The study of lactate is well documented in the field of exercise physiology due to blood lactate levels being a good indicator of an athlete’s level of conditioning and performance therefore lactate testing by a coach who is training an athlete to reach peak performance is very useful. It is a strong indicator especially of endurance performance and has been used via finger or ear blood sampling to help athletes optimize their training since the 1970’s.  However there is no clear parameter as to what lactate threshold is or how it is determined in the sports science literature. There are more energy systems to consider and train to individual optimal levels rather than simply trying to determine lactate threshold.


Lactate is one of the three components used to measure endurance performance along with VO2 max which was the gold standard of measuring endurance performance however lactate is now considered a more accurate indicator of endurance performance and more trainable by many coaches and scientists. The third component is exercise economy meaning the amount of energy utilized to perform a workload. The most efficient and successful athletes are using less energy to perform the same workload as their competitors.


Lactate comes from Glycolysis which is the process resulting from the metabolism of glucose. There are many misconceptions when it comes to lactate. It is not a waste product causing muscle fatigue as many believe but is used as fuel by the muscles for energy. We now know that lactate is a primary energy source, lactate is the major gluconeogenic precursor and lactate is a signaling molecule with effects similar to autocrine, endocrine and paracrine molecules.


It is useful to the coach for a number of reasons such as it provides a profile of aerobic and anaerobic conditioning levels indicating what energy system needs to be trained and targets weakpoints in training. Test results show changes in this profile and indicate whether training has had the desired effect or not. It indicates the training volume and intensity that an athlete can tolerate to increase aerobic capacity and can be used to measure the athlete’s progress and adjust their training to ensure workouts are within the desired intensity range to reduce the risk of overtraining. It can provide an accurate estimate of the metabolic effect of a certain training intensity and volume and inform the coach how much each energy system is being stressed by a particular workout.


Lactate is measured in mmol/L and can vary between resting values close to 1mmol/L up to 32mmol/L peak values after intense exercise. There are many variables that affect an athletes lactate dynamic levels including lactate production, elimination, buffering and shuttling. These components are also trainable. Lactate production is the result of the breakdown of glycogen or glucose. Lactate elimination is the process of clearing lactate from the bloodstream and muscles. Lactate buffering is the bodies ability to neutralize part of the acid or H+ ions produced from lactate accumulation and lactate shuttling is the process that transports lactate around the body.


There have been a few key players who have contributed to applying the science of lactate testing to the world of sports. Dr. Alois Mader, Dr. George Brooks, and Dr. Bruce Gladden. Dr Jan Olbrecht was a national champion and record holding swimmer in his native Belgium. He was also a student of Dr Mader who contributed much of what we know about the applications of lactate testing in the field. Dr Olbrecht applied these teachings to competitive swimmers in the Netherlands and Belgium using the concept of developing aerobic and anaerobic metabolism to optimum levels for the individual athlete to perform well in competition and realizing that performing at anaerobic speeds is not the most effective way to improve aerobic endurance.


Dr. Brooks concept of lactate shuttling suggests that lactate is the link between glycolytic (anaerobic) and aerobic pathways via cells, tissues and organs throughout the body. It was believed that lactate threshold was the point at which energy primarily shifts from aerobic to anaerobic energy sources however Brooks demonstrated that some lactate is produced under fully aerobic conditions and not strictly anaerobic as was previously thought. According to Brooks, cell work stimulates glycolysis and lactate anion and proton formation, but there is persistent controversy over whether glycolysis produces lactate or lactic acid as well as whether lactate anion or proton accumulation interferes with the mechanism of muscle contraction and causes fatigue. He concludes that glycolysis is necessary for muscle power generation and lactate provides a fuel energy source.


Shannon Grady is a sports physiologist and the founder of Go Athletics who devised a scientific method of testing she calls systems based training (SBT) that measures each individual athletes bioenergetic systems via net lactate, velocity, power and heart rate data after over 20 years of lactate testing 100,000 athletes in the field across all sports and levels. This system has been used successfully by many Olympic champions, World champions, NCAA champions and Olympians in over 20 individual events and team sports since the early 2000’s.


Shannon hypothesized her own theory called the Grady Human Performance Theory based on the second law of thermodynamics and similar to Canot’s efficiency theorem which states that if the maximum temperature of a mechanical system, like an engine can be raised, the difference of the input and output temperatures will be greater, thus yielding the maximal possible efficiency of the engine. In general, energy efficiency is the ratio between output energy and input energy.


It’s important to know what energy system needs optimized and lactate testing can be a large piece of the puzzle when it comes to identifying your current level of conditioning, targeting weakpoints in training and identifying the correct energy system to train. This balanced approach will reduce your risk of overtraining a particular energy system and under developing another.



According to Shannon there are eight bioenergetics systems as follows;

Aerobic foundation described as the ability to perform work using primarily aerobic energy sources such as free fatty acids and blood glucose. Aerobic foundation training can range from 5 minutes to hours of continuous low-intensity work performed at zone 1 or zone 2 heart rates. The physiological aim of training this energy system is to build the aerobic foundation, increasing fat metabolism, size and number of mitochondria, number of aerobic enzymes, capillarization, and lactate clearing rate.


Prolonged aerobic capacity is the ability to perform work using primarily aerobic energy sources such as free fatty acids and blood glucose. Prolonged aerobic capacity training lasts 60 minutes or more of continuous low-intensity work performed in heart rate zone 1 or 2.


