------------------------------ From: TMccull230@aol.com Date: Sun, 24 Dec 1995 Subject: The Kinetic Chain Here is a article on why some exercises are better suited to the powerlifter and strength-speed athletes than others. This is a interesting, shortened version of an article titled: The Kinetic Chain and The Powerlifter by Thomas D. Fehey, EdD Professor of Physical Education, Exercise Physiology Laboratory California State University, Chico In athletics, the goal of training is to do exercises that gives you strength you can use in a weight lifting contest or on the playing field. If the strength increases won't transfer to your sport, you are wasting your time. There are three factors involved in improving strength: muscle hypertrophy, neural activation, and stretch activation. Muscle Hypertrophy: Muscle size is the most important factor determining a muscle's strength--the larger the muscle the greater the strength. However, the strength-size relationship is at least partially based on which motor units are developed in training. You should strive to work the muscles in much the same way you will use them in a contest or a sports movement. For powerlifting and other strength-speed sports, you need maximal power--the kind developed through lifting heavy weights, not the watered down strength gains you get from doing lots of reps. Since you only need short bursts of all-out power, it is important that you train that way. Neural Activation: Motor units in a muscle group do not turn on at the same time. During different parts of the range of movement, some motor units are activated while others are not. Therefore, the activation sequence from an exercise will not transfer to a sports movement unless the exercise and sports movement are very similar. Stretch Activation: A muscle can exert more force if it is stretched immediately before it contracts. This is called the stretch-shortening cycle. If you can learn to coordinate muscle stretch with muscle contraction, you can greatly increase you effective strength. Like electrical activation, the effective transfer of stretch activation requires training exercises to be as similar as possible to the way you want your muscle to work during competition. The Kinetic Chain: Movement that requires simultaneous use of one or more joint at the same time form a kinetic chain. In a kinetic chain, movement is generated from coordinated muscle contractions that move more than one joint at the same time. In the squat, deadlift and power clean, a kinetic chain is formed by the ankle, knee, and hip joints. Muscle activation is sequenced according to the movement in these three joints. In a kinetic chain, the movement patterns of an individual muscle, such as one of the hamstrings, is different than when the muscle moves a single joint. Muscle contraction sequencing, motor unit activation, and stretch activation are fundamentally different during multi-joint than when individual joints are isolated. One-joint exercises, such as leg extensions or leg curls, develop movement patterns that will interfere with patterns you use in sport. Such exercises lead to inappropriate muscle recruitment patterns that can lead to injury. Assisting exercises should also be as close to the major lifts as possible. Rather than doing knee extensions, do exercises that work the full kinetic chain, such as hack squats, front squats, power rack squats, power cleans, and snatches. These will also work the hamstrings, but if you want special assist exercises for the hamstrings, make sure the movement is initiated at the hip, not the knee. An example of this would be the Nautilus hip and back machine. The problem with this exercise isolates the hip and doesn't use the kinetic chain principle. The further removed from the kinetic chain sequence, the less effective your exercise routine will be. -------------------------------------