They found the longer the trip, the greater the threat of deep vein thrombosis.
VOA: special.2009.07.14
Eight small boats exploring stretches of the Hudson opening to canoeists in the central Adirondacks all made it through seven moderate rapids interspersed with long flat-water stretches on a 7.3-mile trip through deep forests of evergreens and hardwoods.
Astronauts would then travel to the asteroid where "there could be mining activities, research into ways of deflecting an asteroid from striking Earth and testing to develop technology for a trip to deep space and Mars, " it said.