The length of the muscle fibre at the onset of contraction which is required to attain the maximum active tension is known as

The length of the muscle fibre at the onset of contraction which is required to attain maximum active tension is known as resting length. Resting length is also known as the optimum length. It is about 2mm. At this length, there is a maximal overlap between the actin and myosin fibres and therefore, the maximum number of cross-bridge binding sites are formed. Passive tension is the tension in a muscle when it is not stimulated. Total tension is the tension developed when the muscle contracts isometrically in response to a maximal stimulus. Active Tension = Total tension + Passive tension When the muscle fibres contracts, the active tension developed is propoional to the number of crossbridges between the actin and myosin fibres. Hence, at the resting length, maximum active tension is produced and the muscle fibre contracts with a maximum force of contraction. Ref: Guyton and Hall Textbook of medical Physiology 13th edition Pgno: 81