Roctane, Oreos, and Race Calorie Mathematics

Pursuit Films – 2018 Backcountry Rise 50k

I was once known for taking a breakfast sandwich to the start line of long races. I thought, if I could eat at the last possible moment, then I wouldn’t have to eat while running. Brilliant! I would also be forced to not start too fast while my stomach was trying to settle food. In reality, the biggest benefit was psyching-out the competition with mouth watering bacon, egg, and cheese aroma.  Update: I don’t currently believe that fat and protein digestion make a difference for 50 miles or less (I’ve never run farther).

Beyond the sandwich – I completed my first marathon with guava paste, which took me about a mile to chew and swallow, per bite. I graduated to Shot Blocks, but accidentally bought the strong caffeine version on an 88F race day (Boston, 2012) and they really weren’t much easier to consume. GU gels were next. After I figured out that my body needed way more than four for a 50 k, I started to wonder if there was a more convenient solution while moving fast.

Especially at road-pace, I would get annoyed by cold hands fumbling to open packets and dragging my teeth over plastic wrappers while trying to breathe. My friend (Joe Kelly) suggested I make concentrated GU Roctane syrup – I was hooked for both roads AND trails. For a marathon, I carry 500 kcal of Roctane in a 12 oz handheld. For a 50 k, it depends on the pace of the race (how much elevation/terrain type), but usually I just double to two bottles for 1000 kcal and eat a little more at aid stations. I take in whatever water is provided on the course to make up for the lack of water in the “syrup”.

That’s the simple answer. You could also consult a nutritionist at P3 Running.

Things get complex and really interesting when starting to mess with fat metabolism (ketosis plans) and carbo-loading. I found that I could easily do more harm than good and also that I wasn’t even remotely going to consider giving up beer carbohydrates for running performance. I am still trying to figure out optimal fueling. So is the rest of the world:

If the information in those articles made you even more curious, or you want to find some quantitative approximations, check out the links below and my race analyses (even more below). If you’re interested a quick suggestion on how to improve fat utilization and carbo-loading, go back up to the first Fitzinger link (the June 2007 article) for a succinct summary.

  • Glycogen stores (at race start)
    • The commonly reported value is 500 g (2000 kcal) for a person weighing 70 kg –
    • That’s approximately 20 miles of running (100 kcal/mi), which is a regular distance to “bonk” if not eating significant calories during a race (a high carbohydrate-use scenario). I.e., it’s probably about right: 13 kcal of glycogen per lb for a reasonably lean runner.
    • Me: Eat normal carbohydrate level diet (+2000 kcal), warm up a few miles (-360 kcal), shiver in the start corral (-50 kcal), expend baseline energy since waking up (-300 kcal), overthink the race plan a few times (-10 kcal), retie my shoes (-5 kcal), and digest a smaller than normal breakfast (+500 kcal) = 1770 kcal.
  • Carbohydrates consumed (per race)
    • GU suggests a maximum consumption of 350 kcal per hr – “If you tried to eat more, the body would divert blood from your muscles to handle the excess food.”
    • Me: for a 2.5 hr marathon, 500 kcal.
  • Fat converted (per minute)
    • (this publication is really impressive)
    • Non-fat adapted ultra runners in this study averaged a peak rate of 0.67 g/min, but that was at 54.9% VO2 Max.
    • Fat-adapted ultra runners reached 1.54 g/min.
    • Me: I don’t do any calorie specific training, and I race at a higher effort than 54.9% VO2 Max, so I would expect my conversion value to be lower. 0.4 g/min?

How does this look for a race where I “bonked” right at the end? Answer – maybe my fat conversion rate is closer to 0.55 g/min.

But the calculations don’t hold for a trail race.

It would be reasonable to adjust the calorie expenditure per mile in my model, since my heart rate is not significantly lower for a 50 k even though I’m moving slower. If I take my average 50 k pace at the “bonk” point (10.17 min/mile) and divide it by my closest (to date) marathon pace (5.63 min/mile), I see that I was running 79% slower. For mathematical kicks, I divided 79% by 2 and increased my calories per mile by the result, 39%. Here’s the new chart.

Looking good! Does this work for the Fourmidable 50 k (minor “bonk” at mile 28)? 14% increase in calorie demand (the course is much faster than Backcountry Rise)…

This could be a functional algorithm for calorie planning! Even though it is a bit of a wild guess, the correction factor reflects what my heart rate is telling me to perceive as more work per mile due to trickier terrain, very steep climbs, and descents that require significant braking.

My brain has used all of my available glucose on this post. If you made it to the bottom, give me the secret password next time you see me and I’ll buy you a beer.

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