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Setting your Heart Rate Zones

In my last post I looked at how you could calculate your maximum heart rate, a brief look at the theory behind why you might wish to know it and some of the practical considerations to be aware of. However simply knowing the number is of little value unless you can use it within your training plans and perhaps include it in your battery of “Fitness Markers”.

In this post I take a look at Heart Rate Zones, why they exist and suggest a model you might chose to use for yourself.

If you are less interested in the theory and background knowledge. You can use this link to jump straight to the Zone definitions at the end of the post.

A Quick Recap

You will recall that the purpose of knowing how fast our heart is beating is purely to provide a quantifiable indicator as to how hard we are working. There is a small time lag between the power a muscle produces (“work”) and the associated increase / decrease in HR. But this is relatively small and of no great concern as long as you are aware that it will be the case. 

Measuring HR using commercially available wrist based technology, or chest straps, will not provide a completely scientific reading, but for our purposes “close enough”. Be aware that factors such as temperature, skin moisture and even battery strength in the sensor will all introduce measurement errors. In addition (but more usefully), our HR is influenced by the level of external stress we might be under and a reflection of our mood, whether we have recently eaten and also our general health status. The more familiar you become with your HR, the more able you will be to pre-empt when you might be developing a cold for instance. 

But for all its shortcomings, HR (certainly for running) is probably still the best indicator we have for measuring effort and therefore executing a particular training protocol. Our velocity can be influenced by many external factors (wind, terrain, temperature and so on) meaning it introduces too much variability between sessions. At present we can’t measure power output easily, as we can in cycling, although this is on the horizon and will offer a superior solution. Some people utilise Rate of Perceived Exertion, and for more experienced athletes this can be workable. But ultimately too subjective in my opinion to be a reliable tool for performance training. 

In summary therefore we are interested to know our Heart Rate, and more so its relative percentage to our sport specific theoretical maximum, to understand how hard we are working but I would suggest more importantly from a training perspective which energy system we are predominately utilising. This then enables us to execute a session with a specific purpose. Which is a good thing! 

Energy Systems

I do not plan to explore energy systems in detail here; but suffice to outline the most important factors which we will need to know for the rest of this post to make sense;

  1. There are three Energy Systems and these describe the process that our body is using in order to meet the energy demand of our working muscles. But for simplicity, and sufficient for the training purposes of the Endurance Athlete, we can think of two headings Anaerobic Energy production (that being metabolism in the ABSCENECE of oxygen) and Aerobic Energy production (metabolism that requires oxygen to be present). Of the three real energy systems two are Anaerobic and one is Aerobic in nature.  
  2. At any given time our body is using and has activated ALL of our energy systems. They do not work in isolation, but for a given “work load” one Energy System will have prominence. In other words, depending on what we are doing, will determine which energy system is mostly being utilised.
  3. When we are sedentary, through light and moderate exercise, our body will use our Aerobic Energy system. As we move into more intense exertion energy demand is such that we can no longer meet it Aerobically (as that is a relatively time consuming way to ‘make’ energy), so our Anaerobic Energy system becomes the primary system. Importantly, because of how the Anaerobic system works it is time limited. 
  4. For each individual the tipping point between aerobic and anaerobic will vary and also the length of time that Anaerobic exertion can be maintained. Adapting these factors are very common training goals and underpin why we bother with many aspects of training sessions!

There are several ways to identify which system is being used predominately during exercise. The most accurate of which involves taking blood samples every few minutes. Clearly this is not practical for us out in the field. Luckily it is possible to estimate which energy system has predominance based upon the % of MaxHR and in turn these % can be described in ranges… Say hello to Heart Rate Zones! 

Many Ways to Cut the Cake

First and foremost, heart rate zones constructed by any other means than Lactate measured in blood during a ramp test, are NOT an exact science and we are certainly into the realms of ‘an estimation based on an approximation’, but curiously it does seem to work!

