Final answer:
Running involves complex coordination where the brain sends signals through nerves to muscles, stimulating them to contract or relax, enabling voluntary movement. The process of muscle contraction is a result of actin-myosin cross-bridge formation and sarcomere shortening, both of which determine the force exerted by the muscles.
Step-by-step explanation:
Running does indeed require a great deal of coordination and is accomplished through the contraction and relaxation of many muscle fibers. A signal originates from the brain and travels through the nervous system, reaching the muscles and stimulating them to contract or relax. This process is essential for all voluntary movements, such as moving the bones of the skeleton to get from one place to another.
Muscles and nerves work together to enable movement. Muscles cannot contract on their own without a nerve signal. When you decide to move, for example, raising your hand, your brain sends electrical messages via motor neurons to the muscle fibers, causing them to contract.
The intricate process of muscle contraction involves the formation of actin-myosin cross-bridges, leading to the shortening of the sarcomere, the basic unit of a muscle fiber. The amount of tension and the length-tension relationship of these sarcomeres ultimately determine the force of the muscle contraction.