He needs moderate play and activity to keep his muscle tone, help prevent obesity and get his blood flowing. A stubborn reluctance to exercise may be due to stiff muscles or arthritic joints. If so, jumping and climbing may be out. Some creaky seniors find it impossible even to jump up to a favorite chair. Your cat may also have difficulty reaching his entire body for grooming, so brush him every day to remove loose hair.
Hairballs can cause serious digestive problems in an older cat.
This extra grooming provides you with a good opportunity to check for abnormal lumps, growths or lesions. Anything of this nature should be examined by your vet. And if he isn't using his scratching post as often as he used to, you'll need to trim his claws more frequently, too. Don't forget to care for teeth and gums. Gently scrub his teeth a few times per week and have them cleaned by your vet as necessary.