The length-tension property of a whole muscle (or muscle fiber or sarcomere) is the relationship between muscle length and the force the muscle can produce at that length.

A net force on an object changes its motion – the greater the net force, the greater the acceleration. More massive objects require bigger net forces to accelerate the same amount as less massive objects.

The force-length relationship describes the dependence of the steady-state isometric force of a muscle (or fiber, or sarcomere) as a function of muscle (fiber, sarcomere) length. The force-length relationship is considered one of the basic properties of muscle.

At lengths greater than their resting length (l0), they develop tension or force. This force is passive, since it exists whether or not the muscle is active. Passive force, like active force, acts in a direction from the muscle’s points of attachment toward its center.

Your argument on the previous answer is sound; that Active Forces have fixed values independent of other forces acting, while passive forces do not.” This is clear because active forces have Obvious causative agents while passive forces depend on other forces.

2003) and human muscles (Lee & Herzog 2002), we observed that passive force is increased when activated muscles are stretched along the descending limb of the force–length relationship, when compared with the passive forces following passive stretches or isometric contractions at the corresponding lengths.

There are three types of muscle contraction: concentric, isometric, and eccentric. Labeling eccentric contraction as “contraction” may be a little misleading, since the length of the sarcomere increases during this type of contraction.

An eccentric contraction is where a muscle contract whilst simultaneously lengthening to control the speed of the movement. In terms of striking a football, when the leg is cocked back, the hip flexors and quadriceps eccentrically contract to decelerate the leg.

4 phases

Eccentric contraction is a bit physiologically mysterious, and is known to be harder on muscle, causing more soreness (quadriceps after hiking down a mountain is the classic example). It may be a good stimulus for adaptation in tendon as well as muscle.