You are training too hard and will never reach your full potential!
We hope the headline provoked and made your heart beat a little faster. If you have read this far, we strongly recommend that you continue, and join us on a small deep dive into a discussion about training and intensity control. We firmly believe this could make you a better athlete and/or coach. What do you have to lose? Worst case, we managed to get your heartrate slightly elevated, and our claims can hopefully stimulate to a valuable debate about an important topic.
Introduction
Questions like - which intensity is the most optimal, how do one best manage intensity, and how much intensity one should train, are challenging topics that lead to loud and long discussions about what is right (or wrong), and clearly cause uncertainty among athletes and coaches. To be the best, one must train best, or in other words, train optimally according to one's own physical condition, physical characteristics and training background. Albeit difficult, the questions above, should and must be discussed. There are countless of models that have led to success. In our experience, the athletes that reach their full potential are those who have made the fewest mistakes during training (and otherwise in everyday life). This means that they have trained the best, not necessarily the most. The ever-increasing focus among a growing number of athletes to "collect hours", is probably strongly influenced by the fact that several of the best elite Norwegian cross-country skiers train over 1,000 hours per year. The focus on “collecting hours” is likely one of the main reasons why many athletes/coaches have "forgotten" the importance of ensuring that each training session is of high (and correct) quality. Quality can be defined in many ways, but from our perspective quality training entails focus on; intensity control, technique, continuity, progression, learning and achieving session goals during training. Our experience is that many athletes do not experience the desired/expected progress or continuity as they fail to train at the correct intensity. They simply train “too hard”, during low-, medium- and high intensity sessions.
Many coaches/athletes sound like highly educated scientists when they with ease and confidence talk about training intensity, as if there was only ONE answer - the truth is of course a bit more complicated and complex. Science has its requirements and norms for how to describe, discuss and conclude, but the findings often fall short of being helpful; they are either too vague for most people to accurately adapt into the training plan, or they are not statistically precise enough to 100% adhere to scientific research criteria. It is also important to consider that most studies related to intensity have been carried out on younger men, and not elite athletes. The conclusions are based on group data, and the studies tend to run over a limited time duration. Heart rate monitors and lactate measuring devices also do not tell the whole truth about intensity. Most people have access to a heart rate monitor, while fewer have access to a lactate measuring device. Reference to percentages of maximum heart rate and VO2max can be challenging, as not everyone has perfect control of their exact personal maximum values.
But what is the correct intensity? This article aims to answer this question, and many more. There are most likely some weaknesses in how the “grass roots” in skiing describe, plan, execute, document, and measure intensity. Given what most people have available in terms of measuring devices and knowledge, one must still dare to make the best out of the situation. Our goal is to provide some well-intended, easy-to-understand advice, based on sports literature combined with a bit of common sense.
Why is intensity management important?
The content discussed in this article is best suited for dedicated and experienced athletes ranging from older junior (18-20 yrs.) to senior elite athletes, in other words athletes that train regularly, year-round, with the goal of continuous athletic development. Intensity management is of course important for everyone, but obviously more important the higher the training volumes. Children and young athletes should also learn to master all types of intensities! It often helps to think of training and intensity levels as “risk management”. One must be aware of and consider the costs and benefits of different types of training. If the training is too intensive/fast, the cost of the session/the total load, will increase. This often leads to increased recovery time, as well as greater risk of injury/disease etc. The effects and benefits of a training session are in many cases better if you train with a lower (correct) intensity. Correct intensity = lowest possible cost to achieve optimal outcome. Cost/benefit is possibly an unfamiliar term for many when discussing training and intensity. Slightly simplified, you can compare it to buying a product you need. If you have the choice between paying 2 Euros or 5 Euros for a bottle of water (identical brand, bottle, effect, and benefit), which one would you choose? What if you have the choice between identical ski poles where one shop sells them for 200 Euros and the other shop sells them for 400 Euros? Occasionally making bad choices will not affect your financial situation considerably. Over time, however, the sum of bad financial choices can significantly affect your economy negatively. The same applies to training when making bad intensity decisions. It is important to point out that it is not dangerous to train at a high intensity, but if you do it too often, it could lead to fatigue and/or overtraining/overloading. Since most of the total training is "low intensity", it is most important to carry out this training with the correct intensity and technique. History shows that there are many World and Olympic Champions who have been extremely conservative and precise with the intensity on low, medium, and high intensity training, compared to those who have not been as successful.
It is a paradox that most of the research on “elite” training has primarily focused on the "correct" intensity for the most intensive part of the training (i3-i5 = MIT-HIT). We are anxiously awaiting that competent and curious researcher carry out similar high-quality research to uncover the effects of, and give guidelines for how to best execute, low intensity training (i1-i2 = LIT). After all, historically, low intensity training accounts for approximately 90% of the total training time (11).
Intensity zones
In the literature, various terminology, explanations, and definitions are used to describe intensity training, and how to best ensure that the execution is optimal. It is a challenging task for scientist to accurately define universal intensity zones with terminology that are easily understood by all, and that fit all types of athletes, regardless of sport, gender, age, physiology, temperature, altitude etc. The solution so far has been to define a value range for heartrate, feeling, lactate etc. for each intensity zone. This to ensure that each intensity range suit as many people as possible. The challenge with this practice is that a "value range" is often so wide that it is difficult for most people to precisely estimate what is correct for each individual athlete. Eager athletes and coaches often think that training in the upper part of the intensity zone must be more effective (better) as it hurts more (the "No pain, no gain" philosophy). Does it matter if one trains all the long and slow sessions with a heart rate of 110 or 144? Is level 3 training at 4 mmol/L in lactate better than 2 mmol/L in lactate? When considering the cost and benefit of the training, most people should recognize that there is a difference.
We often expect scientist and professional coaches to give accurate and precise answers when it comes to training and the expected effect. This is unfortunately an unrealistic expectation as all athletes are unique - they respond differently to training. Professional researchers and physiologists can point us in the correct direction, but not give absolute answers that suit everyone. You as an athlete (or coach) must start your venture to find your correct training intensity by reviewing the training literature, and then, through trial and error, discover which intensity gives you the optimal development. In discussions with eager athletes, coaches, and parents, we are often asked what an athlete must train to one day become a World Champion. The correct answer is that it varies extremely. Some train 750 hours, while others train up to 1200 hours (Value range 750-1200). Few people get very excited over such a broad answer, simply because it is not precise enough. Our answer probably often causes people to question whether we have any relevant expertise at all. What people want to hear is that one must train exactly “927 hours 33 minutes and 56 seconds”. The answer is extremely accurate, but unfortunately also extremely wrong. For many, it is however tempting to interpret such a surgically precise answer as an intelligent truth. Unfortunately, we must accept answers given as a "value range", regardless of whether it concerns the number of training hours or intensity levels. Knowledge, coupled with curiosity (trial and error), will over time enable you to identify more precisely what is right for you as an individual.
All definitions of intensity and methods have their strengths and weaknesses. It can therefore be smart to use a combination of several parameters to ensure that the understanding, implementation, execution, reporting, and evaluation are more correct/optimal. To "classify" intensity one has an array of parameters, such as: heart rate, lactate, speed, lap times, ventilation, watt etc. Heart rate is often stated as a percentage of maximum heart rate, or as a percentage of VO2Max.
“Olympiatoppen” in Norway has developed a great overview of five intensity zones: https://olt-skala.nif.no/#ventilasjon_m
The information in the table above gives an estimated range for each intensity zone. Each individual intensity zone has different target parameters. The "range" for each parameter is relatively large in every intensity zone, as all people are different, hence you must experiment a bit to find the correct individual intensity. It is also important to again emphasize that you do not automatically get better from always training in the "higher" end of the defined intensity zone. Always consider the cost and benefit! If you train with too high intensity over time, there is an increased risk that the cost will exceed the benefit, and as a result you will not get the desired development and progression. Truth is, you can become better by training smarter, not necessarily more or harder.
Research and discussion
There are many ways to describe or to classify the desired intensity. The goal is, regardless of parameter, to establish a common language (tribal language) that all understand. If you are planning to train level 3, it is important that the athletes understand what level 3 is, how to execute it optimally AND how to report it precisely. Our experience tells us that when the plan says level 3, the training is by many athletes carried out at an intensity closer to level 4-5 or even in the "balls to the wall" zone, but it is still reported as level 3. Whether one chooses to use heart rate, lactate, breathing, Borg, RPE, Watts, speed or time, is of lesser importance. The most important is that the planned intensity is both executed and reported correctly. “Plan the work and work the plan”.
The terminology jungle
In Norway most people are familiar with a 5-part intensity scale developed by Olympiatoppen (see table further up in the document). In the literature one often talks about LIT, MIT and HIT. The definitions may vary slightly, but roughly speaking, LIT (Low Intensity Training) corresponds to zones i1 and i2, MIT (Moderate Intensity Training) corresponds to zone i3 and HIT (High Intensity Training) corresponds to zones i4 and i5. In addition to these definitions, terminology such as threshold training, sweet spot training, MaxLass, steady state, critical power/speed, FTP etc. are used. Our advice is to use OLT's intensity scale and not spend too much time pondering over the various definitions and different terminologies. Simply put, level 3 is the same as threshold training/sweet spot/MaxLass/FTP, and this training is sometimes carried out as steady state (continuous work), in contrast to interval training with breaks between each interval.
Below is an example from running where you control the intensity of the training by using time. It is not always practical for cross-country skiers as they do not often train on "standardized" tracks. The table can be best used when training on a track. The table was developed by Bjarne Vad Nilsen, based on Jack Daniels' famous VDOT number (VDOT identifies your current running form).
The training and the intensity are regulated with reference to a target time on a given training distance. The estimate is based on your current level (times you have recently run on a given race distance, in contrast to times you have achieved a long time ago, or times you want to run). In the table you first identify your own current capacity by finding the race time for a given distance. When the right time has been identified, follow this column vertically down to the estimated training time for Maxlass (i3). Further down the table are estimated times for harder intensity zones.
Kapasitet = Capacity/Your performance
Maxlass = +- I3/MIT/Threshold
Intensiv Intervall (Hele året) = i4 – (The whole season)
Hard intervall (april-september) = i4-i5 (April-September)
Meget hard intervall (mai-august)=i5/max (May – August)
How the best endurance athletes train
Measurement of blood lactate is one of several important parameters to ensure that the athlete completes the training optimally, thus ensuring continuous athletic development. Particularly during threshold training, many swear to measuring blood lactate to ensure that the athletes execute the training at the desired and planned intensity. The discussions below present findings from scientific literature, but also gives some practical tips that may increase the level of knowledge, interest and understanding. The goal is to encourage more athletes to train at an optimal intensity, and thus get the progress/development they both desire and deserve. As stated earlier, our observation is that many athletes train too hard to be able to achieve optimal athletic development. The main challenge is probably not that athletes/coaches do not believe in threshold training, but rather that the execution of the sessions is not calibrated to fit each individual athlete. Several athletes (and coaches) underestimate the level of intensity – and/or they overestimate own physical ability/level.
Before we do a "deep dive" into the discussion and the literature, it might make sense to look at what some of the very best athletes throughout history have trained. If you analyze the training diaries of the best endurance athletes (regardless of sport: running, cross-country cycling, triathlon, swimming, etc.) you will find that most train approximately 80% of the sessions with low intensity (LIT = i1 and i2) and 20 % of sessions with medium (MIT = i3) to high intensity (HIT = i4 and i5) (including competitions). This is illustrated well in the training of Marit Bjørgen in figure 1. Most successful athletes have had a similar intensity distribution with approximately 90% of the hours easy/low intensity (i1-i2) and approximately 10% with medium or high intensity (i3-i5).
Figure 1: Training distribution in basic period 1, 2 – (GP 1 and GP2 - May to September), Specific period – (SP October to November/December) and competition period – (CP December to March) for Marit Bjørgen Seasons 2010-2015 (11).
Some of the most important arguments for the large volume of low intensity training, in simple terms, are that we have seen that this creates a good base/foundation. Physiologically speaking, it has been proven that low intensity training leads to:
Improved a-vO2 difference (how much of the oxygen the muscles can extract/take up from the blood)
Increased number of capillaries around working muscles.
Increased number of oxidative enzymes, which leads to a greater consumption of lipids (fat) as an energy substrate.
Improved mean transit time (the time used for oxygen molecules to be transported into the muscles cells from the bloodstream).
Increased size and number of mitochondria
Improved muscular/peripheral endurance fatigue (1,4,5,6,7).
The length and number of low-, medium-, and high intensity sessions must be adjusted to fit each individual athlete’s training status and physical conditions. Some athletes train more medium/high intensity and less low intensity training, while others train more low intensity sessions and less medium/high intensity sessions. There is no conclusion as to what is right, hence everyone must experiment a bit to find the optimal mix.
It is common to train 2-3 intensive sessions per week. Historically, the best cross-country skiers complete approximately 104-120 sessions of intensity per season (19). For adult elite skiers, a level 3 session typically last between 60 and 90 minutes. There are many variations of interval lengths and breaks. In general, each interval will have a duration from 10-15 minutes, with a break of approximately 2-3 minutes. There are several good reasons to train in the area just below the anaerobic threshold (i3). The literature shows that it is particularly beneficial for well-trained endurance athletes, and (in most cases) more appropriate than prioritizing training in zones i4 and i5 (more on this later in the article).
Training in the various intensity zones
Based on the discussion so far, the table below is a general summary of the various intensity zones used by elite athletes. When illustrative values are given, the assumption is a person with a maximum heart rate of 200.
Intensity Zone 1:
Easy training should be easy. Most people will benefit from training at around 110-140 in heartrate/0.5-1mmol/L in lactate. There are large variations depending on the type of movement, terrain, altitude, etc. When the training/physiological condition of the athlete is satisfactory, it should be possible to train at the correct intensity AND with proper technique. If it is challenging to train with the right technique and the right intensity, then it may be appropriate to choose easier terrain or train with faster roller skis. Typical length of a session is 1.5– 4 hours of continuous activity.
Intensity Zone 2:
Semi-hard long sessions with a heart rate at around 140-155 bpm and with lactate up to 2 mmol/L, is considered intensity 2 training. Scholars debate over the importance of this training. In our experience, this training costs more than it is worth, and should therefore not be prioritized. I2 can work well to learn/automate correct technique. Again, evaluate cost vs benefit! Typical length of a session is 1 to 3 hours of continuous activity.
Intensity Zone 3:
For most people, threshold training should be at an intensity of 80-85% of HFmax. The pace should be possible to maintain for about 60 minutes with a steady lactate. As a very general rule of thumb (for those with less experience) one can make the following assumption about maximum heart rate: 211 minus (0.64 x age) = approximately your current maximum heart rate. If you subtract 30 beats from this roughly estimated maximum heart rate, you are approximately at your recommended highest threshold heart rate/threshold load. The recommended threshold heart rate/threshold load is an intensity which reduces the risk of too much fatigue while providing an almost optimal yield. The recommendation is not a universal “one-size-fits-all answer” that is 100% optimal for everyone at all times. It should only be used as a starting point for finding your own “perfect” intensity. A better method for more experienced athletes is to execute threshold training at approximately 85% of the highest measured heart rate (pulse) during the last year.
