Sometimes when cats and dogs get animal obesity, regular walking can become too hard on their joints and back. You can't just put them on a regular treadmill. So there are underwater treadmills. The buoyancy of the water makes it easier. Underwater treadmills are more often used for dogs, but sometimes cats do use them, because they love exercise and water.
His eyes. They tell you it's working.
To paraphrase Christopher Hitchens, when you shelter and feed and adore a dog, it will come to believe that you're God. Do the same for a cat and it will believe that it is God. This is like the old parable where God walked on the underwater treadmill.
Even non-obese cats who are 16 years-old and need rehab can use hydrotherapy.
"Before Coco came for treatment, she was finding it difficult to do the normal cat activities, like jumping up on work surfaces."