Tag: running

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A mile squared, a love letter to RunKeeper

Ten years after starting to use RunKeeper I just crossed 5,280 miles.

5,280 feet in a mile.

5,280 miles.

A mile squared.

My adult running career began with this post by Mac Developer and personal hero, Cabel Sasser.

I was inspired and the following year I bought a pair of Nikes and the Nike+ system and started slogging miles. I ultimately logged over 1,000 miles with the Nike+ system. I loved the Nike+ system. The Nike+ system was tied to the iPod and so it was a late innovation for a technology that was an evolutionary dead-end.

In 2008, I bought my first iPhone, an iPhone 3g, and downloaded one of the first running apps, RunKeeper. It used GPS to log your distance. The early iPhones had lots of holes. RunKeeper couldn’t play music, burned the battery, and crashed my phone. But the program kept getting better. Features came. Features left. The scrappy Boston start-up behind RunKeeper was bought by Big Shoe (Asics). But the program kept getting better.

For awhile I was alternating between Nike+ and RunKeeper. That was until September 19th, 2009. It was my 40th birthday and I went out for my first 20 mile training run. At mile 8, Nike+ crashed my iPod Nano and stopped recording my run. That was the last time I used it. Since that run, RunKeeper has tracked every run. Here is my review of RunKeeper after 1,000 miles. And my review of RunKeeper 2.0. And my review of the first RunKeeper Pro.

Since then I ran a Marathon (a better post), a number of half marathons, I spent a year where I averaged 3 miles/day everyday. And though my running has decreased, as is clear from the nomogram, there are very few months where I failed to get out there and run. I have successfully kept fitness high on the priority list.

Miles per month

Items at the bottom of the to-do-list never get done. And because you never get to the bottom, things that are important can’t be put there. If you only exercise when everything else is complete you will never exercise. You need to take care of yourself before everything else is done. Not before anything else is done, but before everything else is done.

Run on.

#NoRestTilEverest

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Nike+ iPod imprecision

I have been running off-and-on for the last 3 years (mostly off) and running regularly for the past 15 months. I love how lightweight it is the antithesis of biking or backcountry hiking with their emphasis on gear. Running is nearly completely free of equipment and gear. All I do is strap on my shoes, plug in the headphones and go. The exception to this is my Nike+ iPod pedometer. This is a cool gadget that consists of a sensor which goes in your shoe and a receiver which plugs into the 30-pin connector on the bottom of the iPod Nano. If you use an iPod Touch you don’t even need the receiver.

I was blown away by the accuracy of the device and have been rediculously satisfied with this $30 gadget. Two events brought home how accurate the pedometer was: I ran a Cinco de Mayo 5k in Brooklyn with my sister a few years ago. The pedometer signaled 5k on the very footfall that crossed the line finishline. It was accurate to the step. Amazing:

I had a similar experience in the Detroit Marathon Relay in 2007. I ran a short segment from Downtown to Belle Isle. As soon as I crossed the timing blocks the iPod signaled I had reached my goal:

Last fall when I did the half marathon the accuracy fell a bit. It recorded 13.6 for a 13.1 mile route but I felt that 5% slosh was okay:

I had the same over estimate occur during the martian Marathon 10k. With the devic recording 6.5 miles for a 6.2 mile run. Again a 5% error:

What inspired this post was the new finding that in 2009 the error has swung in the opposite direction, now the Nike+ is underestimating my distance and speed. I first noted this during an 8.5 mile loop I ran with PBFluids reader and fellow nephrologist Steve Rankin. The Nike+ only recorded 7.98 miles:

Yesterday I did the Dexter-Ann Arbor half marathon and again the Nike+ iPod underestimated the distance and speed:

In the end it was only off by 0.6 miles over 13.1, so 5% but on my next run my Nike+ odometer will cross 1000 miles and its a little less satisfying thinking that I already crossed that milestone at some unrecognized time in the last month or so.

Update: Just discovered that the New York Times recently did a review of the Nike+iPod system.

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What causes hyponatremia in marathon runners

Me, running the NYC Marathon

One of the first blog posts ever on PBFluids was a review of Almond Et al’s study of hyponatremia. With this year’s Boston Marathon now complete I have re-reviewed the subject.

The Almond study was high profile and did a good job of demonstrating the risk factors for marathon induced hyponatremia. (See this post for a review) However some of the findings were self evident: increased weight gain was associated with hyponatremia. What is not answered is, why those who developed hyponatremia gained 3 liters of water. Why didn’t these patients just urinate the excess water? Normally, a falling sodium, shuts down ADH like a bordello on Easter. The retention of water is indirect evidence of ADH. Could it be that marathon running and ultra-endurance events could be added to the list of causes of the Syndrome of Anti Diuretic Hormone (SIADH).

