http://www.intensitymagazine.com/01-15-02/erick_colbert.html
In the evolution of Power development, it is very important to become familiar with the concept of strength deficit. It's an extremely powerful tool that will assist you, the coach, in determining the individual needs of your players, regardless of the sport. In this article, I'll illustrate exactly what the strength deficit is, an easy way to assess the athlete, how to interpret the results, and point you in the right direction as to the proper way to maximize each athlete's potential to express Power on the playing field—Where It Counts!
First and foremost, the strength deficit is "the percentage of maximal strength potential which is not used during a given motor task." The task could be anything related to sport movement in any variety of sports. "Why wouldn't a player be able to use all of his/her strength potential?" Well, let's take a look at some research. Below is a list of various sport motions, and the time it takes to perform these tasks in seconds. Movement Time (s)
Shot put 0.15-0.18
Javelin 0.16-0.18
Sprinting (coming out of the blocks) 0.08-0.10
Long Jump 0.11-0.12
High Jump 0.18
As you can see, these explosive sports movements occur extremely quick. To fully grasp why it isn't possible to express maximal strength fully one must be aware of the time it takes to display maximal strength and force. Research has shown that maximal force is reached between 0.3-0.4 seconds. In some instances, it may be slightly longer than 0.04 for a small minority. What does this tell us? Look at the movements listed in the chart above. They are executed at a significantly faster rate than that of maximal force. Upon comparison, it becomes quite apparent that we simply cannot utilize all of our muscular force within these time parameters.
The most common way to measure the strength deficit in your athletes is through the vertical jump test. The coach needs to get a measurement for the static jump. This simply means a jump from bent legs (the stretch reflex should be totally eliminated, so hold position for 3-4 seconds before allowing athlete to explode upward). One must also use dynamic measure, which is a vertical jump preceded by a sudden dip to activate the stretch reflex which results in greater force. The difference between the two should then be calculated. The dynamic subtracted by the static jump = strength deficit. The standard difference is approximately 20%—that's acceptable. If the difference between the two numbers is large (more than 20%), then the athlete is lacking explosiveness. Therefore, the athlete needs to focus his attention towards explosive training in the form of Olympic lifts for low reps, Plyometrics (shock training), and Medicine ball work. These methods are effective in training the nervous system to fire quicker and with more force. If the difference in the numbers is small (less than 20%), there will be a need to gear towards building hypertrophy (muscular size) using moderate weights with ample repetitions along with a concerted effort to improve starting strength. The strengthening exercises should be basic in nature, and the focus should be on multi-joint exercises that stimulate large amounts of muscle fiber. Never forget the core!
I would recommend testing for this 3-4 times a year during the off-season to assess the effectiveness of your training. It'll give an indication as to whether you've made any headway on increasing your explosiveness or whether or not the muscle mass you are building is translating into functional strength or unnecessary bulk.
Let's not forget that most skill-oriented sports involve ballistic movements that occur much quicker than the time it takes to achieve maximal force. In relation to time, the slower the movement, the more max strength will predominate. To the contrary, when movements are quick, strength plays a much lesser role. Rate of Force Development, RFD (your ability to activate as many muscle fibers in the shortest amount of time) becomes the overriding factor for success. This activation of muscle fiber can be thought of as an explosive burst, as witnessed from a flash bulb when someone takes a picture or flips a light switch, if you will.
I hope this article has been enlightening as to the importance of the strength deficit. Understanding the basic elements should help you to see the big picture in attaining maximal Power. The assessment of strength deficit is easily done and the test doesn't lie. The results will leave you with little doubt as to what is needed. The vertical is used because it is, without question, one of the best markers for assessing overall explosive power of the athlete in a wide variety of sports. Give it a try. You won't be sorry!
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