Improvements in VO2 max occur as a consequence of sufficient physiological disturbance to the factors that determine it, cardiac output (central component) and arterio-venous difference (peripheral component).

1. Improving Your Cardiovascular Endurance - If Only More
People Knew About This!
Cardiovascular endurance is often measured by what's
known as your VO2 max. This represents the maximum amount of
oxygen that your body can intake, distribute, and utilize at the cellular
level.
So it goes without saying that your VO2 max and cardiovascular
endurance will be greater with the proper aerobic endurance training.
But what is the best method to elicit the greatest possible increase in
aerobic endurance?
A lot of people spend hours upon hours doing endless cardio with the
hope of improving their endurance but fail to realize the basics of
cardiovascular physiology.
Cardiovascular Endurance Explained
So bear with me for a moment as I explain the fundamentals of
improving your cardiovascular endurance, and more specifically your
VO2 max.
Improvements in VO2 max occur as a consequence of sufficient
physiological disturbance to the factors that determine it, cardiac
output (central component) and arterio-venous difference (peripheral
component).

2. Cardiac output is the amount of blood pumped out by the heart each
minute. It is the product of your heart rate and stroke volume (blood
ejected per heart beat). As you become fitter, your heart muscle
becomes stronger allowing the stroke volume to increase, pushing out
more blood per contraction. At the same time, your heart rate (at a
given intensity) usually decreases - both indicate an improved level of
cardiovascular endurance.
That's why very fit individuals have a much lower resting heart rate.
For instance, many marathon runners and elite cyclists have resting
heart rates hovering around 30 bpm while the average person's
resting heart rate is between 72-90 bpm.
In particular it appears that cardiac output is the major determinant of
VO2 max and therefore its improvement should be a major focus of
endurance training. It appears that in order to induce the maximum
change in cardiac output, training needs to extend the stroke volume
to its maximum capability, which coincides with the your VO2 max.
Therefore in order to maximize the physiological determinants that
affect your VO2 max, you should sustain exercise training near your
VO2 max for as long as possible.
What If You Don't Know Your VO2 max?
Don't worry too much about the knowing your VO2 max unless you
feel like going through a grueling incremental exercise test on the
treadmill or bike.
Instead, a simple rule of thumb is to simply ensure that you exercise
at a high percentage of your maximum heart rate for as long as
possible. Because your maximum heart rate and VO2 max are closely

3. related, it is easier to track your exercise intensity by using a heart
rate monitor or by simply taking your pulse.
Without getting complicated, just use the simple formula "220 - your
age" to determine your maximum heart rate. So, if you're 40
years old, then your maximum heart rate would be 180 bpm.
Therefore, in order to elicit the greatest possible VO2 max
improvements you'd want to do more of your cardiovascular
endurance training near 180 bpm.
Obviously, most human beings cannot sustain their maximum heart
rate for more than a couple of minutes so the key is to spend more of
your time near that level through the use of interval training.
Try This Interval Training Workout For Maximum VO2
Improvements
A recent study looked at 3 different endurance training protocols:
Treatment 1:
1 min intervals: 10 × 1 min efforts at the velocity corresponding to
VO2 peak (slightly lower than VO2 max) interspersed with 10 × 1 min
efforts at 0.5 VO2peak (50% intensity).
*Treatment 2:
2 min intervals: 5 × 2 min efforts at Vpeak interspersed with 5 × 2
min efforts at 0.5 at VO2 peak.
Treatment 3:
Constant rate run: 20 min constant rate run on a treadmill at a
velocity equivalent too, and determined by the mean velocity of
treatment A and B (75% VO2 peak).

4. So which one do you think produced the greatest improvements in
VO2 max?
Well, the researchers observed that the "2 minute intervals"
resulted in significantly more time above 90% of VO2 peak and
a significantly greater percentage of participants to exceed
90% of VO2 peak than "1 min intervals".
Consequently, the researchers suggest that longer intervals may be
more effective than shorter intervals of the same average
intensity to enhance VO2 max.
Evidence for this contention has also been provided by recent research
that revealed an 8 week training regime of 15 s of running at 90—95%
of max heart rate with 15 s recovery, produced smaller percentage
gains in VO2 max than 4 min of running at 90—95% of max heart rate
with 3 min recovery (5.5 and 7.2%, respectively).
Your Homework
Try the "2 minute intervals" protocols described above and compare it
to the "1 minute intervals" workout. You'll automatically feel a big
difference as you continue to push your body at a higher intensity for a
longer period of time.
With just a few interval training workouts you'll notice some massive
improvements in your overall cardiovascular endurance!
Also, you will want to have a look at my Treadmill Trainer Volumes 4
and 5 interval running workouts. These running workouts were
specifically designed to push you harder and longer so that you

5. become a faster and more endurant runner with just 2 workouts per
week.
Give them a shot!
YURI
References:
(1) O'Brien, et al. (2007). The effects of interval-exercise duration and intensity on
oxygen consumption during treadmill running. Journal of Science and Medicine in
Sport, 11: 287-290.
(2) Helgerud J, Hoydal K, Wang E, et al. (2007). Aerobic high-intensity intervals
improve VO2max more than moderate training. Med Sci Sports Exerc, 39(4):665—
71.