A few of the dogs in my care seem to have boundless energy!
One is a teenage cattle dog who has a ball fixation. He loves his red Kong ball and will chase it all day long if he could!
Another is a black labrador and staffy "mates" ... and esp. the black lab seems to have boundless energy even after spending 2 hours at a local off leash dog park
It's just the dogs being dogs and enjoying life/the moment.