English: Figure 6-4. The first U.S. “treadmill” utilized during spaceflight was a passive device used only on the Skylab 4 mission of 84 d duration. The high loading (175 lbs) via bungee cords provided more of a resistive rather than an aerobic modality. It consisted of a Teflon-coated aluminum plate attached to the Skylab isogrid floor. The exercising crewmember wore a waist and shoulder harness that attached to the iso-grid floor surrounding the treadmill plate by means of 4 bungee cords. Socks had to be worn to provide a low-friction interface between the plantar surface of the feet and the Teflon-coated treadmill plate. From reference.
The NASA website hosts a large number of images from the Soviet/Russian space agency, and other non-American space agencies. These are not necessarily in the public domain.
The SOHO (ESA & NASA) joint project implies that all materials created by its probe are copyrighted and require permission for commercial non-educational use. [2]