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February 4, 2007

Science of Sport: Improving Your VO2Max

Why Can't Your VO2Max Value Go To 100?

Lately, you have probably been thinking about how to improve your speed and endurance for the coming year.

One basic way to accomplish both goals is to expand your maximal aerobic capacity (VO2max). As VO2max increases, your endurance and ability to handle high-quality speeds are usually heightened.

But what is the best way to optimize VO2max? To answer that question properly, we first need to understand what actually limits VO2max. It might be the heart: If the heart is unable to send all the oxygenated blood which the muscles are demanding during exertion, then we would have to say that the heart is the limiting factor - it is preventing VO2max from shooting up to a higher level.

On the other hand, if the muscles are unable to utilize all of the oxygen which the heart is kindly sending to them, we would have to say that the muscles are limiting. We would need to figure out some training method to enhance the muscles' parsimonious appetite for oxygen.

So which is more likely to be limiting - the heart or the muscles? This question was actually answered in 1974 when Swedish exercise scientists at the Karolinska Institute in Stockholm asked athletes to carry out their workouts in a hyperoxic environment, e. g., in air with an unusually high oxygen content. When the runners did so, their blood became more highly saturated with oxygen and their VO2max values shot through the roof, even though their hearts were not actually pumping a greater quantity of blood to their muscles (1).

This research revealed that runners' muscles were quite capable of using oxygen at higher rates - if only they could get their "hands" on the exercise-stimulating gas. And so, it was clear that the heart was limiting VO2max during strenuous running, not the muscles. The human heart prevents VO2max from soaring above 100 ml/kg/min, as it does in other animals such as the hummingbird.

Our key question then is: How do you aggrandize your cardiac output - so that your VO2max can be raised as high as humanly possible? Traditionally, we have often said that the best way to do this is to run long distances at moderate intensities - say at around 60 to 70 percent of maximal heart rate. One factor underlying this thinking is that it was originally believed that stroke volume - the amount of blood pumped per beat - reached a plateau at a fairly moderate heart rate of about 140 beats per minute or so. Above this level, the heart was beating so fast that it had less time to fill between beats, thus decreasing the amount of blood sent out per beat.

This was thought to be bad, because the heart - at higher intensities - would never be sending out the max-possible amount of blood per beat and thus would never develop the capacity to send out huge gushers of blood with each contraction. To use a strength-training analogy, it would be as though the heart was "lifting" a light weight with each beat and thus could never develop its full strength.

However, new research reveals that stroke volume does not plateau as exercise intensity increases in runners who train regularly. In addition, other investigations reveal that high-intensity training (rather than high-volume work at moderate intensity) is the optimal way to expand aerobic capacity.

So how can you max out your VO2max? First, carry out a test in which you run as far as possible in six minutes. Measure how far you have run, and figure your average pace for this six-minute exam. For example, if you cover 1600 meters in six minutes, your tempo is 90 seconds per 400 meters. This tempo is actually a good estimate of vVO2max - the minimal velocity which elicits your maximal rate of oxygen consumption.

Once a week, perform 400s at your estimated vVO2max, with equal-in-time-duration jog recoveries (if your 400s take 90 seconds, jog for 90 seconds after each one to recover). Start with six of these 400s and progress to about 10 in successive weeks. After four or five weeks, re-take the vVO2max exam, calculate a new vVO2max, and then work on 800s at this new vVO2max, with equal-time-duration recoveries (begin with three to four 800s and progress to five). After four weeks of this kind of training (eight weeks total), your cardiac output and VO2max will be through the roof - and you will be running faster and with more endurance.

(1) "Cardiorespiratory and Metabolic Functions during Exercise in Hyperbaric Environments," Acta Physiologica Scandinavica, Vol. 414 (Supplement), pp. 1-10, 1974

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Copyright © 2007 Running Research News, All rights reserved. Posted with permission.

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