Aerobic fitness of young adults born with low birth weight

In some people born with a body size that is too small in relation to their gestational age (Small for Gestational Age, SGA) growth disturbances have been described, and in subsequent periods of life such people face an increased risk of chronic metabolic disorders leading to cardiovascular diseases, type 2 diabetes and hormonal disorders within the reproductive system 1, 2, 3, 4, 5, 6, 7. It has been shown that adults born with body size deficiency are not only shorter, but also often are at a social disadvantage to those born with larger body weight and length 8, 9, 10, 11. Therefore, can the information on small birth body size be considered to be a negative factor for people planning to become professional athletes? It has been concluded that answering such a question requires studying whether birth weight is correlated to maximum oxygen uptake capacity (VO2 max). It should be emphasized that the importance of this issue has been growing with the increasing incidence of metabolic disorders in adolescents even before puberty 3, 12, 13, 14 . 

Birth body size, especially the length and weight, has long been used to assess the maturity of new-borns (as full-term versus pre-term).Since at least the second half of the 19th century, the assessment of new-born maturity was made on the basis of a new-born‟s birth body length (BBL) 15. A change in this approach occurred in the 1930s, when a Finnish paediatrician ArvoYlppö suggested that birth body weight (BBW) should be primarily used for this purpose. Already in 1935, Ylppö‟s suggestions were included in the recommendations of the American Academy of Paediatrics, and in 1961 the experts of the World Health Organization recommended that a baby born of a pregnancy lasting at least 37 weeks should be considered to be full-term, as long as their weight is not less than 2500 grams (g) and babies born weighing less than 2500 g should be considered premature (i.e., pre-term). In this way, the criterion of BBW was introduced into clinical practice16. It is still widely used and considered as a simple and convenient screening tool - babies weighing more than 2500 g are considered healthy and as long as there are no obvious abnormalities in their build and/or the functions of particular organs. Althoughit was soon discovered that such a criterion is too imprecise (and this took place 45 years ago), many medical centres are still using it today. Meanwhile, since the year 1970, scientific journals began to publish papers on the development of full-term new-borns born in a good condition, but bearing distinct features of hypotrophy that is with body size smaller than that of the general population. The classical meaning of the term neonatal hypotrophy was broadened to include intrauterine hypotrophy (IUGR, Intrauterine Growth Retardation or Restriction), and the broad concept of “a baby too small in relation to the duration of the pregnancy” (Small for Gestational Age, SGA) was introduced, so that nowadays less importance is placed on the reason for the slowdown in the growth of the foetus (which often difficult to identify clearly), and more on the necessity to observe the child‟s development in the following years of life 17, 18, 19, 20. It turned out that in all populations, a percentage of full-term new-borns is characterized by small body size, and in some of them it is a factor for an increased risk of growth disorders, impaired glucose tolerance, insulin resistance, abnormal lipid profile, obesity, hypertension or type 2 diabetes in subsequent periods of life. In 1989, British researchers presented a paper explaining the relation between intrauterine foetal growth retardation (IUGR/SGA) and the aforementioned disorders. They called their concept the theory of thrifty phenotype, and in the literature the name Barker hypothesis was adopted, coined from the name of one of the authors 1, 2 . In simple terms, the Barker hypothesis, have now been superseded by “Predictive Adaptive Responses” and “Developmental Origins of Health and Disease”, assumes that given the inadequate supply of energy to the foetus a change or shift of the method of regulating foetal metabolism may occur. Foetal development is not interrupted, but runs at a slower pace, and in some cases disorders detrimental to the growth and health condition of the subject may be observed after birth 1, 2, 4, 21. In consequence of the foetal metabolic shift and the slower growth rate of the foetus, new-born body size is smaller than normal, and as already stated, in some cases growth disorders in childhood may appear, which may finally result in short stature 3, 21. We believe that it is remarkable that despite extensive knowledge of the links between the course of foetal development and the rate of development and health in the subsequent stages of ontogeny, no papers analysing the potential relationship between birth body size and aerobic fitness have been published 22. The ability to take up oxygen in an amount to necessary to perform various physical exercises makes it possible not only to do sports, but above all, to work and perform all the necessary daily activities.