Lactic Acid-good Or Bad?

[Camardo]

Enduring Questions: Is Lactic Acid Really Such a Bad Thing?
Everyone knows you should avoid that nasty stuff that makes your muscles burn. Right? Right?

by: Amby Burfoot  

For as long as I've been running--and I recently passed the four-decade mark--I've been practicing certain key principles of our sport. Run long to develop endurance. Run fast to build speed. Take recovery days as necessary. Sleep well. Eat a varied, low-fat diet. Cross-train to prevent injury and burnout.

These are simple concepts, well within my grasp (and yours). And when we follow them, life is good. But there has always been one more key principle: Avoid the Demon Lactic Acid, that dread substance that turns your legs into cement blocks.

These days, however, respected and reasonable people are saying some nice things about lactic acid, or at least about the lactate that is quickly produced from lactic acid. In a journal article published last year with the title "Biochemistry of Exercise-Induced Metabolic Acidosis," University of New Mexico Professor Robert Robergs makes a strong case that lactic acid has been hopelessly misunderstood. "If muscle did not produce lactate," writes the physiology Ph.D., "acidosis and muscle fatigue would occur more quickly, and exercise performance would be severely impaired."

I've been hearing claims like this for nearly 10 years. But at first they came mainly from just one source, professor George A. Brooks from UCLA, so I figured that Brooks was a lone-wolf type. Now Brooks has a large pack of followers. "I was stubborn, I kept at it, and I was right," he says. "Far from being the Darth Vader of metabolism, lactic acid is a key substance used to provide energy, burn dietary carbohydrates, produce blood glucose and liver glycogen, and promote survival in stressful situations."

Brooks calls all these goings-on the "lactate shuttle" or "lactate transport system." What he's saying, in essence, is that lactate moves around the body from muscle fibers to organs, including the heart, and is an excellent energy source.

How did we get things so wrong for so long? It turns out we were misled by two Nobel laureates, A.V. Hill and Otto Meyerhof, who won Nobel Prizes in 1922 for their studies of carbohydrate metabolism in working muscles. They noticed that lots of lactic acid was being produced at just the point where the muscles stopped functioning. Ergo, lactic acid must be the cause of muscle fatigue.

Oops. This turned out to be a classic mistake in logic--a conclusion based on related events, but not a true cause-and-effect relationship. What's more, Hill and Meyerhof were working with frog muscles, and human muscles have a much higher endurance potential. Final straw: Those frog muscles were cut off from the rest of the frog, and isolated in a jar. When you and I enter races, we're allowed to keeps our legs attached, including the blood and its refreshing supply of oxygen. Personally, I think this is a fine way of doing things.


The Lactate Threshold
When you're reading, walking, or running very slowly, your muscles burn modest amounts of carbohydrate and produce modest amounts of lactic acid, which doesn't do any harm. As you run faster, however, your muscles burn more carbs and produce more lactic acid, which quickly breaks down into a good guy (lactate) and a bad guy (hydrogen ions). The hydrogen ions are bad because they lower the pH of your muscles, decreasing muscle efficiency, and causing that awful burning sensation.

But here's the key: To improve your racing, you need to do workouts that increase your lactate-transport potential. Over the years, these workouts have been described by almost as many words as the Eskimos have for snow. You might have read or heard about some of the following: anaerobic threshold, ventilatory threshold, lactate threshold, lactate turnpoint, Conconi pace, or even OBLA (onset of blood lactate accumulation). All are basically attempts to describe the same thing, and all fail, because we now know that lactate accumulates in a smooth regular fashion as your exercise intensity increases. There is no threshold or turnpoint or onset.

That said, we still need a term to describe a certain training pace. "Lactate threshold" (LT) pace has been the preferred term in Runner's World for the last handful of years. Loosely speaking, LT pace requires a hard but manageable effort, and forces your body to begin producing considerably more lactate. When you train at LT pace, your body conditions itself to move lactate around, and this should improve your performances at distances from the mile to the marathon.

So what's your LT training pace? It's more or less your 5-K race pace, plus 20 to 40 seconds per mile, or your 10-K race ?ace, plus 10 to 20 seconds. (Both formulas should result in about the same pace.) Most top coaches believe you should regularly do 20- to 40-minute runs at your LT pace; these workouts are commonly called "tempo runs" or "tempo training."


A Variety Program
But one workout alone does not make a successful training program. If you do only tempo workouts to build your lactate potential, you risk falling into a rut of diminishing returns. It's far better and more productive to try a variety of fast-paced workouts. I learned this the hard way, many years ago, when I failed to do enough variety in my training. Result: I lost the big, season-ending race.

The scene was my first national cross-country meet, where I finished second to Bob Fitts from Cortland State in New York. At the time, I figured Fitts was simply tougher and more talented than I was. Now, I think he might have been smarter about his training.

Even as a collegian, I was a marathon guy already, and most of my runs were long and slow. Fitts took a different tack. He was lucky enough to have Dave Costill as a coach a few years before Costill became famous as one of the first great running physiologists. Costill made enough of an impact that Fitts went on to get a Ph.D. himself, and is now a Marquette University biology professor and expert in muscle physiology.

I call Fitts to ask how he had beaten me in that meet long ago. "I did a lot of hard three-quarter-mile repeats," he says. "I knew I had to subject the muscles to the same sort of stress they'd face in competition. I tried to extend the repeats up to a mile, but I couldn't hold the pace, which was crucial for building lactate tolerance and biomechanical efficiency."

Sometimes, Fitts says, he even dropped down to quarter-mile repeats, usually the province of milers. He'd run 25 of them in 70 seconds each, with just a 110-yard jog between them. That's not sprinting, but it's enough to build big pools of lactate, and force the body to shuttle the lactate around.

The point is simple: To build your lactate system, include plenty of variety in your program. On some days, run tempo pace for 20 minutes or more. On other days, run shorter and faster. Push yourself to the point of moderate discomfort, then recover, then push again. Together these workouts will increase your lactate transport ability, and with any luck, you'll never have the dreaded cement legs again.