what form of exercise does the muscle contract and does not lengthen nor shorten
Muscle contraction An isometric contraction of a muscle generates tension without changing length.[1][3][4][5] An example can be found when the muscles of the hand and forearm grip an object; the joints of the hand do not move, but muscles generate sufficient force to prevent the object from being dropped.
Cytoskeleton A large-scale example of an action performed by the cytoskeleton is muscle contraction. In the muscle, there are groups of highly specialized cells that work together to perform a function known as muscle contraction. A main component in the cytoskeleton that helps show the true function of this muscle contraction is known as a microfilament. Microfilaments are composed of the most abundant cellular protein known as actin.[8] During contraction of a muscle, within each muscle cell, myosin molecular motors collectively exert forces on parallel actin filaments. Muscle contraction starts from nerve impulses which then causes increased amounts of calcium to be released from the sarcoplasmic reticulum. Increases in calcium in the cytosol allows muscle contraction to begin with the help of two proteins, tropomyosin and troponin.[8] Tropomyosin inhibits the interaction between actin and myosin, while troponin senses the increase in calcium and releases the inhibition.[9] This action contracts the muscle cell, and through the synchronous process in many muscle cells, the entire muscle.