Thursday, April 11, 2013

How To Increase Rate of Force Development







How Do We Increase Rate of Force Development?

The methods used to increase the rate of force development are numerous.  In the weight room there exists a wide variety of lifts designed for this task.  Exercises such as weighted jump squats and other explosive lifts that are done with an emphasis on speed really hone in on the “force development” aspect.  As mentioned above, many exercises done in the weight room can increase both maximum levels of strength and rate of force development at the same time, as long as you emphasize speed of contraction.

Outside the weight room certain plyometric type drills and other bodyweight exercises are inherently good at improving your rate of force development.  All of these methods have a few things in common.  They are inherently explosive and performed with high velocity or speed. The advantage of explosive, high velocity power training is that it trains your nervous system to fire quicker by shortening the time it takes your muscles to contract, especially the fast twitch muscle fibers. Training in this fashion also improves your mind to muscle link giving you better muscular recruitment ability.  Strength training by itself stimulates a high recruitment of fast twitch muscle fibers leading to increased levels of force.  Explosive and high velocity movements increase the speed at which your muscle fibers can contract.  Combine them together in some fashion and you get power improvements across the board.


Plyometrics

No discussion on vertical jump training would be complete without a section on plyometrics.  Before we get into discussing various plyometric drills and how they work Id like to first address their history.  Plyometrics is the term now applied to exercises that have their roots in Soviet training methods. This method was originally known as shock” training and was invented by Yuri Verkhoshansky in the Soviet Union.  Interest in this jump training increased during the early 1970s as East European athletes emerged as powers on the world sport scene. As the Eastern bloc countries began to produce superior athletes in such sports as track and field, gymnastics, and weight lifting, the mystique of their success began to center on their training methods, which consisted of plyometric training.

The actual term Plyometrics” was first coined in 1975 by Fred Wilt, an American track and field coach. Based on Latin origins, plyo + metrics are interpreted to mean measurable increases. These seemingly exotic exercises were thought to be responsible for the rapid competitiveness and growing superiority of Eastern Europeans in track and field events. Although thought to be secretive and exotic, originally plyometrics consisted of only 2 rather simple exercises, - depth” jumps and shock” jumps.  A depth jump entails jumping or stepping off of a bench or object and immediately jumping up as high


as possible at ground contact. A shock jump is pure energy absorption training and consists of jumping off of a very high object and simply landing and absorbing the impact.  After plyometrics were given their now common name, coaches began to lump all types of hopping, jumping, skipping, and bounding drills in with the original plyometrics.

Plyometrics rapidly became known to coaches and athletes as exercises or drills aimed at linking strength with speed of movement to produce power. They became essential to athletes who jumped, lifted, or threw. During the late 1970s and into the '80s, those in other sports also began to see the applicability of these concepts to their own movement activities. Throughout the 1980s, coaches in sports such as volleyball, football, and weight lifting began to use plyometric exercises and drills to enhance their training programs.

So How Do They Work?

Plyometric drills are utilized to bridge the gap between force and explosive power and increase reactive strength.  Reactive strength fits in nicely with power development.  It is also known as plyometric strength, reversal strength, and elastic strength.

You can think of a reactive movement as aspring-like movementt.  The drills are performed to develop force by a quick loaded eccentric, or negative contraction.  This contraction causes a stretching of the tendons and also increases muscle recruitment. Basically the muscle cells lock up as the tendons stretch.  The body stabilizes this negative force, stores this force, and then “releases” this force.  The reflex action brought on by the quick stretch allows you to put out a stronger than normal muscular contraction in the opposing direction.  Pick up a ball, any ball, and throw it.  Now pay attention to what you naturally did without thinking about it.  Did you bring your arm back behind your head and pause and then throw it? I would hope not! Chances are you quickly drew your arm back and let it fly.  That is a plyometric movement! The quick rearing back of your arm quickly stretched the tendons in your shoulders and built up energy, which allowed you  throw harder.  Would you have thrown as hard if you brought your arm all the way back, paused for 3-seconds and then released the ball?  Definitely Not!

By definition, almost all activities (and certainly all sports) rely to some degree or another on this stretch-shortening cycle, plyometric strength, elastic strength, reactive strength, or reversal strength.  Dont let the terminology confuse you, they all mean the same thing! Examples of plyometric activities are walking, running, rope skipping, jumping, and just about any dynamic activity that you can think of (i.e. all of them).

However, I want to differentiate between a plyometric activity (such as walking) and plyometric training. Generally speaking, true plyometric training is very high intensity work like depth jumps (stepping from a box, hitting the ground and exploding) and bounding type exercises that require a strong loading and stretching of the muscle/tendon complex. Even many of the introductory plyometric exercises are not technically plyometric training. They are intended to condition the body for the more intense work to come.  True plyometric training involves high intensity activity.

Plyometric action is much like a rubber band in that, if you stretch a rubber band quickly, it will spring back faster due to storing potential energy. Stretching the elastic muscle and tendon components produces elastic potential energy similar to that of a loaded spring. When the muscle is stretched rapidly the muscle-tendon complex stores a portion of the load force in the form of potential energy. The recovery of that stored energy occurs during the concentric or upward phase. To take advantage of the SSC reflex, the concentric (positive) muscle action must immediately follow the stretching.  When you jump, a great amount of force is gathered as you absorb the negative (downward) forces and gather this energy to propel your body upward.  The body must be able to quickly stabilize and store the negative (downward) forces and then flex and extend to leave the ground.

A muscle that is rapidly stretched before a contraction will also contract faster and more forcefully. This is why the best leapers tend to movedown” into their countermovement the fastest and poor leapers move down slower.

Sources:

Radcliffe, J., and R. Farentinos. High-powered plyometrics. Matoon, IL: United Graphics, 1999. Print.


Chu, Donald A. Jumping Into Plyometrics. Human Kinetics Publishers, 1998. Print.