Week 2 Assignment_Lactate Threshold

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1 Lactate Threshold and the Effects of Lactate Threshold Training Department of Sport and Health Science, American Public University System SPHE314: Exercise Physiology Dr. Tiffany M. Reiss July 18, 2021

2 Lactate Threshold and the Effects of Lactate Threshold Training Lactate threshold is the point at which the body’s lactate concentration rises rapidly and exceeds the rate of lactate turnover, resulting in a decline of activity intensity and performance (De Feo et al., 2003). Lactate turnover is the process by which the body clears accumulated lactate, accomplished by the heart, liver, kidneys, and type I muscle fibers during aerobic glycolysis. Lactate threshold can be reached in one of three ways in relation to anaerobic metabolism processes. First, insufficient oxygen in the mitochondria of cells can cause a backlog of NADH and threaten to stop glycolysis, as a temporary solution, a hydrogen transfer to pyruvate frees NAD for anaerobic glycolysis to occur but results in the formation of lactic acid which changes to lactate and free-floating hydrogen ions in the cells cytoplasm. Second, if anaerobic glycolysis, which produces lactate as a byproduct, increases to a rate where the body is unable to metabolize the lactate fast enough; and third, the recruitment of excess type II muscle fibers powered by anaerobic energy systems are in direct relation to an excess amount of lactate production (Wilkinson, 2020). The anaerobic metabolism and its energy systems ATC/PCr and anaerobic glycolysis are designed to support high and maximal intensity activity for short periods of time. Once an individual’s lactate threshold is reached the body will transfer the majority of energy production to the aerobic metabolism and the aerobic glycolysis energy system will become the body’s primary ATP producer with the use of oxygen in the Krebs cycle and electron transport chain. This energy system, while unable to sustain high intensity activity can support low and moderate level intensity activity for prolonged periods of time using the body’s organ tissues and Type I muscle fibers to process the lactate for energy. The anaerobic and aerobic energy system work together to balance the

3 body’s energy needs based on the required intensity and duration of activity and both are always working in varying degrees (Chee, 2019). An individual’s VO2 max, or maximal rate of oxygen consumption, and lactate threshold are related in that lactate turnover during aerobic glycolysis requires the presence of oxygen. A greater oxygen intake allows for more lactate to be processed for energy and prolongs reaching one’s lactate threshold while maintaining activity at a higher intensity (Morehen, 2018). Conversely, an individual’s lactate threshold can be lowered if the VO2 max is lowered due to a health condition or an illness. There are several other contributing factors that influence the relationship between VO2 max and lactate threshold such as age, sex, body composition, and level of training (Acevedo & Starks, 2011). Of the possible factors affecting VO2 max and therefore lactate threshold, body composition and level of training are the most effective to change and in untrained individuals are often linked. However, a 2014 study showed that the type of training an athlete does has less significance when it comes to lactate threshold. In the study three groups comprised of aerobic athletes, anaerobic athletes, and untrained participants were given in a treadmill test to exhaustion with measurements of VO2 max and lactate thresholds. The data showed that while aerobic athletes maintained a significantly higher VO2 max than anaerobic athletes, the two group’s lactate thresholds were similar. The data also reflected that both the aerobic and anaerobic groups recorded significantly higher VO2 max and lactate thresholds over the untrained participants (Matthew Green et al., 2014). This study provides insight to the possible effectivity of lactate threshold training for untrained individuals. The body maintains a lactate level of 1-2 mmol/L as there is always a small amount of lactate circulating in the bloodstream. This nominal level of lactate is sustained during lower

