View Full Version : VO2 from conconi test, wattage and max aerobic power?

02-06-2011, 02:06 PM
I'm interested in determining VO2 non-invasively. I came across this procedure. It would be good enough for me if it is an approximation, or could be validated from an actual VO2 test. Do you notice any flaws in the logic? : From: BlueIcarus URL: [forum doesn't allow URLs] Yeah I know this is aproximate, but knowing how many watts you put out, and knowing that biking effciency is around 0.25, you can put your whole energy production at kcals/min, and knowing that 5 kcal = 1 liter of oxygen 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 Cheers!!

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