Space legs
The term space legs referred to one's motor control having acclimated to the rhythms of space travel. Not having gotten one's space legs could lead to bouts of space sickness and dizziness, and was comparable to the ancient naval phrase of having sea legs, a similar phenomenon common to sailors at sea.
In 2151, Hoshi Sato confessed that her initial reluctance to go on away missions had passed, and that she felt she had finally gotten her space legs. Captain Jonathan Archer assured her he had known it would only be a matter of time until she did. (ENT: "Sleeping Dogs")
In 2153, Sato remarked that the MACOs appeared to have gotten their space legs. N. Kemper noted that some of them still needed to visit Doctor Phlox each morning.(ENT: "The Xindi")
In 2269, Montgomery Scott assured a new-to-deep-space-travel Mira Romaine that her fainting spell was likely due to her just getting her space legs. (TOS: "The Lights of Zetar")
In 2375, The Doctor assured a space-sickness-suffering Kathryn Janeway that twenty milligrams of inaprovaline ought to restore her space legs. (VOY: "Relativity")