Lots of running injuries coming through the doors at the moment. Must be the fine weather!
There are so many risk factors that contribute to injury in runners. Most people with weak muscles, poor technique and not great form can usually get away with running 5-10km distances I find. The recreational runner who runs 15-30km a week will usually be fine. The injuries however start to ramp up I find once the distance starts going towards half marathon and marathon distance. This tends to be because the repetiveness of running this distance means there is no where to hide.
Strength and conditioning needs to be a part of your running training plan if you are going longer. Check yourself out, is your single leg hop distance similar on both sides? Can you go up on your toes using only one foot 20-30 times, and is it the same both sides? Do you lunge with a similar technique on both sides if you watch yourself in the mirror or is one side really wobbly?
Another huge factor is too much too soon. Increased distance has to be done slowly. And if you have taken 2+ weeks off you have to go back before you can go forward. Tendons HAAATE working hard again after a rest! Especially as you get older. So things you were doing 5 years that were fine might not be now.
Running form, running shoes, running same course every day, not enough rest days.....we could go on and on regarding risk. But for today, if you're a runner and are increasing the distance:
-do it slowly
- consider adding some strength training a couple of days a week
and enjoy!