Wednesday, October 6, 2010

Understanding Lactate Threshold

The lactate threshold (LT) is the exercise intensity at which lactate starts to accumulate in the blood stream. The reason for the acidification of the blood at high exercise intensities is two-fold: the high rates of ATP hydrolysis in the muscle release hydrogen ions, as they are co-transported out of the muscle into the blood via the MCT—monocarboxylate transporter, and also bicarbonate stores in the blood begin to be used up. This happens when lactate is produced faster than it can be removed (metabolized). This point is sometimes referred to as the anaerobic threshold (AT), or the onset of blood lactate accumulation (OBLA). When exercising below the LT intensity any lactate produced by the muscles is removed by the body without it building up. The lactate threshold is a useful measure for deciding exercise intensity for training and racing in endurance sports (e.g. long distance running, cycling, rowing, swimming and cross country skiing), but varies between individuals and can be increased with training. Interval training takes advantage of the body being able to temporarily exceed the lactate threshold, and then recover (reduce blood-lactate) while operating below the threshold and while still doing physical activity. Fartlek and interval training are similar, the main difference being the relative intensities of the exercise. Fartlek training would involve constantly running, for a period time running just above the lactate threshold, and then running at just below it, while interval training would be running quite high above the threshold, but then slowing to a walk or slow jog during the rest periods. Interval training can take the form of many different types of exercise and should closely replicate the movements found in the sport.

Accurately measuring the lactate threshold involves taking blood samples (normally a pinprick to the finger, earlobe or thumb) during a ramp test where the exercise intensity is progressively increased. Measuring the threshold can also be performed non-invasively using gas-exchange (Respiratory quotient) methods, which requires a metabolic cart to measure air inspired and expired.

Although the lactate threshold is defined as the point when lactic acid starts to accumulate, some testers approximate this by using the point at which lactate reaches a concentration of 4 mM (at rest it is around 1 mM).

If anyone in the Kennebunk surrounding area is interested in finding out what their lactate level is I perform MAX VO2 testing. I have a metabolic cart that will determine your oxygen consumption and lactate threshold. This value is beneficial for endurance athletes who are training to improve their distance and time. Also, it can also be beneficial for those that perform in anaerobic activities, such as; skiing, hockey, basketball, weight training. If you are interested in learning more about lactate testing please call visit and contact me. Thanks.

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