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  1. #1
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    Bonking or dehydration?

    I've noticed that when my heart rate(hr) stops recovering (dropping) at stop lights or on easier sections of the ride that the end is near. Yesterday was a good example ... around mile 55-60 on a 75 mile ride and my hr wouldn't drop back down after a hard effort on a climb or a fast section. Even at a stop light it wouldn't drop much and would immediatly jump back in the red zone (about 90% of max) at only a moderate effort. I have noticed this same effect before.

    This is a weekly ride that usually is around 60-75 miles, so I'm used to the distance and this doesn't always happen, though yesterday was a little quicker pace and only a 5-10 min rest stop. It was relatively warm yesterday (60's/ sunny) and I know I didn't drink enough ... 40oz of gateraid, 14 oz water and maybe 500 cal. of energy bars/ gel. I didn't start eating til past the half way point at the rest stop around 2.5 hrs.

    Does this kind of hr response indicate dehydration where the heart is working harder to pump thicker blood? Or did I just run out of energy and need to eat more and earlier? Or maybe I'm weak and just need to ride more miles?

    Thanks for your insights

  2. #2
    sch
    sch is offline
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    Viscosity of the blood is not going to change that much in the early stages of dehydration. 54oz of fluid is a little lite but not so much that it should be a problem at temps in the 60F range. 40 0z of gatorade will be an additional 250 calories on top of the 500 solid food fuel. My feeling is that this is more likely caloric than dehydration but that both contributed, and that eating was delayed a bit too long to benefit you for a time of 30-60min after your rest stop.
    Steve

  3. #3
    Senior Member doctorSpoc's Avatar
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    I've bonked really 'good' (oxymoron) a few times and if anything you can't even turn the pedals over hard enough to get your heart rate to go up.

    When you bonk you get super hungry... I mean a hunger like you've never felt in your life and think irrational thoughts like.. "grass is edible... cow's eat it, why can't I?"... the only thing that stopped me was the thought of the insecticides that must be on it... or you suddenly find yourself in a corn field or apple orchard helping yourself to produce right off the stalk or tree.. funny how good imature, raw corn tastes when you've totally bonked..

    bonking is a survival method when your bodys gylcogen level gets too low... your brain can only use glycogen as an energy source so once it gets to a certain level your brain says ok all the rest is for me... so all your muscles can do is get energy aerobically... so all you can do is tip-toe on the pedal and not enough to raise your HR past a active recovery sort of level.

    Bonkings not fun... eat when your ride over 1.5 hrs.

    Edit: it may be dehydration, exhaustion or you'll get elevated HR if you take a even 1-2 days off before a ride.. your body will adjust your stroke volume even in that short a time... less L/heart beat means more beats per minute to move the same amount of blood...
    Last edited by doctorSpoc; 01-25-06 at 11:29 AM.

  4. #4
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    http://www.multisportsolutions.com/news.html

    Halfway down the page is an article about "Cardiac Drift" and its many causes.

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    Thanks for the responses! I really didn't think of this as a bonk either. I've done that and usually feel like my stomach is trying to digest itself and don't have the energy to elevate my hr at all.

    Mainly trying to figure out what was causing a hr up in my anaerobic area, but at a relatively moderate exertion level. It's happened a couple of times, usually as above, around the 3.5-4 hour mark.

    Interesting article on Cardiac Drift. I can see a couple of factors mentioned there at work. Warmer than normal day, and I was dressed for the 45* start weather with knickers and long sleeves so it was hard to cool off in the 65* sunny afternoon. Some fluid loss from not hydrating enough ... all may have combined for the Cardiac Drift listed.

  6. #6
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    Quote Originally Posted by doctorSpoc
    When you bonk you get super hungry... I mean a hunger like you've never felt in your life and think irrational thoughts like.. "grass is edible... cow's eat it, why can't I?"... the only thing that stopped me was the thought of the insecticides that must be on it... or you suddenly find yourself in a corn field or apple orchard helping yourself to produce right off the stalk or tree.. funny how good imature, raw corn tastes when you've totally bonked..
    Although it's been a while since I've bonked on the bike, the first sign for me is a strange taste in my mouth.

  7. #7
    Senior Member DannoXYZ's Avatar
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    I start feeling cold and clammy about 30-minutes before bonking. Usually a warning sign and I better pull over and grab something to eat. If I don't, you can't even feel the bonk coming on, you just start going slower and slower. Sometimes I get tunnel vision. Another sign is I'm scanning the ground for scraps of discarded candy-bars and any other carbs to eat. You'd only be able to generate something like 75-watts max, so HR wouldn't be very high either.

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