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The scientific application of the lactate threshold heart rate has made training, weight loss, and the prevention from overtraining so much more effective. Lactate threshold heart rate is very easy and effectively determined, and has helped all sorts of cyclist’s right from recreational up to the top elite cyclist.

The scientific application of the lactate threshold heart rate has made training, weight loss, and the prevention from overtraining so much more effective. Lactate threshold heart rate is very easy and effectively determined, and has helped all sorts of cyclist’s right from recreational up to the top elite cyclist.

What is lactate threshold?

While cycling the muscles actively involved use two different energy systems, namely the aerobic energy system and the anaerobic energy system, to supply the body with adequate amount of energy. However, the ratio or percentage of contribution to the overall energy supply for the muscle differs for different intensities from each of the two energy systems. The aerobic energy system is predominantly active during rest and lower intensity exercises of longer duration (> 1 hour). For the aerobic system to work most optimal a constant oxygen supply to the muscles are crucial. Therefore, the aerobic system constantly use oxygen combined with mostly fats (to lesser extent carbohydrates) to produce energy, yielding water and carbon dioxide which is ultimately expired by the lungs. Because the aerobic system predominantly use your fat stored in your fat cells as energy source in the presence of adequate oxygen, lactic acid is not produced at all.

The anaerobic system is predominantly active during higher intensity exercise bouts of shorter duration (< 1 hour) where oxygen supply to the muscle is inadequate and energy must be provided quickly. The main fuel source used during anaerobic metabolism is carbohydrates stored in the muscles, which yields lactic acid.  However, the lactic acid produced by the anaerobic metabolism may be cleared and re-used as energy by the muscles itself, the heart, kidneys and liver. It is only when the body reaches a specific intensity where lactic acid production exceeds lactic acid clearance, where it will start to build up in the muscles and interfere with performance forcing the cyclist to eventually slow down or stop.

Lactic acid is a chemical compound produced from pyruvate (which is derived from fats and carbohydrates) by your muscles during energy production and exercises.

Resting levels can range from 1-2 mmol/L, to as high as 20mmol/L during intense exertion. It is not the lactate itself that causes the problem but rather the hydrogen build-up resulting from the lactate that causes metabolic acidosis. The hydrogen ions irritates the nerves innervating the muscles causing a pain sensation, slowing down the rate of energy production, inhibiting oxygen binding to haemoglobin and ultimately decreasing performance.

The intensity where lactic acid starts overriding the clearance ability of the body is called the lactate threshold. Therefore, it is the point (threshold) at which the body is working predominantly anaerobic (inadequate oxygen supply) and unable to clear the lactic acid from the muscles. The lactate threshold is based on cycling fitness which means that the fitter cyclist will be able to stay aerobic at higher intensities and for longer periods of time.

The advantage of determining the lactate threshold heart rate is that you would then be able to identify the capacity of your body and determine specific heart rate zones that are specific to your body and needs. These heart rate zones are divided into five distinctive training zones to help you get the most out of your cycling.

Benefits of the lactate threshold heart rate training zones

The five training zones each have benefits based on the specific intensities: