Exercise zones are set areas of exercise intensity that cyclists use to train properly. There are two main zone models, the three zone model, and the 5/7 zone model. Both are widely used and are an essential tool to build a training plan.
Why Make Zones
Zones are finite lines in the sand we draw to try to quantify the different intensities that we can ride at while on the bike. This wide range of intensities give different amounts of stress to the body. For example riding at 50% max effort for five minutes will have a very different affect on your body that riding at 75% max effort for five minutes. Zones are the first step to quantifying how hard you are riding. Recall the process of training; stress-rest-overload. Time in zone is used to measure the training stress invoked so that the correct amount of rest is prescribed.
The Three Zone Model
The first zone model to discuss is the three zone model. This is the simplest and most fundamental of the two models. This zone model rests on the two thresholds within human performance.
What are Thresholds?
Threshold: a level, point, or value above which something is true or will take place and below which it is not or will not. Thank you Merriam-Webster. To add more clarity for the specific use of threshold that cyclists use, a threshold is a point of intensity where input and output no longer scale at the same rate. For example, lets say your first threshold is 200 watts. This would mean that your input, or perceived exertion would grow at a relatively set rate as compared to your output, until you hit 200 watts. Past this threshold, your output becomes much more input intensive. Your ratio of input to output changes. For example, the jump from 160 watts to 180 watts is much easier than the jump from 220 watts to 240 watts, despite them both being 20 watts apart. Not only is this true, but the input to get over a threshold is more. It is as if you need to pile extra effort on to make it over the first threshold. Think of the latent heat of vaporization, it is a similar idea here. Consult my graph below.
Again, I should remind you that this model is simply a way to express what humans have found in extensive training. This model exists to show a phenomenon that athletes find in training, e.g. that an increase in effort doesn’t always correlate to it’s expected rise in output. This happens due to a change in energy consumption. When you go up in intensity at a certain point(a threshold), your body is forced to use different/more methods of energy consumption. This most notably occurs with lactate. As your intensity rises, you demand the body to produce more output with the same amount of oxygen. In the absence of oxygen, the body begins to produce energy with Lactate. This Lactate flows in the blood system and can be tracked. At a certain points in the intensity range, the lactate to output production changes rate. This shows a threshold. This identifiably happens twice in the range of intensities we workout in. This is the core of the three zone model.
Three Zone Model
The three zone model simply splits the range of intensity with the two thresholds. This creates three zones. These three zones are the most fundamental and concrete training zones, as they are based on your physiology. As mentioned before, lactate is the primary way to determine your two thresholds, and therefore your three training zones. The figure below shows the two thresholds, marked as VT1/LT1 and VT2/LT2(figure from High North Performance). The way to determine the first threshold via lactate is to identify the first increase in the rate of lactate production. In simple terms, you look for the first kink in the lactate line. Often times the first threshold doesn’t have a very defined kink, so it is standard practice to take the first threshold around the 1.2-2.0 mmol/L concentration point. The exact lactate measurement for thresholds changes between people, so the best practice is to take the threshold at the first kink. When in absence of a defined kink, most take the threshold around 1.2-2 mmol/L. The second threshold displays a more defined change of rate, giving an easier point to mark as the second threshold.
In practice, zone one is noted as the endurance zone. This is the area the athletes can exercise at for a very long time with little fatigue. Zone one is where riders will spend the bulk of there time, building their aerobic engine. Zone two is the middle intensity zone. This is characterized by a pace that feels harder, but is sustainable for a longish period of time. In this zone is where a lot of racing is done. This is hard, but is sustainable enough to push for a while. Above the second threshold(zone three) is where output becomes unsustainable. Due to the build up of lactate and therefore lactic acid, zone three exercise is very uncomfortable and isn’t sustainable. Bike races are often won or lost within zone three, essentially who can go the hardest.
How to find Your Two Thresholds
As said earlier, lactate monitoring is the most practiced method to find thresholds. In addition to this, one can find their thresholds via ventilation tracking. This is the lab equipment that has a respirator that tracks oxygen that your breathe in and out of your lungs. While lactate measuring devices are getting more economical, I will share my methods of roughly determining my two thresholds.
My method for finding threshold one is by feel. This method can be easily inflated by your ego so be honest with yourself. If you noticed earlier, LT1 and LT2 coincide with VT1 and VT2. VT stands for ventilatory threshold. As stated before, ventilation rate and oxygen consumption are used in laboratory settings to determine VT1/VT2. The same test is used to determine VO2, by the way. Regardless, VT1 occurs at the point where the rate of ventilation(how fast you are breathing) rises disproportionately to the rate of oxygen consumption, e.g. this is where you start to breath heavier. Thus you can use your breath rate to determine where your threshold is. Instead of counting your breaths per minute, it is common practice to try to say a sentence or hold a conversation. If you are breathing hard enough to make holding a conversation difficult, you are above VT1. If you can get sentences out with strain, you are around VT1. If you can talk without strain you are below VT1. Riding at or below VT1 is the standardized practice for riding at endurance pace.
The second threshold is less easy to pinpoint. Unlike the first threshold, you are unable to determine it by RPE or breathe rate. Again the gold standard is to use a respiration mask in a lab, followed by a lactate meter. After that comes power testing. The very common model for the second threshold is the Functional Threshold Power model. This is tested a few ways and gives a fairly accurate model for the second threshold. There is some variance in accuracy, mainly stemming from the testing methods used. This stems from differences in physiology between riders. Essentially due to biology or previous training history, two riders could have very different power profiles, meaning one could have relatively higher endurance and lower anerobic punch, and vice versa. Due to differences in physiology, it is difficult to get an accurate threshold number with one steady state test. This is because a rider will fully deplete both their aerobic and anerobic capacities to maximize the test. The correct way to determine your second threshold needs to account for both your aerobic and anerobic capacities.
