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caffine

 
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wyatt3d
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Joined: 11 Feb 2004
Posts: 108
Location: South Texas

PostPosted: Wed Jul 28, 2004 6:20 am GMT +0000    Post subject: caffine Reply with quote

Doc,

I think caffine may lower my heart rate. I am a 30 year old man who drinks 16 to 32 ounces of coffee in the morning, and have noticed that on days when I drink large quantities of Iced Tea or Diet Soda (32 to 60 ounces) for a late lunch my heart rate stays lower and seems to recover faster during workouts. Is this possible. My rides and intensity are the same usually 30 to 40 miles (1.5 to 2.5 hours). During my rides my average hr is usually 170 and on days with caffine it is around 155. My resting heart rate is usually in the 40's and sometimes I can measure it at 38 or 39. Is there any benifit to having a higher or lower hr during intense effort, and more importantly is this an unhealthy amount of caffine.

Thanks Doc.
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The Bike Doc
250+


Joined: 08 May 2003
Posts: 1371
Location: Corpus Christi and Warda, Texas

PostPosted: Wed Jul 28, 2004 8:32 am GMT +0000    Post subject: Reply with quote

wyatt3d:

There are many factors that affect your baseline and workout heart rates. Caffeine typically raises the heart rate, and in some individuals who have underlying heart problems it can trigger a dangerously fast heart rate. To acurately find out what you heart rate is under different conditions and caffeine intake, you would need to have power meter set up so that you are have equivalent power out put under identical environmental conditions with identical body health and hydration status. These kind of studies are difficult in the real world of weather changes, rest hours, work stress and health status. So it is quite difficult for me to comment that it is the caffeine that is the culpable variable in your heart rate varriation.

Caffeine greater than 12mcg/ml of urine consitutes a banned substance by the International Olympic Committee, National Collegiate Athletic Association and Universal Cyclist International (UCI). That translates into about 400mg of caffeine a day equivalent 4 ounces of espresso, 24 ounces of coffee 48 ounces of tea or 48 ounce of caffinated sodas.

Here are some links on caffeine consumption in cycling and caffeine content in foods:

http://www.cycle-smart.com/coaching/articles/caffeine.shtml

http://www.cspinet.org/new/cafchart.htm

Thanks,
_________________
Paul K. Nolan, MD
AKA: The Bike Doc
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Anonymous
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PostPosted: Wed Jul 28, 2004 3:05 pm GMT +0000    Post subject: Reply with quote

Doc - do you have any info on the strength of diuretic effect? For example, if I consume 100 mg of caffeine, how much water do I need to offset it?

Thanks,

-Kyl
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The Bike Doc
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Joined: 08 May 2003
Posts: 1371
Location: Corpus Christi and Warda, Texas

PostPosted: Thu Jul 29, 2004 6:00 am GMT +0000    Post subject: Reply with quote

Sir Huff N Puff:

The amount of diuresis (how much you urinate out) for 100mg of caffeine will vary from individual to individual. Here is PUBMED a summary of an article on this subject:

Ann Nutr Metab. 1997;41(1):29-36.

Coffee consumption and total body water homeostasis as measured by fluid balance
and bioelectrical impedance analysis.

Neuhauser-Berthold, Beine S, Verwied SC, Luhrmann PM.

Institute of Nutritional Sciences, Justus Liebig University, Giessen, Germany.

To investigate the impact of coffee consumption on fluid balance, 12 healthy volunteers were supplied with a standardized diet for 2 days after having abstained from consumption of methylxanthines for 5 days. During the first day, fluid requirement was met by mineral water. On the following day the same amount of fluid was supplied and the mineral water was in part replaced by 6 cups of coffee containing 642 mg of caffeine. This led to an increase in 24-hour urine excretion of 753 +/- 532 ml (p < 0.001), a corresponding negative fluid balance and a concomitant decrease in body weight of 0.7 +/- 0.4 kg (p < 0.001). Total body water as measured with bioelectrical impedance analysis decreased by 1.1 +/- 1.2 kg or 2.7% (p < 0.01). Urinary excretion of sodium and potassium was
elevated by 80 +/- 62 mmol or 66% (p < 0.01) and 14 +/- 12 mmol or 28% (p <0.01), respectively.

Publication Types:
Clinical Trial

PMID: 9194998

Real world translation: caffeine will make you loose more water and salt in your urine. In this particular study population the amount of extra water lost was 1-3 cups (250-750mls) for 642 mg of caffeine in a 24 hour period. For 1 cup of coffee or 100mg of caffeine, you may loose about 1/6 of the amount as those in the study or 1-4 ounces of fluid. Bottom line, increase your sport drink intake to off set any fluid losses for the caffinated beverages.

Thanks,
_________________
Paul K. Nolan, MD
AKA: The Bike Doc
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Anonymous
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PostPosted: Thu Jul 29, 2004 7:59 am GMT +0000    Post subject: Reply with quote

Thanks! I was always curious about the magnitude of the water loss, and never knew if I needed to drink an extra glass or an extra gallon (and now I know it's on the order of an extra glass to pay for that soda I had at lunch). It is not as strong a diuretic as I had feared.

Thanks,

-Kyl
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