Blood lactate measurements are often used as a control parameter to quantify whether a training session is at threshold or not. Values between 2.0-3.5 mmol/L are considered to be in the range of threshold training (Level 3), given that the athlete is physiologically in balance. It is important to remember that blood lactate is only one of several target parameters that quantify if one is training with threshold intensity. For most people it is important to consider blood lactate measurements and other factors such as heart rate, speed/watts, feeling/perceived effort and "how the athlete moves". Remember that blood lactate and heart rate are not constant units of measurement. They can vary considerably based on the form of movement, weather, temperature, daily form, state of nutrition, altitude, etc.
Once you have calculated your "correct" threshold/intensity 3 load, then you must start a “trial and error” phase to identify your correct threshold intensity. If your highest recorded HR is 200, then you can plan a session where you run 6x10 minutes at 170 heart rate. Feel and measure (heart rate and lactate) during this "test session" and evaluate if the load is correct using the various measurement parameters from the table above. If you have access to a lactate measuring device, you can measure every other interval to calibrate your feeling with an "actual number". If the speed was too high, then complete the next session with a heart rate of 165. If the session was too easy, increase the heart rate to 175 during the next session. After a couple of sessions, you have probably succeeded in identifying a more correct personal intensity for the threshold/level 3 training zone.
Intensity Zone 4:
Training at intensity 4 is relatively hard but should nevertheless not be uncontrolled and "all out". A good test to identify if the intensity is correct or not, is that you are able to cover the same distance for each interval. When you for instance do a 5 x 5 minutes interval session, the blood lactate and heartrate should increase from interval to interval, BUT the covered distance should remain the same for each interval. Typical length of a session (total interval time) is 30-45 minutes. The training is most often carried out as interval training with intensity of 4-7 minutes and 2-minutes break.
Intensity Zone 5:
Intensity 5 is hard intervals or competitions. Often the athlete feels a little "stiff" towards the end of the intervals. Speed, heart rate and lactate are relatively high, (often over 10 in blood lactate) Typical length of a session (total interval time) is 15-30 minutes. Most often, this training is carried out as an interval session with intervals ranging from 0.5-5 minutes in length. Breaks are generally 50-200% of the interval length. Test runs and competitions fall under this category of training.
Which intensity training is important to be great in endurance sports?
As one understands from the introduction to this discussion, easy/low intensity training (i1 and i2) is undoubtedly of great importance. It is probably within these intensity zones that intensity management over time will have the greatest effect (both positively and negatively), as this form of training makes up 90% of the total annual training time. Any athlete can tolerate large amounts of low intensity exercise if the intensity is correct. In other words, low intensity training is effective and has a low cost.
The reason why the more intensive training (i-zone 3-5) has received greater focus (both in sports science and in practice) is probably that it is demonstrably more effective in developing a large and efficient "engine", as compared to the low intensity training in zone-1 and 2 (5). With development of the "engine" we refer to the increase in aerobic capacity (VO2max, blood volume, total hemoglobin mass), as well as sport-specific VO2 speed (FTP20 or 60 - Functional Threshold Power). Since sports science considers MIT (i3) and HIT (I4/i5) training to be particularly important and beneficial for athletic performance, it is often referred to as "quality training" (do not confuse hard training with quality, as the word quality in the context of training includes many more quality-parameters, e.g., technique). Threshold training (i3) often makes up the largest percentage of the total “quality” training volume (number of intensive hours) during the training year. When we only look at training in intensity zone 3-5, i3 (MIT/threshold training) often makes up 70-90% of the "quality training" (intensive training) for endurance athletes at an elite level! This is consistent for most sports where aerobic energy processes are limiting for performance, and where competition duration is from 210 seconds (middle distance), and up to "210 minutes" (long distance) (1,2,3,9).
Some of the most important arguments for the effectiveness of i3 training for elite athletes are:
The training requires shorter recovery time, giving better control in maintaining continuity in training. This means you can train longer/more sessions in the intensity zone.
The training leads to a high activation of motor units at velocity/workloads comparable to those in competitions. In technically demanding sports, such as cross-country skiing, it is especially beneficial and advantageous to automate/learn how to move efficiently at a competition specific pace.
The training increases an individual's fractional utilization of VO2max, and often results in a "shift to the right" of the threshold profile curve (Figure 2). This means athletes can maintain a higher workload over a longer period of time.
Elite endurance athletes often have reached their genetic and personal "ceiling" of VO2max. It is therefore relatively little to gain from training seeking to stimulate/further increase aerobic capacity after the U23 age (17).
The intensity allows for a larger training volume (hours, km – or time in zone) compared to intervals of higher intensity (10). Meaning most athletes potentially can tolerate greater training loads (increased amount of training) over several seasons. Training is about breaking down the body, and rebuilding. In an extension of this, both progression and continuity are perhaps two of the most important factors in achieving continuous development over several seasons.
What is anaerobic threshold and threshold training?
