Definitions of Scientific Terms

1. Flexion: includes anteriorly directed sagittal plane rotations of the head, trunk, upper arm, forearm, hand and hip, and posteriorly directed sagittal plane rotation of the lower leg.
2. Posteriorly: toward the back of the body
3. Contract: Result of a muscle's characteristic of irritability, extensibility and elasticity. When a muscle contracts it receives stimuls and responds by developing tension, thereby shortening in length.
4. Gluteus maximus: One of the muscles comprising the hip extensors, it is a massive, powerful muscle that is usually active only when the hip is in flexion, as during stair climbing or cyclying, or when extension at the hip is resisted.
5. Hip Flexors: A group of muscles crossing at the hip to contribute to its stability. Hip flexors include the gluteus maximus and the three hamstrings (biceps femoris, semitendinosus, and semimembranosus).
6. Depress: movement of shoulder girdle in an inferior direction.
7. Scapula: One of two bones comprising the shoulder girdle. It is a flat bone that provides attachment for muscles and ligaments. 
8. Dorsiflex: motion bringing the top of the foot toward the lower leg.
9. Motor unit: A single motor neuron and all the fibers it innervates.
10. Quadriceps: The quadricep muscles consist of the rectus femoris, vastus lateralis, vastus medialis and vastus intermedius. The are the extensors of the knee. The recus femoris is the only one that croses the hip joint as well. All four muscles attach distally to the patellar tendon, which inserts on the tibia.
11. Hamstrings: The hamstrings include the biceps femoris, semitendinosus, and semimembranosus. They derive their name from their prominent tendonds, which can readily be palpated on teh posterior aspect of the knee. These two-joint muscles contribute to both extension at the hip and flexion at teh knee, and are active during standing, walking and running.
12. Force: a push or pull acting on a body. Each force is characterized by its magnitude, direction, and point of application to a given body. Force equals units of mass multipled by units of acceleration and is measured in Newtons or pounds.
13. Posterior thoracic and lumbar region muscle groups: The massive erector spinae (sacrospinalis), the semispinalis, and the deep spinal muscles. The erector spinae group  includes the spinalis, longissimus, and iliocostalis muscles. The semispinalis includes the capitis, cervicis, and thoracis branches. The deep spinal muscles are the multifidi, rotatores, interspinales, intertransversarii, and levatores costarum. The muscles of the erector spinae group are the major extensors and hyperextensors of the trunk. All posterior trunk muscles contribute to extension and hyperextension when contracting bilaterally and to lateral flexion when contracting unilaterally.
14. Abdominal muscles: The main abdominal muscles are the rectus abdominis, the external obliques, and the internal obliques. Functioning bilaterally, these muscles are the major spinal flexors and also reduce anterior pelvic tilt.
15. Flexibility (joint): A term representing the relative ranges of motion allowed at a joint.
16. Prone: applied to body position when lying horizontally, face down.
17. Pubic bone: part of the bony structure of the hip; the forwardmost of the three bones that fuse together to form each of the hipbones.
18. Shoulder muscles: The shoulder muscles include the levator scapula, rhomboids, serratus anterior, pectoralis minor and sublavius and the four parts of the trapezius. One of the functions of these muscles is to facilitate movements of the upper extremity by positioning the glenohumeral joint appropriately. Addtionaly shoulder muscles include: the deltoid (anterior, middle, posterior), pectoralis major (clavicular, sternal), supraspinatus, coracobrachialis, latissimus dorsi,  teres major, infraspinatus, teres minor, subscapularis, biceps brachii (long head, short head), and triceps brachii (long head).
19. Radioulnar joint: A pivot joint made up 3 joints: the proximal and distal radioulnar joints and the middle radioulnar joint. Pronation of the forearm occcurs as the radius rolls medially and laterally over the ulna.
20. Anterior: Toward the front of the body.
21. Pelvic girdle: The two hip bones plus the sacrum, which can be rotated forward, backward, and laterally to optimize positioning of the hip.