# Skewed heart rate zones

Not a specific Zwift question, but a likely place to find someone with answers.

I’m 66 and returned to regular cycling about a year ago. My max HR is 172 and my FTHR (max 20 min average) is 165. I’m fairly sure these figures are more or less accurate. Using the calculator on the British Cycling website produces the following zones:

Z1: 0-112
Z2: 112-137
Z3: 137-155
Z4: 155-175
Z5: 175+

The lower 3 or 4 zones feel about right compared to perceived exertion. It also fits with my impression that I’m mainly a “slow twitch” person. But I’ll never reach the HR that corresponds to VO2-max.

Is there a sensible interpretation of these figures? Thanks in advance.

I’m 63 with similar HR maxima. While these zones are VERY individual (and, to some extent trainable), but are in flux to the extent they are trainable. Obviously the maximum HR (both) are probably sliding slowly downhill as one ages. The standard zone models have been known to be skewed incorrectly with respect to the “masters” ages and up. That said, I would look at the Zones based on a model that looks at heart rate reserve (especially using percentages of HRR). To calculate your heart rate reserve, you also need an accurate (rested - not overtrained) Resting Heart Rate.

Heart Rate Reserve (HRR) is the difference between your Resting Heart Rate and your Maximum Heart Rate. Many so-called “standard models” make no allowances for individual differences in resting heart rate. By incorporating the heart rate reserve into the equation, in theory a more accurate training zone can be determined. This is known as the Karvonen forumulation, and it’s worth noting that the Karvonen formula nearly always calculates a higher target heart rate than the old 220 minus one’s age nonsense.

The question then remains, if you accept this formulation, what are the correct percentages for each specific zone? Well, I subscribe to the importance of 80/20 polarized training, and also to Seiler’s 3 zone model for simplicity. The demarcation between ventilatory thresholds and lactate response mechanisms seems quite clear to me, from my own experience. So, if you want to slice and dice these zone guidelines to make a 5/7/9 zone model, go for it!

Recovery Zone – 60% to 70% of HRR
Active recovery training should fall into this zone (ideally to the lower end).

Aerobic Zone – 70% to 80% HRR
Continuous or long, slow distance endurance training should fall under in this heart rate zone.

Anaerobic Zone 80% to 90% HRR

But it’s a complicated arena. Even the Karvonen/Seiler methodologies have problems, which are constantly being studied. I can cycle all day at a 105 HR. But at 115, I start to get HR drift after 5 hours. Duration must be taken into account, in combination with intensity zones. That’s the trainable bit. Cycling at 215W for 3 hours would have flattened me 3 years ago. Getting a good lab to start with accurate benchmarks is a crucial step to customizing these structures, too. Gas exchange measures, and lactate metrics should be assessed if you are at all serious about your training.

Luck!

That is a very well stated version of what I consider the correct answer.
I prefer to divide my heart rate into 5 zones instead of 3.(90,80,70,60,50).

If you’re a formula person:
HRR= (max observed HR - resting HR X % zone) + resting HR.

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Thanks both. My “Karvonen” HR zones look a lot more sensible than the ones based on FTHR, so I’m going to use those for the time being and see how they work. I doubt I’ll be visiting a sports lab any time soon – I’m only slightly serious about training, but I do like playing with numbers .

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Just to clarify, the max HR and resting HR should be recent Max and resting HR.
You can define recent many ways (past year, 6 month, 2 years) but the point is, your max and resting HR are not static and they do change over time.
I recalculate my zones yearly based upon the highest HR I saw during the previous 12 months.
I do the resting HR the week I do my calculation.
Ideally first thing in the AM before I get up but am still awake.

I’ve not seen any data on using wake resting HR vs using lowest HR while sleeping.
Now days, so many people wear apple watches and Fitbits, they know what their lowest sleeping HR is.
Year to year, I’ve not seen a big change and I usually round the numbers off anyway to keep them more manageable in my head while riding.

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They are recent – I maxed out on both max HR and FTHR doing an FTP test last week.