How does Garmin Connect calculate VO2 Max?
12:05am, 29 Aug 2016
CanuteThe FirstBeat technology (which Garmin use) computes VO2 max from HR at a measured submaximal pace and an estimated HRmax. A similar calculation can be doen from Daniels formula based on pace and HR/HRmax.
There are two clever things about the way FirstBeat do it.
1) The select only those sections of the HR trace that appear to fit the expected relationship between HR and speed (eg they exclude section with artefact or where HR is atypical because of hills or terrain.
2) They use a non-linear algorithm for the relationships between HR, HRmax, pace and VO2max. This algorithm is based on data from a large number of athletes. Provided your HRmax estimate is accurate and you are a typical representative of the runners used to derive the algorithm, this non-linear algorithm will give an accurate answer for VO2max to within about 5%.
If you are prepared to use a section of your HR trace which represents steady running at a measured pace on a level surface, and is free of visible artefacts, you can get a fairly good estimate from Daniels formula, which was also based on observations of many runners, but it uses a simple quadratic approximation rather than the algorithm used by FirstBeat.
If you are familiar with Excel, it is fairly easy to prepare a spreadsheet. The required formulae are:
VO2 = -4.6+0.182*pace+0.000104*pace^2 (pace in metres/min)
%VO2max= (HR/HRmax -0.37)/0.64
VO2max=VO2 / %VO2 (VO2max in ml/min/Kg)
In many cases the greatest uncertainly comes from the estimate of HRmax, but that applies to both the Daniels formula and First Beat.
9:06am, 29 Aug 2016
CanuteSorry for the typos and other inaccuracies.
‘Done’ not ‘doen’
The first numbered paragraph should be:
‘1) They select only those sections of the HR trace that appear to fit the expected relationship between HR and speed. They exclude sections with artefacts or where the relationship between HR and pace is atypical because of hills, surface or wind’
However, the constant -4.6 in the equation for VO2 is correct. The combination of linear and quadratic terms slightly overestimates the best fit to the data across the full aerobic range. The fit is improved by subtracting a small constant amount. As a consequence, the formula is inaccurate at ‘tortoise paces’ less than 30 m/min (i.e. about 1 mile/hour).
About This ThreadMaintained by ❄larkim❄
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