Wiki photo: Adductor muscel
Adductor injuries are rather common with sports that involve sudden stops and sidesteps, e.g. football or badminton. It should be quite rare among runners. It's still a miracle for me that I strained my left adductor twice within a fortnight.
One option might be that the indoor biking came too intensely, another that a new workout to strengthen the hamstring wasn't tolerated.
Running is strictly off-limits until Thursday now when I still hope to be able to take part in the traditional New-Year's-Eve race.