Exercise Physiology MD

admin January 6th, 2009

This question was posed on the wattage forum recently. Here is my response.

VO2 max is typically achieved in an all out effort of 3-8 minutes
depending on your genetics and fitness. Outstanding athletes may be
able to hold their true VO2 max for a full 8 minutes, but most people
cannot.

The whole idea of interval work (at any intensity) is to use shorter
sets with rests to add up to a total of more work that you would
otherwise be able to do as a continuous effort. You can reach your
VO2 max after about 30 seconds of starting an interval at the
appropriate intensity, but after you stop or slow down, your oxygen
needs diminish and your heart rate slows, and you are no longer at
your VO2 max. When you start your next interval, your “bucket” has
only partially emptied depending on the intensity of your rest
interval (how low your HR or Power or Vo2 drops during the
rest)…which determines how far you need to fill the bucket up again
to be back at your Vo2 Max.

So if the goal is to get as much work in as possible at VO2 max
efforts, you can see how shorter, more intense rest intervals would
let you reach your VO2 max effort more quickly once you re-start a
given interval.

So the next question is how long should the intervals be?

Tabata intervals (10 sec max, 20 sec rest) will hit a component of VO2
eventually, but they are really best for anaerobic conditioning.
Billat’s intervals (30 at vo2 max-30 at “rest”) are great for an
introduction to VO2 max efforts for either newbies, or early in the
season, with little worry for injury. In addition, her work has shown
that after a 4-6 week block of VO2 interval work, only 2-3 minutes of
VO2 work per week are required to sustain your gains before they drop
off to far. So you can cycle your VO2 work early in the season and
see some benefits, taper them off in the spring time and resume them
prior to or during race season. Of course, if you can tolerate the
longer intervals (2, 3, 5 mnutes or more) at your VO2 max power, you
will pack in the most time at VO2 max.

Finally, about what power to do your intervals at…since by
definition, your 5 minute power is going to be close to your VO2 max
effort (and could only be confirmed with expired gas testing in a
lab), you might as well use that 5 minute power as your target power
for your VO2 intervals.

There’s no right or wrong as long as you are applying physiology
appropriately. The most important part is to have a plan to follow
and be able to measure your progress. Ways of measuring your progress
could be to do a block of VO2 intervals for 4-6 weeks as part of your
regular training with a progression that makes sense, and then measure
either your all out 5 min power again, OR hold your 465W and see how
long you can hold it after the training block.

Hope that gives you some more ideas.

Suzanne Atkinson, MD
www.steelcityendurance.com

• VO2 , Interval
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admin September 19th, 2007

A new triathlete asks:

When I look at my training plan it seems that Fartliks are sprints in a foundation run, and Lactate thresholds are sprints in a race tempo run?

I run 12 min. miles, I don’t have a tempo run yet. And I’m not very fast on sprints. What does any of this mean for me? What should I be shooting for?

and, what is VOmax something or other?

Fartlik is a Swedish word for “speed play”.

In practice, it just refers to random short increases in pace during an otherwise moderately slow run. THere is no specific speed or pace associated with it. They do not have to be sprints.

I am also a slow runner and remember the feeling of having only “one speed”. Fartleks or pickups or strides are a nice way to increase your pace briefly (even 10-20 seconds will feel like a lot at first) to introduce your body to the idea of a faster pace.

You should only begin to add these if you have been consistently running at least 3 times a week for a month or so for 30+ minutes at a time. That’s not a hard rule, but just a suggestion. Then you can start adding in short fartleks during a run, say 4-6 total for 10-20 seconds. Don’t do it more than once a week for the first 4 weeks, and then re-evaluate things.

Lacate threshold and VO2 max workouts are based on your specific physiology and are much more specific than a “sprint during a tempo run”. It sounds like you don’t quite need to worry about those yet, but educating your self about physiology and fitness will benefit you in your overall training.

Here is a great article from Running Planet that explains several types of running drills that you can integrate into your base training period.

• Running , Interval , Fartlek
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