This can be used to run in place and gain a shinecharge.
Samus must neutral bounce once while morphed before unmorphing;
the bounce can be on a platform above the spikes, or on the spikes themselves if enough space is available.
To build a shinecharge with X-mode, Samus must enter X-mode with dash speed;
e.g. this can be done with a dashing stationary spinjump, and selecting X-Ray before landing on the spikes.
Hold the dash button so that X-Ray is buffered to activate immediately after unmorphing.
See also: Tech Page