The short answer is no effect at all. The more detailed answer is that both the space shuttle and the astronauts move in exactly the same way (due to the acceleration). Consequently, the space shuttle and the astronauts do not move at all with respect to each other. Both the station and the astronauts are in free fall. The situation is analogous to a passenger in an elevator which is in free fall due to mechanical failure. The passenger and the elevator car do not move relative to each other. If the passenger were standing on a bathroom scale, the scale would read zero. This is the 'weightless' condition. Similarly, astronauts in the space station are in the 'weightless' condition.
