When you recruit the muscle it will perform a series of kinetic (movement) contractions that lead to different muscle contraction patterns. When the recruit leads to shortening of the muscle it is deemed to be concentric, when recruit leads to lengthening of the muscle it is deemed eccentric, when recruitment leads to no change in the muscle length it is deemed isometric. These three patterns of contraction are seen in the speed of which movement is produced. The pattern of comparing the type of contraction with the force of contraction and the speed of contraction a distinct relationship develops, called the force velocity curve. Where concentric contractions produce less force then eccentric, but move a faster speed (greater velocity), and that isometric produces force but because there is no movement, there is no speed (or velocity). With a relationship between a lower external force (resistance) being able to be moved at a greater velocity then when there is a greater velocity as the amount of muscle needed to move the resistance gets greater as the resistance gets greater. Thus you should be able to move a 1-lb object faster then you move a 10-lb object. And as you get closer to your maximal strength you will move slower and slower as you need to get more and more muscle involved in the contraction.
To examine this concept we will look at how rapidly a muscle can produce force and a contraction against four different weights of resistance as a group. In which we will ask each member of the group to lift (bicep curl) a series of dumbbells of increasing weight. Where we will be able to see how the velocity of contraction is dependent upon the amount of resistance that the muscle has to move against