The surface and wire electrodes were mounted with lightweight connectors and the signals were conducted directly to small custom-built preamplifiers (input impedance 80 Ma) taped to the skin. The EMG signals were then led through 5-m-long
shielded cables to custom-built amplifiers. The wire setup permitted the subjects to move unrestricted. The signals were sampled by a DT-2801-A analog-todigital converter (Data Translation, Inc., Marlboro, MA) operating at 1000 Hz and fed to an IBM PC DX2 clone.