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VO2 max: What is it, Why
is it so important, and how do you improve it?
Exercise physiologists define VO2 max as your maximal
rate of oxygen consumption. It is a measure of your capacity
to generate the energy required for endurance activities
and is one of the most important factors determining your
ability to exercise for longer than four to five minutes.
Improving your VO2 max by 10 percent without changing any
other performance factors can take more than a minute off
your 5k time, and is an essential factor in races from 800
meters to the marathon. Your sedentary VO2 max values are
genetically determined. However, all individuals can make
drastic improvements in VO2 max with the right training
stimulus. Thus, to attain your best possible performances,
VO2 max improvement is one aspect of your training that
should not be ignored.
There are two ways to take VO2 max to its highest possible
levels; increased volume and increased intensity. Studies
show that sedentary people can improve VO2 max by over twenty
percent when they begin a running program of 25 miles per
week. By increasing mileage to 50 miles per week, VO2 max
is improved a further ten percent. Unfortunately there are
diminishing returns of VO2 max increases with increased
mileage, so drastic improvements will not occur indefinitely.
Based on the available research, it seems that maximal VO2
max gains are achieved with a weekly running volume of 60
to 90 miles. Although increases in weekly mileage have shown
to be particularly effective at increasing VO2 max, it is
important to remember that mileage should be increased gradually,
with careful attention towards preventing over-training
and injury. Also, VO2 max improvements only occur if you
are keeping running intensity the same as you increase your
mileage. If you increase your mileage, but slow down your
daily running pace, little improvement will occur in VO2
max.
This brings us to the topic of intensity, the second method
of enhancing VO2 max. Intensity has actually been proven
to be more potent enhancer of VO2 max than volume. For VO2
max improvement to occur, training runs should be conducted
at an intensity of at least 70 percent of VO2 max. Seventy
percent of VO2 max corresponds to a pace that will bring
your heart rate to 75-80 percent of maximum. Running at
intensities close to 100 percent VO2 max is the best thing
you can do to elevate your VO2 max. This corresponds to
about two mile race pace, so unfortunately this intensity
cannot be maintained for very long, and training this hard
every day would quickly lead to over-training and/or injury.
The best way to complete a significant volume of running
at 100 percent of VO2 max is to use intervals of three to
five minutes at 3k to 5k race pace with about equal recovery
between each interval. By dividing your workload into intervals,
you can run for more total minutes at 100 percent of VO2
max than if you attempted a continuous run. One interesting
note is that running faster than 100 percent of VO2 max
will not improve it more than running at 100 percent of
VO2 max, and is likely to leave you more fatigued and unable
to complete a high volume of work. Faster running is necessary
to enhance other performance factors which I won't go into
here, but when your focus in on enhancing VO2 max, a higher
then 100 percent intensity should not be used.
Q & A on V02 Max
1. What are some different levels of VO2 max, and what
do these numbers mean?
VO2 max values, typically expressed in ml/kg/min., can
vary between 20 and 90 ml/kg/min. The average value for
a sedentary American is about 35 ml/kg/min, while elite
endurance athletes average about 70 ml/kg/min. Your sedentary
VO2 max value is primarily determined by genetics (a sedentary
person may have a VO2 max value as high as 50 ml/kg/min.
or as low as 20 ml/kg/min). Although anyone can improve
their sedentary VO2 max value through training, this genetic
variation helps explain why everyone can't train themselves
to be elite.
2. What are some of the highest levels of VO2 max ever
recorded?
The highest VO2 max value ever recorded, 93 ml/kg/min,
was from a Scandinavian cross country skier. Steve Prefontaine,
at 84.4 ml/kg/min, had one of the highest VO2 max values
recorded in elite runners. Grete Waitz had a VO2 max of
73 ml/kg/min. when she was running at her best, one of the
highest recorded values for women and on par with the values
for some elite men.
3. How do some elite runners make up for lower levels of
VO2 max?
