There are three main types of muscle in the human body: smooth muscle, cardiac muscle, and skeletal muscle. Skeletal muscle is voluntary muscle that enables movement and is under conscious control. Some major muscle groups include the deltoid, biceps, triceps, abdominals, pectorals, latissimus dorsi, trapezius, quadriceps, hamstrings, gluteals, and gastrocnemius. Muscles work in pairs called agonist and antagonist muscles to allow movement in two directions at a joint. Regular exercise and training can cause muscle hypertrophy and increase in size, while inactivity leads to muscle atrophy and wastage.

1. OBHS Physical Education ANATOMY – The Muscular System

3. The Major Muscle Groups

5. Function and Movement of Major Muscles Biceps - Flexes your arm at the elbow.