From: morris@samson.bnr.ca (Morris Bernstein)
Subject: Re: VO2 max (was Re: Heart Rate Survey: Results)
Reply-To: bnrmtl!morris@larry.mcrcim.mcgill.ca
Organization: Bell Northern Research Montreal, Canada.
Date: Fri, 21 Aug 92 21:29:15 GMT

In article <1992Aug21.121417.6321@mic.ucla.edu> scott@eggneb.astro.ucla.edu (scott evans) writes:
>>>I'm particularly curious about this because I recently had my VO2 max
>>>calculated based on 85% of my max heart rate, where max heart rate is
   ^^^^^^^^^^^^^^^^^^^
>>>220 - (my age).  This worked out to about 162.  I didn't believe the
>>>results, so I went and sustaind a heart rate of over 180.  What does
>>>this tell me?

>The value which you were quoted was your anaerobic thresshold (AT) and
>not your VO2 max.  The VO2 max is your maximum ability to take in oxygen
>as a function of body mass.  Usually your VO2 max is quoted in ml/min/kg
>and is a number between 40 and 70 or so.  Remember, the ml is
...


Uh, yes, I knew that.  It says based on the heart rate.

I'm not an expert on physiology, but I remember some chemistry and
some physics.

Here's my understanding of the system.  I'm sure persons on the net
more knowledgable than me will jump in to correct me.  The muscles
burn fuel (glucose or fat) to produce energy.  We are interested in
the power output of the muscles (i.e. the energy produced per unit
time).  The limiting factor is how much oxygen can be pumped to the
muscles.

If not enough oxygen is supplied, the body can (for short periods of
time) produce energy using another reaction.  This anerobic reaction
produces lactic acid as a waste product and eventually leads to
exhaustion.

I assume (and apparently, the VO2 max test also assumes) that the
faster my heart works, the more oxygen can be supplied to the muscles
*to* *the* *limit* of the *anerobic* threshold (AT).

One doesn't really care about the AT; just about the VO2 max.  It's
like an automobile (can I mention those): you don't really care about
the RPM; just the power output and the RPM at which max power is
output for the particular car (you may also care about torque, but
that's a horse of a different colour, which by lemma 1 doesn't exist).

The purpose of the AT is to help you set training targets.  The
objective of (my) training is to increase (sustained) power output.
The max sustained power output is measured in terms of VO2 max (i.e.,
know one, and you know the other).

I'm not particularly interested in the anerobic metabolism.


...
>As an example, let's say Rosa Mota has a VO2 max of 10 units and can
>work aerobically at 8.5 units.  Further, let's say Flo-Jo has a VO2 max
>of 15 units and an AT of 6 units.  Both can jog together at 5 units of
>output but when the pace goes up to between 6 and 8.5 units, Rosa will
>still be cruising and Flo-Jo will start to hurt.  However, if the pace
>goes up to a sprint (>10 units of output), Rosa will have to quit and
>Flo-Jo will hammer away (with lactic acid searing her muscles, of
>course).

Now you've lost me.  The 'units' are volume per unit time (mass held
constant).  I assume that it's monotonically related to power produced
by aerobic metabolism.

Are you saying my max VO2 consumption occurs at a point when I have
exceeded my anerobic threshold??  That I can only achieve max VO2
_after_ I start accumulating lactic acid (anerobic metabolism)?


>The idea of training is to improve both your VO2 max and your AT as a
>percentage of max.  Now, as for your ability to go 180 for a long time,
>I should mention yet another zone of output. There is a zone just after
>the AT and  only a few heart beats per minute in width where you will
>produce lactic acid but your body will still be stable under the load
>for long periods of time.  Above that level, the lactic acid in your
>muscles will eventually lead to exhaustion.

Okay, so maybe this was happening, but I didn't feel the predicted
effects.  I only tried this once in a fitness club.  My usual workouts
are on the road, where I don't have a heart rate monitor (what, me
take my own pulse?  I'm a technophile! I need a machine to do it).

I'll try it again next time I have the opportunity, but I predict that
the limiting factor won't be lactic acid buildup, but will be
depletion of glycogen in the muscles.


>you don't want to be aerobic (for a long TT) the whole time but, rather,
>you want to work in the zone where you produce lactic acid but not at a
>runaway rate.  In so doing, you will be toast at the end but you will
>have sustained power throughout.

Yes, I understand that.  From my own perspective, I'm not in
competition.  I'm not doing time trials or any other kind of racing.
I just want to get into better shape (and lose that persistent 10lbs
of fat, which is also a horse of a different colour).

I'm more interested in the numbers as a way of understanding what's
going on (insert famous quote by Kelvin here).  I'm a great fan of
science.  When I bought my bicyle last year (after several years
without one), I sat down and did a gear chart for the bicycle.  I
guess I'm just looking to do the same thing for myself.  Otherwise, as
has been commented on the net, the numbers are basically useless.

>Lastly,in a study done at UCLA, it was found that in the runaway lactic
>acid regime, you can work as a function of time in a HYPERBOLIC manner.
>That is, if you plot work on one axis and time on another, the curve
                      ^^^^
>will be a hyperbola, asymptotically approaching your AT power output at
>time equals infinity.

Not sure I understand this either.  Work vs. time: as in the integral
of the power curve?  That's a monotonically increasing function that
...

Doesn't the power output tend to drop toward zero as the muscles seize
up?

(too bad ASCII doesn't transmit sketches very well).


>
>Scott Evans
>UCLA cycling (hoping I didn't screw this up) 

Thanks for your input.  It's been most informative and interesting.


Morris

p.s.  I think we got our mailer problems fixed...

--
Morris Bernstein		 phone:	(514) 765-8275
Bell Northern Research Ltd. 	 fax:	(514) 765-0500
worldnet: bnrmtl!morris@larry.mcrcim.mcgill.edu
"Knowlege is a mind-expanding drug."