Someone asked me a question about “lactic acid” buildup in another forum. I thought others might be interested in the latest research on the topic.
Any activity is a mix of the 3 energy systems: Phosphagen/ATP-PC (Power), Glycolytic/Anaerobic (Strength), Oxidative/Aerobic (Endurance). Unfortunately, these systems are taught so that learners tend to think of the systems as on/off light switches. These three systems should be thought of as dimmer switches - where one system predominates and the others are at a lower level.
So, the answer is, it is all - Glycolytic, Phosphagen and Oxidative. It just depends on the individual's level of technique, perception, strength, endurance and power. Having said that, I believe that difficult climbing (and by that, I mean whatever your onsight/redpoint level is) is generally 1.Glycolytic 2.Phosphagen 3.Oxidative depends on the route/problem. A V10 boulderer, who rarely does more than 20 moves at a time, probably can redpoint a 5.12 faster than a sport climber who climbs many 5.11s and occasionally tries a 5.12.
In fact, climbers DO keep elevated heart rates - but comparatively low ventilary rates. This is also seen in racing (ski/motocross/car/truck), where a person's heart (pulse) rate is very high for extended periods but, their breathing at around 50% of VO2Max.
Lactate or "lactic acid" as the cause of fatigue in working muscle was an explanation for a complex physiological process. Lactate increases as climbing intensity increases, and as climbing intensity increases, fatigue increases, so it is assumed that lactate caused fatigue. If sport scientists didn't understand heart rates as well as we do, you could assume that heart rate and fatigue go hand in hand. Heart rate and fatigue both increase as climbing intensity increases, but we know that heart rate does not cause fatigue. The same is true of lactate. Understanding lactate requires a fair bit of biochemistry and physiology. Even many of the current physiology textbooks are outdated regarding the information they provide about lactate. There is interesting new research that has increased our understanding of lactate metabolism.
This is what we now know:
*Lactate does not cause fatigue, conversely it is a useful and efficient source of fuel.
*Lactic acid does not exist in the blood. As soon as it is produced, the substance thought to be lactic acid disassociates into lactate and hydrogen ions. A lactate analyzer measures the concentration of lactate (a useful fuel) in the blood.
*Because lactate does not cause fatigue, clearing it from the blood depends on how well an athlete uses it as fuel. Muscles not only tolerate lactate, but at times prefer lactate over glucose as an energy source.
*Although lactate production increases as climbing intensity increases, the body's ability to use lactate as fuel varies from athlete-athlete and varies with your level or current training, fed and rested state. Your ability to use lactate as fuel also changes the level of lactate that will appear in the blood at maximum sustainable workloads. This suggests that lactate concentration may not be a valid predictor of performance.
*Lactate and hydrogen ions are products from anaerobic metabolism. While the accumulation of hydrogen ions contribute to fatigue, it is not a 1:1 ratio with the appearance of lactate in the blood. There is new research that physiological mechanisms other than hydrogen ion accumulation are the main sources of muscular fatigue at non-sustainable workloads.
The topic is somewhat incomplete without inquiring neuromuscular recruitment. This is the nervous systems ability to recruit more musculature to do the same job. So, instead of doing bodybuilding strength exercises to make one's muscles larger in cross sectional diameter - it is better to work on movement difficulty (ie...bouldering) to increase sport specific biomotor abilities. Many people don't like bouldering because it's hard and the failure rate is high (among other reasons I'm sure). But, if your goal is to climb at a higher grade, then bouldering is the best way to recruit your nervous system. Then do a special endurance period to work your redpoint/onsight muscular abilities before your project.
References
1. Brooks, G. A. Intra- and extra-cellular lactate shuttles. Med Sci Sports Exerc. 32:790-799, 2000.
2. Brooks, G. A. The lactate shuttle during exercise and recovery. Med Sci Sports Exerc. 18:360-368, 1986.
3. Consoli, A., N. Nurjhan, J. J. Reilly, Jr., D. M. Bier, and J. E. Gerich. Contribution of liver and skeletal muscle to alanine and lactate metabolism in humans. Am J Physiol. 259:E677-684, 1990.
4. Donovan, C. M. and G. A. Brooks. Endurance training affects lactate clearance, not lactate production. Am J Physiol. 244:E83-92, 1983.
5. Dubouchaud, H., G. E. Butterfield, E. E. Wolfel, B. C. Bergman, and G. A. Brooks. Endurance training, expression, and physiology of LDH, MCT1, and MCT4 in human skeletal muscle. Am J Physiol Endocrinol Metab. 278:E571-579, 2000.
6. Miller, B. F., J. A. Fattor, K. A. Jacobs, M. A. Horning, F. Navazio, M. I. Lindinger, and G. A. Brooks. Lactate and glucose interactions during rest and exercise in men: effect of exogenous lactate infusion. J Physiol. 544:963-975, 2002.
7. Miller, B. F., J. A. Fattor, K. A. Jacobs, M. A. Horning, S. H. Suh, F. Navazio, and G. A. Brooks. Metabolic and cardiorespiratory responses to "the lactate clamp". Am J Physiol Endocrinol Metab. 283:E889-898, 2002.
8. Nielsen, J. J., M. Mohr, C. Klarskov, M. Kristensen, P. Krustrup, C. Juel, and J. Bangsbo. Effects of high- intensity intermittent training on potassium kinetics and performance in human skeletal muscle. J Physiol. 554:857-870, 2004.
9. Westerblad, H., D. G. Allen, and J. Lannergren. Muscle fatigue: lactic acid or inorganic phosphate the major cause? News Physiol Sci. 17:17-21, 2002.
10. Westerblad, H., J. D. Bruton, and J. Lannergren. The effect of intracellular pH on contractile function of intact, single fibres of mouse muscle declines with increasing temperature. J Physiol. 500 ( Pt 1):193-204, 1997.
11. Watts PB. Physiology of difficult rock climbing. Eur J Appl Physiol. 2004 Apr;91(4):361-72. Epub 2004 Feb 17.
David Wahl
www.athletikspesifik.com
