By Garrett Giles
To understand muscle groups and how training certain muscle groups can be advantageous to your workout and increase efficiency, we must first understand muscle contraction and muscle recruitment. Skeletal muscle is made up of very small contractile units. There are two types of units: thick filament called myosin and thin filament called actin. These filament slide over each other thus causing a muscular contraction. Myosin has finger like structures that grab onto the actin, and then pulls the actin to cause a contraction. In order for the myosin to attach on the actin a few other processes must happen first. First, an action potential, also called a nerve impulse, is sent to the muscle via the T- tubules, which then releases calcium from the Sarcoplasmic Reticulum. The calcium then binds onto a structure which sits on the actin called troponin. Once calcium is attached to the troponin, tropomyosin, which acts like a cover keeping myosin from attaching, moves allowing myosin to complete the cross-bridge and grab ahold of the actin to then perform a muscle contraction.