Doctors have implanted electrodes in Christopher Reeve's diaphragm in an experiment designed to enable the paralysed actor to breathe on his own.
The 50-year-old has been on a respirator since he broke his neck in a horseback-riding accident eight years ago.
He can currently breathe for more than two hours without the respirator, compared with 10 minutes before the surgery.
As his diaphragm muscles get stronger, he is expected to be able to do away with the respirator and speak more normally.
Reeve played Superman/Clarke Kent in the 1978 'Superman' movie and in sequels 'Superman II' in 1980 and 'Superman III' in 1983.
