Fat Miles

[Sasha Pachev]

People have been asking me what I mean by "fat miles" in my training. I want to have a reference post for them instead of having to type the answer over and over again.

First, the idea. At any point during a run the body is receiving energy from two source - glycogen (carbs), and fats. Glycogen helps you run much faster, but lasts only 90 minutes or so, longer if you pace yourself better. Fats can carry you for hours, but only at a very slow pace. So if you could trick your body into using a greater percentage of fats at paces in the range of your marathon pace, you will have more glycogen at the end, and will be able to hold off the wall.

The question is what controls the carb/fat ratio. Definitely as you go faster you burn a greater proportion of carbs. But the ratio is not directly controlled by the pace. The pace only presses the switch buttons, but where are the buttons? I believe the buttons are the hormonal state of the body. Which is controlled by the brain to a great extent. So with practice it should be possible to learn to control your hormones in a way that you can tell your body to use more fat at the same pace.

From this comes an idea for something you can do in your easy runs. You run a slow pace. Let's say 1:00 per mile or more slower than your marathon race pace. You run that pace for a long time. Your body is in the fat mood, it is burning primarily fats at this point. Now you accelerate gradually. The accelerated pace will eventually make your body switch to carbs. But it will not happen right away. So you will have a chance to know what it feels like to run at a fast pace off fats. As you accelerate you are going to feel sluggish. So you run that pace for a mile for a round number, and try to feel sluggish the entire time, but you pay attention to your splits and make sure they are fast. It is not good if they are fast and you are not feeling sluggish, it means you have switched to carbs. If you get too motivated to hit your target pace, you will not get the desired effect.

Then hopefully you will remember that bum-at-marathon-pace feel in the marathon. Many marathons try to get you excited at the start, they bring a band, etc. I also see people wearing iPODs. I can only imagine what kind of music is on that iPOD, I highly doubt it is peaceful music. You will not be burning fat in that kind of mental state. You need that excitement in the last 6 miles when it is time to mobilize the remnants of your glycogen for work. In the opening miles this excitement is a disaster. So you need to learn how to ignore the hype, and fall asleep in the early miles while still maintaining a respectable pace. The fat miles in training can help in the recall.

[Cutika99]

I agree with getting "hyped up" for a race. In fact, unless the race is 1600M or less, you're much better off being relaxed early and fired up late. I often see CC teams getting pumped right before the race. This is actually the worst possible thing. Not only are you burning carbs, you may also be using up some adrenaline -- not really a good idea. I like to tell people, "It's not football. Football is a series of short bursts requiring maximum effort. Time the amount of actual action in a football game. It's somewhere between 9 and 17 minutes. Honestly, the rest is the clock jsut running. And most players play less than half the game (as the only play offense or defense generally). Save that energy for later. You'll need it then."  Good post btw.

[murthy]

Sasha,
Thanks for this post. I Will try this out but do have some questions:
a) When u say run slow for a long time - how long do you mean?
b) You mention the swithover from fat to cards takes a while on accelerating from slow to fast - I just want to get a sense of duration is this something that happens in second or minutes and in your experience does this depend on how quickly the accelleration happens?

Thanks in advance for your response.

[Tara Summers]

Great post and very interesting to think about. Thanks, Sasha.

[Sasha Pachev]

This forum works on an eternal schedule, so I think it is OK to respond to a post that is 2 years old. So running slow for a long time - maybe 7-10 miles for somebody doing 80+ miles per week. How long it takes to switching from fat to carbs I suppose will depend on how much adrenaline you will produce while accelerating. I am going to guess it takes about 3-6 minutes for me based on how I am feeling - at first I feel sluggish but then I feel zippy. I assume that sluggish means I am using primarily fats, and when it becomes zippy the switch to carbs has occurred.