Understanding the concept of the Anaerobic Threshold (AnT) — and how it works — is crucial to improving athletic performance. Knowing what is going on physiologically, when exercising at intensities near this point, helps endurance athletes to work out much more effectively.
But, what is the Anaerobic Threshold? How does it work in endurance sports? And, why should coaches include workouts at intensities near the AnT in their athletes’ training plans?
What is the Anaerobic or Lactate Threshold, and how does it work in endurance sports?
In physiology, the Anaerobic Threshold is the highest sustained intensity of exercise, at which lactic acid starts accumulating faster than it can be removed from the blood and muscle tissues. That’s why it is also called the Lactate Threshold (LT).
We should also clarify that workouts at intensities above the Aerobic Threshold do not signal the transition from the aerobic to the anaerobic phase. It is predominantly the aerobic metabolism that provides the required energy for any intensity maintained until reaching VO2 max. Even though anaerobic glycolysis plays its part in the process, when athletes exercise above their threshold, the anaerobic system is not the dominant energy production mechanism.
Nonetheless, athletes can’t execute exercises above the AnT for long, as pain in muscles — and general fatigue — will make it impossible to go on. For this reason, the greatest percentage of an endurance athlete’s training is based on the utilization of the aerobic metabolism; and only a small one on the anaerobic.
The Anaerobic Threshold and its relationship with MLSS, Critical Velocity, and OBLA
There has been an ongoing scientific debate about using the term ‘Anaerobic Threshold’ in measurement methods. Over the years, researchers have discovered several points that closely relate to the AnT, and this makes it a difficult concept to define; and, an even more difficult physiological point to measure.
Be that as it may, it’s important to recognize that the Anaerobic Threshold is a concept, so its definition should also be conceptual. Hence, it’s best to consider the Anaerobic Threshold an ‘umbrella term’, including several relevant metrics. To explain, among others, these metrics include:
- Critical Velocity (CV) — The intensity an athlete can sustain for a 30-40 minute exercise.
- The Onset of Blood Lactate Accumulation (OBLA) — The point, during exercise, at which lactate begins to increase exponentially.
- Maximal Lactate Steady-State (MLSS) — The highest blood lactate concentration and workload that an athlete’s body can maintain over time, without causing a continuous blood lactate accumulation.
It’s common to use these terms interchangeably with Anaerobic Threshold, yet, technically, they don’t describe the same thing. There are distinct differences among them, both conceptually and practically. Therefore, coaches should be aware of their differences when measuring an athlete’s Anaerobic Threshold level.
The lactate production/removal mechanism and endurance performance
We mentioned earlier that the AnT is the point where lactate starts to accumulate in the bloodstream because, with incremental exercise, it’s produced faster than it can be metabolized. After its formation, lactate is removed through sweat and urine or transported to various organs — like the heart and the kidneys — fibers, and tissues, to be either oxidized or contribute to gluconeogenesis.
When it comes to endurance sports, the lactate production/ removal mechanism plays a critical role, both in monitoring athletes’ training and measuring their performance. Athletes who train at intensities near their Anaerobic Threshold get to improve both their aerobic capacity and anaerobic endurance. In this way, they become more efficient, physiologically speaking, for demanding races.
At what intensity do endurance athletes reach the Lactate Threshold?
As one can gather, anaerobic exercises are high-intensity workouts that athletes are called to complete over a short duration. With this in mind, an average endurance athlete reaches the Anaerobic or Lactate Threshold zone at approximately 80–85% of maximal aerobic power/speed.
Training at intensities above the Anaerobic Threshold
If an athlete trains just above the Anaerobic Threshold, their body will be able to withstand the lactate increase without experiencing a significant change in oxygen consumption. Nevertheless, lactic acid will increase as the exercise intensity increases, resulting in sudden fatigue caused by anaerobic metabolism byproducts. Hence, exercising at intensities near the Anaerobic Threshold for (approximately) longer than an hour is not sustainable, and will quickly result in exhaustion.
Increasing the Anaerobic Threshold
From a performance point of view, the ability to utilize the lactate in the muscles as fuel is one of the most important training adaptations that endurance athletes can achieve. When they reach that point physiologically, they help their bodies remove lactic acid relatively fast, and improve their fitness level. In addition, they improve their aerobic system, and, thus, they’re able to maintain a fast speed for a longer time.
Without a doubt, apart from having a strong aerobic system, building a robust anaerobic system is also essential for maximizing cardiovascular endurance.
Why should endurance athletes train at intensities near the Anaerobic Threshold?
As mentioned, training near the Lactate Threshold increases an athlete’s ability to sustain high power and energy outputs; leading, eventually, to better performance. By training at these intensities — at, or just above, the LT2 — the athlete’s body is experiencing a significant amount of stress, without exceeding the lactate inflection point.
But, what type of training methods are focused on intensities near the Anaerobic or Lactate Threshold? Among others, these include:
- High-intensity intervals (HIIT)
- Tempo runs, or tempo intervals
- Sweetspot training
- FTP-focused workouts
- Fartlek training (speed play)
- Critical Velocity training
Closing thoughts
The Anaerobic or Lactate Threshold is one of the most controversial concepts in endurance sports. However, it is also one of the most important markers that so many coaches and athletes use to measure — and improve on — endurance performance.
When an athlete wants to increase their Anaerobic Threshold level, the key is to train at a higher intensity, but with less volume, to maximize both power and endurance. However, we should highlight that one can’t just start training at intensities near the AnT without building a strong aerobic base, first.
At the end of the day, through LT training, athletes can challenge themselves toward better athletic performance while protecting their bodies from burning out.
