From Quake Wiki
|Saved to config.cfg:||no|
cl_backspeed is the base speed you move when pressing +back. The speed is multiplied by cl_movespeedkey if the +speed button is activated. Note that the Quake menu option "Always Run" doesn't actually always turn on +speed but instead simply attempts to raise the cl_backspeed, cl_forwardspeed, and cl_sidespeed. It is recommended that you do not use "Always Run" and instead add +speed to your autoexec.cfg.
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