Training at the correct intensity for the right amount of time is one of the most important, but one of the most commonly misunderstood, parts of a training programme for trail or ultra running.
A knowledge of the biology behind the intensities will help to shape your training schedule.
What are aerobic and anaerobic systems?
Adenosine triphosphate (ATP) is what makes your muscles contract for movement – the aerobic system produces 36 ATP per cycle, compared with just two per anaerobic cycle.
Traditionally, it was thought that the aerobic zone was when your muscles work with oxygen; anaerobic was when your muscles work without oxygen. New studies suggest that when you reach a certain intensity you are working quicker than the aerobic cycle can keep up because the aerobic cycle produces a lot of ATP but slowly, and the anaerobic cycle produces a little but quickly. So, you supplement the aerobic system with the anaerobic system – it is not to do with oxygen, or lack thereof.
The threshold between the two is not as simple as the commonly thought lack of oxygen and has been the subject of endless debates in sports science.
From a runners’ perspective, the aerobic zone is “easy” and the anaerobic zone is “hard”. Running just under the threshold between the two is tough but sustainable for a long, but not indefinite, time, sometimes called “tempo” running.
Training in different zones
It seems intuitive to train just under the threshold between aerobic and anaerobic zones. This way, you are pushing hard but at a level you can maintain. However, this is a common mistake among trail runners – ‘no pain, no gain’ is no longer based in sound sport science.
Why you should include walking in trail or ultra running training
Around 80 per cent of your training should be firmly “easy” aerobic, not reaching the threshold. The other 20 per cent should be a mixture of intensities including tempo running and in the anaerobic zone.
Firstly, an increasing amount of studies have shown that this 80/20 split is the most effective for producing physiological changes. Secondly, it helps you avoid injury or burnout. And thirdly, particularly for ultras, you are unlikely to work hard enough during the race to leave your aerobic zone, so it is the most relevant training anyway.
How to know if your are in the right zone
The simplest way to know if you are splitting your training time correctly is perception. The 80 per cent aerobic training should feel easy. In fact, a lot of it should feel far easier than you think. Try including power walking, or uphill walking, hiking or light jogging in your training.
One way to tell if you are in your correct, easy, aerobic zone, is if you can talk. Chat to your training partner, and if you cannot speak in full sentences because you are too out of breath, you are training too hard.
Another common incorrect assumption is that you can compensate for lack of time with intensity. Runners think if you only have so many hours to train between work, you can make up for it by pushing yourself harder but the 80/20 aerobic/anaerobic split applies no matter the volume.
If your legs are getting heavy, you are panting hard and feeling yourself slowing down, you are training in your anaerobic zone.
You can also use your heart rate. Roughly, your maximum heart rate is 220, minus your age. Aerobic training is 60 to 70 per cent of your max heart rate. Tempo running is around 80 to 90 per cent of your max heart rate. Above 90 per cent, you are firmly in the anaerobic zone.
All heart rates and intensities have a place in your training programme, but too fast too often is a recipe for injury and burnout. Not too mention it is not as effective as very easy and very often.
