Vincent's NT Word Studies
7. He took (piasav). The verb means originally to press or squeeze; and hence implies taking hold with a firm grasp.Feet (baseiv). A peculiar, technical word, used by Luke only, and described by Galen as the part of the foot lying beneath the leg, upon which the leg directly rests, as distinguished from the tarsov, the flat of the foot between the toes and heel, and pedion, the part next the toes. Ankle-bones (sfura). Only here in New Testament. Also technical. Some of the best texts read sfudra, but the meaning is the same. Received strength (esterewqhsan). Used by Luke only. Compare "the churches were established (ch. xvi. 5), and the kindred noun sterewma, steadfastness (Col. ii. 5). In medical language applied to the bones in particular.
Robertson's NT Word Studies
3:7 {Took him by the right hand} (piasas auton tes dexias ceiros). Doric form piazw for piezw. Genitive of the part affected. Peter had to pull him up on his feet before he would try to walk.