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Body Systems: The Basics
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
Skeletal muscles attached to the skeleton must work together to stabilize the entire body and body parts and to maintain body positions. The nervous system monitors and coordinates the muscular activity required to keep the body in a state of balance against the forces of gravity. The amount of muscle contraction needed, in a standing or seated position, can be quite small when the skeleton is in an idealized erect posture (Basmajian & De Luca, 1985). Muscles form a body wall, surrounding and supporting the internal organs located in the abdomen. Abdominal muscles also help to stabilize the multi-segmented spine and the bony pelvic girdle. While products can be designed to assist stability or good posture, products should not substitute for healthy use of postural muscles.
Working Posture
Published in Céline McKeown, Office Ergonomics and Human Factors, 2018
The muscles of the back—the ‘true’ muscles—form several layers, which are actually covered by the muscles of the upper limbs. The ‘true’ muscles are the primary means by which the spine is kept erect and can be rotated. The main task for the muscles when the back is upright is to resist the pull of gravity. If the body is balanced when upright, the back muscles do little work to maintain its stability. If an individual leans forward, the muscles contract to prevent them from falling forward. The muscles also ‘manage’ the lean so that it is executed smoothly. The farther forward an individual leans, the more active the back muscles become. The same muscles assist in controlling the upward movement as the individual stands or sits upright again. In conjunction with the back muscles, the abdominal muscles are also called on to assist, which explains why people receiving physiotherapy for a back injury often get advice on strengthening the abdominal muscles.
Working Posture
Published in Céline McKeown, Office Ergonomics, 2007
The muscles of the back—the “true” muscles—form several layers, which are actually covered by the muscles of the upper limbs. The “true” muscles are the primary means by which the spine is kept erect and can be rotated. The main task for the muscles when the back is upright is to resist the pull of gravity. If the body is balanced when upright, the back muscles do little work to maintain its stability. If an individual leans forward, the muscles contract to prevent them from falling forward. The muscles also “manage” the lean so that it is executed smoothly. The farther forward an individual leans, the more active the back muscles become. The same muscles assist in controlling the upward movement as the individual stands or sits upright again. In conjunction with the back muscles, the abdominal muscles are also called on to assist, which explains why people receiving physiotherapy for a back injury often get advice on strengthening the abdominal muscles.
The effects of the muscular contraction on the abdominal biomechanics: a numerical investigation
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
Piero G. Pavan, Silvia Todros, Paola Pachera, Silvia Pianigiani, Arturo N. Natali
Different tissues compose human abdominal wall. Linea alba, aponeuroses and fasciae are connective tissues that provide a purely passive action in protecting and supporting the abdominal cavity. Abdominal muscles, namely Rectus Abdominis (RA), External Oblique (EO), Internal Oblique (IO) and Transversus Abdominis (TA), contribute with their active behavior to the accomplishment of physiological tasks as breathing, coughing, phonation and postural control (Iizuka 2011). Each of these muscles is characterized by a specific fiber orientation. The RA consists in a pair of muscles symmetrically disposed with respect to linea alba, with fibers disposed along craniocaudal direction (Ahluwalia et al. 2004). The EO muscle is the most external and the largest of the three flat anterolateral muscles of the abdomen. It originates from the lower ribs posteriorly, to interdigitate with both the latissimus and the serratus muscles. The direction of the fibers is almost horizontal in the uppermost portion, while they become oblique in the lowest portions where they fold on themselves to form the inguinal ligament (Ahluwalia et al. 2004). The IO muscle originates from the anterior two-thirds of the iliac crest and lateral half of the inguinal ligament. It is characterized by a fiber direction almost perpendicular to the EO fibers. Finally, the TA muscle is the deepest of the abdominal muscles. TA originates from the 7th to 12th costal cartilages, the lateral third of the inguinal ligament and iliac crest, characterized by muscle fibers with horizontal orientation (Ahluwalia et al. 2004).