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4 intensity activity as lactate turnover can keep up with lactate production. However, once intensity levels increase and lactate production exceeds turnover an accumulation of lactate occurs. Eventually, the lactate level will reach the threshold where it increases rapidly and is corelated with a decline in performance, this occurs at approximately 4 mmol/L (Hurley, 2020). Lactate threshold training is designed to increase an individual’s lactate threshold and endurance at VO2 max by training in different ranges above and below their threshold. This will enable the body to become more efficient at processing lactate while working at a high intensity for a greater amount of time. Two different methods used in this style of training are supra-threshold interval and tempo training. Supra-threshold training involves performing aerobic exercise intervals in a range just above the individual’s lactate threshold. These intervals would be performed at a high intensity level for three to eight minutes with several minutes of recovery between sets. This training is considered the most efficient at increasing the lactate threshold and VO2 max (Training 4 Endurance, 2021). Tempo training is prolonged training in the range just below the lactate threshold. This form of training, executed for a long duration and at a moderate intensity, is designed to increase muscular endurance and the ability to maintain performance near an individual’s VO2 max. Tempo training is not considered to be the most effective at increasing lactate threshold for athletes, but has benefits for endurance athletes who mainly compete in the range just below their lactate thresholds (Training 4 Endurance, 2021). However, tempo training on untrained individuals has revealed significant improvements to lactate threshold aerobic performance markers. A 2020 study analyzing the effects of lactate threshold training on 36 obese middle- aged women showed that 12 weeks of training at the lactate threshold resulted in

5 improvements in aerobic performance. The women were split into an experiment group and a control group. The experiment group exercised three times a week for 30 minutes each session at a heart rate correlated to their lactate thresholds, the control group did not exercise. At the end of 12 weeks the experiment group showed significant increases in all aerobic performance markers to include VO2 at lactate threshold, VO2 max, treadmill velocity at lactate threshold, and bike velocity at lactate threshold (Park et al., 2020). The experiment group also experienced improvements to body composition and autonomic nervous system showing that lactate training may be beneficial to a range of people from untrained and obese to endurance athletes.

6 References Acevedo, E., & Starks, M. (2011). Exercise Testing and Prescription Lab Manual (2nd ed.). Human Kinetics, Inc. https://us.humankinetics.com/blogs/excerpt/factors-affecting-v- o2max Chee, R. (2019, January 18). 100 Meter Sprinting vs a Marathon: Comparing Metabolic Demands & Energy! Bodybuilding.com; Bodybuilding.com. https://www.bodybuilding.com/fun/sprint-vs-marathon-energy-demands.htm De Feo, P., Di Loreto, C., Lucidi, P., Murdolo, G., Parlanti, N., De Cicco, A., & Piccioni F Santeusanio, F. (2003). Metabolic response to exercise. Journal of Endocrinological Investigation , 26 (9), 851–854. https://doi.org/10.1007/bf03345235 Hurley, S. (2020, July 31). What Is Lactate Threshold and How to Train It - TrainerRoad Blog . Www.trainerroad.com. https://www.trainerroad.com/blog/what-is-lactate-threshold-and- how-to-train-it/ Matthew Green, J., Hornsby, J., Pritchett ǂ, R., & Pritchett, K. (2014). Original Research Lactate Threshold Comparison in Anaerobic vs. Aerobic Athletes and Untrained Participants . https://digitalcommons.wku.edu/cgi/viewcontent.cgi?article=1623&context=ijes Morehen, S. (2018). What is my lactate threshold? | FitnessGenes® . FitnessGenes Official Website. https://fitnessgenes.com/blog/what-is-my-lactate-threshold/#:~:text=As %20oxygen%20is%20necessary%20for%20lactate%20clearance%20in Park, H.-Y., Jung, W.-S., Kim, J., Hwang, H., & Lim, K. (2020). Twelve Weeks of Aerobic Exercise at the Lactate Threshold Improves Autonomic Nervous System Function, Body Composition, and Aerobic Performance in Women with Obesity. Journal of Obesity & Metabolic Syndrome , 29 (1), 67–75. https://doi.org/10.7570/jomes19063

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7 Training 4 Endurance. (2021). Lactate Threshold Training (Updated 2021): The Definitive Guide . Training 4 Endurance. https://training4endurance.co.uk/improve-endurance/lactate-threshold-training/ #:~:text=HOW%20TO%20IMPROVE%20YOUR%20LACTATE%20THRESHOLD %201%20Low Wilkinson, S. (2020). Lactate threshold (lactic acid part 4) [YouTube Video]. In YouTube . https://www.youtube.com/embed/9cqKg9kXfVA?wmode=opaque&rel=0

Week 2 Assignment_Lactate Threshold

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