When your dad is out biking, tell him to sing louder than the birds. No kidding, joining a commnunity choir is the best throat exercise for the larynix.
He can scat sing, sing Hymns, music from his favorite musicals or Operetta's. Gilbert & Sullivan have wonderful music for men. He might try to extend his range or work on ways to breath from the sides as well as shallow breaths.

"I am a Pirate King"
Dianna