The words interval training and intensity are unfortunately as accurate as the words "cold" and "hot". Cold in Spain is probably not the same as cold at the North Pole. It is challenging to give a good and simple explanation of threshold and threshold training. Many have tried to come up with simple and easy definitions, and there are some which most people can relate to. The most common is that:
"Threshold is a workload where there is an equilibrium between production and elimination of lactic acid/lactate. This area is defined as the anaerobic threshold and is a work intensity one can maintain for approximately 60 minutes, where the measured blood lactate is between 2.0-4.0 mmol/L" (1)
The work that one can maintain for 60 minutes is often defined in cycling as FTP (Functional Threshold Power). Sometimes it is written as FTP 60 or FTP 20. FTP 20 refers to the work you can do for 20 minutes. FTP 20 times 0.95 gives FTP 60. In cycling, these values are given in WATT. In running, they have also used the term FTP (Functional Threshold Pace) - the speed you can maintain for 60 minutes.
Figure 2: Shows the relationship between velocity and blood lactate accumulation to estimate anaerobic threshold. The figure is illustrating “a right shift” of the lactate profile curve (dark blue line) as a consequence of athletes either increasing work capacity (VO2max), or having an increased fractional utilization of VO2max.
The definition above gives a good and general picture of what you want to achieve with threshold training. Namely, executing the training at a workload where there is an equilibrium between the production and elimination of blood lactate. In other words, the training intensity should not cause lactate to "accumulate", which would lead to a gradual reduction of the workload over time. Most definitions have their weaknesses, also this one.
There is a relatively large difference between having a blood lactate of 2.0 vs 4.0 mmol/L. The description is not sufficiently precise and probably spans over several intensity zones. Furthermore, the definition does not consider an athlete's unique fiber type composition (% muscle type I (slow) vs muscle type II (fast). It also does not consider whether the athlete in question has sufficient amount of carbohydrates (glycogen) stored in the working muscles, or whether he/she has a high/low muscular surplus (muscular destruction/structural degeneration). All these factors can influence how one should interpret the measured blood lactate values. Blood lactate is not an absolute value that can always be interpreted the same. In other words, you can measure the same blood lactate value (for example 2.5 mmol/L) in two different training periods but reach different conclusions. To assess whether the measurements indicate the same thing, the values must be seen in connection with other relevant factors such as feeling (Borgs scale), heart rate, blood glucose, speed/watt and how the athlete “moves" *often referred to as the “coaches eye”. Our experience is that many athletes and coaches unfortunately forget to take this into account when carrying out/evaluating threshold training using lactate measurements.
For most people who have made it this far in the article, it has hopefully become clear that intensity management is often not as simple as most people think (or say) - it can, among other things, not always be measured with 100% accuracy. Both heart rate and lactate have their limitations. If, we were to generalize, and give some general and simple advice to well-functioning athletes with regards to optimal threshold training (low risk and high reward) it would be:
The blood lactate should be in a range between 2.0-4.0 mmol/L (Figure 2). For the vast majority of athletes, it is better to be closer to 2.0 than 4.0 mmol/L.
Blood lactate of between 2.0-4.0 mmol/L will be around 80-90% of maximum heart rate (HRmax). For the vast majority, it will be safer to plan and execute training in the lower part of the range.
If one were to give a simple rule of thumb, the threshold intensity for an adult would be 30-35 beats below maximum heart rate (15-20% below HFmax). If you do not know HFmax (little experience) and are over 18 years old, take 211 minus (0.64 x your age) = approx. HFmax (20). Then subtract 35 strokes if you are under 30 years old, and 30 strokes if you are over 30 years old. The method will give an approximate HF of your anaerobic threshold intensity. Another method for those with more experience is to use the highest heart rate measured during the last year, and train at an intensity that is approximately 15% lower.
Threshold will be a speed one can maintain without problems for at least 60 minutes, hence threshold is significantly easier than what most people think (1-7).
If you hit the correct threshold speed, you should be able to maintain the same speed on all the intervals without the heart rate increasing by more than 4-5 beats ("Cardiac drift"), (if you complete the intervals at normal temperatures = below ~25°C)
Double threshold sessions
A trend that has spread like wildfire is "double hard sessions" or "double threshold sessions". The training is comparable to the “special blocks” introduced by Roberto Cavano in the 1980s, which was used by among other Sebastion Coe. Today it has not become less popular after Norwegian distance runners compete with the very best and break records on the tracks around the world. Before we go on to describe what the training philosophy is all about, and how it can best be applied in a "cross-country skiing context", we would like to state that this is NOT a training concept that suits everyone. Does it work? Undoubtedly, if it is carried out correctly. But it doesn't work for everyone. Are you, for example, an athlete who has a hard time controlling your speed/intensity? Are you an athlete who always tries to keep up with the best when training? Then this is probably not the appropriate form of training for you yet.
The “double hard sessions” concept is not a "magic bullet" that quickly will give you miraculous results. However, the concept is an interesting way of organizing intensity sessions, and for some it can probably be the key to squeezing out the last performance percentages. Our experience is that most athletes must walk each step of the “development ladder”, be patient, avoid mistakes, build stone upon stone, and train well over a long time period with good intensity control and continuity, to improve. The "spice" is only important when the steak is ready!
