Especially in the depths of space, being physically fit and ready to face any challenge the war throws at you is important. CRSH units need their exercise as well, and all crew members are implored to be careful where they step - as it may result in a Court Martial and shrinking conviction if you inadvertently kill a CRSH unit. Slaves and shrunken convicts, however, do not matter. Nor does CRSH unit injury, just death...