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Notes from my Exercise Phys lab: Vo2 Max

Hey everyone,

We did these two tests in exercise phys tonight, and they're easy, and you can do them at home, so I thought I'd share - at least a couple of you will find this interesting.

Vo2 stands for volume of oxygen consumption. It is measured in ml/min and standardized to mL/kg/min, allowing you to compare your Vo2 max to others, and to predict race times (there's a table for this in Noakes' "The Lore of Running.") The unit means that your body is taking in X milliliters of oxygen, per kilogram of body weight, per minute.

Oxygen consumption is how much oxygen your body can take in and use. Oxygen powers the reactions in the body that release energy. Each hemoglobin molecule has four irons on it - each Fe can attach to one O2. Blood also carries lactate out of cells - when you are gasping for breath at the end of an 800 race, it's not that you're needing air... you're getting rid of lactate. Anyway, the more efficient (higher Vo2 max) you are at using oxygen, the faster you can run. A high Vo2 max is great for endurance athletes. Sprints, it doesn't matter (they are anaerobic, meaning they don't use oxygen).

There are two versions of this test; they should both provide the same results. The first is done running. Prerequisite: an 8 minute mile needs to be an easy pace for you (it can't put you over 70% of your Vo2 max, but since you don't know your Vo2 max, I'll tell you instead that an 8 min mile had better be pretty darn easy :). The second should work for anyone around here, because it's all walking, and you're all in pretty decent shape.

Equipment: a treadmill, and a heart rate monitor. If you don't have a heart rate monitor, you can take your pulse 'by hand' or have someone do it for you (this is hard while you're moving, but possible).

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Procedure for the tests:

RUNNING (incline is 0% for all stages)
1. Run for 3 minutes at 5 mph. Take your HR at the end of the interval. You are working at a Vo2 of 30.3 ml/kg/min.
2. Run for 3 minutes at 6 mph. Take your HR at the end of the interval. You are working at a Vo2 of 35.7 ml/kg/min.
3. Run for 3 minutes at 7.5 mph. Take your HR at the end of the interval. You are working at a Vo2 of 43.7 ml/kg/min.

WALKING

1. Walk for 3 minutes at 3 mph and 0% incline. Take your HR at the end of the interval. You are working at a Vo2 of 11.5 ml/kg/min.
2. Walk for 3 minutes at 3 mph and a 5% incline. Take your HR at the end of the interval. You are working at a Vo2 of 18.8 ml/kg/min.
3. Walk for 3 minutes at 3 mph and a 10% incline. Take your HR at the end of the interval. You are working at a Vo2 of 26.0 ml/kg/min.

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To find Vo2 max:
1. Graph data as (Vo2, HR). In other words, your X axis is the Vo2 you're working at (see procedue above) and the Y axis is your heart rate.
2. Run a linear regression (or draw a "line of best fit") on your graph.
3. Calculate your max HR as 220-age.
4. Draw a line Y = (max HR)
5. Find where your lines intersect, and follow it straight down to the X axis. The number it hits is your predicted Vo2 max.

***note: you can also use this graph "backward" to know what HR will achieve what % of Vo2. So if you want to run at 70% of your Vo2 max, you can calculate that Vo2 (math: vo2 max * .7), find that Vo2 on your line, and draw a line straight to the left to the Y axis, and read the (x,y) coordinate it hits. That y value is the HR you need to run at to run at 70% vo2. coming later: the formula to take that Vo2, and calculate the PACE you need to run at.
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Soooo, if anyone wants to try this, I'd love to see some data... we did a couple people's Vo2 max in class but no one did the running test, and I'd just like to see what the data looks like. Also, I'm curious if someone wants to do the run and walk test, and compare results. (do them on different days, and try to control for other variables - like treadmill, who takes your pulse, etc). THIS IS YOUR CHANCE TO BE AN EXERCISE PHYS LAB RAT!!!!!!!!

love,
Alyie

Vo2 Formulae - Calculating Vo2

These allow you to calculate the Vo2 you're working at for a particular pace.

You'll need to convert min:sec/mi to meters/min, which is simply conversion of units:

min:sec/mi --> min/mi --> mph --> m/min
(Multiplying mph by 26.8 will give you m/min)

Use the Walking Horizontal Vo2 formula for speeds less than or equal to 3.7mph. Use the Running Horizontal Vo2 formula for speeds greater than 5mph. Speeds between aren't covered because it's awkward to go at that pace, you're not really running or walking, so pick either formula but neither will be accuraate (sorry 'bout that).

Both of the Horizontal formulae are useful for just that: flat ground, like a track, or a 0% inclined treadmill. There is also a Vertical Vo2 formula, if you know the incline.
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Walking horizontal
Vo2 (mL/kg/min) = m/min * ((0.1 mL/kg/min)/m/min)) + 3.5 mL/kg/min

Walking vertical
Vo2 (mL/kg/min) = m/min * ((1.8 mL/kg/min)/m/min)) * %grade

Running horizontal
Vo2 (ml/kg/min) = m/min * ((0.2 ml/kg/min)/m/min)) + 3.5 ml/kg/min

Running vertical
Vo2 (mL/kg/min) = m/min * ((1.8 mL/kg/min)/m/min)) * %grade *.5

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Notes on the formulae:

The 3.5 ml/kg/min is your (or my, or anyone else's) Vo2 at rest. It must be added in, because you're using that oxygen to keep you alive, PLUS the oxygen for your activity.

