“My University of Washington Sports Physiology professors say the idea behind SportLegs is ingenious, and we can’t understand why someone didn’t try this sooner.” -2004 email from triathlete Cameron Chesnut, Post Falls, Idaho
 
For most of the twentieth century, what we were taught about lactic acid was deduced from 1922 experiments with dead frogs’ legs, employing two wires and a 6-volt battery. In the defiant 1970s, UC Berkeley Professor George A. Brooks, Ph.D. challenged the 1922 conclusions, this time employing radioactive isotope tracers and magnetic resonance spectroscopy on live human athletes. Unsurprisingly, modern tools revealed an updated theory. In 1986, Brooks renamed what has since become accepted theory with the title of his seminal publication, “The lactate shuttle during exercise and recovery.”(1) In 2018, nearly a century since 1922, Dr. Brooks reflected, “It was thought that lactate is made in muscles when there is not enough oxygen. It had been thought to be a fatigue agent, a metabolic waste product, a metabolic poison. But the classic mistake was to note that when a cell is under stress, there was a lot of lactate, then blame it on lactate. Lactate is actually the body’s major fuel source, preferred by heart muscle and the brain. It’s like the VISA of energetics; lactate is accepted by consumer cells everywhere it goes.”(21)
 
Brooks’s novel concept spurs a fresh look at lactate
The freshly-ruptured theoretical frontier encouraged a flurry of new research and experimentation. At the time, we were competitive triathletes hunting training shortcuts. We suspected lactate supplementation held promise, so we experimented with dosage and timing. A freak southern-California snowstorm helped us discover a significant undocumented effect that period and subsequent research explains: Muscles initially respond to exercise by producing more lactate than they can consume. (5,6,7,8,9) Excess lactate pools in muscle tissues and readily absorbs abundant hydrogen ions left there by glycolysis and ATP catabolism, becoming acidic(2). Resultant acidity cripples lactate’s energy transfer capacity (3). Brooks now understates, “Lactate can be a problem if not used.”(21) He had earlier noted endurance training can improve our lactate clearance rate, but doesn’t curb production (4). We reasoned that if training can only improve clearance, whatever can decrease initial lactate production could accomplish more than training alone. Muscles eventually reduce production to match consumption in response to rising blood lactate concentration (5,6,7,8,9). Raising blood lactate concentration is the “switch” that causes muscles to reduce production, whether blood lactate is raised naturally by exercise or by exogenous infusion (10,11,12,13,14,15,16,17,18,19,20). Our discovery seems obvious now: Trigger this “switch” early. Raise blood lactate before exercise by lactate supplementation. The rest, as they say, is history.
  1. Brooks, George A. (1986) The lactate shuttle during exercise and recovery. Med Sci Sports Exerc 18:361-368
  2. Brooks, G. A., T. D. Fahey, T. P. White, K. M. Baldwin. (2000) Exercise Physiology. Human Bioenergetics and its Applications. 3rd edn. pp 804-805. Mayfield Publishing Company.
  3. Roth, D. A. (1991) The sarcolemmal lactate transporter: transmembrane determinants of lactate flux. Med Sci Sports Exerc 23:925-934
  4. Donovan, Casey M., and George A. Brooks (1983) Endurance training affects lactate clearance, not lactate production. Am. J. Physiol. 244 (Endocrinol. Metab. 7): E83-E92
  5. Wahren, J., P. Felig, G. Ahlborg and L. Jorfeldt. (1971) Glucose metabolism during leg exercise in man. J Clin Invest 50:2715-27258)
  6. Ahlborg, G. (1985) Mechanism of glycogenolysis in nonexercising human muscle during and after exercise. Am J Physiol. 248(5 Pt 1):E540-5
  7. Richter, E. A., B. Kiens, B. Saltin, N. J. Christensen and G. Savard. (1988) Skeletal muscle glucose uptake during dynamic exercise in humans: role of muscle mass. Am J Physiol 254:E555-E561
  8. Brooks, G. A., G. E. Butterfield, R.R. Wolfe, et al. (1991) Increased reliance on lactate during exercise after acclimatization to 4,300m. J. Appl. Physiol. 71:333-341
  9. Brooks, G. A., E. E. Wolfel, G. E. Butterfield, et al. (1998) Poor relationship between arterial lactate and leg net release during steady-state exercise at 4,300 m altitude. J. Appl. Physiol. 275:R1192-R1201
  10. Freyschuss, U. and T. Strandell (1967) Limb circulation during arm and leg exercise in supine position. J Appl Physiol, 23:163-170
  11. Ahlborg, G., L. Hagenfeldt and J. Wahren (1975) Substrate utilization by the inactive leg during one-leg or arm exercise. J Appl Physiol, 39:718-723
  12. Ahlborg, G., L. Hagenfeldt and J. Wahren (1976) Influence of lactate infusion on glucose and FFA metabolism in man. Scan J Clin Lab Invest, 36:193-201
  13. Poortmans, J. R., J. D.-V. Bossche and R. Leclercq (1978) Lactate uptake by inactive forearm during progressive leg exercise. J Appl Physiol, 45:835-839
  14. Stamford, B. A., R.  J. Moffatt, A. Weltman, C. Maldonado and M. Curtis (1978) Blood lactate disappearance after supramaximal one-legged exercise. J Appl Physiol 45:244-248
  15. Gladden, L. B. and J. W. Yates (1983) Lactic acid infusion in dogs: effects of varying infusate pH. J. Appl. Physiol. 54:1254-1260
  16. Dodd, S., S. K. Powers, T. Callender and E. Brooks (1984) Blood lactate disappearance at various intensities of recovery exercise. J Appl Physiol 57:1462-1465
  17. Stanley, W. C., E. W. Gertz, J. A. Wisneski, R.A. Neese, D. L. Morris and G. A. Brooks (1986) Lactate extraction during net lactate release by the exercising legs of man. J. Appl. Physiol. 60:1116-1120
  18. Mazzeo, R.S., G. A. Brooks, D. A. Schoeller and T.  F. Budinger (1986) Disposal of blood [1-13C] lactate in humans during rest and exercise. J Appl Physiol, 60:232-241
  19. Gladden, L. B. (1989) Lactate uptake by skeletal muscle. Exerc. Sports Sci. Rev. 17:115-155
  20. Gladden, L. B., R. E. Crawford and M. J. Webster. (1994) Effect of lactate concentration and metabolic rate on net lactate uptake by canine skeletal muscle. Am. J. Physiol. 266:R1095-R1101
  21. Sanders, Robert. Rehabilitating lactate: from poison to cure. UC Berkeley: Berkeley News May 23, 2018

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