This is where the Critical Power model comes into play. Critical power is a test that typically uses two or three maximal efforts, then calculates both your anerobic and aerobic capacity. The result is a Critical Power value, your aerobic strength, as well as your W’, which represents your anerobic capacity. The critical power metric is found to be the best estimator of the second threshold. This model works well across many athletes as it accounts for multiple energy systems, and with multiple data points(max efforts), it finds two fitness metrics. The W’ metric is how much work over your second threshold you can sustain. Essentially it is how long you can stay in zone three. This is a overlooked metric, but very important as most races are decided in zone three. Read more about Critical Power in my previous blog here. Critical power is held as the next best standard for finding the second threshold.
In sum, the three zone model relies on determining two different thresholds, splitting the intensity spectrum into three zones. These zone are then used to plan and prescribe the proper amounts of intensity, as well as being used to reflect upon training to aid further decisions. Both of these are crucial parts of executing proper training.
Five/Seven Zone Model
The five/seven zone model is one pioneered by Andrew Coggan. He quite literally wrote the book on how to train and race with a power meter. His method relies on finding the second threshold, and calculating more specific training zones from there. Andrew uses the previously mentioned FTP to estimate the second threshold. From this, he has generalized at what percentage of FTP different energy stores are turned on/off, which he then uses to split the intensity model up. To clarify, energy stores aren’t fully turned on or off, just used in different amounts, but the idea still holds. The advantage of using more training zones is to get more granular and have more precision in training. For example, take a rider who rides at a very very easy intensity for 3 hours. Under the three zone model, this three hours counts a zone 1. If this rider would have instead ridden at an intensity barely under LT1, they would still accrue 3 hours at zone 1, but one session clearly did more work and was more stressful. The Coggan training zone model splits the area under the first threshold into zone 1 and 2, giving a coach/athlete a better view of what actually happened.
To be clear, the 5 and 7 zone models are very similar, only differing at intensities above threshold. The 7 zone model simply places one more split above the VO2 zone, giving more granularity at very high intensities.
As well as using FTP as a watt based way to split training zones, Coggan also added max heart rate, threshold heart rate, and RPE as methods of determining training zones. This is important, as they give athletes and coaches another method to prescribe rides by. I will dive into what this means for riders in a later blog, but it is an important addition.
Which Model is Right for Me?
The easiest to eliminate is the five zone model. This was originally made before extremely high intensity training was popularized, and therefore didn’t account for tracking such areas. The seven zone model does everything the five zone model does, plus having more granularity at higher intensities. This is why the five zone model is phasing out of use.
The seven and three zone models both have their strengths and weaknesses. The three zone model excels at giving more accurate models of the two thresholds. This is very important for riders who want to strengthen these areas of their physiology. For the most part training at/around a threshold is the best way to raise that threshold. This style of training is particularly useful for gaining pure fitness. The accuracy of actual thresholds to training zones/intensities give athletes a way to very closely target and control intensity, to have the maximum fitness gained for training stress accrued. This is the core principle of the Norwegian training model, very precise intensity control. This is why the three zone model is primary used for this training method. Where the three zone model falls apart is with intensity granularity. Past the three zones, there is very little specificity within intensity to base your training off. This is why Norwegian method goers rely so heavily on the lactate meter. In the area between thresholds, they use the lactate meter to prescribe and control intensity very closely. The three zone model is really a gateway drug into getting a lactate meter and getting very anal about your training sessions. To be fair, it works extremely well as it get athletes very fit.
What the three zone model lacks is granularity. The seven zone model has more granularity. What the seven zone model lacks is accuracy. The seven zone model relies on an FTP test, which in itself starts flawed, as it is a less accurate measure of the second threshold. From this, Coggan generalizes where the rest of zones should be placed. This is also flawed as specific physiology changes from person to person. This means the true zones for a rider could vary from the seven zone model, as it is generalized for most riders. For example, a rider who has a very developed endurance engine, and also has a very low anerobic strength, could have a first threshold that is closer to 80% of FTP, instead of 75%. This would lead to undertraining at the first threshold. The same could apply for an opposite rider, who could end up training the first threshold too hard. These are both bad. This combined with the inaccuracy of FTP testing in the first place give the seven zone model far less accuracy than the three zone model. When one gives granularity to the three zone model with a lactate meter, it is easy to see which the Norwegian method, which prides itself on accuracy, choses to base itself on.
Before you give up on the seven zone model, I want to add some context. While the Norwegian method is the gold standard for maximizing fitness, the seven zone model gives flexibility. I should remind you that bike racing is far more than fitness, particularly on the amateur level. Being skillful on the bike and smart about how you race plays far more into how you perform in a bike race. I will quickly note that the Norwegian method shines in sports like running and triathlon, which tend to be very not tactical and purely about fitness. In these sports, tactics don’t need much work, as fitness is the main race predictor. In cycling, both fitness and skill predict race performance. For this reason, it makes sense to dedicate some training time specifically to skills practice, not specifically fitness. These sessions don’t control for intensity, thus are very hard to put in a training plan based on the Norwegian method. The seven zone model helps here. The seven zone model is used after a race/race practice session in order to keep intensities in check. The seven zone model is simply a tool to make sure intensities are relatively correct, while allowing flexibility in training/racing.
In sum, the three zone model/Norwegian method is what you use if your training defines your racing, and the seven zone model excels when racing is what defines your training.
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