Lactate threshold is the point during the exercise of increasing intensity at which lactate levels within the blood accumulates above resting levels and therefore where clearance can’t be maintained at the same rate as production. An increase in intensity can be anything from the distance in a marathon run to an increase in your stroke rate during a swim. If you took a 400m run, athletes often break the race down into two sections - the start and the end.
The start holds 'fresh' legs and rapid turnover rate, however at an athlete specific point the body is no longer efficient enough to clear the lactic and a build up occurs along with the feeling of fatigue. This becomes a problem as unbuffered acid is added to the blood and is a lasting game of which an athlete can maintain this burning, an aching feeling the longest.
So what is lactic acid I hear you ask?
Covered in a little more detail that described initially, Lactic acid is the state of constant turnover within a cell being produced by glycolysis and then being removed, primarily through oxidation. Many refer to lactic acid as a metabolic waste product and the cause of fatigue however, it can be used as a useful fuel source during exercise. Anaerobic breakdown of glycogen leads to an intracellular accumulation of inorganic acids, of which lactic acid is quantitatively the most important. Since lactic acid is a strong acid, it dissociates into lactate and hydrogen (H+). Lactate ions would have little effect on muscle contraction however, the increase in H+ (i.e., reduced pH or acidosis) is the classic cause of skeletal muscle fatigue. So to simplify this concept and starting from the beginning; our cells produce adenosine triphosphate (ATP).
The breakdown of ATP produces the energy required for exercising the muscle to contract. ATP is created in a three step procedure dependant on event duration: Glycolysis, Krebs Cycle and the Electron Transport Chain (ETC). All systems feed into each other and are paramount to sustained muscular contraction. The glycolytic system involving the process of glycolysis breaks down glucose and glycogen into pyruvic acid. However, when this occurs without oxygen, lactic acid is produced. Therefore if we take our 400m runner, the first 200m they are able to initially utilise their ATP stores, when this is depleted they are able to move onto the glycolytic system. This is maintainable for around 30 seconds at maximal effort for a trained athlete before oxygen consumption runs out and pyruvic acid is broken down into lactic acid. The later stages of the race are attempting to maintain stride rate and pace while your muscle is now in a 'fatigued state'.
It’s a physiological marker associated with endurance performance - the higher the threshold the better the performance capacity. It is something that can increase significantly within a 6-12 month endurance program.
An increased lactate threshold enables exercise at a higher percentage of your VO2max (higher intensity basically) before accumulating in the blood and fatiguing the muscle.
The most important physiological factor for high performance in a marathon is to possess a high aerobic capacity or VO2 max. An elite marathoner exhibits a high VO2 max (more than 80 ml/kg/min), similarly the VO2 max is an important parameter of middle and long distance runners, road cyclists, long distance swimmers (70–80 ml/kg/min) and team game players (60–70 ml/kg/min), whereas, the sprinters exhibits a comparatively lower VO2 max (45–55 ml/kg/min). It is, therefore, noted that by training at lactate threshold for endurance events one can perform at higher intensities without significantly increasing blood lactate levels. It has been observed that individuals with similar VO2 max have variability in endurance capacity and that highly trained athletes perform at a high percentage of their VO2 max with minimum lactate accumulation. Furthermore, trained athletes accumulate less lactate than untrained athletes at a given submaximal workload. This concept has prompted the consideration of anaerobic threshold as a determinant of physiological fitness. While the appearance of lactate in blood during exercise is the result of increased glycogenolysis, it is important to recognize that its concentration is, at any time, the result of a balance between the rate of production and removal.
So what’s the practical application here?
To test it yourself without scientific equipment - The goal of this test is to exercise for 30 minutes at the highest effort that can be sustained and monitor your heart rate throughout the test. Your average heart rate during the final 20 minutes should correspond to your LT.
For runners, a great way to increase your LT is the addition of Tempo Runs - The easiest way to determine proper tempo pace is to add 24 to 30 seconds per mile to your 5k PB or to train ever so slightly above the heart rate you tested. The result should be about the pace you would be able to sustain for a full hour of running without needing a break. Typically, tempo runs are about 20-40 minutes in length and should NOT feel like a race at any point.
Additionally, do a 20-30 minute high intensity effort at 95%-105% of your LT.
It can also link in with nutrition. To boost your LT during training and racing, you need to make sure you can exercise at a high intensity without running out of glycogen stores. This requires careful nutritional meal planning both in the pre-exercise meal and post-exercise meal.