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Oximeter + bike = VO2 max?

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Frank O'Donnell

Apneic shutterbug
Apr 23, 2003
I reckon that there's probably a way to use my handy pulse oximeter in conjunction with my recumbent stationary bicycle (which displays data like energy output in watts, calories burned, etc) to calculate VO2 max ... but I'm not sure what the approach or formula would be. Can anyone help me out here?
There is no way to calculate VO2 max with an oximeter, unfortunately. The minimum you would need is:
- etCO2 monitor
- oxygen monitor
- two volume monitors
- lots of technical know-how

You need to calculate how much air volume goes into the lungs (on each breath), and how much O2 comes out of each breath, to figure out how much O2 was absorbed/consumed on that breath.

For example,
inhale 20% O2
exhale 10% O2


inhale 20% O2
exhale 16% O2

Under the same conditions, case #1 is higher VO2 max.
Yeah I know this is aproximate, but knowing how many watts you put out,
and knowing that biking effciency is around 0.25 (for every watt you put out,
you 'burn' three), you can put your whole energy production at kcals/min,
and knowing that 5 kcal = 1 liter of oxygen (or was it the other way?? haha)
you can go from watts to ml/min/kg of O2
So, you do a Conconi or incremental power test, see the Power in Watts
when you drop out and then go from your Max Aerobic Power to VO2max

So... onto the numbers... I do a test starting at 100 Watts, incrementing 50 Watts every minute (there are variations on this, like 2,3 minutes, etc) and have to drop out at 400 Watts. So in a minute (by VO2 units definition= ml/MIN/kg) I'm working at 400x60=24kJ,
which are 24kJ / 4.16 kJ/kCal= 5.76 kCal/min. But this is the power put on the bike.. but the body is at 0.25 efficiency, so 5.76 kCal/min x 4 = 23.08 kCal/min the body is 'burning' to put 5.76 (0.25 of this) on the bike.
Now... you use 1 litter of Oxygen to produce 5 kCal of biochemical energy, so for 23.08 kCal/min you absorb 23.08 kCal/min / 5Kcal/litO2 = 4.616 lt/min
So this makes for 4616 ml/min of O2, and with my body weight of 83 kg its
a final number of 4616/83 ml/kg/min = 55.6 ml/kg/min VO2 max

You can also use this 'ramp test' to plot your HR against your Wattage
and know where your Lactate Threshold is by finding a deflection point in the graph. And also if you include a 30 second sprint before dropping out, you can use this test to find your true max hr ON THE BIKE. A fan should be put
for doing this test because above 150 Watts on the bike simply your body cannot dissipate the heat produced and this will produce overheating... which will
make your HR go up and distort the results.. Also you must be fit and healthy and medically checked before attempting this 'max' tests...

Of course (did I say this before?) this is a VERY rough aproximation, but I use this to track progress....

Ready to hear all of you about all the downs of this method... but is the only one I can afford :duh

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