# Simple question about an Expression

1. Jun 21, 2009

### X_Art_X

Hi Guys,
I'm doing a fitness course, and trying to understand an exercise in my text book
involving the prediction of a person's volume of Oxygen uptake.
The test is done in an indirect way, predicting V02 Max based on physiological responses to exercise.

The Procedure goes like this:

1. Record the client's weight in kilograms, and record their resting heart rate.

2. Instruct the client to step up and down to a metronome at a rate of 22 steps per minute.

3. Once 3 minutes has elapsed, measure the client's heart rate for 15 seconds, and multiply
that figure by 4, to give a heart rate in BPM (beats per minute).

4. Use the following equation to obtain a predicted V02 Max in l.min-1:

VO2 max (mL.kg-1.min-1) = 65.81 - (0.1847 hr bpm)

Now note that the -1 in the text book is a small "to the power of" style of printing set to
the top right of the character to it's left, just like the 2 in O2 is a small 2 printed to the bottom right of the O.
Also there is a dot over the V which I know means that this volume is to be expressed per unit of time.

Now I'm no math guru, but:
1. Why do we measure the client's weight at all?
2. Why do we take resting and working heart rate and only appear to use one?
3. What does this equation mean in English?

Cheers, Art.

Last edited: Jun 21, 2009
2. Jun 21, 2009

### X_Art_X

Photo of the text book:

3. Jun 22, 2009

### daviddoria

I'd assume $$O_2$$ is Oxygen, and $$kg^{-1}$$ means "per kilogram" (i.e. inverse kilograms = $$\frac{1}{kg}$$.

4. Jun 22, 2009

### tiny-tim

Hi Art!

3. It means "the maximum rate-of-change" (that's the dot, of course) "of the volume of oxygen (measured in units of millilitres per kg per minute) equals 65.81 minus the heart rate (in beats per minute)"

1. Because the LHS of the formula says "per kg", so you have to put the weight in.

2. dunno