When we talk about threshold run, we often talk about the anaerobic threshold. However, there is also the aerobic threshold, which is much less well known but also very interesting to know in order to progress. Aerobic threshold training is what could be called active endurance training. Integrated into a varied training, it can be very interesting to develop your general endurance. So I suggest you understand what the aerobic threshold is. Understand the advantage you may have in using it and how to effectively integrate it into your training.
Aerobic threshold, active endurance, ventilatory threshold 1, lactic threshold 1....
Don't be surprised if you hear several names for the aerobic threshold. The aerobic threshold as most commonly used is equivalent to ventilatory threshold 1 (SV1) or lactic threshold 1 (SL1). These are different concepts, based on different measures but which simplify them, all correspond to this aerobic threshold. Purists may not like this simplification... But in any case, in our daily lives, as amateurs, we do not have enough to measure these thresholds precisely. So it doesn't matter to simplify a little because we will ultimately summarize the aerobic threshold to a single value. And this value will be in percentage of maximum heart rate / running speed.
What is the physiologically aerobic threshold?
The aerobic threshold corresponds to the end of basic endurance. This is the threshold at which the body will have to work harder to provide the energy that we use to move forward. Fundamental endurance mainly uses so-called slow muscle fibres to move forward. These muscle fibres know how to use fats and sugars as energy sources. But the process of energy production via fats is slow. As a result, it cannot supply large quantities of energy. And slow muscle fibers.... are made to last a long time, not to produce a large amount of energy. So, the faster we go, the faster the muscles will recruit their fast fibers to produce energy. And these fast fibers, they work mainly with sugar. So the faster we go, the more we run on our sugar reserves.
And the more we use sugars to create energy, the more we will create what we call lactate. It is most often referred to as lactic acid (wrongly). This lactate is a very useful element for the muscle since it can recycle it in real time during exercise. This recycling aims to reuse lactate to produce energy and thus save our sugar reserves. Another part of the lactate produced will be sent to the blood for recycling by other muscles and organs such as the heart or brain. But these recycling processes have a limited capacity. And if we produce more lactate than our body's ability to recycle it, it accumulates in the blood. The notion of an aerobic threshold was born here. More details on lactic acid by clicking here
In short: the aerobic threshold is the rate at which the lactate level in the blood is no longer stable but begins to accumulate slowly.
What pace to run at the aerobic threshold?
The aerobic threshold corresponds for the majority of runners to a value around 80% FCM. This is obviously not universal, but it is impossible to be precise without an effort test. We are all different. But this average value is the one that seems to be the closest to reality. If you can do an exercise test, go ahead, it's very useful, but if not, start at this value and you'll train in the right area to work on the aerobic threshold. In terms of sensation, you should feel a slight acceleration of breathing around the aerobic threshold. You go from a pace where you are able to talk without problem to a very light breathlessness that only allows you to exchange by short sentences.
In the end, it is in terms of speed that the variations will be significant depending on the individuals and their level of training. The aerobic threshold is a pace that can be maintained for a few hours before exhaustion, unlike fundamental endurance, which could be maintained almost "indefinitely", if one has training as a matter of course. The aerobic threshold can correspond to less than 60% of the Aerobic Maximum Speed (AMV) for a very low endurance runner, and up to more than 80% AMV for a very endurance runner. Kenyans are known for their great efficiency on this side, I told you about it here. It's quite logical but the shorter we run, the better our endurance is and the longer we'll be able to maintain a high speed.
Is the aerobic threshold fundamental endurance?
There are two schools on fundamental endurance. Some consider that this basic pace of the runner goes up to 80% FCM. And so it should include the aerobic threshold. I am one of those who think that setting the limit at 75% FCM. The goal is to differentiate between fundamental endurance and the aerobic threshold is important. Differentiating clearly between these two types of gaits helps to better manage your training.
Telling a runner that he is in fundamental endurance up to 80% FCM is opening the door for him to run all the time at 80% FCM. And even if this aerobic threshold pace is interesting for development, running only at the aerobic threshold is far from ideal for progress. Doing basic endurance most of the time and including aerobic threshold regularly in these sessions is much more interesting.
Why running at the aerobic threshold makes progress?
I told you that the aerobic threshold can correspond to 60% VMA as well as 80% VMA... Well, that's exactly why training to run at the aerobic threshold is effective. Especially for long distance runners (half, marathon and more). Running in fundamental endurance and sometimes at the aerobic threshold means training your body to be more efficient. More efficient in processes related to energy creation, in the use of fats as an energy source and in the recycling of lactates.
In this way, we teach our bodies to save their sugar reserves for longer. Running more on fat means using less sugar. And reusing more lactates in the muscles that produce it also saves your sugar (and also prevents the accumulation of lactate in the blood!).
The more the body improves in this area, the more we will be able to maintain high speeds while being more economical. And gradually nibble to be able to run at the aerobic threshold at 70% VMA, even 75% and why not 80% VMA after several years of training! And the pace that we can take on a marathon for example depends directly on this kind of data... The faster we go to the aerobic threshold, the more our marathon pace will increase. And if we work on our anaerobic threshold in parallel, it will improve all our competitive gaits!