Can i take out my retainer for a hour "sports game", and it will be safe from shifting?

Absoliutely !: Teeth don't move that fast . Wear a mouthguard during sports

YES!: Retainers are not there to get in your way during life events. An hour here or there is of no consequence. However, inconsistent wear will allow your teeth to gradually shift away from there desired postions. Have fun, play sports. Retainers of certain types can also function as a mouth guard.

Yes, but: If it is a contact sport (football, basketball, hockey, soccer, sliding into second base, etc., have your Dentist or Orthodontist make you a custom mouth-guard to protect teeth, reduce concussion risk, etc. Mouthguard will also help to stabilize teeth. Put retainer(s) back in immediately upon leaving the playing surface. Look for reasons to put retainer in, not excuses to take it out.