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The Science of Performance |
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Part 3 – Lactate Threshold By Richard Gibbens In parts one and two of this series, I dissected the theory of VO2max and explained the significant challenges that have been mounted against it. In order to answer these challenges, physiologists have advanced several additional factors related to VO2max. The two most prominent of these factors are lactate threshold and running economy. We will discuss lactate threshold this time and running economy next time. Lactate Threshold: what it is and what it means Your body has 3 methods of producing energy, and only 1 of them, the aerobic system, uses oxygen. The other two do not require oxygen to produce energy. A by-product of producing energy without oxygen is lactate (also commonly called lactic acid). As the intensity of exercise increases, the amount of lactate also increases. Physiologists have noted in laboratory tests that as running speed increases so do blood lactate concentrations. They further noted that above some running speed, lactate levels appear to rise much more quickly. This has been called the lactate threshold, lactate turnpoint, or the anaerobic threshold. The explanation for this sudden rise in lactate was that the oxygen supply to the muscles was inadequate to meet their needs (VO2max again). The muscles became increasingly “anaerobic” and in turn released lactate into the blood stream. Physiologists also observed that with training runners could increase the speed at which they could run before reaching their “lactate threshold”. For many years physiologists and athletes thought lactate was a bad thing. It was believed to cause the “burn” you feel in your muscles when you are exercising intensely and to cause your muscles to shut down from fatigue when the intensity got too high. It was also believed to be the cause of the muscle soreness athletes oftentimes experience one to two days after a hard workout. These beliefs have all been refuted – lactic acid doesn’t do any of those bad things. Even so, there are plenty of coaches, runners, and writers who still preach that lactate is a bad thing. Based on observations and beliefs about lactate, coaches invented training programs designed to improve runners’ lactate thresholds. Does your workout program include threshold runs, tempo runs, cruise intervals, or LT runs? If so, you’ve conducted workouts that are believed to improve your lactate threshold. If you’ve read the first two parts of this series, I can hear the questions forming now. Is there really a lactate threshold? Does increasing blood lactate concentration in my body mean I’m going anaerobic? Does lactate shut my muscles down? How do I improve my running? The answers to your questions are no, no, no, and I’m getting to it. Reliable studies have shown that lactate concentrations do not show a distinct, abrupt rise above some running speed(1). That means there is not a lactate threshold. Instead lactate concentrations have been shown to rise as a continuous function of exercise intensity. Second, muscle lactate production occurs all the time, even when there is plenty of oxygen available for your muscles. There is no conclusive evidence that your muscles become anaerobic during intense exercise, or even during maximum exercise. Third, there is no real evidence that lactate causes your muscles to burn, that it causes fatigue or even that it causes muscle soreness. Instead, lactate has been shown to be a potent source of energy for your body, not the metabolic waste that it was first believed to be (2). Where does all this leave us? Here’s the bottom line. Your body produces lactate all the time and as your exercise intensity increases so does your lactate concentration. That much is certainly true. Lactate levels have even been used as a fairly accurate measure of running performance. However, lactate is not a limiting factor in performance. Here’s that question again. If lactate does not limit your running performance, does it make sense to employ a training program concentrated on changing your lactate levels? Do you really need to conduct tempo runs, cruise intervals, LT runs, or threshold runs to improve your lactate threshold if lactate levels aren’t preventing you from running faster? Instead, shouldn’t your training program be crafted to improve those factors that are truly limiting your performance? If your lactate levels improve as a by-product of your workouts that’s fine, but it shouldn’t be your primary focus. Next time we will discuss running economy. Till then keep on running. References: 1. Noakes, T (1991). The Lore of Running, 91-96. 2. Anderson, O (1998). Lactate Lift-Off, 20-22
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