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4. 8. 2012.

Special issues of children training

During the period of growth and development from childhood through adolescence, these special issues need to be addressed:
·         Thermal stress
·         Growth and maturation with training.

Thermal stress

Laboratory experiments suggest that children are more susceptible to heat- and cold-induced illness or injury than adults. But the number of reported cases of thermal illness or injury have not supported this theory. A major concern is the child’s apparently lower capacity during exercise in the heat to dissipate heat through evaporation. Children appear to rely much more on convection and radiation, which are enhanced through greater peripheral vasodilation. Compared with adults, children have a greater ratio of body surface area mass, meaning that they have more skin surface area from which to gain or lose heat for each kilogram of body weight. Unless the environment is hot, this is an advantage, because children are better able to lose heat through radiation, convection and conduction. However, once the environmental temperature exceeds the skin’s temperature, children more readily gain heat from the environment, which is a distinct disadvantage. A child’s lower capacity for evaporative heat loss is largely the result of a lower sweating rate. Individual sweat glands in children form sweat more slowly and are less sensitive to increases in the body’s core temperature than those in adults. Acclimatization data are not available for girls.
Only a few studies have focused on children exercising in the cold. From the limited information available, children appear to have greater conductive heat loss than adults because of a larger ratio of surface area to mass. This should be expected to place them at higher risk for hypothermia and to necessitate more clothing layers during exercise in cold temperatures.
Few studies have been conducted on children in relation to either heat or cold stress, and conclusions from existing studies sometimes have been contradictory. More research is needed in this area to determine the risks faced by children who exercise in the heat and cold. In the meantime, a conservative approach is advisable. Children may be at an increased risk of heat- and cold-related injuries compared with adults.

Growth and maturation with training

Many people have wondered what effect physical training has on growth and maturation. Does hard physical training slow down or accelerate growth and development? In a comprehensive review of this area, Malina made some interesting and relevant observations. Regular training has no apparent effect on growth in height. It does, however, affect weight and body composition.
As for maturation, the age at which peak height velocity occurs generally is not affected by regular training, nor is the rate of skeletal maturation. But the data concerning the influence of regular training on indexes of sexual maturation are not as clear. Although some data suggest that menarche(the initial onset of menstruation) is delayed in highly trained girls, these data are confounded by a number of factors that generally have not been properly controlled in each study’s analysis.

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