By: Sarah Neumar, PT, DPT
At the beginning of a training block, it is important to gradually reintroduce specific workouts in training in order to boost performance. “Speed training”, track workouts, fartleks, and tempo runs are terms that often get blurred together, and therefore the relative effort of these runs may not match up with the actual goal of the workout. As a new or experienced runner, it’s important to be aware of how to manage these efforts, in order to appropriately distribute increases in mileage and intensity throughout a training block. From an injury-prevention and performance standpoint, prescribing the minimum stimulus necessary to improve fitness and speed over time is the best way to see consistent progress.
There are many ways to manage effort on runs, including tracking heart rate (HR), rate of perceived exertion (RPE), and pace. In order to more precisely define training zones, assessing blood lactate levels at various paces may be beneficial.Â
What is Lactate?
Lactate is a metabolic byproduct of one of the body’s main energy-producing processes: glycolysis. In the presence of oxygen (aerobic metabolism), pyruvate is produced at the end of glycolysis and can be oxidized to supply more energy. In an anaerobic environment, pyruvate is converted into lactate (along with the release of H+ ions), which builds up in the muscles and then the blood. When lactate builds up faster than it can be cleared, an acidic environment results, along with the body being deprived of energy production, leading to fatigue. There are specific enzymes that can transport and convert lactate back to pyruvate to be utilized as fuel. These enzymes can be upregulated in skeletal muscles through high intensity training due to the body’s need to manage the amount of lactate that builds up during exercise. Uptraining one’s aerobic and anerobic systems can lead to greater amounts of efficiency in endurance sports.
Why and How Do We Measure Lactate?
There are two lactate measures that are important for training purposes: LT1 and LT2. LT1 is typically measured at 2.0mmol/L of lactate in the bloodstream, and marks the initial increase of lactate production in the muscles. LT2 is a marker of blood lactate accumulation, measured at 4.0mmol/L. These thresholds can be measured using a progressive treadmill test and assessing blood lactate levels every 4 minutes. A lactate meter is used to analyze a small blood sample. Paces are incrementally increased until LT2 is reached. This data can then be used to identify training zones.
How Do We Apply It?
LT1 marks the top of your Zone 2, and LT2 marks the top of your Zone 4, based on a 5-zone system. Training in Zone 2 promotes muscular endurance. It’s most beneficial for gaining similar amounts of muscular and aerobic adaptations as Zone 3 with shorter recovery times.
Zones 4 and 5 help to upregulate lactate-converting enzymes and improve VO2 max when built into interval training. Depending on the amount of time you have to train and your racing goals, weekly workouts can be tailored to maximize your training.
Performing a lactate threshold test will help provide the specific data and insight needed to be more intentional about your training. Not only will this aid in improving your performance, but it will help to stay below the line of over-doing it when it comes to training and reducing the risk of injury. It is more important to make consistent, small gains, than to get caught in an injury and/or burn-out cycle.Â
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Sources:
Dantas, J. L., & Doria, C. (2015). Detection of the lactate threshold in runners: What is the ideal speed to start an incremental test? J Hum Kinet., 45, 217-224. https://doi.org/10.1515/hukin-2015-0022
Subbarayalu, A. V., Sivakumar, C., Purushothaman, V. K., Muralidharan, C. K., Rajkumar, K. V., Kannan, K. R., Pradeepa, M., Sivasankar, P., Ameer, A. M., & Anand, U. K. A. (2024). Lactate threshold training to improve long-distance running performance: A narrative review. Monten. J. of Sports Sci. Med., 20(1), 19–29. https://doi.org/10.26773/mjssm.240303
