Shannon Grady- M.S. Physiologist, Author "The Lactate Revolution"
September 9, 2024
In the quest for peak performance, athletes are always on the lookout for the most effective training strategies. Unfortunately, many of those training strategies are popular buzzwords or concepts that yield very little physiological return. One such approach that has gained popular attention in the world wide running community are the double “threshold” workouts. While this training method is all the rage in the distance running community and may yield some initial performance gains in some athletes, it’s also crucial to understand its potential drawbacks.
In this article, I will delve into why double “threshold” workouts might have a negative impact on performance and why a more balanced approach is more beneficial to overall physiological development and performance outcomes.
Understanding Double “Threshold” Workouts
The popular belief and understanding of the physiological benefits of double “threshold” workouts is to push the “anaerobic threshold” as high as possible and if you ask the masses what is “anaerobic threshold” or “lactate threshold” they will all parrot the same vague, nonspecific answer. The standard answer heard around the world is the point in which lactate begins to accumulate in the bloodstream faster then it is removed and the point in which the body shifts from predominantly aerobic to anaerobic energy production. Some coaches have even turned into mad scientists and actually spend time and resources to collect lactate samples at random points during workouts. The majority of them believe that if they collect random samples during random workouts and the reading is between 2.0-4.5 mmol/L of net lactate that is the athletes’ “lactate threshold” and they are effectively pushing the “anaerobic threshold” in a positive direction.
The practice of “double threshold training” involves completing two “threshold” workouts in a single day. The theory behind "double threshold" workouts is that training at this level can enhance the body's ability to clear lactate, do more training without fatiguing and improve overall training adaptation.
The REAL Science Behind Double “Threshold” Workouts
The term “threshold workout" is used to describe workouts of almost every track coach around the world, yet, the definition and term are very ambiguous with really no agreeable defined parameters across the coaching world or scientific literature.
Personally, I never use the term “lactate threshold”, when discussing lactate, lactate dynamics, or lactate application in training for several reasons but the main one being THERE IS NO SINGLE “LACTATE THRESHOLD” !!!
There is no one training speed or intensity that can accurately be called the single lactate threshold for all athletes. In reality, EVERY NET LACTATE VALUE HAS A THRESHOLD. For those in the back of the room who didn’t hear me, EVERY NET LACTATE VALUE HAS A THRESHOLD.
Each net lactate threshold is trainable and needs to be re-evaluated via blood lactate profile or capacity testing regularly.
There is not a sudden shift from aerobic to anaerobic metabolism at readings between 2.5 and 4 mmol/L of net blood lactate.
The emphasis of training design to enhance the "lactate threshold" or “anaerobic threshold” is often responsible for bioenergetic deficit, impaired metabolic adaptability, and underperformance.
Training At 2.0-4.5 mmol/L Of Net Lactate Is Not Anaerobic
Training at 2.5-4.0 mmol/L of net lactate can provide physiological benefits and is an area that can contribute to the overall development of almost every athlete but the volume, intensity, and frequency of this type of training needs to be considered through a new lens. The reality is, 2.0-4.5 mmol/L of net lactate is not indicative of primary use of anaerobic sources, in fact, it’s not even slightly close to anaerobic on the human energy spectrum. This idea that energy shifts from aerobic to anaerobic in the range of 2.0-4.5 mmol/L is not only scientifically inaccurate, it’s completely illogical. The types of workouts performed during “double threshold” or a typical “threshold” workout are generally higher volume 5 km or more of intervals longer than 3 minutes with short rest or a continuous effort up to 60 minutes or more. To somehow believe that an athlete is capable of sustaining an “anaerobic” effort for this long defies not only basic human physiology but also logic.
The reality is, human physiological capacity and energy shifts to anaerobic sources occur at much higher net lactate levels for most athletes. Using a range of 2.5 to 4 mmol/L of net lactate as an athlete’s "anaerobic threshold" will be between 64 to 78% below an athlete's ACTUAL anaerobic energy shifts. Making the assumption that such low values are an athlete's anaerobic energy shifts will lead to underperformance, especially in events shorter than 10 km.
Impaired Training Adaptation
Training adaptations occur when the body is given the appropriate training stimulus and adequate time to recover from the stresses imposed by training. Double “threshold” workouts can hinder the amount of physiological adaptations made by athletes since too much time is spent training at such a low intensity that the athlete’s physiology, metabolic adaptability, and net lactate output will be diminished. Doing a lot of low intensity work, will not yield much development in the areas important for events shorter than 10 km or in athletes with a strong anaerobic system. As a result, the body wastes energy on unproductive training sessions and is inhibited from adapting to productive training.
Most successful mid-distance athletes will have a genetic predisposition for stronger anaerobic systems. I conducted a physiological profile analysis of 250 NCAA DI middle distance runners who were underperforming. Consequently, those who trained too frequently at or near the "lactate threshold" were found to have significant decreases in performances. The overwhelming evidence revealed that in order to properly develop the physiology of these types of athletes and improve their performances over 800 to 3000 meters, a weakening or slowing down of their textbook defined "lactate threshold" or speed at 4 mmol/L of net lactate was necessary.
