Ensign Melora Pazlar, a female Elaysian.
The Elaysians are a humanoid civilization native to a low-gravity planet.
The Elaysian physique and neural motor cortex is adapted to cope with a low gravity; on their homeworld they are virtually able to "fly". When exposed to Earth-normal gravity environments they need physical support to function. The type of support varies but includes wearing an external skeleton with integrated servomotors which help supporting the person's own skeleton, although this only functions for short periods of time. For longer-term physical support other forms of support are needed, like a wheelchair or an anti-grav unit.
A medical treatment was developed by Doctor Julian Bashir based on earlier neuromuscular adaptation research by Nathaniel Terros. By elevating the neural output to the brain's motor cortex via neural analeptic transmitters, he improved his theory and made this treatment possible. The drawback of this treatment is that if started, no exposure to low gravity environments is advised because this would confuse the person's body and motor cortex. When finished, the person can move naturally in 1 G as if they were in their low gravity environment. A side effect of this treatment is that once finished, it is not possible to reverse it.
Only a handful of Elaysians have ever left their planet. One of those people was Melora Pazlar who became the first Elaysian to enter Starfleet. (DS9: "Melora")