Seeking asylum in the hills & transcendence on the trails

Running on Empty

Friday was my last opportunity for a long training run before the Cateran Trail Ultramarathon next Saturday.

I’ve started to mix up my longer runs meaning I generally now include 2 x types of long runs in my training. Both very different and both much debated / discussed by the running community.

Friday’s run was to be a ‘bonk’ run. A run that’s long, steady and fairly slow. Sounds easy eh? The objective of the run however is to deplete the normal glycogen energy stores in the muscles to a point where there’s nothing left and the body has to start burning fat to fuel the ongoing demands. On a normal run / race you would take in some carbs through energy drinks / gels / food but on these runs it’s water and electrolytes only.

And the purpose? Well, this is a big part of the debate. The theory is that by pushing the body to burn fat for fuel it gets more efficient at doing so and at the same time better stores glycogen in the future (when it’s in ready supply – in a race or normal training run). I guess there’s a stronger argument that there are benefits when training for ultra’s as generally the pace is slower than say a 10K or half marathon meaning that fat can be an important source of energy. Fast runs rely more on carbohydrates for fuel.

This type of run also presents you with the likely conditions you face towards the end of a 40+ mile race. Tired and heavy legs as well as the mental challenge of having to run when you really want to stop. All good practice I tell myself.

So, on Friday I skipped breakfast (something I never do) and set out just before lunchtime towards the Old Kilpatricks.

They say it takes 90 – 120 mins to really lower the carbohydrate stores. Run was tough but I was pretty much enjoying it despite the changes in weather (including hailstones) until pretty much 2 hrs in exactly. I guess this is where the carbohydrate energy stores had run dry. The next hour and a half were really hard going and even the scenery wasn’t doing anything to lift my spirits.

By the time I finally made it home (without cracking into the emergency energy gel in my bag) I was shaky and tired. It felt like I had run much further.

There will be a few more of these runs to follow and I’m hoping they get slightly easier. For now, I’ll be concentrating on getting ready for the The Cateran Trail Ultra on Saturday. Should be a good one.


6 responses

  1. Lilacswizzle

    Good post. My worry only is you dont have a lot of fat to eat into, so how does that work?
    Yer sis

    May 16, 2011 at 9:16 pm

    • Good question! Will get back to you with some science 😉


      May 17, 2011 at 6:15 pm

  2. Interesting – I complete most of my long runs with only Gatorade for fuel, but I always eat a lot before. Always wondered if the gels had more impact during the race because I wasn’t used to relying on them.

    May 17, 2011 at 1:07 am

    • That and I guess a psychological impact too maybe (which can be just as valuable!)


      May 19, 2011 at 8:04 am

  3. Alasdair McGill

    I do this type of training on the bike quite often Paul. For exactly the same reasons and it’s a well known & used technique for bike racers. Feels pretty awful, but you know that you’re improving your engine 🙂

    July 30, 2011 at 7:42 am

  4. Pingback: Exercising whilst fasted | Lorn Pearson Trains…

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