Treadmills are great like Joe said. Or an indoor spring pole if you have space. Mind games and mentally engaging them can also tire dogs out. Start looking into nose work or look into a barn hunting club that you could train and participate in. Or your own new tricks and training.
"There are two temptations to which people fall prey with dogs. The first is to think that biology counts for everything. The second is to think it counts for nothing"
- Tom Junod
“When you KNOW better you DO better.”
― Maya Angelou