Yup and some ESC's require that you move the stick to full throttle and back down before they will ARM, as a safety and calibration feature.

This way the ESC can figure out the range of the TX's throttle signal.

As everyone states. read the manual about arming the ESC.

Sometimes GP/Tower ( and E-Flite/Horizon too! ) does not provide the ESC manual, but you can typically find these on-line.