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What happens to your body during a long run?

By Michael Crawley

The Physiology

Runs over about 90 minutes in length deliver a whole range of physiological benefits. Your heart will get stronger. Your muscular endurance will improve as mitochondria (the ‘powerhouse’ of your cells) increase in size and number, and the capillaries that deliver blood to your muscles grow. Your very ability to breath – or your ‘ventilatory capacity’ – will improve as you work your respiratory muscles. Finally, you will train your metabolic system, as your body learns to use fat rather than glycogen as a fuel source.

Twenty’s Plenty?

At about twenty miles, levels of glucose in the bloodstream start to drop and your stores of carbohydrate energy are almost depleted. If you’ve never run this far before – and even if you have – this is where it starts to get tough. Towards the end of a long run your body will probably start to ‘recruit’ muscles that aren’t normally called upon, which explains why you tend to be so sore in the following days.

The Mystery

Whilst sports scientists produce endless physiological data to explain what happens to the body during a long run, there is really only one way to understand how it feels, and that’s by repeatedly doing it. In the course of such a long run you’re almost guaranteed to go through a ‘bad patch’ as my coach puts it. And if you’re lucky you might also experience something like a ‘second wind’ – the feeling that it’s suddenly and inexplicably very easy, at least for a while. As Alex Hutchinson, author of Endure, notes, these aren’t necessarily phenomena that can be explained in terms of ‘unambiguous physiological changes’. In fact, they are more likely to be linked to neurochemical or psychological factors, which leads me to my last point.

The Mind

Running for three hours is physically hard, but it can also be boring and mentally challenging. Getting through these runs is mental training as much as it is physical training, and it also builds your confidence that you can handle the distance. In my next blog, I will discuss the visualisation and positive thinking techniques that might help you get through them, but for now here are a few ideas about how to mix up your long runs and keep them interesting.

Livening Up the Long Run

Instead of just running at a steady pace, try these variations:

  • 60 minutes of easy running, 10 x 90 seconds on/off, 30 mins steady.
  • 18 mile ‘progression’ run: 6 miles at marathon pace +20 seconds, 6 miles at marathon pace +10 seconds, 6 miles at marathon pace.
  • Long Fartlek: Alternate between marathon pace and ‘easy’ pace, but without a predetermined structure. Just pick a landmark in the distance and think, ‘I’ll run at marathon pace until I get there then I’ll ease off’. This one definitely helps to pass the time!

Michael Crawley is one of our sponsored athletes, and focuses primarily on the roads. He is also an ESRC-funded PhD student at Edinburgh University, studying the culture of long-distance running in Ethiopia.

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