In track and field, it is primarily runners at distances from 1,500m to 10,000m who have used double threshold sessions. Here, the sessions are usually relatively short (up to 30 min intensity time), and the sessions are cleverly organized so that the speed is high (preferably close to competition speed) without the internal intensity (heart rate, lactate, etc.) exceeding the threshold parameters. Due to the large mechanical load in running, it is perhaps smart to divide the threshold sessions into several shorter sessions rather than fewer long ones? At the same time, we should not forget that there are several successful runners who rather choose to run longer single threshold sessions, and through this approach achieve the same number of kilometers at threshold intensity as those who run double sessions. At longer distances, such as half and full marathons, this (single threshold sessions) is still the most used concept, while triathlon, which uses several forms of movement (a bit like cross-country skiing), uses different methods for organizing the intensive sessions.
It is important that coaches are curious about double hard sessions, as more and more young cross-country skiers have already adopted this training approach based on the exceptional results from Norwegian track runners. When the athletes who are the future of Norwegian cross-country skiing experiment with this intensity training concept, we as coaches should become more curious and find answers to whether, and how, double threshold sessions can provide a better training benefit. The start of this journey is probably already described earlier in this article, find YOUR right intensity BEFORE you start with double threshold sessions.
The risk of "shopping" concepts from different sports and environments is that one forgets the “whole”, and often end up putting together a toxic cocktail of training that leads to an uncontrolled emergency landing far from the (training) target. If you combine current trends: several 5-hour sessions per week + 1200 training hours per year + intervals lasting over an hour + double hard sessions, then few will achieve their desired continuous development. The total load of the training must always be considered and evaluated. Remember to reduce risk by considering cost and benefit. What is better? Quantity, long sessions, double hard sessions, or a combination thereof? We lack experience and knowledge but given our previous claim that most people train too hard, a cocktail of more quantity and intensity will probably be "risky business".
The trainers in Team Aker Dæhlie have some experience with double hard sessions, but not to such an extent that we can conclude whether this new approach is advantageous compared to a more traditional approach. We are committed to sharing our thoughts and experiences and hope that more people will do the same. We also hope that the research community will take interest in the topic and shed light on the advantages and disadvantages specifically related to cross-country skiing. It undoubtedly seems like the concept works extremely well in running. HOWEVER, work requirements, form of competition, number of competitions, amount of training, muscular load, number of muscles working, etc., are different in cross-country skiing than in running. Even though running has succeeded in integrating double hard sessions into the overall plan, this does not automatically mean that cross-country skiers should uncritically copy the approach. Cross-country skiing should recognize the good work that many runners have done and ask what we can learn from their experiences. Several cross-country skiers have tried training double hard sessions. Some with great success and others with the opposite effect. For those who fail: could it be that they trained with too high intensity? What is better: One long and progressive i3 session or two shorter i3 sessions in a day? Which training incurs the highest cost? Which variant gives the best quality (technique, implementation according to plan, feeling, etc.)? Each individual athlete and coach must test and give themselves an honest answer based on personal experiences.
Here is a summary of our experiences and thoughts about double hard sessions:
Is best suited for experienced athletes who have trained well over a long period of time, and who have control over their intensity zones.
In general, training at the right intensity with good continuity, is much more important than double hard sessions.
A good test battery and follow-ups are extremely important to ensure that the athlete respond well to the training.
Accuracy, discipline, and the ability to listen to the body are important to get maximum benefit.
The first intensity session should be considered as preparation for the second intensity session of the day. It is important that the second session is carried out with high quality. (By quality we mean that the session is carried out according to the plan. For those who are interested in reading a bit more about quality, we recommend this article: https://journals.humankinetics.com/view/journals/ijspp/18/5/article-p557.xml
Use different forms of movement in the double hard sessions, for example running during the first session and roller skiing during the second session.
Nutrition before, during and after the sessions is very important - make sure to consume sufficient amounts of carbohydrates.
Sleep and recovery are very important.
Intensity management is extremely important. Our tip is therefore to have a heart rate of 5 beats below "normal i3" on the first hard session, and then complete the second session with a "normal" i3 heart rate.
The first hard session is a little easier level 3, where the intervals are longer. Example of a session is 4-6x8-10 minutes. Duration 40-60 min. The second session is a "normal i3" session with shorter intervals (which gives the opportunity to maintain a higher speed without the intensity becoming too high and the cost too great). Examples of a session are 5-6x4-6 minutes with a 2 min break, or 20x400 meters with a 100m break, or 3x (10x45 seconds intervals/15 seconds break) with a 3 min set break.
Double hard sessions are often carried out 2 days per week but can also be carried out 1 day per week.
Test of cost vs benefit: Train a longer and progressive i3 session. Record how tired you get after the session and the day after + quality of speed and technique. After 2-3 days of normal, low intensity training, complete another intensive day with double threshold sessions. How tired were you after the first session? Second session? The day after? How was the speed/technique? Consider the cost and benefit before deciding how to proceed.
Test of training effect: Perform a lactate profile test before starting the test with double hard sessions. Then train the following 6-week program of intensive days in addition to your “normal training”:
two weeks with 2 intensive days/week of double hard sessions.
one week with 2 intensive days of single hard sessions.
two weeks with 2 intensive days/week of double hard sessions.
one week with 2 intensive days of single hard sessions.
