Exercise Physiology MD

admin January 22nd, 2009

The first physiologic change happens within hours of arrive at altitude…you begin to breathe faster to compensate for less oxygen tension in the air. This helps up to a point where your ventilation lowers your CO2 level too much. Your brain says WHOA, stop breathing so fast!

At this point, the CO2 builds back up, but you are still not getting enough O2. The kidneys start to kick in by trying to get the PH of the blood back in order and start secreting bicarbonate ions, so the first few days yoru brain is fighting your lungs and your kidneys are trying to keep the peace.

all along your heart is trying to pump more blood to get more O2 around, and your vascular system responds by filling with more fluid that it sucks from the rest of your body. So you get a triple whammy of deydration…the air is dryer, you are breathing faster, and your vascular system pulls fluid out of yoru body into the blood vessels.

So, the FIRST thing you can do to help acclimitize is to drink TONS of water. I need 3-5 liters a day in teh first few days I go to altitude.

The worst days for most people are generally days 2-5. Day one feels OK, and after a week you start to feel better.

But the real long term adaptation is generating new red blood cells, which is a hormonal response to the decreased O2 tension. EPO is secreted by the kidneys which stimulates the growth of new baby red blood cells in your bone marrow. A previous poster was correct that this takes about 3 weeks to get into full force. Needless to say that in order to build blood cells you need to have the building blocks which includes adequate iron intake, folic acid and b vitamins, so nutrional support during this time is key. I get buffalo cravings during my first week at altitude (local pub serves yummmmy buffalo stew!)

You can speed this up by blood doping or taking EPO injections, but that’s not really advisable! LOL.

Legitimate, legal, medical ways to ease the transition include a variety of medications that assist along the pathways I mentioned above to help yoru body acclimate, but full acclimitization will not occur until the red blood cell production is back up to speed. Those medications include diamox, viagra (yes!), and ginko.

It takes me about 6 weeks to feel 100% at altitude, and even then I’m not as fast as I am at sea-ish level. The last 2 weeks I am there (I spend 2 months in the summer) I feel great, and wish I could stay longer.

• Altitude
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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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