Are you referencing the actual study? The article states, “The study involved restricting mice from using their hind legs, but not their front legs, over a period of 28 days.”
Yes. They achieve those restrictions by holding up the mouse by the tail so only the front legs are on the floor of the cage.
Which makes the whole study bullshit because what they actually measured was effects of stress not of the lack of leg exercise
They also didn't control for other muscles so who's to say that it is specific to leg exercise, or even, sedentary life, living life at a 45 degree incline, too much blood flowing to the brain, or any other factor.