“Overpronation” is a widely used and abused word by runners and health care professionals in the framework of oversue injuries and also the design of running shoes. Pronation is really a normal motion of the rearfoot where the ankle rolls inwards and the mid-foot ( arch ) of the feet flatten. This is exactly what the foot is supposed to do because it is how the foot adapts to unequal surfaces and absorbs shock. It is healthy and there is nothing inappropriate with it. The way many runners speak about what they've heard about it, you would believe that they have some kind of illness.
Where the problem comes up is that it is frequently regarded as a risk factor for getting an injury when running. For this reason, there are design characteristics in running shoes that are sold to assist runners with this alleged too much pronation. They are what are called the staility running shoes. In comparison, the neutral running shoes do not have these kinds of design features aimed at helping the so-called overpronation.
The problem with the perception of overpronation is that there isn't a consensus on what is ‘normal’ what is actually ‘over’. Some runners with severe overpronation get no issues and other runners with only small amounts get plenty of complaints. The actual research associating it to a running injury is also very weak. The general opinion of the systematic evaluations of the evidence is that it is only a small risk factor, so it is not really a big issue due to so many other reasons that go into runners getting an injury.
Therefore should too much pronation be treated? Yes, if it is contributing to the problem. No, if it is not causing the issue. This is often difficult to determine. A key in deciding if it is contributing to the problem is to figure out if the loads in the tissues that it is causing are sufficient to damage the tissues. The supination resistance test can be helpful here in helping determine this. If that assessment is higher, then the forces are high, so the overpronation should probably be treated. When the loads are low, then it is probably not necessary to manage it.
When it should be treated, then the reason for the problem should be addressed. There isn't a one-size-fits-all in relation to too much pronation. If a muscle weakness could be the cause of the overpronation, then strengthening such as the short foot exercise should help (it won’t help other reasons). If limited calf muscles are the problem, then stretching is what is essential (muscles strengthening or foot orthotics will fail in these); when a bony positioning, for example forefoot varus, problem is the reason, then only foot supports will help (strengthening muscles and calf muscle stretching will fail); and so it continues. The reason needs to be dealt with.
There are numerous misconceptions and junk being written about overpronation. A key red flag is that when someone is speaking or blogging about overpronation is, if they promote a one-site-fits-all when it comes to this, then they almost certainly have no idea of what they are talking about.