In the case of muscle contraction, there are three basic types of events: isometric contraction, isotonic contraction and isokinetic contraction.
The isometric contraction, according to Lippert (2008), occurs when the muscle contracts, producing force without changing its length. Refers to muscle action during which there occurs no change in the total length of the muscle (KRAEMER and Fleck, 2006). In this case, the voltage generated by the muscle is not sufficient to overcome a particular resistance, resulting in a static force where there is no change in the angle of the involved joint.
The isotonic contraction is characterized as a contraction in which the muscle fibers shorten or lengthen as exert a constant force corresponding to a load or resistance. This force leads to a change in muscle size, thus generating a movement in the involved joint.
This dynamic isotonic muscle contraction or split between concentric action (positive), where the force generated is greater than the resistance offered (the muscle is shortening) and eccentric (negative), where the generated voltage to be lower, it is overcome by the imposed load (occurs muscle stretching).
The isokinetic contraction is through the use of the apparatus termed “Isokinetic” where the individual performs a maximum muscular effort or submaximal that accommodates the device resistance. The contraction occurs at a constant angular velocity, allowing measure the force applied by the muscle throughout the joint range of motion (Terreri, et al. 2001).
Considering that there are different types of muscle contraction, also is justified the existence of different manifestations of strength. According to Fox (2005), as regards their manifestations, muscle strength may take three different expressions: maximum strength, rapid strength (power) and resistance force.
Maximum force is characterized as the largest available force that the neuromuscular system can mobilize through a maximum voluntary contraction of a muscle or muscle group.
Fast power (explosive), also known as potency is defined by the author as whole way force that becomes active in the shortest possible time interval.
Since the resistance force corresponds to the capacity of the body must resist fatigue strength to provide requests for a prolonged period of time.
Image reference: bp blogspot