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My name is Sarah Wilkinson.

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This is the second of the video series

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showing how to convert VO2 values.

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In this video I am going to show you how to

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easily convert a relative VO2 value to an

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absolute VO2 value.

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Please make sure you have watched the first video

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which shows you the basic mathematical principle

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I am using to do these conversion factors.

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As a well as a little background of what VO2 is.

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In this video I am going to show you how to

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convert a relative VO2 value,

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which is measured in ml per kg body mass per minute

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to an absolute value, in litres per minute.

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I am going to set it up by putting [br]my relative value on the left hand side

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and on the far right hand side, I have put in

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what I am trying to convert to,

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so the absolute value of L per minute.

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Let's use a theoretical example, and say we have

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someone with a VO2max of

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45 ml of oxygen per kilogram body mass[br]per minute

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This is essentially 45 ml per 1kg minute.

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Normally we don't put the '1' in.

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Just to show you what should be on the denominator.

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I need to do two conversions factors.

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I need to convert millilitres to litres

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minutes will remain, but I [br]need to remove kilograms.

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For some people, whether to divide or multiply by 1000

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and divide or multiply the the body mass becomes

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a little confusing.

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So setting up in this manner helps you decide

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whether you need to divide or multiply.

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Again the principle I am using,

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is that if one unit is on the numerator, [br]for this example 'ml'

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I can multiply by a conversion factor and put[br]the 'ml' on the denominator in the conversion factor,

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and those two will cancel out.

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We know how how many millilitres are in 1 litre.

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That is what we are trying to convert to here.

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There is 1000 ml in 1 L.

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If I stopped at this point, by cancelling out 'ml'

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I would take 45 and divide by 1000.

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However, if I stopped at this point,

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I would end up with litres per kilogram per minute

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Remember an absolute value is measured in L/min.

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Therefore, I must also "get rid" of the kilograms.

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So I need to either divide or multiply by kg.

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For some people, what to do may be clear to you.

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For others, not so much.

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We are going to use the same principle again.

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We need to "remove" kg in the next conversion factor.

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And it is on the denominator, on the left hand side.

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In order to cancel it out, I need to put is on the numerator.

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Remember top is going to cancel out bottom.

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Let's say for this example, the person is 78 kg.

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And again that is over '1'.

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'kg' will cancel each other out.

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Top cancels out bottom.

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To finish this off, all I need to do, is multiply all

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numbers together and [br]divide by all the bottom numbers.

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Because anything divided or multiplied by one

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is one, I am going to worry about the numbers

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that are not one.

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I am going to take 45 and multiply it by 78

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and divide by 1000.

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This gives me the answer of 3.51 litres per 1 min.

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In this example, I have converted a relative VO2max

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of 45 ml per kg per minute and converted it

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to an absolute value of 3.51 litres per minute.

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Let's do another example now.

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I want you to convert Stanley's relative [br]VO2 of 30 ml per kg per minute

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to an absolute VO2 value in L/min.

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His body mass is 80 kg.

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Please pause this video now. [br]Try this out on your own.

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Once you have come up with the answer,[br]or if you get stuck, press play again.

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Again we are converting a relative value in ml per kg per min.

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to an absolute value, in L/min.

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Stanley's relative value is 30 ml per 1 kg minute

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We want to convert ml to L.

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We set it up so that the numerator [br]cancels out the denominator.

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We know there is 1000 ml per 1 L.

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'ml' cancel out.

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We need to multiply by kg because

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in the relative value it is on the denominator.

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We need to kg on the numerator.

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And we know Stanley is 80 kg.

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'kg' cancel out.

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In this example, I am going to take

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30 multiplied by 80 and divide by 1000

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to get my absolute value of 2.4 L/min.