It would have been nice to see a U/A or urine osmolality in Almond’s data to confirm this.

Siegel et al. (PDF) has done the most detailed study I am aware of on exercise induced hyponatremia. They did detailed biochemical assessments on 39 runners in the 2001 Boston Marathon. They drew pre-race (day before) and post-race (within 2 hous of finishing) samples for:

  • CPK
  • IL-6
  • ADH (vasopressin)
  • cortisol
  • prolactin
  • CRP

They also looked at 308 runners who collapsed during the 2004 Boston Marathon and measured:

  • IL-6
  • ADH (vasopressin)

Additionally they did some blood tests on 2 runners who had died of cerebral edema from exercise induced hyponatremia. One from the 2002 Marine marathon and the other from the 2002 Boston Marathon.

The normal patients had spikes in their CPK from 150 to 2,323. They also had a doubling of cortisol and prolactin but no change in ADH levels. The rise in CPK was matched by increases in IL-6 followed by an increase in CRP.

Of the 308 collapsed runners only 16 had hyponatremia. All of the hyponatremic runners reported a lack of urination during the race. 7 of the 16 had inappropriately high ADH levels in the blood. The authors concluded that lack of urination (though only driven by ADH in half the patients) rather than fluid loading was the predominant cause of hyponatremia.

The article then describes the laboratory and clinical scenario surrounding the two deaths in 2002. The data is summarized in the following table:

Importantly, both patients were initially treated with 150 mL/hr of normal saline without improvement. Two years later, two patients presented with similar symptoms and responded well to 3% saline:
The primary conclusions from this study, which admittedly is a bit schizophrenic with numerous anecdotal reports from various populations, is that exercise induced hyponatremia is not due to sodium loss but rather from fluid retention. Some of this fluid retention is driven by ADH and hence introduces exercise induced hyponatremia as a novel cause of SIADH. The diagnosis of SIADH is backed up by elevated urine sodium, elevated urine osmolality and normal (or high in the case of cortisol) cortsiol and TSH levels.

The elevated urinary sodium levels (consistent with SIADH) are a critical fact in the etiology of hyponatremia. If we were dealing with hypovolemia (commonly, but erroneously, referred to as dehydration), a cause of hyponatremia, one would expect a low urine sodium (usually less than 10 but always less than 20). The high urine sodium means that these patients were not volume depleted, It was not loss of sodium through the sweat which lead to the low sodium. This means that changing the sodium content of sport drinks is unlikely to prevent the complication.

The authors point out NSAIDs (ibuprofen, Motrin, Advil, naproxen) enhance renal response to ADH and should be avoided in the 24-hours prior to a race.

The authors recommend treating acute symptomatic hyponatremia from a marathon with 3% saline 1 mL/kg/hr to raise serum sodium 4-6 mEq/L and then to slow the rate to target 12 mEq/L in the first 24 hours of therapy. Just as is in all cases of SIADH 0.9% saline may not improve the serum Na.

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Hyponatremia and Marathons

I love it when some of the arcane nephrology knowledge makes headlines. When I heard NPR covering hyponatremia I almost cried. I am training for a half marathon in October and so I have been thinking about this topic.

Almond, Et al’s study published in the NEJM looked at 488 blood samples from 766 runners recruited from the 2002 Boston Marathon. They found post-race:

  • Average sodium 140±5 mmol/L
  • 13% had a sodium <>
    • 22% of woman
    • 8% of men
  • 3 runners had Na <>

When they looked at predictors of hyponatremia, univariate predictors included:

  • Female gender (p<0.001)
  • Lower BMI
  • Fewer prior marathons (p=0.008)
  • Slower training pace (p<0.001)
  • Longer race duration (p<0.001)
  • Hydration frequency (p<0.001)
  • Hydration volume (p=0.01)
  • Urination during the race (with more frequent voiding having a higher risk of hyponatremia) (p=0.047)
  • Weight gain during the race (p<0.001)

Of note use of sport drinks compared to pure water made no difference. In the multivariate analysis, hyponatremia was associated with:

  • weight gain
  • longer racing time
  • body-mass index of less than 20

Of note the female gender falls out in the multivariate analysis as it likely was accounted for both by the longer running time and lower BMI.

In the discussion the authors mention that most sport drinks have only 18 mmol/L of Na.