Of the 600-plus muscles within the human body, there are 11 major muscles. These major muscles are categorized as voluntary skeletal muscles and are controlled by the somatic nervous system. Each major muscle possesses its own joint action and is identified by its origin (the attachment point at which the muscle begins) and its insertion (the attachment point where the muscle ends). To improve overall strength, endurance and functionality, The American College of Sports Medicine recommends training these muscles at least two times per week, performing resistance exercises consisting of one set of eight to 10 repetitions.
Trapezius
The trapezius muscle is located toward the upper back area around the neck. The origin is at the base of the skull and along the middle of the spine into the last thoracic vertebrae. It inserts at the collar bone, the tip of the shoulder bone, and into the shoulder blade. The trapezius is responsible for the elevation, depression, retraction and upward rotation of the scapula, also known as the shoulder blade. Perform shoulder shrugs with dumbbells to exercise the trapezius muscles.
Deltiods
The deltoids are the shoulders. The deltoids are separated into three sections, anterior deltoid (front of the shoulder), medial deltoid (middle of the shoulder), and posterior deltoid (back of the shoulder). The deltoids originate at the collarbone, tip of the shoulder bone, and spine of the scapula (shoulder blade). The deltoids insert at the humerus bone, the long upper arm bone. The anterior deltoids are responsible for moving the arms forward. The medial deltoids are responsible for moving the arms out to the sides away from the body. The posterior deltoids are responsible for reaching the arms backward. To exercise the deltoids, perform overhead shoulder presses with dumbbells.
Latissimus Dorsi
The latissimus dorsi (lat) is a large muscle located on the back. When they are well defined, the lats look like wings. The origin of the lat is at the lower back and inserts at the humerus. The lats extend the arms and rotate the arms medially. They are also responsible for a pulling action. For example, bending over, picking something up off the floor, and pulling it off the floor toward you uses the lats. To exercise the lats, perform lat pulldowns on a machine or one-arm rows with a dumbbell.
Pectorals Major
The pectorals major are located in the chest of the human body. The origin of the pectorals major is at the sternum of the chest. The insertion is at the humerus. The pectoral majors flex and adduct the arms, bringing the arms toward the center of the chest. To exercise the pectorals, perform a bench press with a barbell.
Biceps Brachii
The biceps brachii is located within the upper arm. The biceps brachii has two heads, the short head and the long head. Both heads of the biceps brachii originate at the scapula and insert at the ulna and radius, the forearm bones of the arm. The action of biceps brachii is flexion of the arm, decreasing the angle of the elbow joint and bringing the forearm closer to the upper arm. Perform bicep curls with a barbell to exercise the biceps brachii.
Triceps Brachii
The triceps brachii is located on the back of the upper arm. There are three heads with three origins. The origin of the long head is at the scapula. The origin if the lateral head is at the humerus. The origin of the medial head is at the bottom half of the humerus. The insertion point is at the olecranon process of the ulna, better known as the elbow. The triceps brachii extends or straightens the arm, increasing the angle of the elbow joint. To exercise this muscle, perform overhead extensions with a dumbbell.
Quadriceps
The quadriceps is a group of four muscles (rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis) that are located on the anterior front of the thighs. The quadriceps originate at the top of the femur, the long bone of the upper part of the leg, and insert at the front of the tibia (shin). The rectus femoris, however, crosses the hip joint and originates on the pelvis (hip bone). The function of the quadriceps as a whole is to extend the knee. The rectus femoris not only extends the leg but also bends the hip because it crosses the hip joint. To exercise the quadriceps, perform leg extensions on a leg extension machine.
Hamstrings
The hamstrings are a group of three muscles (biceps femoris, semimembranosus, and semimembranosus) that are located on the posterior back of the thighs. These muscles originate just underneath the gluteus maximus on the pelvic bone and insert on the tibia (shin). The hamstrings bend the knee. To exercise the hamstrings, perform leg curls on the leg curl machine.
Gluteals
The gluteals, also known as buttocks, are a group of muscles comprising the gluteus maximus, gluteus minimus and gluteus medius. The gluteus maximus originates at the pelvic bone crests and inserts to the rear of the femur (the long bone of the upper part of the leg). The gluteus medius and minimus also originate at the pelvic bone, but they insert to the side of the femur. The gluteus maximus is responsible for hip extension (moving the leg backward from the hip) while the gluteus medius and minimus are additionally responsible for hip abduction (moving the leg away from the midline of the body). To exercise the gluteals, perform squats and side squats with dumbbells.
Gastrocnemius
The gastrocnemius, also known as the calf muscle, is located at the back of the lower limb. This muscle originates behind the knee on the femur (the long bone of the upper leg), crossing two joints and inserts at the heel of the foot with the Achilles tendon. The purpose of the gastrocnemius is to elevate the heel (plantar flexion) by standing on the toes. To exercise the gastrocnemius, perform standing toe raises with dumbbells.
Abdominals
The abdominal muscles include the rectus abdominus, internal and external obliques, and transverse abdominus and are located on the front of the torso. The abdominals originate along the ribcage and insert along the pelvis. The rectus abdominus is also known as the "six pack" and is responsible for flexing the spine. To exercise this muscle, perform abdominal crunches. The internal and external obliques are responsible for rotation of the spine and bending sideways. To exercise these muscles, perform cross-over crunches or lateral flexion exercises holding a dumbbell. The tranverse abdominus muscles wrap horizontally around the abdominal area and are located deep under the abdominal muscles. These muscles act as a girdle supporting the spine and maintaining posture. To exercise these muscles perform planks.