Secondly there are many different opinions (expressed as models) as to where these heart rate zones should be. In the world of Endurance Sport some of the more prevalent ones are Jack Daniels (‘Daniels Running Formula’ often used by runners) and Joe Friel’s Heart Rate Zones (popular with triathletes and cyclists). Both of which have various books published relating to this and therefore you can explore their ideas further if you desire. Similarly Garmin have a go at setting your heart rate zones when you purchase their technology. But there are no shortage of others too. 

I have evolved the model I use based on the work of several others, and then combined with the context I am going to be using it in; Endurance Sport training adaption. It works for me and is proving to be equally effective for others that I coach. I am certainly not claiming to have broken any new ground or discovered anything novel! Simply that I have synthesised several ideas that seemed incomplete to me, into a slightly different presentation that makes more sense for coaching methodology.  

Whether you decide to use 5 zones, 7 zones or any other version, I would suggest that remaining consistent with that model is important and understand how you will then apply your zones to a given training methodology. Be aware that if a training plan says x minutes in Zone 2 – you need to know who’s definition of Zone 2 it is talking about. And how to translate that to the model you are using. 

The Common Ground

Pretty much all models agree on some general principles. The body is at rest / warming up or engaged in a level of work that is so light it is not really ‘exercise’. There is then a range of zones that describe intensities where the Aerobic Energy system is most prominent. Then we hit a tipping point where the intensity has increased and outstripped the Aerobic systems ability to keep up, so we become Anearobic. Intensity can then increase a little further until theoretically we die. For clarity hitting this upper limit should not be a training goal and your body will do everything it can to deploy the brakes before you reach a heart attack!

Of important zones to the type of run coaching and endurance support training that I engage in (both for myself and those that I coach), are the following; 

  1. The point at which the body is warmed up. This is important to avoid injury and to know that I am actively producing some level of “work output”. Very definitely principally using the Aerobic Energy System. 
  2. The fuel source that the Aerobic Energy System is likely to be using; Fat or Carbohydrate… (A lot of people are interested in exercising to ‘burn Fat’ but fail to do so as they are in totally the wrong heart rate zone. Contact me if you want to know more about this specifically!). You will recall that in earlier posts I wrote about Eating Clean and Getting Fat, understanding Macronutrients? You are now at a point of understanding the importance of eating correctly for the type of exercise you are doing. In terms of Heart Rates I want to know if I am in low aerobic or high aerobic to understand which fuel source is being relied on. 
  3. Next I want to understand the tipping point (approximately!) of when I switch into my Anaerobic Energy system. This will likely occur within a range that I can describe. 
  4. Finally, I want to know when I am definitely dependant upon my Anaerobic Energy System. This is important because in this ‘mode’ I can produce a LOT of power (which is one reason we do strength & conditioning training…) but for a limited amount of time. Obviously if I can find ways to train myself to produce more power for longer, this is a VERY GOOD thing even for an Endurance Athlete. Hence the need to know when I in my Anaerobic Zone and for how long in certain training sessions. 

The Zone Definitions

Finally, the model that I use and how to calculate it. I am interested in knowing where I am in terms of my Aerobic Range and similarly my Anaerobic Range. I also know there is a transitionary “grey” zone as I move from one to the other:

ZoneDescription FromTo
Z1Rest / Warm-up1%69%
Z2Low Aerobic70%72%
Z3High Aerobic73%76%
Z4Transition Zone77%81%
Z5Low Anaerobic82%87%
Z6High Anaerobic88%99%
Percentage are expressed as % of MaxHR.

Key take away points:

  • This is not a precise science, but it does give a foundation to many approaches to training.
  • Understand there is a margin for error in this, so don’t get OCD about being at 76% or 77%. It won’t matter.
  • This is useful for Endurance Athletes (much less so for strength or sprint athletes). In running an Endurance Event is typically a 3000m race and upwards. 
  • There are many different views on this, and they are only views. Find one that makes sense to you and you can trust then stick with it. Ultimately there is more in common than in conflict between pretty much all the mainstream models. 
  • MaxHR is mainly useful to be able to calculate Zones . Zones are only useful when linked to a training plan that you can follow consistently. 
  • Naturally you will need a Heart Rate monitor to be able to follow a HR based plan. Monitors have their own margin of error, so try and stick to the same physical device and use it in a consistent way. 

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