Anaerobics Part II
By
Woody Green
of
RUNNERS NICHE
In part one of this article we examined the two ways the body gets
energy. Aerobic, meaning "with oxygen", is the method the body
normally employs. The body "pays" oxygen from the bloodstream to
ATP molecules, they happily split and give off energy that you can
use.
Anaerobic metabolism is the method the body uses to get quick
energy. This is when the body can't "pay" oxygen fast enough, so it
uses a sort of physiological credit card to get energy now, and pay
the oxygen later. We call this "oxygen debt."
When we run longer distances, the bulk of energy has to come from
aerobic metabolism, because the ability of the body to produce
energy anaerobically is very limited. Why, then, should distance
runners care about anaerobic energy systems?
If you race, you use the anaerobic "credit" system. When you make
that little surge to pass someone, when you push through an uphill
section of a road race, or when you turn on the afterburners and
sprint the final two hundred meters to the finish, you get your
energy anaerobically. The lactic acid that accompanies anaerobic
metabolism accounts for the extra discomfort in your legs when you
push to the limit.
To be able to run well in races, you should train to maximize your
ability to produce energy aerobically AND anaerobically. As I said
last month, this is like emptying your bank account AND maxing your
credit cards. You want to spend everything in order to run as fast as
you can.
You train your body to produce energy aerobically whenever you
train in a manner that raises your heart rate significantly. Generally,
20 minutes is the suggested minimum to have an affect on fitness.
(Of course, if you average 100 miles a week, this 20 minute workout
isn't going to do as much for you as someone who is just starting an
exercise program.)
When you go out for a training run and your pace stays significantly
slower than your race pace, you are training your aerobic energy
system. Your body will adapt to the stress of training by "learning" to
take in and deliver more oxygen to the working muscles. There are
also cellular and chemical adaptations in the body that make it better
at using the oxygen and producing energy. This type of training does
very little to make adaptations to anaerobic energy systems, though.
It's like getting a raise in pay, but not extending your credit limit.
Running at a pace close to race pace, but a tad slower, is called
"anaerobic threshold" or just "threshold" training. This type of
training teaches your body to do more work aerobically before it
calls on the anaerobic systems. (The "anaerobic threshold" is the
point at which your body starts pulling out the credit card.)
Training done at about 5 K race pace and faster starts to work the
anaerobic energy systems. When you do intervals, such as 400 meter
runs on the track with a jog recovery, you are using and training the
anaerobic systems. All sorts of adaptations occur in your body with
this type of training. Your body becomes more efficient at producing
energy anaerobically and better able to tolerate lactic acid. But,
here's the interesting part, this kind of training also improves your
aerobic capacity!
It has been shown many times in scientific studies that interval
training improves the VO2 Max, that is the amount of oxygen taken
into the body per unit of body weight per unit of time. Simply said,
you get another pay raise. Interval training, some people call it
"speed work," can actually improve your endurance as well as your
speed.
So, if someone wants to run a great marathon, can they replace their
long runs with short, quick intervals? No. It isn't that simple.
