Terminal stance begins when the center of gravity is over the supporting foot and ends when the contralateral foot contacts the ground. During terminal stance, around 35 percent of the gait cycle, the heel rises from the ground. Preswing begins at contralateral initial contact and ends at toe off , at around 60 percent of the gait cycle. Thus, preswing corresponds to the gait cycle's second period of double limb support. Midswing is the period from maximum knee flexion until the tibia is vertical or perpendicular to the ground.
Terminal swing begins where the tibia is vertical and ends at initial contact.
An overview of normal walking. Observational Gait Analysis Handbook .