Speed Boost lets you increase a teammate's sprint speed for a short period. You cannot administer this buff to yourself.
This allows a Medic to increase the running speed of a target. It is administered like a Life Buff, by injecting them with a syringe. As such, the Medic needs to be close enough to the target in order to interact with them.
The effects of this Ability are particularly useful for Carry Objectives as it enables runners to escape pursuers easier. It can also be used for defending as it allows reinforcements to move slightly faster.