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How not to run a half marathon


Today’s blog is a video blog, a vlog, but you can read the transcript below:

Hello, it’s Angela Isherwood here from I Run Success. And today’s blog is all about race fuelling.  So, I had planned to talk to you this week about carb-loading, and I even started recording some videos for that as i had a race on sunday. 

Unfortunately my race did not go to plan and my carb-loading did not go to plan because on Saturday, I fell ill. It was a very minor illness and don’t worry; I’m absolutely fine now but my illness meant that I had to do a “Paula” on my run on Saturday afternoon, and actually I struggled to eat anything  for the rest of the day.

The Race

So, although I woke up on Sunday morning feeling fine within myself, I knew that I didn’t have the energy reserves as usual.

I decided to race as I felt and i felt full of energy at the start. I had some residual carb-stores in my body obviously. But, when these ran out, they ran out quite catastrophically and my pace dropped quite dramatically as you can see in this image (fuelling crisis began mile 8):

So, I will tell you about the energy systems we use during a race.

Ideally as we start a race, you’re really well fuelled, and you know what pace is going to be a good one to run.  As you start and you’re increasing your pace the anaerobic system switches on quite quickly to its full capacity and the aerobic system switches on a bit more slowly.

The aerobic energy system is the one that we think about when we’re thinking about long distance exercise and it is using oxygen and it is using predominantly fat as fuel.  So, when you’re going for a walk for example, that’s aerobic exercise.

Now a lot of us think of running as aerobic exercise (and it is) but in fact when you are doing a longer race, you are using the aerobic system the whole time, as you can see in this graph, but in order to get the speed, you need an energy system that is a bit quicker at producing energy in your muscles, and that is the anaerobic energy system.

Ideal energy usage when racing

So, they work together, and as you can see in this graph, the anaerobic system switches on a bit quicker together with your race pace, and it is using sugar as fuel, so the glycogen that’s stored in your muscles that you would have built up over a couple of days of carb-loading is what’s being used here.

Ideally, you’d get up to your target race pace and you’d hold on and be using a nice balance and even mix throughout the race of the anaerobic and aerobic energy systems.  And you can even do a little bit of a kick at the end because you haven’t completely run out of your glycogen stores.

Energy usage when starting off too fast

Now I’m gonna show you a different graph. This is what happens if you start too fast. If you start too fast what happens is your aerobic zone is still going to go to the same sort of level. The anaerobic zone is going to switch on quickly but you’re going to be burning sugar at an alarming rate to cope with that pace.

And what’s going to happen is that is going to drop over time as the fuel source becomes more scarce. IT will become less and less efficient which means you’re more reliant on the aerobic system for your pace, and as the race goes on your pace drops and drops as there’s less sugar available and you’re unable to use that anaerobic energy system.

So this is where pacing is a really important part of running a good race strategy because as this happens you feel worse and worse. The fat-burning system is not a very comfortable way to run because it is a bit slower and inefficient in getting the energy to the working muscles.

Energy usage when there isn’t enough glycogen stored

And lastly, this is exactly what happened to me on Sunday. So, I had some glycogen stores just from what I’d eaten in the morning. I had some porridge in the morning and that stayed down alright. And I’d had some pasta the night before and that had also stayed alright, but the previous 24 hours anything that I had eaten hadn’t stayed in my system long enough for me to gain much from it.

As a result, I was able to start the race quite well and I was running it at what I thought was my half marathon pace based on recent training. But as I went on (and I took some energy gels along the way) I got to a point in the race, and this happened at some time in the 8th mile where i just completely HIT THE WALL. I crashed out.

So, I had absolutely no energy, and it feels really horrible. I started thinking of giving up. Those feelings of hitting the wall are not that familiar to me, as it hasn’t happened in quite some time because i’m always so good at doing my carb-load and fuelling effectively on the run. But what happens here is you crash out and you can no longer run at anything like your race pace.

I ended up doing the majority of the second part of the race at what’s my easy run pace. When you look at the chart, you’ll see where I’m really having a struggle mentally and i stop to walk a few times, you can see exactly where that happens, and then when I get back into running at the pace I can go, it’s back into the aerobic fat-burning zone.

This is the pace I could run on and on and on because it’s in the fat burning zone. It’s slow and inefficient. The only thing that’s going to stop me running at that pace is very extreme muscular fatigue, or any injury that pops up (or just having a mental block).

I hope those graphs have helped you to understand the point of fuelling prior to a race and then during the run. As you can see, not everybody’s perfect. I know exactly what to do to do better, but sometimes we just can’t stop illnesses from affecting our preparation.

Now I wanted to see what I could do, as I wanted to test out my half marathon pace, and I’m quite confident that had I been correctly fuelled, I could have held on for the next 5 miles, because when I crossed the finish line and for the rest of this week, I don’t feel all that fatigued. I just really lacked energy on the day.

How do I avoid hitting the wall?

So make sure you download the free marathon nutrition guide to learn how to do it the right way! and I will see you on the blog next week.

This week’s race really showed what can happen to runners toward the end of a longer race, or even a long run if they are under-fuelled and run out of glycogen. Make sure you download the marathon nutrition guide to learn how to do it the right way, so that you can delay hitting the wall.  The later it happens in a race, the more likely you will be able to cope with it mentally and keep pushing on.

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Angela Isherwood

Angela Isherwood is the founder of I Run Success
She is a REPs Level 3 Personal Trainer, a Run England Running coach, and a multiple marathon runner. She is a London Marathon Good for Age runner, a Boston Marathon Qualifier, a parkrun Run Director and Trainer for Goodgym Colchester.

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