The spacewalk was conducted on Tuesday to finish work started on December 23. The spacewalk was initially scheduled to last for some five hours and 45 minutes, but the astronauts returned to the station after four hours and 50 minutes.
U.S. astronaut Sandra Magnus was the only crewmember inside the ISS for the duration of the spacewalk.
The pair installed a device, as part of European Space Agency's EXPOSE-R experiment, on a platform of the Zvezda module to test the effects of space on a number of materials.
The astronauts also removed straps from a docking compartment of the Pirs station to ensure that they would not impede future dockings of Soyuz or Progress spacecraft.
During their last spacewalk in December, Lonchakov and Fincke installed a Langmuir probe on an ISS dock to measure electromagnetic fields, in an attempt to solve a problem relating to Soyuz landings.
Some analysts say these fields may have been a factor in the steeper-than-normal reentry of Soyuz capsules in April last year and October of 2007, which raised concerns over the safety of the landings.