Heart rate decreased each lap.

Pat Fleming said:

I was in a 12 hr race recently with a 32 mile loop. My average heart rate
on the 1st lap was 150, 2nd lap 143, 3rd lap 139, 4th lap 133, 5th lap 129,
and 6th lap 128.

My perceived exertion was the same for each lap.

My speed dropped slightly for the first 3 laps but the 4th, 5th, and 6th
laps were the same speed.

Why was my average heart rate reacting this way?

Were your lap times getting progressively slower? From what little I
know, this is not unusual for long endurance events.

Steve

Quoted message said:

"Pat Fleming" <[email hidden]> wrote in message
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Quoted message said:

I was in a 12 hr race recently with a 32 mile loop.

Wow. How does your back handle this? My back starts to hurt after two
hours and have to stretch every other minute.

"Pat Fleming" <[email hidden]> wrote in message
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Quoted message said:

I was in a 12 hr race recently with a 32 mile loop. My average heart rate
on the 1st lap was 150, 2nd lap 143, 3rd lap 139, 4th lap 133, 5th lap

129,

Quoted message said:

and 6th lap 128.

My perceived exertion was the same for each lap.

My speed dropped slightly for the first 3 laps but the 4th, 5th, and 6th
laps were the same speed.

Why was my average heart rate reacting this way?

Excitement on the first two laps before you started finding your rhythm.
By those numbers you were pretty relaxed your last two laps.
I suspect you were not in contention or your last HR reading would have been
much higher.
-tom

"Pat Fleming" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I was in a 12 hr race recently with a 32 mile loop. My average heart rate
on the 1st lap was 150, 2nd lap 143, 3rd lap 139, 4th lap 133, 5th lap

129,

Quoted message said:

and 6th lap 128.

My perceived exertion was the same for each lap.

My speed dropped slightly for the first 3 laps but the 4th, 5th, and 6th
laps were the same speed.

Why was my average heart rate reacting this way?

I can't remember the details, but I remember attending a seminar some years
ago in which it was postulated that with extended aerobic activity, some
fatigue of the central nervous system can occur, which will lower max
achieveable heart rate. I have read of a similar effect with some of the
RAAM riders as well.