Thanks for these questions! Pre-swing occurs as weight is effectively shifted to the contralateral lower extremity and the toes of the reference limb rise from the ground. Heel rise occurs in mid-terminal stance (during weight-bearing). Heel rise occurs as the plantarflexors are stretched and is an indication of achievement of an effective trailing limb posture. The eccentric activity of the plantarflexors during terminal stance provides the ankle rigidity necessary to allow heel rise. If the plantarflexors are weak, the heel may not rise and the limb could enter swing phase from a foot flat position.
Heel rise is quite a significant part of the gait cycle. I don’t think you need to get too in the weeds for NCS prep purposes, but, if you are interested, this article is a great resource: Kerrigan DC, Croce UD, Marciello M, Riley PO. A refined view of the determinants of gait: significance of heel rise. Arch Phys Med Rehabil. 2000;81:1077-1080.
Here’s an excerpt:
“Weak ankle plantar flexors also will tend to reduce heel rise. Concentric ankle plantar flexor activity, which affects ankle plantar flexion motion, should contribute directly to heel rise. But even aside from active plantar flexion motion, the ankle plantar flexors (and/or tendons) should provide rigidity to the foot and ankle that is necessary for heel rise. Thus, in the case of weak ankle plantar flexors without other mechanisms to reduce collapse into dorsiflexion (such as an ankle plantar flexion contracture or an ankle-foot-orthosis with a plantarflexion stop), there would be little if any heel rise until body weight were largely shifted to the forward limb.”