January 2017 Running Challenge

7lenny7 wrote: »

MNLittleFinn wrote: »

@7lenny7 I plan on doing nearly all of my long runs unfuelled, it's more just practicing eating while running if/when I take fuel. for runs out to 14 miles, I haven't taken any fuel with me and have actually run fasted for most of them. big thing for me will be proper fueling BEFORE the race, that's been my downfall before, not having enough fuel to start.

There's a limit to how much glycogen your body can store (typically estimated at 1.5 to 2 hours worth at marathon pace). Clearly 2 hours of glycogen is not enough. Because of that, I feel that proper fueling DURING the race is critical for peak performance.

While there are certainly gains to be made by glycogen-depleted long runs (improved glycogen storage and increased fat utilization), there's a limit to how much can be gained by doing so, and too many long runs in the fasted state will impair your performance and limit your fitness gains.

Running fully fueled allows for better performance and quicker recovery. Personally, I alternate between glycogen depleted and glycogen loaded in the middle of the training cycle then within 3 to 4 weeks of the race, I'd go only glycogen-loaded because by then you should have increased your fat burning ability sufficiently and you won't lose it in that amount of time.

I highly recommend this article by Runners Connect for a more thorough discussion.

Lenny, while I agree with most of what you written and Runners Connect is one of my favorite go to websites, I kinda take issue with both of you guys.

Specifically: "typically estimated at 1.5 to 2 hours worth at marathon pace" or "marathon intensity" as the article stated.

Obviously, your specific "marathon pace" should take into account your ability to conserve glycogen and utilize fat for fuel.

There's still a lot that science has to learn on how all things work. But what we do know is that in order for the body to utilize fat for fuel, the mitochondria in your muscle cell will need oxygen. If the mitochondria is lacking oxygen, then that muscle cell is forced to use glucose and will burn it only through anaerobic means (glycolysis) and instead of pyruvate being the output to the aerobic system (Krebs Cycle and ETC) lactate and hydrogen ions will be the output which contribute to fatigue. The body will prefer to use glucose for energy because using glucose is a simpler process than fatty acids. However, the brain will eventually make a decision (for reasons we still don't fully understand) to utilize more fat for fuel. In order to do so, the brain will tell your body to release specific enzymes that promotes the breakdown of fat into fatty acids and those enzymes that influence the muscles to prefer fat over glucose (despite it being a more complex process). One major reason is to preserve carbs for the brain since the brain relies solely on carb burning.

For those of us that haven't trained for marathons, we don't normally force our body to prefer fat over glucose especially in high performance scenarios such as running. We tend to eat high carb diets and feed ourselves with carbs when our brain signals hunger. So our enzyme production becomes diminished. The only exception is when we go to bed and sleep 8 or more hours where our bodies will undergo a fast and burn fat while we sleep. So as the article explains, running our long runs (especially fasted) teaches our body to rely more on fat for fuel. And when it comes to marathons, this is crucial because our bodies does have a limit as to how much glycogen we can store. And it's impossible to refuel enough while on the run. So we have to teach our body through fasted long runs (or very long runs of 90 minutes or more) to rely more on fat. (sorry most of that was for the benefit of other readers). The issue I have is 2 hours at marathon pace. This is a tricky phrasing. Because what exactly is your marathon pace? Or marathon intensity? If you can run a marathon in 4 hours, then your marathon pace 9:09/mile. You tell me that after this particular runner ran a 9:09 pace for 2 hours, he/she ran out of glycogen? I don't think neither you nor the article meant that.

Now what I will buy is that out of those 4 hours of running at marathon pace or marathon intensity, 1.5-2 of those hours worth of running was powered by glycogen.

I would rather say that your body can store only a certain amount of glycogen. According to Wikipedia, 100–120 g in an adult in the liver and 1–2% of the muscle mass. "The amount of glycogen stored in the body—especially within the muscles, liver, and red blood cells mostly depends on physical training, basal metabolic rate, and eating habits."

Also, the faster you run closer to your lactate threshold, the more you are forcing your body to burn glucose faster (thus go through your glycogen store faster).


Sorry to nit pick, but that one kinda hit me hard. LOL

Elise4270 wrote: »

@Stoshew71 nerd .

Haha!

A few months ago was toying with my carb demand. I found that on days that I walked 2-2.5 hours I burned all the glycogen my body could store on 100- 120 g carbs/day, of course, trying to force it it burn fat.

I noticed that I get ravenous about 90 minutes in to a run (back when I was running, even walking now if I haven't eaten).

No real point to my contribution here, only to further the "nerd war".

I do agree with the option of allowing your body to learn to utilize fat as energy. The same thing happens when one cuts carbs, your body adapts. I think I read something about losing the ability to tolerate carbs after a prolonged low carb diet... I think that was a real thing.

Hahahaha Takes one to know one? ...isn't that what you said?

The point of all of this is that you need to teach your body to fuel a different way if you plan on running (or walking) long distances or huge amounts of time. And you can control two things, the amount of time you run, and how much you eat (or don't eat) before and during a run.

One more point if I can bring up here, and you made a very good point by mentioning walking for 2 hours. The point of the long run is getting time on your feet, not speed work. On your long runs, it's important to run at that comfortable conversational pace. Go too fast on your long run, and you miss out on that very important aspect of the long run which is to teach your body to use fat for fuel. Run too fast that you go into your lactate threshold and beyond, and you keep forcing your body to use carbs. The idea is to go a slow enough pace that your body is able to use fat for fuel. And the point you made is that you can even walk for 2 hours on a fast and still get that same effect.