[hatsubai]

When I injured my back (years ago), I had to go to physical therapy and use specific machines that isolated the muscles in order to help regenerate muscle in the area. The physical therapy office was connected to a health center which was essentially a public gym. Together with my trainer, we used the facility's weight lifting and resistance band machines in a safe and controlled manner.

It has since healed, and I am better now. However, there was a point in time where I had to continue going to the gym and keep using those weight machines. It took a few years before I was back to normal and could start working with more generalized equipment. So there's more than just a sports-focused need (like MMA fighting or football) for gym equipment, and that equipment cannot easily be substituted, nor can it be done safely with a bike or a heavy stone.