There is still debate as to exactly what causes shin splints, but it is usually a bony stress reaction of the tibia (shin bone) or an irritation of where some muscles insert into the shin.
What can be done about it?
Address your running load.
Usually, MTSS is associated with a sharp increase in running load. In most overload injuries, there is a link between the load that the tissues undergo and the onset of your symptoms. If the load (the distance you are running) is too much for the muscles and bones to cope with, or the body has had inadequate time to adapt and recover, there will be a reactive response, which usually manifests itself as shin pain. Remember to gradually increase your distances rather than bump them up too quickly.
Over recent years, there is some moderate evidence for taping as a short-term solution to your shin pain. It will help to decrease the load on the tissue while you get to the bottom of the issue. Kinesiotape has been the subject of a lot of research, and the results are actually quite promising. Taping will not be the panacea that fixes your problem but might help relieve your symptoms whilst you’re correct the underlying cause. It can also help you to get through a particular race (if you are desperate!).
Importantly, you need to strengthen two groups of muscles:
a) the muscles at the site of pain. One of your calf muscles called soleus is usually the culprit here
b) any other muscles of the lower limb that are not working properly and thus causing incorrect form and overload on your shins. This might (and often do) include glutes, quads, and hamstrings.
Footwear and orthotics
Old footwear will lose most of its capacity to control and support your foot. If the sole of your shoe has lost its spring or rigidity, its time for a new pair. As a very general rule of thumb, you should look to replace your runners after every 800-1000 kilometers. Ensure you have the correct running shoe for your foot type, a running gait assessment may help this.
A poor running technique can be a big contributing factor to the onset of shin pain. This can be a result of lack of ankle joint range, muscle tightness, muscle weakness or habits that have been formed over time. A running biomechanics assessment can help to identify a few key things that will help you to improve your technique (and also your running economy so that you ran further and faster!).
Visit your physio
As always, I suggest getting a proper diagnosis by your physiotherapist or other qualified healthcare professional as there are quite a number of different sources of shin pain.
Remember: if in doubt, get checked out!