Revel Sports - Lactic Acid Reduces Fatigue

THE RUNNING RESEARCH NEWS WEEKLY TRAINING UPDATE

ISSUE # 42 APRIL 7, 2005

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Hi Everyone,

In 1929, the revered exercise physiologist A. V. Hill isolated frog muscle cells and forced them to fatigue by stimulating them electrically. He noticed that as the frog fibers became increasingly tired, they tended to accumulate large quantities of lactic acid (1). Adroitly, Hill transferred the froggy sinews to a saline solution which allowed the lactic acid to dissipate, and with this dissipation came a renewed vigor on the part of the cells.

Although many explanations were possible for these interesting events, Hill settled on the idea that the piling up of intracellular lactic acid was a principal cause of muscle fatigue. His hypothesis was "verified" by later work which seemed to suggest that intracellular "acidosis" caused by a build-up of lactic acid could thwart force production by the key proteins inside muscle cells (2).

Of course, when A & B occur together, and the removal of B is associated with the reversal of A, it is tempting to think that B causes A. But just as high rates of under-age drinking are not really linked with improved SAT scores, lactic acid does not truly promote tiredness in muscles. The problem is that when one focuses strictly on A & B, then C, D, and E are ignored. The occurrence of two things together does not prove causation, especially in biological systems - where an incredible number of variables are interacting simultaneously.

Later research, in fact, showed that the lactic-acid-fatigue link was very tenuous. One study, for example, found that individuals whose muscle cells are incapable of producing lactic acid actually experience fatigue more quickly, compared with persons whose muscles spew out large quantities of lactic acid (3).

Another investigation found that the acidosis effect, by which an acetous intracellular milieu puts the stopper on muscular force production, was present at low temperatures - but was barely noticeable at typical body temperatures (4). Other work carried out with single muscle cells has shown that acidic conditions have no effect at all on fatigue (5)!

And now, the capper: A very recent study causes us to reject Hill's hypothesis completely. In very new work, researchers have shown that in fact the addition of lactic acid has beneficial effects on the force production of very tired muscles (6). You heard it here first!

In this up-to-date research, investigators revealed that increased levels of lactic acid influence the activity of chloride-ion "channels" in muscle cells; this change in activity sustains force production by muscles, instead of limiting it!

What does all of this have to do with you, the endurance runner (or cyclist, swimmer, skier, rower, or canoeist)? It means once again that developing a huge capacity to bring lactic acid in to your muscle cells will have a major impact on your performances.

Believe it or not, that capacity to bring lactic acid home is not fostered by 100-mile weeks, or by the traditional "development of aerobic capacity." It is in fact enhanced by sizzling, red-hot workouts which flood the blood with lactic acid, a flooding which causes the muscle cells to perk up and say "Hey - we need to get better at clearing this stuff out of here!"

Your muscle cells, you see, have receptors for lactic acid which grab the little lactates as they swim feverishly in the blood; these receptors can pull the fine lactate fellows inward. If you run 100 miles per week at moderate intensities, your receptor fauna is impoverished, because your muscles don't like to do anything they don't need to do. If there's not much lactic acid in the blood, they see no need to fire up receptor production.

On the other hand, if you pencil Lactate-Stacker Sessions into your program with regularity, your muscles will have no choice but to drum up lactate-receptor synthesis, a production which will reduce your fatigue during fast running and lead to better performances in your races.

The Lactate-Stacker Session is one of the easiest workouts to put together: After a good warm-up, all you need to do is blast along at close-to-max speed for one-minute work intervals, with two-minute (jog) recoveries. Start with just six work intervals for your first Lactate-Stacker session, and progress to more reps over time.

Research carried out by the godfather of modern exercise physiology, Per-Olof Astrand of Sweden, has shown that just eight one-minute intervals (with two-minute recoveries) produces a blood-lactate concentration of almost 16 mMoles/liter in the typical athlete, an incredible outpouring which will have your muscle cells stacking up dense growths of receptors on your leg-muscle membranes (7). As your muscle membranes become tangled forests of lactate receptors, your performances will improve at all distances from 800 meters up to 800 miles. Use the Lactate-Stacker session often, and have fun with it (it's nice to know that you can perform this session anywhere you like to run).

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Owen Anderson



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