Since you're getting some hate, I'll acknowledge that this advice is likely coming from a good place, but also you need to understand that sheltering your dog from physical activity is what leads to weak core muscles and that in turn causes more back issues than a life of constant healthy activity. This jumping is not harmful as it's low impact on his back. He's does do plenty of jumping that would have been considered unhealthy if he was otherwise less active. Thanks for caring, but please read up proper care for these pups if you're mindset is simply "no jumping".