Carbohydrate Effect on Heart Rate

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Apr 2013
11:38pm, 2 Apr 2013
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Has anyone got any thoughts or charts on this?

I suspect there much be lots of data given people used to deplete & then load to store more glycogen.

I'm trying to work out if heart rate & therefore effort would be lower when running a distance event after carb loading compared to a carb neutral or depleted state. Or maybe heart rate & effort would remain more or less then same but time to fatigue might change? So many questions
Apr 2013
1:06am, 3 Apr 2013
558 posts
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I have never directly assessed this. Maybe someone will have an answer informed by direct observation. Meanwhile, I think that relative to a carb neutral state, carb loading will produce a very small initial increase in HR at a given pace due to the increase in body weight. However over the duration of exercise, this extra weight will be gradually lost. The time to fatigue should be lengthened because exhaustion of glucose supply will be delayed. So overall effect during prolonged exercise is expected to be less effort.

Carb depletion would be expected to produce increased HR relative to carb neutral state due to increased release of adrenalin. Time to fatigue will be reduced.
Apr 2013
11:56pm, 3 Apr 2013
3655 posts
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Thanks for the reply Canute :)

I've found an answer from an observation of one on letsrun.

After a very long carb deplete the runner estimates that the subsequent carb load gave him an extra 7 minutes off his marathon time which he ran in 2:40:xx

I tend to run steady state & slower in a fasted state, mostly hovering around 155bpm. That's the heart rate I intend to the London marathon at and I'll probably try a deplete and load myself. Not to set any times, just out of curiosity. An observational of one is not very valid though and my results will be particularly unreliable as I am returning to running and making all those newbie gains.

Still, it might be something others visit or have input on.
Apr 2013
3:54pm, 27 Apr 2013
3669 posts
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Ok, sp I ran the marathon fully carb loaded & with constant refueling taking a gel approximately every 5 miles and sports drinks that were offered on the course.

My observations are just that, observations as race day excitement / nerves may have played havock with nerve and the weather was warm (vs cold training).

I thought carb loaded I could run faster for the same heart rate / effort level that I trained fasted on my long runs (155-160BPM)

However I for the same heart rate I actually ran at the same pace but perceived effort was less. I actually felt like I could have run a sustained effort easily at 165BPM and maybe even upto 170BPM. However, given it was hotter than normal I decided to stick to what I know so can't be sure.

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Maintained by Kieren
Has anyone got any thoughts or charts on this?

I suspect there much be lots of data given people ...

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