There are three major types of muscle contractions that you should know about in order to understand strength training thoroughly. First is the most common, the Concentric Muscle Contraction is defined as the controlled shortening of a muscle under stress. Most exercises focus on the Concentric Contraction to increase strength. When you do a Bicep Curl, you are using a Concentric Muscle Contraction to lift the weight up toward your shoulder. You will definitely get some improvement in muscular strength, integrity and every Hypertrophy (big word that means increase in muscle size). But, if you focus on slow and controlled motions on the way up and on the way down, you will get much better results. This leads to the second type of muscle contraction, or the Eccentric Muscle Contraction. Eccentric Muscle Contractions are defined as the slow elongation of a muscle stress. This is probably the most stressful type of contraction and requires the most amount of control and focus. Therefore, Eccentric Muscle Contractions are best used for increasing strength, muscle integrity and muscle Hypertrophy. But, Eccentric Muscle Contractions have to be used cautiously, because they cause the greatest amount of micro-tears in a muscle (this is the normal response to resistance training, micro-tears occur and then the muscle repairs itself stronger than before).
You will see most people exercise by swinging the weight up quickly and then letting the weight almost drop down. This uncontrolled motion is not using a controlled Eccentric Contraction and will cause damage to the muscle tissue over time. It also uses the muscle to initially Concentrically contract the muscle, causing the weight to Accelerate and have a greater Potential Energy (the amount of force that the weight builds up because of the quick motion of the weight) at the end of the movement. You swing the weight up, using initial energy to move it. Then no energy is used until the weight is stopped or slowed, when the force on the muscle increases exponentially (causing excessive stress on the muscle, excessive Micro-tears, and Delayed Onset Muscle Soreness).
The last type of muscle contraction is know as Isometric Muscle Contractions. This is defined as a Static (no movement) contraction of a muscle, causing constant tension throughout the muscle. This muscle contraction is most commonly found in Postural Muscles or Stabilizers. Postural Muscles hold the body in place for long periods of time. These muscles are most efficient with an Isometric Muscle Contraction and should be trained in the same manner. Your low back, neck and abdominal muscles are all examples of Postural Muscles and should be trained with either very slow movements or with Static holds (example: doing a Abdominal Crunch and then holding the crunch at the end range for 5 – 30 seconds). Moving a Postural Muscle quickly is very ineffectual because these muscles are not designed for quick movements.
What you can take away from this article is:
Perform all exercises slowly and controlled, focusing on the Eccentric Muscle Contraction.
Performing a slow and controlled Concentric and Eccentric Contraction allows for consistent stress on the muscle throughout the movement causing an efficient use of the entire muscle belly.
The consistent stress placed on the muscle will allow the muscle to develop uniformly (all parts of the muscle will get stronger together, and less damage to the muscle will occur).
Performing the exercises slowly will also decrease the excessive Micro-Tearing and will avoid excessive muscle soreness.
Performing an exercise slowly will give you an accurate acuity for knowing how much weight you can lift (if you go quickly, you will think you are stronger than you are, putting your muscles at more risk of injury).
Know what exercises are best for each muscle. Don’t do quick movements for a Postural Muscle.