Wednesday, January 11, 2012

Increasing the Impact Force of the Rear Hand Punch - Part 2

Rear Leg Drive was covered in the previous post. This post will deal with the other 4 concepts from that article.

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Turner, A., Baker, E., Miller, S.,  (2011). Increasing the Impact Force of the Rear Hand Punch. Strength and Conditioning Journal, volume 33 (number 6), pages 2-9.

The article discusses the kinetics and kinematics of the rear hand punch to show ways of increasing the impact of the punch. Turner indicates that the material is generalizable to other strikes, which I don't doubt. The rear hand punch is used as the basis of the analysis because it is well understood, used in many arts and the most powerful punch.

Five key aspects of the punch are identified to optimize the strike:
1. Rear leg drive
2. Landing with a rigid front leg
3. Stretch-shortening cycle of the trunk
4. Velocity of the strike
5. Effective mass of the strike

These key aspects align with the key elements of the kinetics of the strike
Rear Leg Drive - the rear leg is used to initiate the strike and extended explosively to contribute power. This is done with the front leg in the air and moving forward. The more powerful the rear leg drive the harder the strike.
Rigid Front Leg - the front leg must land rigidly to provide a brake on the forward motion of the body. This focuses the rear leg drive on the upper body. The more rigid the braking action, the more force is transferred to the strike.
SSC of the Trunk - the rear shoulder is pulled back early in the strike coiling the trunk to generate more power. This occurs because of the elastic nature of musculature. Stretch Shortening Cycle (SSC) is the neurologic component that increases the elastic reaction of the muscles. A better trained SSC in the trunk increases the trunks contribution to power.
Velocity of the Strike - the arm can move at tremendous speed and is quite light, so it's primary contribution to force is through velocity. The faster the arm moves the harder the strike.
Increase Effect Mass - the arm actually slows down just before the strike lands. Activation of the muscles in the arm to make it rigid cause this effect. A rigid arm allows more of the mass of the body to be contributed to the power of the strike.

Rigid Front Leg
Landing with a rigid front leg will cause more force to be transferred to the strike. Substantial bend in the knee is the most likely indicator that the front leg is not rigid enough. Training for a more rigid leg should be done gradually, because we are training to overcome the body's natural defense against impact/landing. As long as this process is done gradually then the connective tissues and related structures will strengthen appropriately.

Training for a more rigid landing can be done with box drops. Simply step off a plyometric box (or similar) and land. Don't focus on trying to land rigidly, let that develop at it's own pace. Start with small boxes and work your way up to taller boxes, as well as single-leg drops. When incorporating this with other plyometric programs it is important to take into consideration the total number of contacts per training session, so as not to overload the tissues.

Olympic lifts and squat jumps will also help develop this characteristic.

Stretch Shortening Cycle of the Trunk
The rear hand punch, and many other strikes, include a wind-up action that brings the elastic nature of the muscles into play. This elasticity is the reason that untrained folks will naturally pull their fist back before punching. It's also the reason why when you jump you naturally drop down just a bit before moving upwards.

The elasticity of the musculature is the result of two factors: connective tissue is elastic similar to the way that rubber bands are; and our nervous system has controls on the muscles that produce a similar effect - which is known as the Stretch Shortening Cycle (SSC). These two together can substantially add to force production.

Medicine ball exercises can be used to train this capacity. The most basic is a side pass.
  1. Stand in your typical striking stance with your left foot forward. 
  2. Hold a medicine ball at arm's length with both arms. 
  3. Rotate clockwise a short distance, quickly and then reverse direction and throw the ball. 
  4. If possible catch the ball and repeat, making sure to counter turn a little with each catch or before each throw.
  • Focus doing the throw with the torso, not the arms.
  • For this exercise, we are concerned with rapid action so a light ball of around 2 kg is sufficient. 
  • Not all med balls are equal, some bounce better than others. For fighter training I think the bouncier kind are more useful for a wide variety of drills.
A forward and backward pass can be done as well, following the same principles. For the forward pass face the wall with your feet squared and the ball over head. Arch back just a little bit before throwing forward. The backward version is done while facing away from the wall and you crunch forward just a bit before throwing overhead and backwards.

There are plenty of good variations on these exercises. This is meant as a good start.

Increase the Velocity of the Punch
Training to increase arm velocity will focus on ballistic type exercises. The focus is on speed not just weight. Here again, medicine ball exercises will help. A variety of throws using form similar to strikes will work for this kind of training. Again, use a light medicine ball to focus on velocity of action. However, the simplest ballistic upper body exercise is the clap push-up.

Another option is to use resistance bands for conventional weight training exercises (not discussed in the article). These increase resistance progressively and so the action starts off fast with a light resistance and the load increases as velocity decreases. This method also plays well into the next concept.

Increase the Effective Mass
The effective mass of the hit is determined by how rigidly linked the parts of the arm and body are at impact. The more rigid they are at impact the more weight is behind the punch. Studies of muscle activation in punches show a double-peak effect. As the hand starts to move forward the muscles activate strongly. Then the relax and the hand sort of glides forward. Last the muscles activate again making the arm and wrist rigid.

This double peak is not observed in shadow-boxing or other training done "in the air". So training with a solid striking target is necessary to train the body to transfer force on impact. Pad and bag work is the basic way to do this. For weapon arts it's necessary to have a striking target like a pell to hit.

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The article also has a sample program to show the combination of these various training elements. That's a whole other topic though, and I'll get into it with later posts.

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