Negative Mach

Negative Mach is a trick that allows you to slow down while still retaining the current mach state.

An example of Negative Mach is shown below.

Technical explanation by Vexxter: By releasing dash as soon as you exit a wallclimb, your horizontal speed value gets set way lower than your movement speed value, because the game bases your mach state using your movement speed and your horizontal speed is the speed you actually move in, you can run at a low speed while being in a higher mach state than intended.