Determination of VO2 from conconi test, wattage and max aerobic power?

[juanfhj]

Determination of VO2, lactate, max HR from wattage and max aerobic power?

I'm interested in determining VO2 non-invasively. I came across this procedure. Will it work? Do you notice any flaws in the logic?
:
From: BlueIcarus
http://forums.deeperblue.com/freediving-training-techniques/58008-oximeter-bike-vo2-max.html

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!

 

[Zefram]

I would like to provide some feedback on your proposed method for determining VO2, lactate, max HR from wattage and max aerobic power. While I appreciate your efforts to find a non-invasive method, there are some flaws in the logic and potential limitations with this approach.

Firstly, using a bike's efficiency factor of 0.25 to estimate energy production is not accurate for all individuals. Efficiency can vary greatly depending on factors such as fitness level, body composition, and bike setup. This could result in significant discrepancies in the calculated values.

Additionally, using a ramp test to determine VO2 max and lactate threshold can also lead to inaccurate results. These tests are highly dependent on the individual's effort and can be affected by external factors such as fatigue, hydration levels, and nutrition. A more accurate and reliable method would be to use a graded exercise test with gas exchange analysis, which takes into account both oxygen consumption and carbon dioxide production.

Furthermore, using a 30-second sprint before dropping out of the test to determine max HR could also lead to inaccurate results. Sprinting requires a different energy system and could skew the results for max HR. It would be more appropriate to use a separate test specifically designed to determine max HR.

Lastly, it is important to note that this proposed method may not be suitable for everyone. Individuals with certain medical conditions or taking certain medications may not be able to safely perform a max test or may have different physiological responses to exercise. It is always best to consult with a healthcare professional before attempting any max tests.

In conclusion, while your proposed method may be a cost-effective way to track progress, it may not provide accurate and reliable results. I would recommend using more established and validated methods for determining VO2, lactate, and max HR.