BONE AND MUSCLE GROWTH ASYMMETERIES IN CHILDREN TENNIS PLAYERS (7-13 YEARS): A 9-MONTH FOLLOW-UP STUDY ACCORDING TO PUBERTAL STATUS

D. Palaiothodorou¹, E. Tsepis², T. Antoniou³, D. Mandalidis⁴, G. Vagenas¹

¹National and Kapodistrian University of Athens, School of Physical Education and Sport Science, Department of Physical Education and Sport Science, Athens, Greece, ²School of Health Rehabilitation Sciences, Physiotherapy Department, Patra, Greece, ³Blocks Rehab Filoktitis Rehabilitation Center, Medical Imaging Department, Athens, Greece, ⁴National and Kapodistrian University of Athens, School of Physical Education and Sport Science, Department of Physical Education and Sport Science, Sports Physical Therapy Laboratory, Athens, Greece

Background: The effects of exercise on bones and muscles in children are growth- and health-relevant. These effects are typically explored via Tennis in accordance with the age-progressing training volume and the pubertal status. The highly asymmetric patterns of Tennis create osseous and muscular asymmetries between the dominant (D) and non-dominant (ND) arm. The shape of dependency of these asymmetries on age and pubertal status required further clarification.

Purpose: The study aimed to determine how asymmetries in bone and muscle growth in the upper arms of children and adolescent tennis players progress over a period of 9 months of systematic participation across the developmental age-span of 7-13 years in relation to pubertal status.

Methods: A sample of 46 children (25 boys and 21 girls) was split into four groups: A: pre-puberty1 [PrP1] (8.18 ± 0.48 yrs), B: pre-puberty2 [PrP2] (9.47 ± 0.14 yrs), C: pre/peri-puberty [PrPerP] (10.53 ± 0.32 yrs), D: peri/post-puberty [PerPostP] (12.28 ± 0.60 yrs). Bone mineral content (BMC), bone area (ΒΑ), and lean body mass (LBM) of the upper arms were measured using DXA, while hand-grip strength (HGS) was measured with an analog hand dynamometer. Sexual maturity was assessed by the Tanner method. Statistical analysis included ANOVAs, Bonferroni-adjusted paired t-tests, and effect sizes (Hedges' g and η²).

Results: Overall, BMC, BA, LBM, and HGS were 8% to 20% greater in the D compared to the ND arm. There were significant differences among the four groups in BMC, BA, and LBM asymmetry pre- and post-test (p < 0.01, η² = 0.19 – 0.61), but not in HGS asymmetry (p > 0.05, η² = 0.8 – 0.16). During the 9-month period BMC asymmetry changed less for groups PrP1 (10.9% to 9.6%, p = 0.88, g = 0.03), PrP2 (20.2% to 21.0%, p = 0.15, g = 0.30), and PerPostP (20.8% to 22.1%, p > 0.01, g = 0.56), and more for group PrPerP (17.3% to 24.5%, p < 0.001, g = 1.4). The respective changes in BA, LBM, and HGS asymmetry were generally small except for group PrPerP (BA: 11.6% to 16.7%, p > 0.01, g = 0.88; LBM: 6.9% to 8.7%, p > 0.01, g = 0.58), and for group PrP2 (HGS: 12.3% to 15.4%, p > 0.01, g = 0.50).

Conclusions: The systematic participation in tennis from early childhood to post-puberty elicits substantial hypertrophy of the D arm in bone mass and thickness, and in muscle mass and strength. The rate of this hypertrophy is sharper during pre- to peri-puberty and slower during peri- to post-puberty. This data improves our understanding of the pattern of structural and functional adaptations of the upper limbs in youth tennis during growth.

Implications: The results could guide training decisions and the implementation of targeted interventions (i.e., more symmetric training of the arms) to limit excessive bone and muscle imbalances especially during pre- to peri-puberty. Implications are thus relevant not only to performance but also to the conditions that predispose to injury and osteoporosis in later life.

Funding acknowledgements: This scientific paper was supported by the Onassis Foundation - Scholarship ID: GZJ039-1/2013-14.

Keywords:
Tennis asymmetries
Bone-muscle growth
Children

Topics:
Musculoskeletal: upper limb
Paediatrics
Sport & sports injuries

Did this work require ethics approval? Yes

Institution: National and Kapodistrian University of Athens

Committee: School of Physical Education and Sports Science

Ethics number: (1019/6/9/2017)