In strength training, there are seven ways to express strength, including: push, pull, squat, hinge, lunge, carry, and twist. Nearly everything you do in strength training is directed at increasing load in these seven ways. Similarly, there are generally eight methods for generating power in Shotokan karate. (However, some group them differently so you could count them as seven or even nine.)
These methods, in the order easiest to learn, include (1) hip vibration, (2) body shifting, (3) body rising and body dropping, (4) hip rotation, (5) hip counter rotation, (6) hip pendulum, (7) expansion and contraction, and (8) stomping or ground vibration. In the simplest terms, each is described as follows.
Pull with one foot hard enough to activate the posterior chain of muscles up to the glutes. This will slightly advance that hip. Instantly pull with the other foot in the same way, which will realign the hips, creating a “vibration” of the hips. Most common in higher stances or side stance. The linear pull of the foot converts to rotational force at the hips. Keep the lower spine tight so the rotational force travels up the spine and into the shoulder. When done correctly, the energy at the shoulder is so amplified that the arm is literally and violently thrown to execute techniques. See also Hip Vibration
In short, this is either stepping or sliding the body to create power. When stepping, pull the body with the lead foot; do not push with the back foot. Accelerate the body to create force. In sliding, compress the body using the hamstrings of the back leg and instantly reverse the action using the stretch reflex and quads to accelerate the body. Reverse these actions to move backward.
To rise, when in a lower stance, pull with the foot while contracting the adductors. Which foot you pull depends on whether you want to advance while rising or slightly retreating. Pull with the front foot and allow the back foot to slide inward if you want to move slightly forward. To retreat, pull with the back foot and allow the front foot to slide inwards. You should go straight up while anchored to the pulling foot. Do not move the foot under you and attempt to stand or push upwards. Doing so is too slow and does not activate the anterior or posterior chain to create vertical strength in the upper body and arms. The upward action is as if there is a string attached to the top of your head pulling you straight up. Do not wobble. To use body dropping, think more about lifting the knee to the chest without allowing support with the opposing leg. You can only fall as fast as gravity allows. Apply your technique just before needing to brace the “fall” to avoid collapsing. How far you drop depends on flexibility. Use stomping power to continue attacking.
Hip rotation is performed primarily in front stance. It can be performed in two ways depending on need and positioning. You can anchor to the lead leg or the back leg. If anchored to the lead leg, you will pull backward with the lead foot without it moving while contracting the adductors (pulling the thighs together). The lead hip does not move backward. The back hip and shoulder swing around the lead hip like a door on a hinge. It is okay for the back heel to rise or shift because the front foot pull and anchor generate all the power. To rotate using the back foot as an anchor, compress the back leg by strongly contracting the hamstrings and use the stretch reflex to “bounce” out of compression, tensing the quads and posterior chain from the glutes up. It is okay for the front foot to rise off the ground or shift as all power is from the rear leg and anchor. Advanced karateka can learn to do both forms together.
In hip rotation, the front hip is anchored, the back hip rotates forward, as if the front hip is a door hinge, and the back hip is the outer part of the door. In counter-rotation, the opposite occurs. The back hip is anchored, and the front hip rotates backward.
In simple terms, rotate the butt under as if pointing the knot of the belt upwards. To grasp the feeling, lie on the floor with your knees flexed (90/90 position). Slowly contract the lower abs below the belly button as your knees rise toward the chest. Continue until the lower back is pressed against the floor and the lower glutes are lifted off the floor. This is the pendulum movement when standing. This pendulum motion is used almost exclusively for front kicking. Reverse the motion (extension) to backkick. For side kicks, you will use extension (stick the butt out) while raising one hip. Stand with feet close together to practice side hip pendulum and support your balance. Lift one hip such that the same foot rises off the ground as high as possible. As you do so, put the low back into extension (rotate butt out). If you don’t put the hip in extension, you risk damage to the hip socket. Note extension is unnecessary for side kicks lower than 30 degrees depending on flexibility.
This is often called “compression and expansion.” Humans are stronger and faster pulling inward toward the center than pushing outward away from the center. We also experience a stretch reflex that allows for reversing the direction of movement quickly and powerfully. Contraction is pulling in toward the center. Focus more on pulling with the elbows and knees than hands and feet. Consider the reflex of touching a hot stove and how quickly you can move. We have these reflexes in the upper back and lower spine to control the arms and legs, respectively. Contraction allows for fast, powerful defensive actions as well as pulling and grappling. After contraction, instantly expand to express movement outwards. The feeling is like balling up in the fetal position and then expanding like a starfish. This has to be taught in person to capture its depth.
There is an opposite and equal reaction to force, which applies to force against the ground. Stomping is not merely stomping with the foot or leg but tensing up the kinetic chain so that the reaction jolts up through the body and can be expressed in the hands or feet. If you were to hop up and lock the legs when you land, the reaction would be intense and dangerous for your joints. Nevertheless, this experiment demonstrates how much force travels through your body when stomping. Mixed with body dropping, stomping effectively and safely delivers power up the body nearly instantly. Guided instruction is essential to avoid injury.