Lactate threshold is a common term used by athletes, coaches, and sports medicine professionals but it remains highly disputed on its exact definition. Lactate threshold is commonly referred to as the level of high-intensity exercise, which leads to increase lactate levels that can only be sustained for a period of time. Eventually, blood lactate levels reach a point where the body cannot convert lactate into energy and expel waste levels, coinciding with muscle fatigue. The intensity level will begin to slow down as lactic acid builds up. The disagreement centers around the exact timing and level of blood lactate when the threshold is achieved.
The lactate threshold is commonly a measurement that is used to determine aerobic and anaerobic thresholds. Aerobic metabolism, which occurs at 65-80% of the maximum recommended heart rate, is optimal to concurrently train cardiorespiratory endurance and muscle strength. The aerobic threshold is a long-lasting effort that can be performed for a prolonged period of time. During aerobic metabolism, the body burns carbohydrates and fats to create energy resulting in energy pathways aiding energy production. During aerobic metabolism, the blood lactate levels rise above resting levels but dodo not cross the lactate threshold.
Meanwhile, the anaerobic metabolism begins once the lactate threshold is cross, and lactate concentration is not linear with exercise intensity alone but its duration as well. Anaerobic metabolism kickstarts when intensity is increased, and the anaerobic system cannot maintain the energy demand. At this point, stored sugars are used to supply energy, and lactic acid is rapidly produced to be metabolized until the lactate threshold is reached and muscle fatigue occurs.