Repeat the lactate profile test towards the end of the last week. Evaluate the test results against your own assessment of cost/benefit, technique etc., before deciding how you want to plan your future training.
Double hard sessions have mostly been used in the period from mid-summer to the start of the season, and in some cases during training periods in the season when there are no competitions.
The coaches in Team Aker Dæhlie actively seek knowledge about double hard sessions and about training in general. When we have more knowledge and experience, we will share it with anyone who cares to listen. Our experience so far indicates that patience, discipline, lots of proper training over a long period of time, progression, accuracy, fun, and passion, lead to improved results. BUT all athletes are unique and therefore the training must be individually adapted and adjusted to achieve development. Cost vs. benefit, as well as risk analyzes (plus the fact that we dare to admit that we do not know everything) often lead us to more "correct" choices.
Discussion part II - "The nerdy part" about Lactate and lactic acid
For people (nerds like us) who are interested in understanding how one could use blood lactate measurements as a tool to evaluate the intensity of threshold training, one should recognize the need to understand what blood lactate really is, as well as reflect over why we measure blood lactate to qualify threshold training. Such discussions can for most people often become too technical and theoretical. If you belong to this category, don't worry, because the topic is in fact relatively complex, and not as easy and straight forward as many people might think, or as easy as the definitions earlier in this article describe. It also does not help that several of those who discuss the terminology have not thoroughly understood the science/biochemistry related to the terminologies, but still continue to discuss…….
Let's start with some simple facts. Lactic acid is something that can be found in for instance fermented food and drinks, and gives a "sour" taste e.g. yogurt and beer. Lactic acid was discovered by the Swedish chemist Carl Wilhelm Scheel who identified the special chemical as early as 1780. Many (especially in the endurance community) refer to the term lactic acid and lactate interchangeably. However, what one must distinguish between, and which is correct, is that during physical work our muscles produce lactate (and H+ ions), not lactic acid. This happens as a consequence of glycolysis (anaerobic energy release) forming lactate together with the release of H+ ions (Figure 4).
Figure 3: Lactate and lactic acid are not the same, however they are extremely similar; they only differ by a single hydrogen atom. That hydrogen is very important though to be an acid, a molecule needs to have an extra hydrogen ion to donate. In a sporting perspective this enables us to continue our exercise, at least for a period of time.
Sports scientists are actually still today not entirely sure where all the H+ ions come from when the pH drops in the working muscle cells, and blood stream (12). It seems that to maintain muscular function, lactate and H+ during anaerobic energy release is converted into lactic acid (Figure 3). It is therefore somewhat humorous, and paradoxical, that lactic acid is an acid, while the lactate ion (La-) is the opposite, namely a base.
Earlier, it was common to blame lactic acid when people "hit the wall" during hard intensity sessions or competitions. The conclusion was based on that there was an observed relationship between increase in lactic acid and athletes feeling “finished”, and/or reduced power/force production. The observations lead to the conclusion: "Lactic acid causes the muscles to reduce their power production ability". This is likely where much of the confusion between these terms started. "Lactate" and "lactate acid" are two very similar words that have probably been used interchangeably in the English-speaking parts of the world. Molecularly, both substances are very similar, with the only difference being one hydrogen atom (Figure 3). Contrary to popular belief, it seems like neither lactate nor lactic acid can be blamed for you being unable to maintain your workload. The truth is that, as of today, we do not exactly know why this is happening. It has been speculated, amongst other things, that the cause could be potassium accumulation in the muscle cells. When an athlete exercises, the cells pump the element potassium in and out continuously. If the intensity is too high, potassium will accumulate outside the cell. This happens because the cell's "potassium pumps" cannot keep up. Consequently, this could reduce neurological drive from the brain to the working muscle cells. The reduction in neurological drive from the brain, giving explanation to fatigue, is one of the main theories for the “central governor theory” by Timothy D. Noakes (which we will not discuss in this article). In other words, a smaller amount of motor units is recruited, and consequently the force from the muscle decreases, and the pain and blood lactate increase (18). In other words, it is difficult to understand and explain exactly (scientifically) what happens. Since we cannot measure the potassium, or lactate acid content of working muscles during exercise, the practical approach has been to measure blood lactate to be able to say something reasonable about the anaerobic energy contribution. It is therefore, based on the theory above, important to be a little careful about concluding on the amount of anaerobic contribution based on blood lactate measurements alone.
The introduction of anaerobic threshold
The anaerobic threshold was first introduced in 1964. In the study by Wasserman and colleagues, they reasoned that "the anaerobic threshold pointed to a specific area where a marked increase in blood lactate was observed". They believed that this was directly linked to the fact that one had too "low oxygen availability" in the working muscles (8). Wasserman's conclusion is not wrong, but not completely correct either. This probably comes from the previously mentioned "misunderstanding" around the function of lactic acid, lactate and oxygen.
Figure 4: The end products during aerobic and anaerobic energy conversion.
