Science: A better formula for fitness

By Joe Beer | Wednesday, December 12, 2007 12.00am

How do you work out your maximum heart rate? The simple formula '220 minus your age', right? Wrong. Sports scientists have discovered a better formula, but it's still no substitute for a proper lab test.

That simple formula allows fitness seekers and athletes alike to find out their maximum heart rate by simply subtracting their age from 220. They can then use this number to estimate HR zones to regulate training efforts, recovery intensity and race pacing (see 'Heart rate zones', below). It is so simple and has been quoted by so many personal trainers and magazines that it has become a fact without anybody actually citing the original research.

If I said that I could work out your weight by knowing your height, how happy would you be to take that as fact?

Some get max tested by a sports science department or by one of the range of companies who offer it. Others work out their own max HR derived from beating themselves up in race or hill climb. However, most use '220 minus age' to guesstimate their maximum heart rate. For a very few it actually works out right - it did for me briefly but has been wrong many more years than it has been right.

Note that the 'maximum minus minimum' Karvonen theory of heart rate reserve for exercise prescription is just that, a theory. It uses maximum and resting HR to give approximate training areas. However, published research almost always uses HRmax to define training prescription, assess output or ascertain correlations with lactate levels and so forth. Indeed little empirical evidence has actually been found to support Karvonen. It varies such that you would need to take resting HR every day and work out zones based on each day's resting HR data, a chore. So forget it.

Where did it come from?

Coaches, sports scientists and magazines have fuelled the 220 minus your age theory to the extent that it is now a 'fact'. It took two researchers, Robert Robergs and Roberto Landwehr, until the end of the 20th century to fully investigate the origins, accuracy and legacy of the '220 minus age' formula. And it turns out that for one, the first published maximum heart rate formula (HRmax) was actually 212 - (age x 0.77). Secondly, even though a host of research papers and textbooks refer to the equation few cite legitimate references.

Those authors that do cite '220 minus age' as originating from 1971 research by Fox et al fall into a trap: it appears, subsequent research has found, that Fox reviewed 10 studies and then set an 'arbitrary' equation, the hallowed '220 minus age' formula. What this source of the formula actually observed was: "no single line will adequately represent the data on the apparent decline of maximal heart rate with age. The formula maximum heart rate='220 minus age' in years defines a line not far from many of the data points".

It was not a formula, it was a bad guess. So, Robergs and Roberto reproduced the data points that the whole myth of 220 had been resting upon and then did clever statistical analysis. Low and behold they found that it did not support the 220-age 'equation' but instead it was: 215.4 - (age x 0.9147).

There's more...

So, the modern day myth debunkers Robergs and Roberto set forth to see what studies on healthy people tended to estimate as being HRmax. They used 30 of the most robust studies to derive a formula of 208.754 - (age x 0.734) [2]. Yet, in their conclusion these authors actually cite a male-only study from 1994 that equates to a HRmax of 205.8 - (age x 0.685).

Trying to estimate your HRmax from an equation is fraught with problems. Even the experts have varying conclusions.

But three things are clear:

1. HRmax is a personal trait that cannot be predicted and can only truly be found by an exercise test on that individual of some sort. But if you want to guess it 205.8 - (age x 0.685) is better than most equations.

2. HRmax is mode specific so if you subsequently run, row or swim your HRmax and perceived effort will not exactly mirror the HR data you get on the bike.

3. Experience of your HR data in training and racing can build your knowledge of personal zones, the correlation with perceived effort and HRmaximum.

Heart rate zones

Given the simplicity of the 220-age formula it seems that keeping it simple is what busy riders want. I therefore use just a three-zone training regime, backed up by research of elite HR training data and used effectively to train athletes to PBs, goal achievements and medals.

Zone 1. 55 to 80% HRmax You should do at least two thirds of your training at a steady state eff ort - less than approx 75%HRmax is better for beginners.

Zone 2. 81 to 85% HRmax This can be useful late winter to early season to start to work the system harder but once racing or doing intervals this is no mans land. Fitness riders can use this for their interval work but it is not to be used for continuous sessions.

Zone 3. 86% and above Around a third of training time is performed way above lactic threshold, ideally as intervals of 3 to 10 minutes in other sports.To hit this zone on a bike try a series of 8-12 30 second sprints with 4.5 mins of rest in between.

Note maximum power eff orts of 8-10 seconds will raise HR around 10-15 beats, in this scenario HR does not refl ect the training eff ort as well as power measurement. For a table to estimate your HRmax based on the new 205 equation go to www.JBST. com, click downloads, then click tools and look under HR Tools.

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