During endurance exercises such as long-distance running and cycling, when the demand for energy is high, lactate is produced faster than the ability of the tissues to remove it. As a result lactate concentration in the blood begins to rise.

The use of a lactate analyzer helps coaches and athletes to determine optimum training programs, define training zones, and avoid inefficient training exercises.

In fitness, sports, and cardio-rehabilitation measuring lactate is supportive to define training intensities for maximum fat catabolism, increases in endurance, and avoid critical over-exhaustion.

Lactate is produced when the muscles use carbohydrates to create energy for exercise. The underlying metabolic process is the glycolysis. It happens continuously but increases when energy demand is high for a prolonged period of time and availability of oxygen to the cells is limited.

Increased glycolysis produces hydrogen ions and lactate, and it's the hydrogen ions that cause pain, sore muscles, cramps and fatigue. The body protects itself by telling you: "I can't do this anymore".

Regular endurance sports should only take place within the respective 'lactate steady-state' - a well-balanced relationship between lactate production and elimination.

Lac [blood] = Lac [produced] ­ Lac [eliminated ]

With higher exercise intensity the lactate level in the blood reaches the anaerobic threshold or the onset of rapid blood lactate accumulation. This point can be determined in step tests with increasing training intensity in defined intervals e.g. on a tread-mill, bicycle or in a field test. The higher the level of effort is when the rise of lactate indicates the anaerobic threshold the better is the performance status of the athlete.

Intense training teaches the body to use lactate as a source of fuel on a par with the carbohydrates stored in muscle tissue and the sugar in blood. Athletes increase their lactate threshold by training which means their blood lactate increases later and at higher intensities.