Another idea would be to go biking with him on the street for a while, but that should wait until he is at least one year old as forced running on pavement at 7 months could be to much for his little body. But you could start walking him next to the bike to get him used to being near it. Also if you have any doggy daycares or doggy play socials ( we have these
at least once a week at one of the doggy daycares near us ) you could go to, they will tire him out like nothing else, not at a kennel where him will be caged all day, but one where he can run in a fenced in place and play with other dogs all day. They are great for if you know you will be busy all day and may not have the time to go for a couple hour long walks!