Anyway, I purchased new running shoes that were on sale, Adidas Response Stability 4M:
Today I had time to try them in the evening. My aim was to run just relaxedly and be careful to not run too fast, avoiding 'jamming' my muscles. It didn't feel too bad.
The loop was 6.45 km long. I'm using RunKeeper to record my training. A nice thing about it is that I can use my old Polar S710i with it and add the heart rate file afterwards:
The best thing about this kind of training is that it's very effective when you don't have time for longer exercise.
The new shoes feels pretty good, so I'm looking forward to more of this.