Dissertation committee:
Βαγενάς Γ., Αφυπηρετήσας Καθηγητής, ΣΕΦΑΑ, ΕΚΠΑ
Γελαδάς Ν., Καθηγητής, ΣΕΦΑΑ, ΕΚΠΑ
Μπουντόλος Κ., Καθηγητής, ΣΕΦΑΑ, ΕΚΠΑ
Τσέπης Η., Καθηγητής, Πανεπιστημίου Πατρών
Μπογδάνης Γ., Καθηγητής, ΣΕΦΑΑ, ΕΚΠΑ
Τσολάκης Χ., Καθηγητής, ΣΕΦΑΑ, ΕΚΠΑ
Βενετσάνου Φ., Αναπληρώτρια Καθηγητής, ΣΕΦΑΑ, ΕΚΠΑ.
Summary:
The effect of physical activity on the bone and muscular development of children has been of particular research interest. Tennis is a model of one-sided sport for the methodical study of this effect as it provides the ideal internal control through the non-dominant (ND) hand. The extra strengthening of the dominant (D) hand leads to bone and muscle hypertrophy. In the present study, bone and muscle growth of the upper and lower extremities and the grip strength of childhood and adolescence tennis players were evaluated over a period of 9 months, with the main purpose being to determine the effect of physical maturation and total training time. The sample consisted of 46 children (25 boys, 21 girls) divided into four groups: 1st: 8.18 ± 0.48 (pre-puberty), 2nd: 9.47 ± 0.14 (pre-puberty), 3rd: 10.53 ± 0.32 (pre/peri-puberty), 4th:12.28 ± 0.60 (peri/post-puberty). Bone mineral content (BMC), bone area (ΒΑ) and lean body mass (LBM) were measured using double-energy X-ray absorptiometry (DXA). The grip strength was measured with an analog hand dynamometer. The evaluation of sexual maturation was done using the Tanner method and the age peak height velocity (APHV) and maturity offset (MO) markers were calculated. The data were analyzed descriptively, with ANOVA and with multiple linear regression. The D hand showed significant hypertrophy in BMC (pre:11-21%, post:10-25%, g=0,03-1,40) and in BA (pre:7-12%, post:8-17%, g=0,10-0,88) and greater grip strength (pre:11-21%, post:10-25%, g=0,26- 0,50). In the lower extremities there were no significant asymmetries. Within the 9-month period the bone growth of the ND hand showed slight changes between the 4 groups (10-14% στο BMC & 9-11% στο ΒΑ), while the D hand showed similar growth during pre-puberty (13-14% in BMC, 10% in ΒΑ), a sharp increase in peri-puberty (20% in BMC, 15% in BA) and a sharp decrease in post-puberty (11% in BMC, 9,5% in BA). During the transition from pre/peri-puberty to peri-puberty (3rd group), the asymmetry of bone markers and LBM changed significantly (59% in BMC, 54% in ΒΑ & 38% in LBM), with the grip strength not showing significant changes (p>0,01). The linear combination of the change in maturation, the total training duration and the general physical activity interpreted 56% and 48% of BMC change and 40% and 42% of BA change of the D and ND hand, respectively. Physical maturation was the main interpretative factor of bone growth of the upper limbs and their change in the 9-month period, with the total training time being significantly correlated with the development of the D hand and asymmetries. Participation in tennis from infancy brings about a gradual strengthening of the D hand in bone mass and thickness and in muscle strength until peri-puberty, with a faster growth rate during peri-puberty and stabilization in post-puberty. The lower extremities are not affected asymmetrically, obviously due to insufficient chronicity and intensity of the asymmetrical function of the upper limbs. The findings are interpreted and discussed in the context of the value of bone and muscular strengthening of children developmentally, educationally and in terms of health in old age to reduce osteoporosis.
Keywords:
growth, children, puberty, bone mass, bone size, tennis, asymmetries
