Is a treadmill bad for dogs? The answer is “no.”
Treadmills have been used for many years to train working and agility dogs in order to build up their endurance, heart and lungs. Just like a treadmill for a human being, it gives the dog the ability to walk or run at a pace that they set, providing them with the ability to burn as many calories as they want to. There are two types of dog treadmills, the motorized treadmills and “slatmills” which are treadmills without a motor. The way they work is by leashing the dog to the treadmill so they cannot fall off the front or back, then motivating them to run forward using some form of toy, treat or energy. The dog then walks or runs in place as a belt moves under their feet. These types of treadmills are preferred by many trainers as they provide resistance as well as being able to be stopped any time the dog wants to stop moving. Since they work using positive motivation, if the dog does not want to walk or run, they cannot be forced to. This allows for the exercise to be more enjoyable as well as strenuous for the dog, who in turn builds stamina and muscle mass while doing exactly what is natural, chasing things.
Treadmill exercise for dogs is believed by some to be cruel or bad for the animal. This is primarily due to them being illegal in some states in the United States. Unfortunately the reason they are illegal in some states has nothing to do with their effectiveness at building muscle and stamina, or forcing dogs to run. They are illegal because they are a common tool that dogfighters use to train their dogs. In the dogfighting world, the strongest dogs are going to be the best at fighting for lengthy times, leading authorities to realize that most dogfighters will have treadmills on the premises. In order to make criminal convictions stick, evidence of dog fighting is necessary to present. Because the treadmill is such a common tool to use to build strength and endurance, it is almost always present when police raid dog fighting rings. As a result of the desire to more easily convict dog fighters, authorities made it illegal to own treadmills that are designed for dogs in many states. Unfortunately this is very much like saying that leashes or collars should be illegal, because dog fighters use them too. A misunderstanding of why the tool is being used by this particular group leads many people to assume that the tool itself must be cruel. Nothing is further from the truth. Treadmills are no more cruel for dogs than they are for humans, and nobody is raiding gyms to confiscate the equipment.
Naturally, any tool can be misused and be co-opted by bad people for bad purposes. Treadmills have been used for decades by the best trainers in the world to provide weight control, aggression and destructiveness training as well as general canine fitness. They will almost always be met with criticism from uninformed people who believe things based on a lack of knowledge and understanding.
Love your dog? Run your dog!