The Puzzle, Part 2

I just felt the need to post something on this blog (the bad movie blog already has 500 posts in one year).

Two posts back, I detailed the problem I'd had with hitting the wall in marathons. If I ran slowly enough to not hit the wall, I was running at my standard training pace. The solution was obvious: store more glycogen and use it more efficiently. I'll try to cover the storage issue this time.

In 1967, carbohydrate loading was first described in the medical literature and within two years, it had become ingrained in marathoning lore. Doing a depletion run, then not eating carbs for three days, then eating a lot of carbs for three days, could increase muscle glycogen content by as much as 200%. This did not work for me, as it took me more than a week to recover from a depletion run. Looking at the original data, glycogen levels were still increasing seven days after loading began (they stopped measuring at that point); then I remembered David Costill having noted that it took him as much as 10 days to return to normal after a depletion run.

One of the great lessons of sport: Any new idea works extremely well for just a few people (and they're the ones you hear from), works well for some, works okay for some, doesn't work for some and actually makes things worse for a few.

Perhaps I needed to start my dietary taper earlier than I'd thought. 

The other possibility was to "top off the tank" during the race. In longer ultramarathons, eating during the run is necessary and it makes sense that, if you supply muscles with exogenous carbohydrate, they may spare what they've been storing.

This brings in another lesson: never do anything in a race you haven't had success with during training runs.

If I eat before a run, I tire very quickly. I thought this was an insulin thing - rising blood glucose causes an insulin spike, which drops glucose, which makes you feel tired. Now I've seen reports that consuming carbohydrates before a marathon or early during it (perhaps for the first hour) causes the muscles to burn a higher percentage of glycogen and less fat, which would cause an earlier exhaustion. I don't usually take in calories in runs under 4-5 hours, but would figure I needed "the extra" in the race because I was running faster for along time - this might be why I crashed as early as 8 miles in one marathon.

So... the way for me might be to try to carbohydrate load for a week or more and not eat the morning of a marathon or for the first hour of it.

But what about training to burn more fat and less glycogen at a faster rate of running? That'll be part 3.