Don't be Running on Empty

Fill 'er up!
(Courtesy freefotouk @ Flickr)

If you want to keep your conveyance running, you simply have to keep it fueled. Fail to do that and she'll leave you sitting on the side of the road. True for cars. Also true for your body ... especially if you're involved in an endurance event like the marathon. The timelapserunner has been testing out a refueling plan on the last two long runs (i.e., the 13 and 15 milers) but has been looking from time to time for a more quantitative, even scientific approach to refueling during long training runs and on race day as well. He may have found such an approach.


Dr. Kim Mueller offers an easy-to-figure-out but still-logically-scientific formula to identify a workable marathon refueling strategy. I'll walk through it for you by working out my own plan for this week's 17-mile training run.

Step 1: Determine running calorie expenditure per mile.

To do this, multiply your weight by 0.63, which for me looks like 155 * 0.63 = 97.65 calories per mile.

Step 2: Determine how many miles you'll cover in one hour.

Let's see. For this week's run, my planned average pace will be 13:11, or 13.18 minutes per mile. In miles per hour, that works out to be: 60 / 13.18 = 4.55 miles per hour.

Step 3: Calculate hourly calorie expenditure base on that pace.

OK. Just multiply the results from Steps 1 and 2 like this: 97.65 * 4.55 = 444.3 calories per hour.

Step 4: Determine hourly calorie replacement need.

The human body can only absorb about 30% of this expenditure rate, so we get: 444.3 * 0.3 = 133.3 calories of fuel per hour.

Step 5 (added by timelapserunner): Determine intervals between Clif Gel Shots:

Each Gel Shot is 100 calories, so we get: 60 * 100 / 133.3 = 45 minutes. Dr. Mueller's example suggests that the first refueling event should occur about 90 minutes into the run.

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Looking at this 17-mile training run, we'll have the first Gel Shot at 90 minutes, then another at 2:15:00, another at 3:00:00 and the final one at 3:45:00, or thereabouts.

This will be the plan. Training runs are the place to try such things out, not race day. We'll let you know how it went when we report on the results of this training run - which, by the way, may very well be this Saturday morning, if the weather reports hold up.

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Inasmuch as we're in the music mode (see last post), might as well serve one up for this theme: