Aerobic Threshold, Anaerobic Threshold and Lactate threshold, these are frequently used terms in the endurance world yet most don’t quite understand the terms and how they translate over to training.
In today’s blog I want to explain:
· What is Lactate?
· Methods to improve your Lactate threshold
· How to test Lactate Threshold
· What is Aerobic Capacity and Aerobic Power
What is Lactate?
Lactate is a product due of the utilization of glucose in the muscles. Research from Dr. George Brooks (a metabolism expert from the University of California at Berkeley) identified that lactate is not a waste product as often quoted but in fact an important gluconeogenic precursor (new glucose generator) in the body, infact 30% of all glucose we use during exercise is derived from lactate recycling to glucose.
Lactate was once believed to be a waste product as a result of anaerobic exercise and was thought that it crystalized after exercise, which resulted in muscle soreness.
Lactate is unique. It is a metabolic variable that demonstrates the ability of the muscles that effect an athlete’s potential. It is an output of the anaerobic systems and a fuel for the aerobic processes.
Lactate is the byproduct of glucose utilization. More glucose in the cell can result in an increase in lactate production. When working at a high intensity, there is a higher recruitment of Type II- Fast twitch muscles fibers. These fibers have a high concentration of glycogen and as such results in high amounts of lactate being produced.
Hydrogen ions (H+) are associated with lactate and an excess can result in reduction of muscle pH which can cause acidosis. The accumulation not only from lactate, but also from ATP breakdown interferes with muscle contraction due to:
• Competing with Calcium (Ca++) for Troponin C binding site
• H+ may also inhibit calcium release and re-uptake from sarcoplasmic reticulum.
The above causes a decrease in peak force and a decrease velocity and performance.
When intensity is high the mitochondria in muscles become more stressed to clear lactate in a timely manner. When the exercise intensity continues, muscle mitochondria become saturated and cannot keep up with lactate clearance. Lactate is then exported it to the blood and this is when we see a rise in blood lactate levels and it is then not possible to maintain that given exercise intensity.
Lactate threshold is commonly known as the exercise intensity or blood lactate concentration that one can only sustain a high intensity effort for a specific period of time. However, consider the following:
• What is that period of time?
• What is that blood lactate actually means?
• What is the exercise intensity that it elicits?
• How long can you sustain that given exercise intensity?
There is multiple hypothesis as to what it is. The bottom line to understand what lactate threshold means is, as muscles get more metabolically stressed there is a higher lactate accumulation and H+ and there will reach a point where the lactate concertation will affect the power/ performance of the athlete.
Methods to improve your Lactate threshold
Endurance training specifically Zone 2 aerobic training can improve the body’s ability to clear lactate by increasing the number of mitochondria to clear lactate mainly in slow twitch muscle fibers by increasing the number of MCT-1 (Monocarboxylate facilitate the transport of lactate in and out of cells) and mLDH (catalyzes the conversion of lactate to pyruvate and back, as it converts NAD⁺ to NADH and back).
Often athletes and coaches believe that training at “lactate threshold” will to improve lactate clearance capacity. This is not exactly true, during exercise lactate is mainly produced by fast twitch fibres which are the ones recruited at “lactate threshold”. However, we know that lactate is mainly cleared by slow twitch fibers that have a very high mitochondrial capacity and a much higher amount of mLDH enzymes and MCT-1 transporters.
Therefore, to improve lactate clearance capacity, and although totally counterintuitive, it is key to train those slow twitch muscle fibers to stimulate mitochondrial growth.
That is not to say there is no gain from training at lactate threshold. This type of training should be conducted when looking to improve glycolytic fibers and to increase the number and function of glycolytic enzymes. However, a caveat, spending too much time at lactate threshold is very tasking as well, as it is a high effort and can lead to overtraining.
How to test Lactate Threshold
Lactate testing is mostly done via blood testing and allows an assessment of muscle metabolic stress. It is probably the best method to predict performance, especially in endurance events as well as an effective means to prescribe individual exercise training zones for athletes.
As we do not have a laboratory setting at our disposal we as coaches can test Lactate threshold using lactate threshold heart rate test (LTHR). The test requires carrying out a short 30 minute time trail. This is a maximal bout and the data gained ( average HR) from the final 20 minutes is a great indicator of lactate threshold HR. Thereafter specific Zones can be set:
Run Zones Zone 1 Less than 85% of LTHR Zone 2 85% to 89% of LTHR Zone 3 90% to 94% of LTHR Zone 4 95% to 99% of LTHR Zone 5a 100% to 102% of LTHR Zone 5b 103% to 106% of LTHR Zone 5c More than 106% of LTHR
Aerobic capacity is the most important variable determining the lactate threshold in an endurance event but it certainly is not the only one.
It is often called VO2 max and it varies considerably over a training season. It is the maximal oxygen transported from the environment to the muscles and used there to create energy for physical activity. It varies depending on the specific activity, since the amount of oxygen that can be transported and utilized for different activities may vary. So an athlete's VO2 max will be different for running versus cycling. It will also vary throughout the training and competitive season. Improving aerobic capacity is the objective of most training for an endurance athlete.
Aerobic Power is the percentage of aerobic capacity or VO2 max that can be sustained during an event. It is not possible to utilize all of one's aerobic capacity during an event; in reality nearly every athletic event is completed at some fraction of VO2 max. The actual percentage is the aerobic power or the percentage of capacity that can be utilized.
Like aerobic capacity it is the ability to generate energy, but through the glycolytic system or the breakdown of glucose. We define it as the maximal or organic potential to produce pyruvate or lactate, which is the output of the anaerobic glycolytic system.
This glycolytic system is where lactate originates in the body, and it uses glucose for fuel. The anaerobic system does not produce much energy in an endurance race – most comes from the aerobic system.
Give it a few reads if needed, and I hope that it has helped you all.
Until next time