Shin splints isn't really a specific diagnosis, more of an umbrella term. If you are feeling it in the outside of the lower leg during activity, it could be one of many things, but might involve your peroneal muscles and or lateral compartment. If you are feeling it during exercise, it might be the result of excessive work being done by the peroneus longus to stabilise your foot/ankle when running, which is likely due to (as many lower leg injuries) to over-pronation or flat feet, especially if you are feeling it during hte toe off phase of running or the heel strike. Essentially, either the muscles is straining and that is what you are feeling, or the excessive work of the msucles is leading to increased pressure in your lateral compartment (a sheath around the lateral group of muscles in your lower leg) thereby cutting off blood supply etc during exertion. You would probably benefit from an orthotic assessment, or at least a physio assessment where they could identify any biomechanic issues you have. This is only a possible cause, not definite, seek help if it continues, cheers