Personal Liability at Work

Some of our employees want to bring exercise equipment (treadmill, rowing machine, stationary bike, etc.) in from home and set up an exercise room at work. The machines can be used by any employee either directly before or directly after working hours. The department supervisor has okayed this idea.

Question: What, if any, liability is there to the employees who own the machines from others who may be injured during use, and is the employer at risk by allowing this plan to move forward?

We work in New York State.
Thanks