"There's only one hard and fast rule in running: sometimes you have to run one hard and fast."

Monday, March 24, 2008

Hang a banana bag, stat!

(There is no occasion on which one would need a "banana bag" - saline with potassium - desperately enough for a doctor to use the term "stat." I just liked the sound of it.)

Recent runs

I needed to take an easy week and let my body heal. I realised I was getting out of chairs in three separate motions to balance stresses to my back, hip and knees. Not good. So, no hills and no fast runs until I'm mended.

3/17. 11 miles in 102, in snow. Later, developed a peripheral neuropathy that turned both my index fingers blue. I must be some sort of freak to have stuff like that happen.

3/18. 12 in 107. After shoveling. Later, my knees hurt going up and down steps.

3/19. 13 in 98 with 9 in 63 (HRav=156,pk=167) Involuntarily slowed at 9 miles, or I would've done more. Knees still creak.

3/20. 4 in 36. Tired (slept badly).

3/21. 3 in 27, heavy snow and bad footing. Again, after shoveling.

3/22. 31 in 271 (HRav=124, pk=145). Well, so much for the easy week. This felt much more difficult than previous long runs, especially after 20 miles. Knees were a little off at the start and the left hamstring was tight. Ran miles 27-30 with Don Dornfeld, who kept saying, "Dude! You gotta run FANS. You gotta redeem yourself for last year."


3/23. 0 miles. Nice Easter, though. He is risen, indeed! Half a dozen people commented on my haircut, so it must be a bigger change than I thought.


In many ways, potassium is the opposite of sodium. There's very little sodium in most foods and yet most people get much more than they need; there's potassium in everything and yet most runners get less than they should. The body has an intricate system for maintaining sodium - if you need it, salty foods taste better (it's actually chloride ion that you detect in salt, which is why salt substitutes work) and, if sodium is low enough, you crave it; if sodium is too high, you get thirsty and dilute your sodium concentrations with water and lose the excess through urine. Because potassium is so prevalent, there's no way that the body regulates it and it doesn't get stored like most minerals, so you need to replenish it every day.

Good diets have more than 3 grams of potassium per day and it's almost impossible to get less than 2 grams unless one's starving. One loses about a tenth of a gram of potassium per liter of sweat, much less than the sodium one loses, but an appreciable amount. It's very easy to make up the lost potassium after a marathon or even a 50 miler just by eating normally.

So why do I recommend a fluid replacement solution with six times the amount of potassium one loses? First, it's the level that's been found to be best for water absorption (with adequate sodium and other considerations). Second, in extremely long runs, one tends not to eat enough to replenish potassium. The food everyone hears is high in potassium is bananas (many foods are higher); if one eats a banana every two hours in a 100 miler, one would get enough potassium - it's not unreasonable, but almost no one eats that much, especially late in the race. Third, one loses potassium in urine, which isn't measured in sweat rates.

The main symptom of acute severe potassium depletion is muscle cramping, but cramping can also be caused by dehydration and sodium or magnesium depletion, as well as other more unusual reasons. Chronic moderate depletion of potassium happens fairly often in runners and the symptoms are malaise, fatigue and tiredness, which cause most people to think it's just overtraining (which, in a way, it is).


Runner Brewer said...

Funny title to the post.

I visited a good friend in the hospital last week who had a ruptured appendix. I looked at his bag, studied the contents, and said "hey, this is what I drink when I am running really long!"

It would be nice if there was a Camelback with an IV hook up.

Aid station... "hey, change my banana bag, stat!"

Did I link that correctly?

Andy said...

I like the title too, but "banana bag" in hospitals typically refers to a bag with vitamin supplements (making it yellow in color).