sport and health

Physical activity for the pediatric age

Physiological assumptions for the compilation of a motor program for the little ones.

Sedentariness and obesity are a widespread problem among the children of our society, About 4% of all children in Europe are affected by obesity and 25-50% of these maintain excess weight even in adulthood, developing early pathological situations.

It has now been proven that exercise can solve most of these problems. Unfortunately, the movement that is proposed during the pediatric age does not always respect the canons of psycho-physiological maturation. In fact, for a long time, children were considered as restricted adults.

Their physical characteristics, on the other hand, are different from those of their parents and it is therefore good to analyze the physiological requirements before approaching them to a particular sporting discipline or to a physical exercise program. We therefore propose a series of evidences arising from numerous scientific studies, with which we hope to be able to make trainers and technicians of motor activity think.

Cardiovascular system

Children, being smaller than adults, also have small internal organs and among them the heart. The Systolic Range is therefore also decreased, that is the quantity of blood expelled with 1 single beat (about 70 ml for the adult).

To compensate for the lower systolic range the heart maintains a faster beat and a higher maximum heart rate (FCM). In fact, unlike the 195-200 bp / min of a twenty-year-old, a child can even reach an FCM of 215 bpm / min. (Sharp, 1995). However, the maximum heart rate remains constant during the pre-puberty years, so it does not seem to play any role in improving aerobic activity.

It should however be kept in mind that, despite the fact that the FCM is higher, the latter cannot completely compensate for the lower systolic volume, which can be demonstrated by the fact that the volume in l / min of arterial blood is lower when compared with adult individuals.

Unlike the latter, however, children receive a greater volume of arterial blood to the muscles during exercise, derived from a greater difference in O2 concentration between arterial and venous blood (DAV - Difference Artero Venosa). Computed DAV values ​​seem to be lower (between 12 and 20%) in pre-pubescent children compared to puberty-aged children, although it is still uncertain whether the O2 difference follows the same development as the child.

Respiratory system

During childhood the cardio-respiratory function begins its development and then ends when it has matured. During this long journey, important changes in lung function will be produced, with a progressive increase in ventilator volumes at rest and during exercise.

The maximum ventilation values ​​will increase from 40-45 l / min at the age of 5-6 years up to 140-150 l / min in the adult male. The children also have a lower depth of breath and therefore need an increase in the number of breaths.

Sharp (1995) found about 60 respirations / min in children compared to about 40 respirations / min in adults. This will produce, especially after intense physical exercise, a more breathless breathing than the adult, a condition known as Tachypnea (from the Greek Tachi, fast and Pneuma, air) which could worry parents and coaches, but which must instead be considered as a normal reaction of the lively gaming activity.

Aerobic capacity

As a result of what happens with the organs most directly connected to this quality, such as the heart and lungs, aerobic capacity also increases with age. Studies in this regard (Krahenbuhl, Skinner, and Kort, 1985. and Bar-Or, 1983) report that the improvement progression of this quality is quite similar for both males and females, with minimal variations throughout the pre period -puber, in which the VO2max (maximum oxygen consumption) can report increases of around 200 ml / min per year. It was also found that the VO2max of some children increased from 1.42 to 2.12 l / min in a period between the ages of 8 and 12, ie a 49% increase compared to the starting values ​​(Bailey, Ross, Mirwald and Weese, 1978).

There are, of course, also discrepancies in the two sexes, which become clearer in the pubertal period. The girls, in fact, reach a plateau of the peak of improvement for aerobic capacity, around 12-14 years, maintaining values ​​lower than about 15%, compared to boys, who, instead, improve until the age of 17-18 years (Cerretelli, 1985). To tell the truth, in females, a first gradual decline in values ​​is appreciated even after 8 years. Girls of this age, in fact, have an average value of VO2max of 50 ml / kg / min which drops to almost 40 ml / kg / min at the age of 16 years.

