or Gravity Block.
Large blocks of composite material similar to concrete, housing an artificial gravity generator for the purpose of training and developing F-Gene fighters.
Regular issue gravity trainers are limited to producing 25 standard gravities. Pressures beyond 25 gravities are possible, but begin to affect the mechanism itself so that the generator would crush itself or, at the very least, render itself inoperable. Custom rigs are available, but they are difficult to produce and expensive to maintain.
F-Gene fighters practice their various martial styles upon gravity trainers under ever-increasing pressure, building up a cumulative tolerance until they are able to operate freely--which is to say, until the increased gravity offers no more resistance than one standard gravity would.
An individual's gravity rank is the highest number of standard gravities he or she has achieved on the gravity trainer.