Maybe your dog is not running and playing as he used to. You are concern and you are right to be so. Every living being with the years passing by gets slower and weaker. That is life.
What we recommend in these cases is for you to adapt to his limited mobility. There are plenty of activities and plays you can still do together. Understanding their limitations is key in to keeping your dog healthy and happy.
#1 Modify your behavior and your expectations accordingly with your dog’s age and needs. We have to understand that, that once playful puppy has grown up. If you notice him having trouble moving, climbing stairs than find a way that helps him.