These differences in the two sexes are often interpreted by means of variations in body composition, that is to say, caused by the increase in the fat mass of the girls, as a direct consequence of maturation (although, according to other authors, some socio-cultural factors could affect a decrease in motor activity in females). However, some research reports that if we link the values ​​of VO2max with the muscular volume of the lower limbs, the differences tend to disappear. This data is confirmed by some works concerning the behavior of VO2max / Kg, (ratio between max. O2 consumption and body weight), used as an index of work power.

Possibility of VO2max training in pre-pubescent subjects

In general, research indicates that if children follow an aerobic workout 3-5 times a week, with a continuous activity of at least 20 minutes for 12 weeks, improvements of VO2max are possible from 7 to 26%. On average, however, a child can expect an improvement of about 10% of VO2max after a cardiovascular training program.

Pre-pubescent children, subjected to systematic training, are able to improve their VO2max, but not as effectively as adults do after a program of aerobic resistance exercises.

In any case, we have seen that training sessions aimed at this purpose show no particular effect until after 11-12 years, so much so as to suggest that aerobic fitness can be trained near the pubertal phase, especially in males.

Many dispute the value of aerobic training because, the improvements of VO2max reported, should not be linked to training, as to a refined mechanical-coordinated efficiency. During the pre-pubertal period we actually witness a continuous and rapid adjustment of motor coordination, due, for the most part, to variations in body size.

Furthermore, during childhood, nerve fibers improve their myelin coating (myelination) which allows a faster conduction of the nerve impulse, with a consequent increase in the transmission of sensory and motor information and a better economy of energy expenditure, which it will translate positively towards physical fatigue and oxygen consumption.

Anaerobic metabolism

Running, jumping, throwing, as well as being of fundamental importance for the maturation of the child's basic motor patterns, represent gestures that could make us understand a child's predilection for anaerobic activities. Some explain that this type of activity turns out to be more a psychological behavior rather than a predilection for anaerobic activity. Moreover, if compared with the general context of children's activities, short-term efforts are probably more limited than they seem at first sight.

Until now, the understanding of the child's muscle metabolism has been based on a limited number of studies, especially those carried out during the early 1970s by Eriksson, Saltin, Karlson Saltin and Gollnick, who were the first to use techniques of muscle biopsy in children.

At the time the conclusions suggested the existence of a potential relationship between muscular anaerobic metabolism and physical maturation, which however is not always confirmed today. In general, children have limited capacity for Anaerobic Glycolysis up to post-puberty, as they have significantly lower activity than glycolytic enzymes.

Eriksson et al. (1973) indicated that 11-13 year olds have about half of the enzyme PFK (PhosfoFruttoKinase) compared to adults, with the consequence that children cannot produce much energy through anaerobic metabolism and must count for much more on the aerobic one. For this reason, children present an activity of enzymes linked to aerobic metabolism much higher than adults which, consequently, also allows them a better oxidation of fats during aerobic activity. Some studies (Kaczor-Ziolkowski-Popinigis-Tarnopolsky and Macek, -Mackova) have confirmed that children have low activity of LDH (Lactate Dehydrogenase) enzyme deputy to the metabolism of lactic acid.

Concluding

As we have seen, the organs and metabolic systems of the little ones present some substantial differences compared to those of adults. Although still incomplete, research on anaerobic and aerobic metabolism has shown that these two systems are not two separate entities but, rather, two metabolic systems that often interact with one another, not only in adulthood but also during the years preceding puberty. Moreover, scientific reality seems to suggest that aerobic-type physical activity is the one most suited to the physical activity of pre-pubescent children.

There are no specific exercises to report, rather it is essential to propose exercises and games that stimulate, in addition to learning, the right energy substrates, always keeping in mind the anatomical-physiological peculiarities of children. Once the technician has become aware of these characteristics, he will have to provide a rich and quality motor base, which favors complex technical learning and the most varied possible (in the form of multidisciplinarity) to stimulate an optimal structuring of the motor schemes.

It is therefore useless to look for precocious specializations in the pediatric age, above all when the scientific evidence informs us that up to 12-13 years the abilities to manage intense activities and complex motor gestures are definitely limited.

Alessandro Stranieri

Personal Fitness Trainer

www.stranieri-fitnesstrainer.it