Re: [Paddlewise] AT: was race training

Dan asked about aerobic threshold.  Here is a description.

Aerobic threshold is the maximum heart rate that can be supported for long 
periods of time.  As you demand more and more power from your body, the 
cardiovascular system provides more and more fuel and oxygen to provide that 
power.

At some point, as your power output increases, you reach the limit of your 
aerobic system; and then you can not put out more power without bringing 
other processes (anaerobic) to bear.  The anaerobic processes don't last very 
long.  A bicycle sprinter can go for about 10-seconds.  A track sprinter will 
get to like 43MPH and do the last 200 meters of a sprint in under 11 seconds. 
 After some recovery (aided by training), he can get another 10-sec or so of 
maximum output.  The frequency and number of super efforts can be increased 
by training.

A good way to find your aerobic threshold is to get on that stationary bike 
with a 3-digit speedometer or a pedal cadence monitor and a heart rate 
monitor.  Select a comfortable gear ratio and use it throughout the following 
test.

Pedal at a low speed (say 8-MPH) and record your heartrate.  Increase speed 
by 1-MPH (or like 5 pedal RPM) and record your heart rate.  You will find 
that your heartrate will stabilize very quickly --a few seconds to give a 
stable reading.  As soon as it stabilizes at its new, higher rate, record the 
value and increase the speed.

When you can't get more speed out of your body, stop.

Enter the speed in a column in a spreadsheet.  In the adjacent (second) 
column, enter the heartrate.  Make a plot of your heart rate, and set the 
hear rate axis to a logarithmic scale.  You will see that the sequence of 
points proceeds upward to the right in a straight line to some bike speed.  
Looking at the set of points from the upper end, you will note that they form 
a second straight line.  These two lines intersect at your aerobic threshold.

You can pedal at that heart rate until you have burned all of your glycogen.  
Then, you will be into fat matabolism.  If you work hard enough to put your 
heart rate above your aerobic threshold, you will go into oxygen debt and 
have to drop below your aerobic threshold to recover.  That is part of the 
skill in racing on a bicycle.  You exceed your aerobic threshold for a while 
then manage to lower your power output and recover --without getting dropped 
by the competition.

The "headroom" between your aerobic threshold and your maximum heartrate is a 
competitive working range, and bike racers operate in there a lot during 
attacks (hard accelerations) --either leading or responding.

If you monitor your heart rate while exercising and ease off you will see 
your heartrate drop rapidly if you are below your aerobic threshold.  If you 
are above your AT, your heartrate monitor will not drop for a while after 
easing up; you are paying back your oxygen debt.  This is an alternate way of 
estimating your AT.

A rule of thumb, proven to be erroneous, is that you can estimate your 
maximum heartrate  by subtracting your age in years from 220.  I am 60; so 
this rule of thumb gives 160 beats/min.  In fact, my max HR is like 182 
(painful, short exertion).  My AT is 162 bpm cycling and 172 on skis.  
Evidently, my cardiovascular system can supply my leg muscles with enough 
left over to support some stomach crunches and flailing with my arms.
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