# Calculating the power that elicits a % of VO2max, based on results from a VO2max test.

#### tomos

##### New Member
Hey

For my dissertation I am performing a VO2max test on an SRM ergometer. I then need to work out what power would elicit 70% of their VO2max.

Is there an equation that calculates this?

For example (numbers pulled out of the air here)

A VO2max of 60 ml/kg/min is achieved, and the power at which exhaustion occurred is 500W.

Does this mean to cycle at a steady state of 70% VO2max, they would cycle at 70% of the power at exhaustion, i.e 350W

I would really appreciate some help here. I have searched for hours for an answer and have come up short.

Originally Posted by tomos
Hey

For my dissertation I am performing a VO2max test on an SRM ergometer. I then need to work out what power would elicit 70% of their VO2max.

Is there an equation that calculates this?

For example (numbers pulled out of the air here)

A VO2max of 60 ml/kg/min is achieved, and the power at which exhaustion occurred is 500W.

Does this mean to cycle at a steady state of 70% VO2max, they would cycle at 70% of the power at exhaustion, i.e 350W

I would really appreciate some help here. I have searched for hours for an answer and have come up short.

350 W would be considered 70% of their 'Wmax', and would elicit significantly more than 70% of VO2max (since to achieve a plateau in VO2 during an incremental or ramp exercise test means progressing to a power that requires >100% of VO2max).

Instead, you need to establish the relationship between power and VO2 during *sub*maximal exercise for each subject (i.e., each individual's cycling economy), then use that relationship to back-calculate to the required power.

As an example: assume that your subject above weighs 80 kg. Furthermore, assume that their personal VO2-power relationship agrees exactly with the ACSM prediction equation, i.e., VO2 (L/min) = 0.0108 x power (W) + (7 mL/min/kg * 80 kg). You want them to exercise at 70% of (60 mL/minlg * 80 kg), or at 3.36 L/min. To elicit that VO2 they would need to exercise at (3.36 - 0.56)/0.0108 = 259 W.

Alternatively, you skip all of the above and simply have them exercise at 60-65% of Wmax. Unless it is a cardiovascular study, this simpler approach is likely going to be just as good, as 1) inter-individual differences in metabolic fitness (a.k.a., lactate threshold) means that 70.00000....% of VO2max really isn't the same for everyone in the first place, and 2) ideally, you're doing a longitudinal study, i.e., each subject is only being compared to themselves anyway.

Hope that helps...but what I'm left wondering is why you're having to seek an answer to your question here? Presumably this was covered in coursework, and/or you could ask your dissertation advisor?

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