Pacing, hyponatremia risk
by on Monday, January 12, 2015  (2 comments)

I took some time off during the holidays but I'm back with a couple links that I thought were real interesting. I hope you enjoyed the holidays and that you will find these topics interesting.


Pacing is an interesting topic on many fronts. Here's an interesting study on what happens when you throw pacing out the window during interval workouts and just go all out.

This study was done with cyclists so power output was measured. Not surprisingly, power output decreased not just within repeats but also across repeats. Power output wasn't only lower at the end of the first repeat than at the beginning but overall power output was lower in the second repeat than the first and in the third than in the second.

In the control portion of the study, paced workouts were done at the average power output of the all out workouts. So the total work done was equal. However, here's where things get interesting. Perceived exertion was significantly higher during the all out intervals than during the paced intervals. Even more interesting, oxygen consumption and time spent near VO2max were both lower in the paced workouts than in the all out workouts. Especially when a computer was controlling pacing, ensuring that the cyclists held the most even power output possible.

So what does this mean? To me, the first thing that came to mind as I was reading through this is that's why I always stress not getting out too hard early in a race. When you start fast then fade, I definitely think there is a psychological aspect that drags on you and makes the later stages harder but there is clearly also a physiological aspect. You actually are working harder when you start too fast and fade than if you go out on pace and maintain or even start a little slow and accelerate.

I also think there's a lesson for workout days. While we may sometimes want to tap into this effect, maybe with ladder-type workouts where you intentionally start faster, in most workouts I think we're better off going out on or slightly slower than target pace and maintaining or even speeding up.

Hyponatremia risk

This is a topic that is fading somewhat but I still think it's good to know more about the topic as it can potentially be a pretty serious risk.

So what do we know about hyponatremia? Well, we know it's a fluid/electrolyte imbalance. Given that, some people think taking salt tablets to increase your electrolytes helps prevent hyponatremia.

Here's a study that tested that theory.

We conclude that a low sodium intake in supplements has minimal responsibility for development of hyponatremia during continuous exercise up to 30 hours, whereas overhydration is the primary characteristic of those developing hyponatremia.

That seems like a pretty clear conclusion. Focus on proper hydration, not maximal hydration.

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Melissa (Guest)

I've been working on running negative splits. Pacing is always a challenge for me because I feel like I could have had a better time if I would have went out just a little faster, but just never know how much faster should I start out. I don't want to burn up and fade away so I have no kick at the end. How much slower than my VO2 Max should you start out?

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Melissa, thanks for the question. Where you start in relation to your pace at VO2 max is dependent on many variables, especially race distance obviously. Generally, I say take a look at your goal. Most of us who have experience know what kind of time we want to shoot for.

Maybe you've run a 4:10 marathon last time out and you want to shoot for sub-4:00. In that case, 4:00 pace is 9:09/mile. So, all other things being equal, you'd want to start at 9:10-9:15 pace and progress from there.

I say all other things being equal because, unless you're running on a track or a treadmill, you're likely going to face conditions or course features that will require pace adjustments in order to maintain an even effort. Miles with hills, for example, would require a slower pace to maintain that even effort, as would headwind stretches. Tailwind stretches would require a faster pace to maintain even effort, as might net downhill miles. That's where pacing can get tricky and it's good to know how the race day effort should feel so you can adjust on the fly for those things.

Make sense? If you're looking for a more specific answer, could you offer a more specific example?

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