Lactate tolerance, clearing and capacity (LTCC) is the ability to perform work using primarily aerobic sources such as blood glucose along with glycogen. LTCC training totals up to 60 minutes or more of continuous work or 5 minutes (2 minutes if using LTCC pace) and longer intervals with less than 2 minutes rest at moderate intensity performed at zone 3 heart rates or LTCC pace. The aim of training this energy system is to increase lactate clearing and tolerance and sub-maximal aerobic capacity.


Aerobic rate capacity 1,2 and 3 is the ability to perform work using primarily aerobic energy sources such as blood glucose along with glycogen. Aerobic rate capacity training lasts up to 45 minutes of 1 to 10 minutes of work intervals with 1-5 minutes rest at moderate intensity performed at specified ARC system pace. The physiological aim of this type of training is to develop and increase major training adaptations such as stroke volume, maximal aerobic capacity, maximal aerobic rates, the velocity of maximal rate of oxygen consumption and lactate production.


Anaerobic rate capacity 1 and 2 is the ability to perform work using primarily anaerobic energy sources such as glycogen. Anaerobic rate capacity training totals up to 15 minutes of 10 seconds to 3 minute work intervals with 1-12 minutes rest at high intensity performed at specified ANRC system pace. The physiological objective of training this system is to increase maximum lactate production, maximum anaerobic capacity, lactate buffering capacity and rate of anaerobic respiration.

Shannon has devised 3 specific training systems to train all eight bioenergetics systems optimally. Recovery and maintenance is the ability to perform work using primarily aerobic energy sources such as free fatty acids and blood glucose. This type of training is less than 45 minutes of continuous low intensity work performed in heart rate zone 1 and 2. It helps to promote recovery, gluconeogenesis, and lactic acid removal following glycogen depleting training such as high intensity intervals or workouts longer than 60 continuous minutes. It also helps to maintain any cardiovascular or skeletal muscle adaptations.


The second training system devised by Shannon is called the neuromuscular adaptation glycogen sparing (NAGS) which is the ability to perform work using primarily aerobic energy sources such as free fatty acids and blood glucose. This type of training should be less than 30 minutes total and should consist of 20 to 60 seconds of interval work with 1-2 minutes rest between each interval at specified system pace. The purpose of this type of training is to increase neuromuscular economy, efficiency,  speed, muscular tendon elasticity and strength without glycogen depleting effects.


The third training system is called Hybrid MCT (HMCT) and develops the ability to perform sustained velocity or power in events lasting less than 10 minutes. It is 5-10 minutes of ANRC1 or ANRC2 work followed by 10-30 minutes of ARC 1, 2 or 3 work. The purpose of this type of training is to increase the stimulation of monocarboxylate transporters and lactate shuttling efficiency at aerobic rate capacity.


According to Shannon the following factors mainly influence lactate elimination or clearing.

  • Aerobic enzymes or molecules of protein that act as catalysts in the steps of metabolism.
  • Number and size of mitochondria, also known as the powerhouse of the cell. Mitochondrial density plays a significant role in improving aerobic energy contribution therefore improving lactate elimination and sparing early onset anaerobic energy contribution. Sparing anaerobic energy will delay fatigue in sports that require repeated anaerobic energy contribution or events that are continuous in nature even as short as 30 seconds.
  • Capillarization or formation of new capillaries.


By increasing any of these factors will significantly improve lactate elimination rates, which therefore can improve an athlete’s muscle endurance, velocity, capacity and power.


So lactate production occurs at all times at some level as a product of glycolysis or glycogenolysis. Changes in net lactate values, especially maximum lactate and velocity at similar net lactate values between tests, are most often due to limited carbohydrate consumption or glycogen stores and inappropriate training prescription rather than changes in fitness levels.


There are two components of lactate dynamics that are critical to performance especially in shorter, high energy demand sports. An athlete’s ability to buffer and shuttle lactate will enable them to perform higher power outputs and/or velocities repeatedly for longer periods without fatigue.


To ensure the athlete is sufficiently fueled and maximizing each energy system Shannon recommends the following

  • Track total calories and carbohydrate intake for at least 7 days by keeping food logs
  • Don’t train with a depleted glycogen supply
  • Consume 100-200 calories of solid or liquid food one hour prior to workout depending on body weight
  • Eat or drink at least 100-200 calories with at least 50g of carbohydrates within 1 hour post workout
  • Aim for 7-8 hours of sleep each night with frequent 10-20 minute power naps during the day for bonus energy.
  • Get a Physiological profile test to determine current bioenergetics status


According to Shannon if you’re trying to achieve metabolic efficiency and/or lose weight then you shouldn’t restrict carbohydrates and rely on fats as the primary fuel source as this will increase fat storage and decrease athletic performance. Shannon also states that training the “lactate threshold” too frequently is the most detrimental type of training to an athlete’s physiological profile and performance.


To summarize there is still a lot we don’t understand about lactate and human physiology however there is strong evidence to support lactate testing for athletes as an important piece of the puzzle on our journey to improving athletic performance. Athletes need to consider what energy system they are training and what is the purpose of their training. How do they know which energy system is optimized or which one is overtrained? Physiological profile testing can help answer this question. I am one of the very few coaches in Texas certified with systems based training. Message me for more details if you would like to get tested.