Tsuki is translated as ‘thrust'. Tsukis is the title given to any thrusting technique. Punches in karate are termed as tsuki. It is with the help of two knuckles of the fist which are called seiken (fore-fist) that these attacks are traditionally delivered. The techniques performed with the fore-knuckles of the fist and spear-hand attacks are also referred to as tsuki.
The most popular form of attack in karate is the punching techniques (using the seiken). Punching techniques are quick, powerful and versatile and for this reason they are often used. In order to be capable of withstanding impact, punches keep their hands in a very solid and stable position. There are certain other attacks that can turn out to be of more effective than punching, theoretically.
Tsuki can be categorized as follows:
A full spreading or extension of the arm is required by all basic punches and they are linear. These punches are often considered to be the most powerful and possess the longest range. It is very easy to learn them and they can be used in a simple manner. In karate, they are the mostly used form of attack. It is likely that a punch is a basic one if it is used in dojo. It is in kata that other punching techniques are used.
The way of performing with both hands at the same time is referred to as double-hand punches. It is however ironic that double-hand punches are not actually strong as single-hand punches. Since both hands are used at the same time, it is hard in coordinating power. Hip rotation is smaller in these movements. One of the benefits of these punches is that even though they are not used as an offensive attack, two targets can be hit at the same time. They are used in a defensive manner, as a response to an attack. Sen no sen is achieved by the frequent use of these double-hand punches.
Punches performed by the middle knuckles of the fingers are referred to as fore-knuckle punches. The contact point s much smaller and these techniques are known to be sharper. Greater penetration of force where in on a smaller surface are, the same amount of force is used thereby creating a greater pound-force per square-inch (psi) can be attained by these techniques as the point of contact is smaller. The joints of the fingers are likely to be in danger while using these attacks. There is a strong possibility of the joints of the fingers breaking if they are not strong enough to withstand the impact with the target. Thus for this reason, they prove to be effective in small targets or soft vital areas thus safe guarding from injury. It is very important that fingers and knuckles are properly conditioned before using them on solid targets.
The tips of the fingers are involved in a thrusting motion in spear-hand techniques. The potential for penetration force is (psi) often greater when it comes to these techniques as the fingertips are small or sharp. These can turn out to be very deadly if used by a person whose hands are greatly trained or conditioned. The hands are likely to be broken as the force behind this technique is quite massive. Proper training is extremely important without which it would turn out to be ridiculous a real situation even on soft targets. It is appropriate for it to be left in kata if you do not have proper training in it.