You should coordinate your training frequency with your previous training volume, your running goals, your ambitions, and, of course, with the rest of your life. Always remember that training and recovery go together and need to be in a healthy relationship. Moreover, be advised to gently increase the training frequency if you want to remain symptom-free. One additional session per week per semester is as good as it gets. Ideally, you do not increase overnight but gradually: do one additional run this week but run the usual 3 times, for example, next week. The following week, run 4 times again etc.
The table below should help you find your optimal training level. At the same time, you should absolutely keep working on the other fitness factors (strength, agility, speed, and coordination).
Finally, you have certainly asked yourself how often you have to train to reach a specific goal time. The table below shows the number of training sessions that are required for a set marathon and 10km time.
We are aware that there are always exceptions to the rule. Try it out and prove you can do better, if possible!
Keep on running!