The Fitness Test Result Nearly Killed Me

(VO2 max estimation method comparison)

Alan McDonley, Jan. 2007

Recently, as part of an employer sponsored fitness assessment, I chose to take a 1.5 Mile Aerobic Fitness Test. The test was described as "run or walk for 1.5 miles and time yourself. The objective is to cover the distance in the shortest time possible." When I entered my resulting time into the website calculator, I received a surprisingly poor result. After more research, I have concluded the website calculator is not appropriate to the test and found validation in the fitness assessment method I have been using for the prior seven months.

Seven months ago, a "negative" (no excessive risk) Bruce Protocol stress test reported I had a "mild to moderately reduced exercise tolerance". My time was 6 minutes 16 seconds, which correlates to a VO2max of 21 by the estimator:

VO2 max=14.8 - (1.379 × T) + (0.451 × T*T) - (0.012 × T*T*T)

That was an indication of "very poor" fitness for my age, and I resolved to begin exercising three times a week at a local community center.

Since I had not been exercising much and was then 53 years old, I decided I should purchase a heart monitor to make sure I did not exceed the guidelines for my age. I chose to purchase a Polar F11 watch primarily because it also contained a "fitness test" function.

The F11 fitness test measures heart rate variability during a five-minute undisturbed rest lying on the floor and reports an estimate of VO2max. Before beginning my exercise program the watch estimated my VO2max at 27, which correlated to "poor". That assessment was higher than the Bruce Protocol test result, but still strong motivation for me to start exercising.

I continued to perform the F11 fitness test periodically. After the first two weeks my VO2max moved up slightly to 31. The test results remained quite constant until beginning a slow climb in the third month of exercise. By the middle of the fourth month I had entered the "good" range with a test value of 37 and the slope was looking good. At six months I was coasting along the bottom of the "very good" with a value of 42.

In the seventh and eighth months, I didn't work hard enough, skipping two whole weeks, twice in fact, and my F11 test score dropped back into the "good" range with values around 40.

When my employer enticed me to do a run/walk treadmill fitness test, I was excited to see if the result would correlate with my Polar F11 test results. I warmed up for a tenth of a mile at 2 mph, and then started the stopwatch and distance count. I ran at 6 mph for a short while till my heart rate was pushing 95% then backed off the speed to 4.2 mph to hold a steady 90% (150 bpm) till the 1.5 mile mark at 21 minutes even.

I rushed home to plug in my result and when I did, whoa baby, there's a problem here. The fitness assessment website calculated the VO2max for my 21 minute run/walk as 26.5 and labeled my fitness as *poor*. It appears that the website is using a "maximal effort" VO2max estimator developed by KH Cooper. There are many Cooper tests, and several sites list the 1.5-mile Cooper estimator as:

VO2max = 3.5 + 483 / (time in minutes)

This was quite a shock. The next morning I tested myself with the Polar F11. The test estimated a VO2max value of 42, which is the bottom of the "very good" for my age.

Thanks to the Internet I was able to discover two more ways to interpret my treadmill test that correlate extremely well with my Polar F11. The first is a study by Brigham Young University of telling subjects to run, walk, or jog "somewhat hard, at a steady pace" for 1.5 miles. By having the subjects also perform a standardized maximal graded exercise test they developed estimators for the 1.5-mile sub-maximal of:

VO2 max = 65.404 + 7.707 x gender (1 = male; 0 =female) - 0.159 x body mass (kg) - 0.843 x elapsed exercise time (min; walking, jogging or running).

VO2 max = 100.162 +/- 7.301 x gender (1 = male; 0 =female) - 0.164 x body mass (kg) - 1.273 x elapsed exercise time -0.156 x exercise heart rate

Using the first estimator, my 1.5-mile test would indicate a VO2max of 42, exactly the value of my Polar F11 test.

Using the second formula, (with a +7.301 male coefficient), gives a value of 43. The formula is taken from the abstract citation and has a plus/minus in front of the gender coefficient. Using the minus coefficient yields a 29, which does not agree with their non-heart-rate estimator.

Next I found the Rockport Walking Fitness Test. This is a 1-mile sub-maximal walking test with instructions "Walk 1 mile as fast as possible". The estimator for this test is:

VO2max = 132.853 - (0.0769 × Weight in lbs.) - (0.3877 × Age) + (6.315 × Gender: 1=male, 0=female) - (3.2649 × Time) - (0.1565 × Heart rate)

Since I "walked" at a steady 4.2mph at 150 bpm for most of my 1.5-mile test, I can use 14 minutes (21min * 1/1.5), which results in a VO2max estimation of 43, again close to the Polar F11 heart-rate variability test value.

As a result of this shock and the further research, I now have increased confidence in the Polar F11 VO2max estimation and feel that I can use the watch to measure the results of my exercise program. I feel "very good" about my exercise program results, although I don't actually believe that I have achieved "very good" fitness!

Update: June 2007 - I've been doing the C25k (couch to 5k in 9 weeks) running program for the last five months now. I've discovered by doing a running Conconi test that my HRmax is 20 bpm higher than age predicted so I can allow my heart rate to go over 150. I still am no where near the "average" but I am now able to continue with the program. I am able to run 8 minutes at a 17:00 mile pace (3.5mph) and my heart rate levels off around 160.

Go to Alan's Home Page

References:

a) Bruce Protocol VO2max estimator:
http://www.brianmac.demon.co.uk/bruce.htm

b) Cooper 1.5-mile VO2max estimators:
http://www.exrx.net/Calculators/OneAndHalf.html

c) BYU 1.5-mile sub maximal VO2max estimator:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11926486&dopt=Abstract

d) Rockport Walking Fitness Test VO2max estimator:
http://www.brianmac.demon.co.uk/rockport.htm

e) Polar F11 Heart Rate Variability:
http://www.heartratemonitor.co.uk/research.html