Length-Tension Relationship

The length-tension relationship describes the fact that a single muscle fiber does not produce the same amount of isometric force at various static lengths 

A crucial aspect of determining muscle function is determining the ideal length of the muscle fiber. The length-tension relationship describes the fact that a single muscle fiber does not produce the same amount of isometric force at various static lengths. Long-tension relationships are formed by the extra force generated during muscular contractions when the passive elements are included. This happens when the muscle is stretched to long lengths during strength training as well as during eccentric exercises.

The length-tension relationships describe how different positions or lengths of the basic contractile unit of muscle fibers will produce different levels of muscular tension and force. When muscle fibers are too short (overloaded) or too long (underloaded), you will have a weaker ability to generate force (cross-bridge cycling) as the movement of actin and myosin relative to each other will be impaired.

Muscle fibers produce force during muscular contractions through active and passive mechanisms. During actin-myosin cross-bridge cycles, the active force is generated by energy metabolism and the movement of myofilaments against one another. When fibers are pulled apart, passive force occurs because structures within the muscle fiber extend.

Furthermore, there is decreased intramuscular tension, which eventually keeps the strength-inducing stimulus and reduces the recruitment of motor units, and, as a result, muscle strength is diminished. A moderately stretched sarcomere results in the most torque and force from the muscle. This would indicate that some stretching is good, but too much can result in sub-optimal results in terms of muscular tension and cross-bridging. A great example of this range is the squat: it is ideal to perform it between 90 degrees and parallel.

There is a big takeaway here: force is produced by each muscle fiber. Due to this, strength training is more likely to cause mechanical overload to occur on the muscles when there is passive resistance to tensile force.