Although all elite runners have VO2 max values well above
the population mean, the correlation between VO2 max and
performance is not absolute. Derek Clayton only had a VO2
max of 69 ml/kg/min. and Frank Shorter only recorded a value
of 71 ml/kg/min., yet both of these runners ran marathon
times of under 2:11 and surely outperformed runners with
higher values. This variation in VO2 max values among the
elite is possible because VO2 max is only one of several
factors that determine running performance. These other
factors include mental attitude (ability to tolerate pain),
running economy (how efficiently one runs), and lactate
threshold (fastest pace you can maintain without accumulating
large amounts of lactic acid in your blood). A runner with
a relatively low VO2 max, but high in these other performance
factors, could outperform a runner with a significantly
higher VO2 max but with poor running economy and a low lactate
threshold. For example, Derek Clayton and Frank Shorter
compensated for their lower VO2 max values with their high
efficiency and ability to run their marathons at a high
percentage of their VO2 max without accumulating too much
lactic acid (high lactate threshold).
4. Why do some people assimilate more oxygen than others?
Although there is still some debate among physiologists
as to what limits VO2 max, the variation in maximal oxygen
consumption in our population is likely determined by several
factors. In order to produce the energy necessary for our
muscles to contract at high rates, there must be a delivery
system to bring oxygen to the working muscle cells as well
as a means of utilizing this oxygen for aerobic respiration.
The delivery of oxygen to muscle cells is limited by hemoglobin,
the oxygen-binding protein in red blood cells (this is one
of the reasons women tend to have lower VO2 max values than
men), the number of capillaries surrounding each muscle
cell, and the maximum volume of blood that the heart can
pump each minute (cardiac output). The utilization of this
oxygen is primarily limited by the amount of mitochondria
available in the muscle cells to produce aerobic energy.
It has also been theorized that utilization may be affected
by the contractility of the muscle fibers. Muscle fibers
with greater contractility can achieve higher work loads
and thus utilize more oxygen.
5. How does oxygen play a role in the production of energy
for aerobic exercise?
Oxygen is used by the mitochondria in the muscle cells
as a reactant to produce ATP, the fuel for all cellular
processes in our body. Although ATP can also be produced
in the absence of oxygen (anaerobic respiration), it is
a less efficient process yielding much fewer ATP and producing
lactic acid as a byproduct. In addition, aerobic respiration
allows our body to obtain energy by breaking down fats,
which we have a much more abundant supply of than the 400-500g
of carbohydrate stored as muscle glycogen.
6. Do other non-running factors that improve fitness (fat
loss, increased muscle, etc. from cross-training) also increase
VO2 max?
Other non-running factors that enhance fitness will not
necessarily result in an increase in VO2 max. Since VO2
max is expressed in terms of body weight, a decrease in
weight that is the result of fat loss can result in a significant
increase in VO2 max. However, an accompanying loss of any
of the muscles used in running can counteract this increase.
Increasing muscle mass through weight training or some other
non-running activity is unlikely to enhance VO2 max. This
is because resistance training causes the muscle cells to
grow larger without an increase in the number of mitochondria.
This decrease in the density of mitochondria per muscle
cell explains why an excessive body-building program can
be counterproductive for runners who bulk up easily. However,
this doesn't necessarily imply that increased muscle mass
will never improve performance. Having a body that is balanced
in terms of muscle strength may mean that you are injured
less frequently, and thus able to train and race more consistently.
It may also increase your running efficiency, so you use
less energy to run at any given pace.
David Hampson is currently a student at Wake Forest University
in North Carolina pursuing a degree in exercise science.
His permanent residence is in Exeter, New Hampshire. He
aspires to obtaining a doctorate in exercise physiology
and possibly pursuing research in that field. He is an accomplished
distance runner, competing in cross country and track for
Wake Forest. His PR's include 15:35 for 5 km, 32:35 for
10 km, and 54:57 for 10 miles.
Article Source: David Hampson - Cool Sports 1998
Article Author: N/A
Net Reference 101
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