My Walking Test

Brian J. Sharkey's Fitness & Health has a formula on page 83 which lets me estimate my VO₂max, a measure of how much oxygen my muscles are able to use, at the extreme of aerobic intensity or effort.

Though this figure is often called an individual's "aerobic fitness" score, it doesn't really measure endurance, only the highest intensity of aerobic exercise one can sustain for spans of 5 to 15 minutes at most. The figure is expressed in milliliters of O₂ per kilogram of body weight per minute (ml/kg/min).

The formula is:

VO2max =	132.853
	- (0.0769 x weight in lbs.)
	- (0.3877 x age in years)
	+ (6.315 x 0 for female, 1 for male)
	- (3.2649 x time in mins., to nearest hundredth)
	- (0.1565 x heart rate in beats/min at end of test)

Today I speed-walked a 1.0-mi. (1.6-km) course (2 laps x 0.5 mi./lap). I did it in 15:40, which in decimal form is 15.67 minutes. My heart rate at the end was 154 beats per minute. Given that my weight is 165 lbs., my age is 58 (or will be in less than a week), and I am male, my VO₂max computes to 29 ml/kg/min, rounded to the nearest whole number.

For good measure, I did a third lap, which gave me a total walking time of 23:30 for 1.5 mi. (All three laps had exactly the same time: 7:50!) At the end of the third lap, after I had put on a final burst of speed which put me just on the edge of a run, my HR was up to 163 bpm — quite close to my measured maximum, 170 bpm.

An aerobic fitness score of 29 puts me in the low fitness group, the one for scores under 35. Scores of 35 to 45 are of medium fitness. Scores over 45 are of high fitness.

It's probably a fallacious extrapolation, but if my same aerobic fitness score could be carried over from walking to running, Fig. 4.4 on page 84 of Sharkey's book suggests I ought to be able to run 1.5 miles (2.4 km) in less than 15:30. Yesterday, the best running time I could manage for that distance was 22:10, only 1:20 faster than I can walk the same course. Of course, I didn't pace myself aright and had to walk part of the way anyway.

Based on my experience, I'd have to say that Sharkey is corrrect in claiming that aerobic fitness is dependent on the specific activity and muscle group being exercised. I assume it will take me quite a while to get my running fitness score up to 29.


In fact, there seems to be a catch-22 operating here. Since I'm of low fitness, page 102 tells me not to exceed 75% of my maximum heart rate: nominally, my anaerobic (lactate) threshold. Exercise over that threshold does not qualify as aerobic.

With an HRmax of 170, my 75% level is 128 bpm ... and I find it impossible to jog on level ground for more than 50-75 paces without putting my HR above that!

But if I stop jogging and just walk, although my HR goes back down nicely, then I'm not training my muscles for the specific activity of jogging or running! Catch-22!

I'm considering finding a fairly long downhill stretch in my area — luckily, there are some — and jogging easily down it at < 128 bpm. Then I'd walk (as slowly as possible) back up the hill and do it again, and maybe again.