technique, that of and that of , are considered essential to aikido training. Both are studying aikido principles of blending and adaptation. learns to blend with and control attacking energy, while learns to become calm and flexible in the disadvantageous, off-balance positions in which places them. This "receiving" of the technique is called . continuously seeks to regain balance and cover vulnerabilities (e.g., an exposed side), while uses position and timing to keep off-balance and vulnerable. In more advanced training, will sometimes apply to regain balance and pin or throw . refers to the act of receiving a technique. Good involves attention to the technique, the partner, and the immediate environment—it is considered an active part of the process of learning aikido. The method of falling itself is also important, and is a way for the practitioner to receive an aikido technique safely and minimize risk of injury. Initial attacks Aikido techniques are usually a defense against an attack, so students must learn to deliver various types of attacks to be able to practice aikido with a partner. Although attacks are not studied as thoroughly as in striking-based arts, attacks with intent (such as a strong strike or an immobilizing grab) are needed to study correct and effective application of technique. Many of the of aikido resemble cuts from a sword or other grasped object, which indicate its origins in techniques intended for armed combat. Other techniques, which explicitly appear to be punches (), are practiced as thrusts with a knife or sword. Kicks are generally reserved for upper-level variations; reasons cited include that falls from kicks are especially dangerous, and that kicks (high kicks in particular) were uncommon during the types of combat prevalent in feudal Japan. Some basic strikes include: is a vertical knifehand strike to the head. In training, this is usually directed at the forehead or the crown for safety, but more dangerous versions of this attack target the bridge of the nose and the maxillary sinus. is a diagonal knifehand strike to the side of the head or neck. is a punch to the torso. Specific targets include the chest, abdomen, and solar plexus, sometimes referred to as , or . is a punch to the face, sometimes referred to as . Beginners in particular often practice techniques from grabs, both because they are safer and because it is easier to feel the energy and