University of Northern Iowa



Lab 2

Understanding VO2 Units

The purpose of this lab is to become familiar with the different units used to quantify both oxygen consumption (VO2) and power.

VO2 Units

VO2 is expressed in absolute units and in relative units. The absolute units are a volume per minute and the volume is either milliliters per minute (ml.min-1 ) or liters per minute (l.min-1). The absolute units are expressing the oxygen consumption as a total quantity for the entire body mass. In contrast the relative units are a volume for every kg of body mass per minute (ml.kg-1.min-1 ). The relative units are identifying how much oxygen is being consumed for every one kg chunk of body mass. That is why the volume of oxygen is so much less in relative units than in absolute units.

Converting between the two sets of units for VO2 is very simple and makes sense if you just remember what each set of units is expressing. To convert from the absolute set to the relative set you just divide the absolute units in ml.min-1 by the body mass in kg. To covert from the relative set to the absolute set you just multiply the relative set by the body mass in kg.

To help you understand when each set of units should be used we will compare responses to exercise using two types of exercise, walking and biking.

Instructions for Data Collection: You must collect the data indicated below before you come to lab. You must also do it in the order indicated. Do the bike first, then the treadmill. Record the necessary data on the Excel spreadsheet provided. Send a copy of the spreadsheet in Excel via email to your lab instructor (springem@uni.edu) by 4:00 pm on the second Monday of the semester.

1. Using one of the upright electronic LifeFitness bicycles (not a recumbent) upstairs in the WRC Fitness area, ride the bicycle in the at a level 10 intensity (100 watts) for 5 minutes maintaining 60-90 rpms. As you start riding, put the bike in the Constant Cal/Hr Mode. On the older upright bikes (95Ci) the mode is located on the right side of the bike’s digital panel just to the right of where the numbers are located (See the S label on the diagram at end of this lab). On the newer upright bikes (95C) with the interactive screen, the mode can be selected by going to the Change Program located at the left edge of the video screen. After riding for 5 minutes at level 10 intensity, grab the metal plates on the handlebars and get your heart rate. Do not stop pedaling until your heart rate pops up on the screen. Record your heart rate.

2. Using one of the treadmills upstairs in the WRC Fitness area, walk on the treadmill at as fast a walking pace as you can maintain for 1 mile (most should be able to walk at least 4 mph which is a 15 minute mile pace). About 20 seconds before the end of the mile, grab the heart rate plates and get a heart rate and note the time it took to walk the mile. Record both the heart rate and the time it took to walk the mile (time must be in minutes and fraction of minutes, ie. 14 min 30 seconds would be 14.5 minutes).

3. Using one of the treadmills upstairs in the WRC Fitness area, run on the treadmill on the level at 6 mph for 5 minutes. During the first minute of your run, grab the appropriate place on the treadmill that will record your heart rate and hold until you get a heart rate and then let go and continue running at 6 mph until you complete 5 minutes. After 5 minutes and while still running, grab the heart rate handles again and get your heart rate and record the heart rate. After recording your heart rate, increase the speed of the treadmill to a speed you subjectively feel is a speed you could run at for 15 minutes (the 6 mph may be the speed but if you feel you could run at a faster speed, increase to whatever that speed is). After running at this speed for 1 minute, increase the grade (incline) on the treadmill 2% each minute and continue running until you cannot continue (This should be a maximal effort. If for some reason you cannot perform a maximal effort, tell your lab instructor). When you reach your maximal effort, grab the appropriate place to get your heart rate (try to keep running until you get your HR but if you need to stop running before you get your heart rate, just straddle the treadmill belt until you get your heart rate. Once you get a heart rate, slow the treadmill down to a walk and walk a couple of minutes to cool down. Record your heart rate.

Data Organization

1. A spreadsheet in Excel with the appropriate data will be provided in the appropriate format. In the spreadsheet make all the computations indicated below in separate columns appropriately labeled.

2.In the Excel spreadsheet, compute VO2max in ml.kg-1.min-1 from the 1-Mile walk using the following equation

VO2max (ml.kg-1.min-1) = 132.853 – (0.0769*weight)

- (0.3877 * age) + (6.315 * gender)

- (3.2649 * mile walk time)

- (0.1565 * ending heart rate) - 6

Where: Gender = 1 for male, 0 for female

Weight = pounds

Mile walk time = minutes and fractions of minute (14:30 = 14.5 min)

3. Determine the oxygen consumption at 6 mph and 100 watts using the formula below in the same Excel worksheet by just adding appropriate columns and making the computation. These formula compute VO2 in ml.kg-1.min-1 for the given speed of running and the power on the bicycle. In the equation for bicycling the M is the average weight of the males and females in kg. After computing the VO2 in ml.kg-1.min-1, compute the VO2 in ml.min-1.

|Running VO2 ml.kg-1.min-1 = (mph x 5.36) + 3.5 | |

Biking VO2 ml.kg-1.min-1 = [(watts/mass) x 10.8] + 7.0

4. Calculate the % VO2max for VO2 running at 6 mph and the % VO2max for VO2 biking at 100 watts . Calculate the average values for all males and for all females for all the variables in the spreadsheet.

Answer the following questions in MS Word. Put the name of each member of the group in the top right corner. Double space all responses and number the responses the same as the questions below:

1. Which gender had the highest VO2 while running at 6 mph and biking at 100 W when expressed in relative units? What was the percentage difference between the genders?

2. Which gender had the highest VO2 while running at 6 mph and biking at 100 W when expressed in absolute units? What was the percentage difference between the genders?

3. What is the effect of the mode of exercise (running vs biking) on the differences in VO2 between the genders? Explain.

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