The reality is, athletes, especially middle distance athletes, get little or no improvements in performance with an emphasis on "lactate threshold" and double “threshold” workouts.
Impaired Metabolic Adaptability
The physiological strain of the double “threshold” method is not the fact that the workouts are necessarily high intensity, it’s the fact that the workouts do require a lot of mental focus and energy expenditure with very little physiological return. I conducted a physiological profile analysis of 20 elite runners who were implementing double “threshold” training on a regular basis and also experiencing performance plateaus or declines. All of the athletes displayed impaired metabolic adaptability and mild to moderate bioenergetic deficit. Bioenergetic deficit is simply a state of chronic calorie and glycogen depletion which leads to an inability to produce an optimal range of net lactate or physiological range. Optimal physiological range is accomplished by athletes that have, what I have termed metabolic adaptability, or ability to utilize substrates across the entire metabolic spectrum. The decline of performance and health will be accelerated when an athlete is experiencing impaired metabolic adaptability and a bioenergetic deficit. Improving metabolic adaptability and bioenergetic availability are both dependent on adequate substrate availability AND the appropriate training stress.
The reality is, double “threshold” training will undoubtedly lead to impaired metabolic adaptability and bioenergetic deficit.
Increased Fatigue and Recovery Time
Most of the field tests to determine "lactate threshold" consist of protocols that assume “lactate threshold” is between 2.5-4.0 mmol/L of net lactate for all athletes, which will lead to either underloading or overloading most athletes. Most coaches assume athletes have the capacity to work for long periods of time at these low levels of net lactate but in reality, the capacity of each athlete at these levels of net lactate can be as little as a few minutes. The combination of poor methods to determine an athlete’s “lactate threshold” and an overemphasis of training “threshold” will increase fatigue and recovery time. Various academic studies have also concluded that training too frequently at the "lactate threshold" can overstress the sympathetic nervous system, slow recovery, and decrease glycogen utilization.
The reality is, the mental and physical strain of double “threshold” workouts can lead to underperformance, decreased motivation, mental fatigue, and a loss of enjoyment in their training, especially in middle distance athletes. Long-term or frequent implementation of double “threshold” training can have long-lasting effects on both performance and overall well-being.
Reduced Training Quality
Those who seek to train only at the "lactate threshold" are missing the big picture that encompasses the entire spectrum of human energy involved in training. Unfortunately, emphasizing "lactate threshold" will underload most elite athletes, overload some elite athletes, and hit the mark on appropriate training load for very few elite athletes. Training too often and too much at “lactate threshold” will offer a very minimal training effect and waste time and energy in zones that will not yield improved performance in the events contested in high school and college running. An overemphasis on “lactate threshold” training will not develop the aerobic and anaerobic energy spectrum which all play important roles in athletic performance in any event.
The reality is, the quality of workouts will ultimately suffer with double “threshold” training. After several months of double “threshold” focus most athletes will fall into bioenergetic deficit which will make it challenging for them to effectively train at higher intensities. Lower quality workouts lead to diminished gains in fitness and performance.
Alternative Approaches to Optimize Performance
To avoid the pitfalls of double “threshold” workouts, consider these alternative approaches to training:
Balanced Training Plan
An overemphasis of any area of physiology, level of net lactate, or workout type will undoubtedly lead to underperformance, impairments in metabolic adaptability, and bioenergetic deficits. A key concept in the proper application of training using lactate data is that only focusing on one area of physiology or workout type, such as training too frequently at the “lactate threshold” is proven to be detrimental to physiological development and performance. On the other hand, a training plan that includes training one’s physiology from low end and upper end aerobic to anaerobic across one entire net lactate range are all valuable areas to develop. A balanced training plan will yield greater overall development of one’s physiology and performance gains.
Single Stimulus Block Periodization
Block Periodization involves organizing training into distinct phases, each with specific goals and intensities in blocks of 4-6 weeks at a time. A “Single Stimulus” approach simply means that the main workouts for the phase have the same physiological objective and provide the same biochemical stimulus for each main or intense training session. Analysis of over 1,000 physiological profile tests of D1 middle distance athletes along with their performances revealed that a single stimulus block approach of training yielded far superior physiological adaptations and performance improvements.
Optimize Training Load
Optimize physiology, adaptation, and performances by spacing out main workout sessions and moderate to long aerobic runs by at least 2 days. Do not do more than one main workout or long aerobic run in the same day. Place recovery runs of low intensity and volume on the days in between main workouts and long aerobic runs. This approach allows for adequate recovery while still reaping the benefits of main workout.
Monitoring and Adjustments
Monitoring an athlete's lactate profile 3-4 times a year will ensure that the training load and stimulus is appropriate for that athlete. Adjust the training plan based on lactate profile data to ensure that the athlete is developing their physiology and getting adequate recovery.
Conclusion
While double “threshold” workouts might seem like a promising strategy to boost performance, it comes with notable risks. Increased fatigue, reduced training quality and adaptation, and a higher likelihood of performance declines. By adopting alternative training approaches and prioritizing recovery, one can achieve optimal performance without the drawbacks associated with double threshold workouts. Remember, effective training is not just about training at one intensity it is about balance and recovery.
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