% grade on the vertical formulae needs to be a decimal. If you are at a 5% incline, don't multiply by 5. You will get a screwy answer :) multiply by 0.05, and it will be correct.

***THIS IS IMPORTANT! if you are running at an incline and you want to know your Vo2, you need to calculate BOTH horizontal AND vertical Vo2. If you add the, you'll get the Vo2 you're working at.

There are different formulae for walking and running because running requires more oxygen. Why? Look at the mechanics of each - running has a flight phase. Walking does not. That airborne part makes the difference.

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Remember that Vo2 is volume of oxygen you're consuming... running at 5mph on a track, your vo2 is 30.3. If you don't believe me, use the formula and you'll find just that answer. Anyway, that "30.3" means that each kilogram of muscle in your body is using 30.3 mL of oxygen every minute.

Lets say that a bunch of us go out for a run at 5 mph on the track. We are all working at a Vo2 of 30.3 ml/kg/min --- all of us, becuase that is the oxygen consumption required for that pace. So why is that pace hard for some of us, and way easy for others? It depends on what your Vo2 max is. If your Vo2 max is only 35 ml/kg/min, then you are pretty close to your Vo2 max, and that's a hard pace. If your Vo2 max is 60.6, then you're at 50% of your Vo2 max, and it's an easy pace.

By Alyie at 3 October, 2007 - 16:23 | login or register to post comments

example: a 7:30 mile

Running horizontal
Vo2 (ml/kg/min) = m/min * ((0.2 ml/kg/min)/m/min)) + 3.5 ml/kg/min

7:30 = 7.5 min mile = 8 mph
8 mph * 26.8 = 214.4 m/min

Vo2 = 214.4 * 0.2 + 3.5
Vo2 = 46.4 mL/kg/min

See? pretty easy. Now, lets say you're running that mile on a treadmill with a 2% incline,

Horizontal vo2 + vertical vo2 = total Vo2
46.6 ml/kg/min + vertical vo2 = total vo2

Vertical vo2 = m/min * ((1.8 mL/kg/min)/m/min)) * %grade *.5
Vertical vo2 = 214.4 * 1.8 * 0.02 * .5
Vertical vo2 = 3.9 ml/kg/min

46.4 + 3.9 = 50.3 ml/kg/min = Vo2 for a 7:30 mile at a 2% incline

By Alyie at 3 October, 2007 - 16:32 | login or register to post comments

Caculating target pace, given Vo2

Say you want to run at 60% of your Vo2 max, and you want to know what pace that is.

First, calculate the Vo2 you're aiming for. (math: .6 * vo2 max (ml/kg/min).

Next, use that for Vo2 in the running or walking horizontal formula... solve for m/min using algebra.

Convert m/min back to mph, then min/mi, then min:sec/mi.

By Alyie at 3 October, 2007 - 16:34 | login or register to post comments

target pace example

My Vo2 max is 64 ml/kg/min. Suppose I want to run 3 miles at 80% of my Vo2 max. What pace do I need to run?

64 * .8 = 51.2 ml/kg/min (target Vo2)

51.2 = m/min * 0.2 + 3.5

(51.2 - 3.5)/0.2 = m/min

238.5 = m/min

238.5 + 26.8 = 8.9 mph

60/8.9 = 6.7 min/mi

6.7 min/mi = 6:42

So I'd need to run at 6:42 pace.
Again, easy... it's just math!

By Alyie at 3 October, 2007 - 16:38 | login or register to post comments

Calculating caloric expenditure from Vo2

If you know what Vo2 you're working at, and how much you weigh, you can figure out how many calories you've burned in a given workout. When a treadmill (or elliptical, etc) has a "calories burned" number for you, it's just using these formulae. The numbers on the machines are fairly accurate if you've typed in your body weight at the start.

Remeber that we're working in kilograms here. To convert pounds to kilograms (because who in the US knows what they weigh in kg?!), divide by 2.2.

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Step 1: find oxygen consumption

body weight (kg) * Vo2 (ml/kg/min) = ______ mL/min

Step 2: convert O2 consumption (mL) to O2 consumption (L)
_______ ml / 1000 = _______ L

Step 3: Every liter of oxygen requires 5 kcal of energy. Thus, multiply L of O2 by 5. This will give you calories/min.

Step 4: multiply calories/min by minutes of exercise.

(For Bruce: step 5, convert to a useful unit, like cookies. Though this takes a little longer than just converting from the unit of "miles" to "cookie jar miles.")

By Alyie at 3 October, 2007 - 16:45 | login or register to post comments

vo2 from daily log discussion

linking this in case I want to find it again. Like, to study for my final. This is free practice!

vo2 from daily log discussion

By Alyie at 30 November, 2007 - 20:49 | login or register to post comments