https://www.thesprucepets.com/best-dog-treadmills-5296147
https://www.goodhousekeeping.com/life/pets/g45688215/best-dog-treadmills/
From the American Kennel Club...
https://www.akc.org/expert-advice/health/use-your-treadmill-to-exercise-your-dog/
Use Your Treadmill to Exercise Your Dog
Key Points
A treadmill is great for indoor exercise for your dog.
Use a treadmill year-round for warm-ups and conditioning for your dog.
You can use a human treadmill for all but the largest dogs.

Getting On the Treadmill
Training your dog to use the treadmill means breaking the process down into small steps and building a positive association with each one. Start by treating your dog for simply getting up on it. Dog gets on, click and treat. Dog gets off, click and treat. Repeat this step many times, then end the training session, says Johnson. If your dog is not clicker trained, simply feed treats. Remember never to force the dog to get on equipment. The goal is for your dog to want to get on the treadmill on his own, she says. If your dog is nervous about the treadmill or not used to getting up on things, you may need to start slower by treating for simply being near, or looking at it, before working on getting up on it.
Once your dog is comfortable getting up and standing on the treadmill, the next step is to turn the power on. But dont start the motion yet this step is just to get the dog accustomed to the sound of the motor and fan. Treat for standing there listening to the noise. My machine was so quiet that my dog didnt seem to notice it, so this step went quickly, but be sure to look for signs of stress and make sure your dog is completely comfortable before moving on.
HTH