The human body moves voluntarily and involuntarily via our muscular system. Muscles contract and shorten in response to nerve stimuli as they counter gravitational forces and maintain posture and balance. There are over 600 muscles in our body, which make up 40 percent of our total body mass (e.g., 65 lbs. of a 160-lb. person).
The three actions muscles produce are eccentric, isometric and concentric contractions. An eccentric contraction is the lengthening of a muscle. An isometric contraction is the muscle maintaining a certain length. A concentric contraction is the shortening of a muscle.
Neck Musculature
The most common neck muscles are the sternocleidomastoid, scalenes, longus colli and longus capitus. They control cervical flexion, extension and rotation in addition to stabilizing the cervical spine.
Shoulder and Arm Musculature
Shoulder and arm muscles include the latissimus dorsi, rhomboids, trapezius, pectorals, deltoids and rotator cuff. The latissimus dorsi controls shoulder and spinal extension, flexion and rotation. The rhomboids control scapular protraction and rotation along with stabilizing the rotator cuff.
The trapezius muscles control scapular elevation, abduction and rotation along with stabilizing the scapula and helping control cervical flexion and rotation. The pectorals, deltoids and rotator cuff muscles help with shoulder flexion, extension, adduction, rotation and retraction along with stabilizing the shoulder girdle.
Abdominal Musculature
Abdominal muscles stabilize the spine and the lumbo-pelvic-hip complex. These muscles include the obliques, abdomini and diaphragm. The external and internal obliques also control spinal flexion, extension and rotation. Additionally, the diaphragm helps increase volume in the thoracic cavity while breathing.
Back Musculature
The most common back muscles are the erector spinae and multifidus. Both of these muscles control spinal flexion, extension and rotation. The erector spinae also stabilizes the spine during functional movements.
Leg and Hip Musculature
Leg and hip muscles include the psoas, piriformis, gluteus muscles, quadricep complex, hamstring complex, adductors, abductors, tibialis muscles and calves. The three gluteus muscles (minimus/maximus/medius) control hip adbduction, adduction and rotation along with stabilizing the lumbo-pelvic-hip complex. The psoas, piriformis, quadricep complex, hamstring complex, adductors, and abductors all control hip flexion, extension and rotation.
The psoas assists in stabilizing the spine in functional movements. The piriformis stabilizes the hip and sacroiliac joints. The quadricep muscles control knee flexion and extension along with stabilizing the knee.
The hamstring muscles help control knee flexion along with pelvic and tibial rotation, while the adductors and abductors control hip adduction and abduction along with stabilizing the lumbo-pelvic-hip complex.
The posterior and anterior tibialis and all three calf muscles (gastrocnemius/peroneal/soleus) control ankle dorsiflexion and plantarflexion. Both tibialis muscles also control ankle inversion and eversion along with stabilizing the arch of the foot. In addition, the calf muscles stabilize the foot and ankle complex along with helping control dorsiflexion and plantarflexion.
References
- "Anatomy Reference Guide"; Wolters Kluwer | Lippincott Williams & Wilkins; 2010
- "Optimum Performance Training for the Health and Fitness Professional"; National Academy of Sports Medicine; 2004.
- Health and Fitness Provider Network: Anatomy
