What is the load shift keying?

They use them in biomedical telemetering. You have a coil outside the body, sends 8 MHz RF to another coil inside the body. The 8 MHz is rectified to provide DC power. Then, inside the body, a data source sends return data by either puting a short circuit across the coil, or an open circuit, which the outside sending circuit can sense.

One paper:
Data Transmission from an Implantable Biotelemeter by
Load-Shift Keying Using Circuit Configuration Modulator
Zhengnian Tang, Brian Smith, John H. Schild, and P. Hunter Peckham
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING. VOL. 42. NO 5. MAY 1995