites during extreme exertion results in the burning sensation often felt in active muscles, though which exact

metabolites are involved remains unclear. This often painful sensation also gets us to stop overworking the body, thus forcing a recovery period in which the body clears the lactate and other metabolites.

Researchers who have examined lactate levels right after exercise found little correlation with the level of muscle soreness felt a few days later. This delayed-onset muscle soreness, or DOMS as it is called by exercise

physiologists, is characterized by sometimes severe muscle tenderness as well as loss of strength and range of motion, usually reaching a peak 24 to 72 hours after the extreme exercise event.

Though the precise cause of DOMS is still unknown, most research points to actual muscle cell damage and an elevated release of various metabolites into the tissue surrounding the muscle cells. These responses to extreme exercise result in an inflammatory-repair response, leading to swelling and soreness that peaks a day or two after the event and resolves a few days later, depending on the severity of the damage. In fact, the type of muscle contraction appears to be a key factor in the development of DOMS. When a muscle lengthens against a load--imagine your flexed arms attempting to catch a thousand pound weight--the muscle contraction is said to be eccentric. In other words, the muscle is actively contracting, attempting to shorten its length, but it is failing. These eccentric contractions have been shown to result in more muscle cell damage than is seen with typical concentric contractions, in which a muscle successfully shortens during contraction against a load. Thus, exercises that involve many eccentric contractions, such as downhill running, will result in the most severe DOMS, even without any noticeable burning sensations in the muscles during the event.

Given that delayed-onset muscle soreness in response to extreme exercise is so common, exercise physiologists are actively researching the potential role for anti-inflammatory drugs and other supplements in the prevention and treatment of such muscle soreness, but no conclusive recommendations are currently available. Although anti-inflammatory drugs do appear to reduce the muscle soreness--a good thing--they may slow the ability of the muscle to repair the damage, which may have negative consequences for muscle function in the weeks following the strenuous event.

Muscle Pain and Soreness After Exercise - What Is Delayed Onset Muscle Soreness

Preventing and treating DOMS - muscle pain and muscle soreness after exercise By Elizabeth Quinn, About.com Guide

Updated July 11, 2010

What Causes Muscle Pain and Muscle Soreness After Exercise - What is DOMS?

Delayed onset muscle soreness (DOMS) describes a phenomenon of muscle pain, muscle soreness or muscle stiffness that is felt 12-48 hours after exercise, particularly at the beginning of a new an exercise program, after a change in sports activities, or after a dramatic increase in the duration or intensity of exercise.

This muscle pain is a normal response to unusual exertion and is part of an adaptation process that leads to greater stamina and strength as the muscles recover and build hypertrophy).

This sort of muscle pain is not quite the same as the muscle pain or fatigue you experience during exercise. This delayed pain is also very different than the acute, sudden pain of and injury such as muscle strains and sprains, which is marked by an abrupt, specific and sudden pain that occurs during activity and often causes swelling or bruising.

The delayed soreness of DOMS is generally at its worst within the first 2 days following the activity and subsides over the next few days.

Delayed onset muscle soreness is quite common and quite annoying, particularly for those beginning an exercise program or adding new activities. A beginning exerciser who bikes 10 miles, followed by push-ups and sit-ups is likely to experience muscle pain and soreness in the next day or two.

Delayed Onset Muscle Soreness - Causes

Delayed onset muscle soreness is thought to be a result of microscopic tearing of the muscle fibers. The amount of tearing (and soreness) depends on how hard and how long you exercise and what type of exercise you do. Any movement you aren't used to can lead to DOMS, but eccentric muscle contractions (movements that cause muscle to forcefully contract while it lengthens) seem to cause the most soreness.

Examples of eccentric muscle contractions include going down stairs, running downhill, lowering weights and the downward motion of squats and push-ups. In addition to small muscle tears there can be associated swelling in a muscle which may contribute to soreness.

Delayed Onset Muscle Soreness - Treatment

There is no one simple way to treat delayed onset muscle soreness. In fact, there has been an ongoing debate about both the cause and treatment of DOMS. In the past, gentle stretching was one of the recommended ways to reduce exercise related muscle soreness, but a study by Australian researchers published in 2007 found that stretching is not effective in avoiding muscle soreness.

So does anything work to reduce delayed-onset muscle soreness? Nothing is proven 100 percent effective, but some people have found the following advice helpful, but it's best for an individual to try a few things to see what works for them. Ultimately, best advice for treating DOMS is to prevent it in the first place.

Tips for Dealing with Muscle Soreness After Exercise

If you do find yourself sore after a tough workout or competition, try these methods to deal with your discomfort. Although not all are backed up with research, many athletes report success with some of the following methods.

 Use Active Recovery. This strategy does have support in the research. Performing easy low-impact aerobic exercise increasing blood flow and is linked with diminished muscle soreness. After an intense workout or competition, use this technique as a part of your cool down.

 Rest and Recover. If you simply wait it out, soreness will go away in 3 to 7 days with no special treatment.

 Try a Sports Massage. Some research has found that sports massage may help reduce reported muscle soreness and reduce swelling, although it had no effects on muscle function.

 Try an Ice Bath or Contrast Water Bath. Although no clear evidence proves they are effective, many pro athletes use them and claim they work to reduce soreness.

 Use R.I.C.E., the standard method of treating acute injuries, if your soreness is particularly painful.  Perform Gentle Stretching. Although research doesn't find stretching alone reduces muscle pain of

soreness, many people find it simply feels good.

 Try a Nonsteroidal Anti-inflammatory. Aspirin, ibuprofen or naproxen sodium may help to temporarily reduce the muscle soreness, although they won't actually speed healing. Be careful, however, if you plan to take them before exercise. Studies reported that taking ibuprofen before endurance exercise is not recommended.

 Try Yoga. There is growing support that performing Yoga may reduce DOMS.  Listen to Your Body. Avoid any vigorous activity or exercise that increases pain.  Allow the soreness to subside thoroughly before performing any vigorous exercise.

 Warm Up completely before your next exercise session. There is some research that supports that a warm-up performed immediately prior to unaccustomed eccentric exercise produces small reductions in delayed-onset muscle soreness (but cool-down performed after exercise does not).

 ** If your pain persists longer than about 7 days or increases despite these measures, consult your physician.

 Learn something from the experience! Use prevention first.

Tips to Help Prevent Delayed Onset Muscle Soreness

While you may not be able to prevent muscle soreness entirely, you may reduce the intensity and duration of muscles soreness if you follow a few exercise recommendations.

 Progress Slowly. The most important prevention method is to gradually increase your exercise time and intensity. See the 10 percent rule if you need some exercise progression guidelines.

 Warm Up thoroughly before activity and cool down completely afterward.  Cool Down with gentle stretching after exercise.

 Follow the Ten Percent Rule. When beginning a new activity start gradually and build up your time and intensity no more than ten percent per week.

 Know the 10 Tips for Safe Workouts.  Follow the Spring Training Fitness Tips.

 Hire a Personal Trainer if you aren't sure how to start a workout program that is safe and effective.  Start a new weight lifting routine with light weights and high reps (10-12) and gradually increase the

amount you lift over several weeks.

 Avoid making sudden major changes in the type of exercise you do.

 Avoid making sudden major changes in the amount of time that you exercise.

Certain muscle pain or soreness can be a sign of a serious injury. If your muscle soreness does not get better within a week consult your physician.