Ovidius University Annals, Series Physical Education and Sport / SCIENCE, MOVEMENT AND HEALTH Vol. XII, ISSUE 2 Supplement 2012, Romania The journal is indexed in: Ebsco, SPORTDiscus, INDEX COPERNICUS JOURNAL MASTER LIST, DOAJ DIRECTORY OF OPEN ACCES JOURNALS, Caby, Gale Cengace Learning 491 LATERALITY - DETERMINANT FACTORS AND INFLUENCES STRATON ALEXANDRU 1 , ENE VOICULESCU CARMEN 1 , STRATON CORINA 2 , GIDU DIANA 1 Abstract Environmental factors or genetic instructions seem to be two processes that can cause variations in the upper and/or lower limb preference. Preferential use of the upper and/or lower limb in moderate or high (sport performance) intensity physical exercise can cause an unbalanced muscle behavior (especially in terms of force) between the right and left side of the body, which can have undesirable implications on normal development of the human body. In other words, asymmetrical sports specific biomechanics may predispose the subject to neuromuscular disbalances. Therefore, understanding laterality determining factors and influences may lead to a better knowledge of this phenomenon. Key words: laterality, preference, dominance, right, left. Introduction From anatomically and functionally point of view, people present two identical external anatomical halves centrally merged. Even if the two external anatomical halves are identical, people give a greater preference to one of the body sides or to one of the upper and/or lower corresponding limbs (B. J. C. Perera, 2009). Fundamental basis of this perception is represented by the concept of laterality. Laterality is defined as functional inequality of a body part as a consequence of the difference in development and distribution functions in the cerebral hemispheres. Therefore, functional weight of a pair limb or organ is called "laterality", and is manifested by the fact that humans execute certain activities with more pleasure, skill, efficiency, ease and speed, with one pair of limbs or organs, giving a systematic priority to it (K. Mekota, 1976). Laterality is linked to a dominant cerebral hemisphere function that causes inequality of the body left and right halves. Sensory asymmetry phenomenon seems to be innate and is based on a certain functional organization of brain structures. Cerebral dominance is one of the most often used factors to explain laterality and especially to explain the hand dominance. It appears that hereditary and cultural mechanisms are indispensable, and work together in determining laterality. In this study, laterality determining factors and influences are examined in detail, to a better understanding of this phenomenon. Laterality reflection in the cerebral hemispheres In right-handed adult subjects, left cortical motor area controls the right upper limb and in left-handed adult subjects, right cortical motor area controls the left upper limb. The cerebral hemisphere that controls language is called the dominant hemisphere. In the vast majority of people, language functions are processed in the left hemisphere. Brain lesions that adversely affect language are found in the hemisphere in about 95% of cases, as evidence of left brain dominance (D. E. Haines, 2008). About 90% of right-handed subjects have nerve centers that control speech located in the left hemisphere, and the remaining 10% have nerve centers that control speech located in the right hemisphere. Also, about 65% of left-handed subjects have nerve centers that control speech, located in the left hemisphere, 20% have nerve centers that control speech, located in the right hemisphere, and the remaining 15% have nerve centers that control speech, located in both cerebral hemispheres. 60% of ambidextrous subjects have nerve centers that control speech, located in the left hemisphere, 10% have nerve centers that control speech, located in the right hemisphere, and the remaining 30% have nerve centers that control speech, located in both cerebral hemispheres (C. R. Noback et al., 2005). D. E. Haines, (2008), speculates that almost all right handed subjects and about half of left handed subjects are left cerebral dominant. So, the right cerebral hemisphere, in most of general population, is the nondominant hemisphere. Observations realized by autopsy have shown that larger and more numerous groups of nerve bundles connect both cerebral hemispheres in left-handed subjects, then right-handed subjects, suggesting that more nerve impulses are traveling between cerebral hemispheres in left-handed subjects. Hand position during writing correlates with cerebral dominance. Subjects, who write by hand in a non-inverting position (normal), present cerebral dominance in opposition to preferential utilization of the upper limb. Thus, a large number of subjects with right upper limb preference present left cerebral dominance and only a small number of subjects with left upper limb preference present left cerebral dominance. Also, individuals who write by hand in an inverted position, have cerebral dominance in the same side as the upper limb preference. Thus, a large number of subjects with left upper limb preference present left cerebral dominance and a very small number of subjects with right upper limb preference present right cerebral dominance. Cerebral dominance cannot be determined in some subjects, by observations of hand writing position, probably because of the cerebral hemispheres interconnection (J. G. Creager, 1992). Subjects, which have the right part of the body dominant, have a higher 1 Ovidius University of Constanta, Faculty of Phisical Education And Sport, ROMANIA 2 Mihai Viteazul School From Constanta, ROMANIA Email: axelcorro@yahoo.com. Received 10.03.2012 / Accepted 12.08.2012