You probably need some more information before making your final decision. Contact someone involved with the study and find out exactly what's being done. They may be doing a study using electrical stimulation, which doesn't necessarily involve shock treatment.

Electrodes or patches are placed over muscles and the muscles are forced to contract. This is one way to help strengthen muscles weak from pain and disuse. Most researchers explain everything on the first day. You still have the option to bow out before starting.

When using electrical stimulation, the therapist usually lets you feel a small dose first. There's a tingling sensation. As the current is turned up, the muscle fibers start to twitch. With enough stimulation, the entire muscle contracts. It's an odd sensation, but it's usually not painful or dangerous.

Research shows electrical stimulation applied along with exercise can help restore muscle strength after a knee replacement. Sounds like you have a chance to get help while also helping others.