I have no experience with this, but I do know that maintaining bone density is not one of the benefits of cycling, because it is not weight bearing. The running and weight training will help you with it, though. You should aim for 2-4 rest days between weight training sessions, so twice a week is better than once (assuming you hit all the major muscle groups in each workout; if you only focus on one area, you would want to rest a couple of days before working that muscle group again, but you could work out different muscle groups the next day.)
Good luck.
- Gray 2010 carbon WSD road bike, Rivet Independence saddle
- Red hardtail 26" aluminum mountain bike, Bontrager Evoke WSD saddle
- Royal blue 2018 aluminum gravel bike, Rivet Pearl saddle
Gone but not forgotten:
- Silver 2003 aluminum road bike
- Two awesome worn out Juliana saddles