Learning How To Pace Yourself

What a better time to talk about pacing and energy systems than during this little heatwave we’re having in the UK- straight from hoodies and wondering whether you’re legally allowed to put the heating on in June to THIS…

So, it’s hot (at least for today) and of course pacing becomes even more important in ours runs. But why an article on pacing and energy systems? Well, both are inextricably linked to one another so in my head and in my coaching they come as a package deal. And I also think it’s important to provide a bit of evidence of why I’m always going on about why you should run your runs on feel.

My aim is to keep it as simple as possible so here goes and let’s see if I achieve it, shall we?

Even before we get out of bed in the morning, our energy systems require energy to simply keep us alive and healthy. We need food and water even if we didn’t do anything all day. This system is called the Aerobic energy system and creates energy with the presence and the consumption of oxygen for an indefinite period. This system is used if you are resting, walking or easy/moderate running, anything that is a non-intense form of movement. Your body is so efficient that if you kept fuelling, you could literally run all day, it would be your musculoskeletal system that would let you down or of course that annoying blister/chafing (delete as applicable).

The problems occur in running when you switch from this aerobic system to the Anaerobic system.

The Anaerobic energy system can create energy without the presence of oxygen; however, this system has a finite and shorter duration during which it can create energy. The harder you work, the faster you run, then the shorter the duration in which this system can provide energy. 

As you pick up the pace you have trouble consuming enough oxygen to meet your needs and your body responds by relying less on fat for energy, shifting instead to burning more glycogen as it switches to the anaerobic system.  Fat cannot be mobilised or burned quickly enough to meet the energy demands of a more intense pace, because the burning of carbs for energy requires less oxygen and so carbs become the preferred fuel whenever oxygen is a limiting factor.

So once you have moved into the anaerobic system you’re into the body’s limited carb/glycogen stores, and it’s important to remember this system has a finite and shorter duration than the aerobic system. It doesn’t matter how ample your fat stores are, after you deplete your muscle glycogen stores you will experience fatigue and will be unable to sustain your current pace.

 When you no longer have enough energy to power your body, you hit The Wall and it doesn’t have to be the dreaded “20 mile” wall, it can happen at any mileage. For 5ks you can usually hang on but sometimes even a badly paced 10km can feel like a living hell if you switch the anaerobic system on too soon, especially if you haven’t eaten breakfast or fuelled properly before the race. Once you get to the last of your available glucose in the bloodstream it becomes difficult to replenish it, even if you continue to ingest carbs, the gels and jelly babies will not make a lot of difference, you cannot just simply switch to using oxygen and your aerobic energy system when you start to get in trouble- this is because glucose is still necessary for the aerobic system to use oxygen to create energy.

 Basically, if you don’t properly train your body to efficiently create and utilize energy and/or stick to running within the limits of your aerobic system you will sabotage your performance either in training or in your race. Even if you run too fast on an easy 5k training run you will be switching on the anaerobic energy system, become out of breath, and have to walk, so you never train your body to run efficiently and burn the right fuel. Of course there are also other factors that can affect your aerobic threshold/increase your HR- heat, humidity, elevation, hydration level, stress, and sleep quality- all of which can hit us hard in the warmer months.

So if you’re running your “easy” pace this week and it feels hard, please don’t beat yourself up. No matter what level runner we are, the distances we are running or have run, or the years we have in the bank, there are other factors that effect which energy system you use, and some of those are simply out of your control. Train for what you can control, but don’t waste any extra energy worrying about what you can’t! (Which is also not such bad advice for life really is it…)

Good luck out there!