The six-person Expedition 40 crew of the International Space Station wrapped up another workweek in space Friday supporting medical and physics research, maintaining station systems and gearing up for next week's spacewalk.

Following the crew's normal 2 a.m. EDT reveille, Commander Steve Swanson and Flight Engineers Reid Wiseman and Alexander Gerst participated in a variety of experiments aimed at understanding the effects of long-duration spaceflight on the human body and developing countermeasures to mitigate the health risks. This research is vitally important as NASA works toward sending humans on longer voyages beyond low Earth orbit.

Swanson began his day with the Sprint investigation, which measures the effectiveness of high-intensity, low-volume exercise training in minimizing the loss of muscle mass and bone density that occurs during spaceflight. Station crew members currently work out around 2 0.5-hours every day, and the researchers behind Sprint aim to reduce that total exercise time while maintaining crew fitness.

...Wiseman meanwhile served as the subject for a session of the Cardio Ox study, which is investigating the risks of cardiovascular disease related to long-duration spaceflight.

With guidance from the ground team, Gerst performed an ultrasound scan on Wiseman and measured his blood pressure. Results from this experiment will help researchers determine if biological markers of oxidative and inflammatory stress are elevated during and after spaceflight, and how those markers correlate with the long-term health changes in astronauts.

Wiseman also logged his meals and followed a prescribed diet for the Pro K study as nutritionists monitor how dietary changes may affect spaceflight-related bone loss.

For the Circadian Rhythms investigation, Gerst donned sensors and an armband monitor to track his body's core temperature over a 36-hour period. Since the station orbits the Earth 16 times a day, an astronaut's body clock can get disrupted from experiencing a sunrise or sunset every 45 minutes.

Results from this investigation will provide insights into the adaptations of the human autonomic nervous system in space and will help optimize crew schedules and workplace illumination.

...Gerst also set up samples and configured hardware for a combustion experiment known as the Burning and Suppression of Solids, or BASS. In the absence of gravity, materials burn quite differently, and some materials may actually become more flammable than on Earth.

BASS takes a look at how a variety of materials burn and extinguish in microgravity, which will lead to improvements in spacecraft materials selection and strategies for putting out accidental fires aboard spacecraft. The research also provides scientists with improved computational models that will aid in the design of fire detection and suppression systems here on Earth.

Working in the station's Kibo laboratory, Swanson swapped out a seedling test sample chamber inside the Cell Biology Experiment Facility, which includes a centrifuge for controlled gravity levels. The Resist Tubule experiment examines the mechanisms for gravity resistance in plants to help researchers learn more about the evolution of plants and enable efficient plant production both on Earth and in space.

After a break for lunch, Swanson and Wiseman worked together in the station's Tranquility node to remove and replace a failed heat exchanger for the Common Cabin Air Assembly, a component of the station's Environmental Control and Life Support System which collects condensate out of the air.

In the Quest airlock, Gerst wrapped up verification work on the new spacesuit delivered to the station by the SpaceX-3 commercial resupply services mission in April.

Gerst performed a water dump and fill of the spacesuit to satisfy maintenance requirements for on-orbit stowage. Since this is the first U.S. spacesuit that has traveled to the station on anything other than a space shuttle, Gerst has been conducting an extra-thorough checkout of the suit to certify it for readiness.

With their own spacewalk looming next week, Flight Engineers Alexander Skvortsov and Oleg Artemyev attached spacewalk tools and other hardware to their Russian Orlan spacesuits, including gear on loan from their NASA crewmates.

During the 6 0.5-hour excursion slated to begin at 9:50 a.m. Thursday, the two spacewalking cosmonauts will mount a new integrated command and telemetry system on the Zvezda service module and replace a payload rack on the Russian segment with a payload boom previously installed in a temporary location. NASA Television coverage of the Russian spacewalk begins at 9:15 a.m. Thursday.

The spacewalk will be the 180th in support of space station assembly and maintenance and the first for both Skvortsov and Artemyev. The third Russian cosmonaut aboard the station, Flight Engineer Max Suraev, worked with Skvortsov to install a docking mechanism for the ISS Progress 55 cargo craft connected to the Pirs docking compartment. Suraev also conducted an audit of the docking and internal transfer system tools and equipment aboard the station.

Over the weekend, the station's residents will have some free time to relax, speak with family members back on Earth and take care of weekly housekeeping chores. They'll also have a chance to catch up on the action at the World Cup 2014 games in Brazil. The crew sent down a special message earlier to wish good luck to all the players and teams.