A 2h run burns about 1400kcal, which means after 2h your body will be putting all sorts of stops trying to maintain the last carbs.
So why is it so important to use fat as fuel?
It’s about the body’s ability to store fat as fuel vs storing carbs. Carbs can be stored in the
liver, blood and muscles and you can have somewhere around 2-2300kcal total. A 2h run burns about 1400kcal, which means after 2h your body will be putting all sorts of stops trying to maintain the last carbs.
This also means you need to steadily need to supply your body with carbs to keep functioning while running.
The fat stores on the other hand are almost unlimited with over 150 000kcal of energy. The more efficient the body becomes in using fat, the faster you will be able to run. And you will not need to rely on the small storage of carbs.
So how do I get my aerobic zone mapping to be able to train in?
The easy way to do this is the Maffetone Method, by Phil Maffetone. Take 180-your age. In my case it will be 180-42=138. That means I should do all my runs under 138 in heart rate. There are some variables around this that you can read here:
The more scientific way to calculate your aerobic training zone is using what Joe Friel teaches by his 30 minute test. Go to a track and warm up for 10 minutes. Then do a 30 minute run at 85% of max. After 10 minutes you press lap on your HR running watch. The average HR (heart rate) of the last 20minutes is your LTHR (Lactate Threshold Heart Rate) or the point where your body goes straight to burning carbs instead of fat. When you have you LTHR you can calculate your zones here:
The good thing about the Joe Friel test is that you redo the test every 6-8 weeks and with your progress you move your aerobic zone upwards.
When first starting to run in your aerobic zone you will probably run extremely slow. And your mind will tell you that slow is not fast right? But it will be. As your body will be more efficient with burning fat as fuel you will be able to boost you pace in the same HR zone. But it takes a little while so don’t quit, it will benefit you in the long run.
Ultra running seems cool – Part 2 – Muscle fiber
Ultra running seems cool – Part 3 – Energy systems
Ultra running seems cool – Part 1 – How do I start?
I want to start running – Part 3 – The first 5k
I want to start running – Part 2 – The first 30 minute session
I want to start running – Part 1
Are you lost in quick fixing your health?
Are you still waiting for motivation to show up?