Hi! I had my THR fitted 2nd May 2017, was back to max HR on road bike and 5k running by 9 weeks – somewhat slower than before but the HR was right up there.
Having to look back through my Garmin stats I was amazed just how quickly the biking came back – I sat on my indoor trainer for aerobic 30k / 1 hour sessions for about 3 weeks then started back on the roads, in the July I logged over 450km, longest ride 58 miles at a decent pace. I had carried on running and biking right up to my operation, which probably helped. If it hurts, stop, but otherwise go for it!