Types of Muscle Contractions
The basic principles of weight training involve a manipulation of the number of reps, sets, tempo, exercise types, and weight moved to build strength, endurance, and size. The specific combinations of the metrics depend on the goal set by the individual. Sets with fewer reps can be performed with heavier weights, as well as sets with higher reps with lighter weights.
The bones are in effect a system of articulated levers which are moved by the skeletal muscles. Muscles may be regarded as machines which store chemical energy and convert to mechanical work in response to impulses conducted by the nervous system. There are approximately 434 muscles making up about 40 to 45 percent of the body weight, but only about 75 pairs are involved in the general movement of the body.
A muscle consists of a large number of cells filled with a liquid protein solution called sarcoplasm. Running through this material are elements called myofibrils. These are the actually responsible for the process of contraction.
There are three types of muscle contraction, each of which has been used as the basis for training systems:
The muscle actually shortens and moves a load, such as a barbell or dumbbell through a distance, thus accomplishing a certain amount of work. Such contractions are also said to be concentric. In practice the weight that can be handled is limited to that which can be moved through the weakest point in the range of motion of a joint.
This is a modification of isotonic exercise. It utilizes a machine which controls the speed (tempo) of the movement. This prevents the dissipation of muscular energy in acceleration and provides resistance which is proportional to the input of muscular force and the alterations in skeletal levers throughout the range of motion. In simpler language, it compensates for the variations in the muscle force which can be developed at various angles of a joint and provides maximal resistance at any angle. These machines are common in gymnasia now days unlike 30-40 years ago. These are known as variable resistance machines. They do not train your stabilizers very well because there no need to balance the load.
The muscle is unable to move the load, such as a fixed bar, so that apparently no joint movement takes place. The muscle does not visibly shorten, and technically no work is accomplished even through the muscle is subjected to great stress. This is known as static contraction. The value of this type of exercise will be reviewed in a future article.
This is the lengthening of the muscle, the load forces the contracted muscle to extend, as when a barbell is taken from supports and slowly lowered. This is also a form of isotonic contraction and is known as eccentric contraction in order to differentiate it from concentric movements. In practice it is utilized every time a weight is lowered in a controlled manner during isotonic exercise.
This article in memory of the late Dr.Philip J. Rasch, who wrote this in 1966 and very word of it applies today. Man has changed very little since the day of the cave man. Dr. Rasch was a pioneer in the fitness world.
All my training programs list a tempo cadence i.e. 3-2-1-0 ,time-under-tension is what makes a muscle grow, the longer a muscle is under tension the more myofibrils are engaged.