In a typical workout routine the concentric (muscle shortening) contraction is king. Some athletes also include eccentric (muscle lengthening) contractions (when the muscle returns to its original length after shortening). Rarely does anyone use isometrics (muscle shortening but no movement). This is understandable since the concentric contraction is most important for the development of strength and muscles mass. The eccentric contraction also contributes to strength and is needed in explosive training. However, few people realize that isometrics are also needed for the greatest strength gains and for explosive power.
For the fastest and most effective increases in strength you need all three types of muscular contraction regimes. The concentric regime remains as the major muscle contraction and should be used approximately 75% of the time. Eccentrics should be done for approximately 15% of the time and isometrics, 10%. This ratio, in addition to producing more effective strength results, also puts variety into your program which prevents staleness and stimulates the muscles. As a result you get maximum gains.
The isometric contraction plays three important roles. First, it is needed for overcoming sticking points which most athletes experience in execution of different exercises. For example, in the bench press, a sticking point usually occurs at the halfway or slightly below point of the barbell lift. In the squat, the sticking point is usually found below or about halfway up to the standing position. Thus, the use of isometrics at the angles where you have the greatest difficulty can help you overcome the sticking point and make your lift more productive.
Second, you need isometrics for stabilization of body parts during exercise execution. In other words, you must fix your body in a position to effectively do the exercise. For example, in the bench press, you must stabilize the trunk and lower body so that the shoulder joint and shoulder girdle muscles have a strong base against which to contract. This usually occurs automatically with contraction of the trunk (rib cage) muscles and holding your breath. In addition, the spinal (midsection) muscles undergo contraction to stabilize the trunk. This is one reason why you see the trunk arching during execution of the exercise.
When you execute the squat, isometric contractions are needed to hold the spine (your upper body) in position as the legs do the work. This entails contraction of mainly the erector spinae muscles of the spine. In the overhead press you need isometric contractions to hold the trunk erect and to maintain a strong connection with the legs. In execution of lateral arm raises the isometric contraction is needed to hold the mid-section firm, keep the legs stabilized and to maintain an erect body as the arms go through their actions.
Isometrics are used to develop the strength needed to stabilize your body during execution of lifts. This is done by duplicating the positions in which you hold your body during execution of the exercise. For example, to do isometrics for the stabilizing muscles in the squat you should assume a position similar to an ice skater. Assume a half squat, bend the trunk slightly forward from the hips and hold this position with an isometric contraction against an immovable bar. It does not have to be a maximal contraction or entail the use of maximal weights. Use about 30% of body weight on your shoulders and hold this position for five to six seconds.
To develop the stabilizing muscles in the overhead lifts, hold a barbell on extended arms over your head and take one or two steps in various directions. Use about 30% of body weight and hold the position for five to six seconds.
There are many reasons for using isometrics in your workout. But, you should still use a combination of methods with the isometric exercise being the least used. However, this does not mean that it should be ignored. Understand that a maximal isometric contraction is 10% greater than a maximum concentric contraction. However, use less than 110% of maximum when exercising isometrically for best results.
For example, when working on sticking points you should only use up to 70-80% of maximum. For stabilization only 30-40% of body weight is needed which is about 20-30% of your maximum lifts. Also, the isometric contraction should be held only for five to six seconds. Holding longer does not produce greater gains and may greatly increase your blood pressure.
The third reason for inclusion of isometrics in your workout is to strengthen the muscles in this regime to enhance an explosive muscular contraction. Understand that when you execute an explosive movement, the muscles first undergo an eccentric contraction which is the first step in preparing the muscles for an explosive contraction. However, to stop the movement in one direction and before initiating movement in the other direction, the muscles undergo an isometric contraction. The stronger this isometric contraction, the greater the tension that can be developed which can then converted into an explosive concentric contraction when you execute the final movement.
The isometric contraction occurs in all exercises when you change direction and when you change from one muscle contraction regime to the other. It is a momentary contraction, but it still occurs and plays a very important role. Thus, you need isometric muscle strengthening to enhance the different roles that it plays.
The isometric contraction is beneficial for all level athletes. On the higher levels, the stabilizer muscles are usually quite strong but it is still a good practice to exercise them every once in a while with the isometric contraction.
Isometrics are also very effective for prepubescent youngsters who should use about 10-15% of maximum body weight. At ages 14 to 15 it increases to 20-25% of maximum body weight, and after age 16, 30 or more percent. Youngsters should hold the isometric contractions for only 3-4 seconds. When you are 16 or older hold for 5-6 seconds.
Thus, for best results and greater progress in your training, include isometrics in your arsenal of lifts. They will allow you to do your exercises more effectively and as a result get greater strength, muscle mass and explosive movements. In addition, isometrics help prevent injury especially if the muscles are weak.