Although heart rate training is not as accurate as power-based training, it still provides an inexpensive way to estimate how hard you are working and can help you create a useful training program.
The reason I say “estimate” is because heart rate can vary from day to day for the same amount of effort, depending upon your levels of fatigue, current activities, what you are digesting, and your individual fitness. Two different people of the same age can exhibit very different heart rates for the same level of effort.
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If you have a heart rate monitor, it is easy to set up your training zones with a simple test. This is a much more useful way of doing it than a generic and inaccurate formula based upon age.
This article will show you how to improve your cycling performance through consideration of the energy systems you are using. We will use heart rate zones to guide us, and determine these zones through a simple twenty minute test.
Heart Rate and Energy Systems
Before getting to the test, it is important to establish what we want to achieve by using the heart rate data. Your heart rate is a basic measure of the following:
- How hard you are working
- The duration of your work
- Which energy system is being used
The heart rate relies upon a number of neurological and chemical signals and is just one factor related to the amount of work being done by an individual.
Your body’s energy is produced by a number of mechanisms that all eventually result in the breakdown and reforming of adenosine triphosphate (ATP). Three different energy systems are constantly in use to varying degrees at any given time.
- The first of these is based upon the levels of ATP naturally stored in your muscles. This process might last for a few seconds and then be depleted. Then, the body has to supply more energy from another energy system.
- The second of these is the breakdown of sugars and carbohydrates in the body. These can be broken down with and without the presence of oxygen.
- The third of these is the breakdown of fatty tissues stored in the body using oxygen.
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If you keep on working, eventually the body has to start to supply higher rates of oxygen with energy substrates (fats and sugars), while also delivering a faster rate of waste product removal. It does this by continually assessing the rate of work and the rate of production of waste materials. The result of the greater demand is an increase in heart rate.
Your Performance Depends on Your Energy Systems
If you are a cyclist wishing to improve your performance, then your ability to perform over the duration of your activity eventually comes down to how effectively your energy systems are working. The nature of this feedback mechanism means that, in practice, it takes a while for your heart rate to increase to match the level of demand.
“If you are a cyclist wishing to improve your performance, then your ability to perform over the duration of your activity eventually comes down to how effectively your energy systems are working.”
The diagram below shows the heart rate trace of a time-trial cyclist at the start of the event. The heart rate in this example takes two minutes to build up a steady level.
If you are a sprinter, then production of large amounts of energy over a short duration will rely upon large quantities of stored ATP. Thus, developing large muscles through resistance training would be an appropriate training activity. Although your heart rate will rise to a high level, due to the time lag this measurement may not be an accurate assessment of your actual level of work.
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For longer duration events, developing the ability to consistently deliver and metabolize large quantities of high energy-producing substrates such a body fats would be an appropriate training activity.
(A full discourse of body’s physiology and energy systems is beyond the scope of this article, but I have included a reference for further reading.)
The Twenty-Minute Test to Establish Heart Rates Zones
One way of establishing heart rate zones is to start with a twenty-minute test. A local race, a solo ride, or a session on a turbo trainer can be used for this test. You will ride as hard as you can, trying to keep a consistent level of output for twenty minutes.
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Twenty minutes is used as it represents a trade-off between being too long to cause fatigue and energy substrate depletion and being too short to rely on short-term production from breakdown of sugars and ATP. This average heart rate will be a representation of the highest level of effort you can maintain at the point at which you transition from mainly oxidation of fats and sugars to the breakdown of sugars and ATP. We will call this your twenty-minute heart rate threshold, abbreviated to T20 in this article (to avoid confusion with various other threshold terms in use).
“Twenty minutes is used as it represents a trade-off between being too long to cause fatigue and energy substrate depletion and being too short to rely on short-term production from breakdown of sugars and ATP.”
If we add this heart rate to our previous chart, the twenty-minute average line will be somewhere between oxidation and breakdown of sugars. Going below this level will result in mainly oxidation of fats and sugars. Going above this level will result in mainly breakdown of sugars and stored ATP.
Using Heart Rate Zones to Develop Your Riding
There are many books and training manuals that describe various training zone regimens. These protocols include anywhere from two to five zones, and some even have seven.
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To use your twenty-minute test effectively, you need to refer back to your training goals. Remember, it is by overloading that progression can take place:
- To develop endurance and long-duration riding, your activities need to develop the energy systems that oxidize sugars and fats. This means working at a level below your twenty-minute average, but still retaining a high enough energy production to create a level of overload. An approximate guide to an appropriate level would be at five to ten beats per minute below the twenty-minute average.
- To develop shorter-term bursts of energy, you need to work above this average heart rate, remembering it can take a while for your heart rate to respond. You could work for three or four minutes at a level of five beats per minute over the T20. This would develop resilience to the breakdown of sugars and ATP and the ability to recover quickly.
- For anything shorter than a couple of minutes, heart rate is not a good indicator of effort. Although your heart rate will rise, by the time heart rate has caught up with what you are doing, your interval is likely to be over.
Sample Winter Training Session Based on T20
Warm up and ride for an hour at approximately T20-10 beats per minute.
Short-term break training:
Warm up and ride for 4 minutes at T20+5 beats per minute. Recover by easy pedalling to T20-10 beats per minute. Repeat the cycle for 45 minutes.
- Hargreves, M., and Spriet, L., Exercise Metabolism. Human Kinetics, 2006.
Photo “If you’re not the lead dog” by Adam Barker Attribution 2.0 Generic (CC BY 2.0)