Monday, January 4, 2010

The Myth of the Cardiovascular / Aerobic Model: Part One

VO2 max: the maximum capacity of an individual's body to transport and utilize oxygen during incremental exercise, which reflects the physical fitness of the individual.

VO2 max is supposed to be important, right? Lance's success stems from his 89 ml/kg/min VO2 max; cross-country skiers have the highest VO2 maxes of any athletes, in the low to mid 90s.

Lactate threshold (LT) is the exercise intensity at which lactic acid starts to accumulate in the blood stream.

Lactic acid causes the burn you feel when doing hard intervals. When your body can no longer keep up with the demand for energy, it goes into oxygen debt. It starts powering your legs with other energy systems, with chemicals, and lactic acid is a byproduct of this. Good athletes have the ability to "clear" the lactic acid from their bloodstreams. Right?

This, the cardiovascular/aerobic model, has been the dominant model since 1920; according to it, great endurance athletes are those who can most rapidly process oxygen and deliver it to their muscles.

Tim Noakes argues for another model.

Consider horses. Draft horses are much larger than Thoroughbred horse, but Thoroughbred horses are not only faster but also, surprisingly stronger than draft horses. The difference is not muscle size, although draft horses are much more muscular, but in muscle type. Specifically, Thoroughbreds' muscles have greater myosin ATPase activity; that is, they have a greater capacity to bind calcium.

In other words, Lance's muscles are what set him apart, not his extraordinary VO2. As Noakes states, "A high VO2 is the result, not the cause, of an athlete's superior exercise capacity."(12)

Of course, the heart itself is a muscle. When it pumps oxygen, the heart itself is sustained. The heart's ability to absorb this oxygen would seem to be a limiting factor. Thus, more important than VO2 is maximum pumping capacity of the heart, which is determined by the flow of blood to the coronary itself.

As predictor of athletic performance, Noakes replaces VO2 max with two factors--muscle composition and maximum pumping capacity.

In my next post I'll examine how focusing on these two factors instead of V02 max and lactate threshold can improve your training.


Tim Rugg said...

ANXIOUS for part 2. Good stuff.

lifein360 said...

If you can also find a way to train these levels without "popping", that would be helpful as well. ;)