This is really cool! In the video below, astronaut Jeff Williams demonstrates the acceleration experienced inside the cabin during a planned International Space Station reboost on January 24, 2010.
At 350km above Earth’s surface the vacuum of space is not perfect and the International Space Station is constantly slowed down by drag. Although the drag is really small the station’s orbital height can drop by 20 km in a year. Without periodic reboost maneuvers the station would become a big fireball in just a few years. The ISS is also reboosted to prepare for visiting spacecraft, such as the space shuttle and Progress vehicles.
As can be seen from the plot, the rate of descent is not constant and this variation is caused by changes in the density of the tenuous outer atmosphere mainly due to changes in solar activity.