We know today that Wasserman's assumption is not 100% correct. Among other things, it has been shown that dogs who exercised the thigh muscle (while the dogs were under anesthesia) had a significant lactate production in the muscle tissue even though the oxygen availability was more than sufficient for energy turnover in the mitochondria (13). In later studies, such as in the study by Connett et al (1984), it was observed that blood lactate production was a direct consequence of the speed of glycolysis. This process will always take place both with and without available oxygen in the cell (14). Another example is that when athletes are "exhausted" after performing hard endurance exercise, they often measure high blood lactate (over 10 mmol/L). However, this does not mean there is a direct (causality) connection between exhaustion and the level of blood lactate. The best example is observed during long intensive sessions (over 90 minutes of continuous work, such as a marathon) where the athletes are exhausted, but the blood lactate values are rarely very high (above 4.0-6.0 mmol/L). Furthermore, it is important to point out that the blood lactate does not necessarily give a complete and representative picture of the situation in the working muscle cells, since the lactate molecules must be transported from the working cells and into the bloodstream. This formed the basis for the "Lactate shuttle theory" which was introduced by Brooks GA in the 1980s. Here it was proven that lactate molecules can be transported into the mitochondria, but also out of the cell, via the blood from working muscles, and used by other muscle cells. Since lactate preserves as much as 95% of the energy of the glucose molecule, lactate acts as an efficient energy source. In fact, both the brain and the heart prefer lactate over glucose as an energy substrate (12).
In conclusion, we think the document by Nils van der Poel "How to skate a 10k" brilliantly summarizes what we believe to be a general misunderstanding when measuring blood lactate during training. At least if one is going to use the blood lactate measurements to say something reasonable about how the threshold training has been executed.
Nils van der Poel "How to skate a 10km" - Short term blood lactate development:
Lower than normal: Indication of a tired body or lack of carbohydrates
Higher than normal during training: Indicates good shape
Takes longer to stabilize at a low level after a high intensity set: Indication of a tired body
These remarks from Nils van der Poel are "spot on", and in line with what we see in well-trained athletes. One must be careful and not automatically conclude that "high blood lactate" is always negative, and further entertain that blood lactate is probably only one of several important pieces of the puzzle when measuring and controlling optimal implementation of the threshold training in relation to the training plan and goals.
A somewhat ignored and little discussed physiological response in connection with carrying out threshold training is what is called "cardiac drift". Cardiac drift happens when one repeats the same speed/workload several times and the heart rate rises (drift). This increase in heart rate is often explained by reduced stroke volume (the heart's pumping capacity) during the activity. On the other hand, there is a lot of data indicating that little, or almost no, cardiac drift, during threshold sessions, and with measurement of stable blood lactate (+/÷ 0.5 mmol/L difference), you are often within what we define as the anaerobic threshold. If one then combines these two parameters, and includes RPE, blood glucose, and how the athlete "moves", we get a more full-fledged toolbox that can say something reasonable about whether an athlete is able to carry out the threshold training with the desired/optimal/ planned quality.
Take home message and summary
To become the best version of yourself you have to train at your individually and correct intensity as often as possible. Invest the time needed to understand the definitions, and experiment until YOU find YOUR correct intensity. You don't get better by training at someone else's optimal intensity. As a starting point, it may make sense to use Olympiatoppens's 5-part definitions of intensity zones, such that you are not confused by all the different terminology. If one summarizes what the best athletes have trained one find that approximately 90% of the training time is at low intensity (i1/i2), hence the most important is to first identify the correct intensity for this training. In total, around 20% of the sessions, or 10% of the training time, is carried out in the intensity zones i3-i5. A large proportion of this training is carried out as threshold training (i3). For most people, threshold training should be carried out at an intensity around 85% of HFmax and be at an intensity that can be maintained for around 60 minutes. As a very general rule of thumb, inexperienced athletes over the age of 18 can calculate the threshold heart rate by using the formula: 211 minus (0.64 x age) = approximate current maximum heart rate. If you subtract 30 beats from this number, you are approximately at the correct threshold heart rate/threshold load. Another method for the more experienced athlete is to execute threshold training at approximately 85% of the highest measured heart rate (pulse) during the last year. Many in the endurance community use blood lactate measurements to quantify whether an actual session is at threshold intensity. Values between 2.0-3.5 mmol/L are for most athletes within the threshold (i-zone 3), given that the person is in physiological balance. Most people should strive to start with values closer to 2.0 mmol/L during the process of finding the right personal intensity. Again, it is important to remember that blood lactate is only one of several target parameters that indicate if one is actually training threshold. For most people, it will be important to evaluate lactate measurements up against other factors such as: heart rate, speed/watts, feeling/perceived effort and "how the athlete moves". It is not wrong or dangerous to train hard sessions in zone 4 or 5, but it is wrong to plan and document the training as i3 when the execution was in a harder intensity zone. For you to learn what is the right composition of the training (percentages in the different intensity zones), intensity management, and how to get optimal development over time, you must complete as many training sessions as possible with "your" right intensity while always maintaining optimal technique.
Good luck with your training!
Written by the coaches in Team AKER Dæhlie - Trond Nystad, Knut Nystad, Jostein Vinjerui, Hans Kristian Stadheim and Chris Jespersen
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