Change of Direction Asymmetry in Youth Elite Tennis Players: A Longitudinal Study.

Longitudinal investigations into the development of inter-limb asymmetry in sports are scarce. This study examined the development of change of direction (COD) asymmetry magnitude in youth elite tennis players. Dominant (overall best performance) and non-dominant (best performance on the other side) scores and COD asymmetry magnitude were quantified annually (up to six years) in 323 male and 235 female players (ages 6 to13 years). Linear mixed effects regression models examined the development of COD performance and asymmetry magnitude according to players' chronological age and sex. Kappa coefficients examined the consistency for the direction of asymmetry across test occasions. Regardless of sex, COD performance significantly improved (p<0.001) while COD asymmetry magnitude significantly decreased (- 0.17±0.87% / year) with increasing chronological age. Regardless of age, males showed significantly lower COD times (- 0.111±0.091 s) and lower COD asymmetry magnitude (- 0.30±1.00%) compared to females. The slight and poor (k-value=0.02-0.00) kappa coefficients for males and females, respectively, highlight the direction specificity of functional asymmetry. These data show that whereas performance of the COD test improved, the magnitude of COD asymmetry declined across chronological age in youth tennis players.

Development of upper and lower extremity functional asymmetries in male and female elite youth tennis players: a longitudinal study.

BACKGROUND: This longitudinal study aimed to examine the development of both upper and lower extremity functional performances, together with asymmetry magnitudes and directionality in youth tennis players. METHODS: Dominant and non-dominant physical performance values of 90 players (53 males, 37 females) were determined yearly (with monitoring up to 3 years) using unilateral strength, power, speed and agility tests from which asymmetry magnitude percentages were calculated. Linear mixed effect models examined the development of performance values according to youth players' maturity offset, performance dominance, sex and training volume. Similarly, the development of functional asymmetry magnitudes was examined according to players' maturity offset, sex and training volume. Kappa coefficients (k) examined the consistency in directionality across test occasions. RESULTS: Regardless of sex, the dominant and non-dominant physical performance values of every test significantly (P<0.05) improved with increasing maturity offset. No sex differences were apparent except for strength and power related tests where male players performed significantly better. Functional asymmetry magnitudes (ranging from 2.0 to 15.9%) did not significantly change with increasing maturity offset (range=-0.3-0.4% per year). Training volume was not significantly associated with the performance values and asymmetry magnitudes. The dominant upper extremity (which holds the tennis racket) consistently displayed the dominant performance value (k value: 1.00) across test occasions, which was not the case at lower extremity level (k value range: -0.28-0.31). CONCLUSIONS: The functional asymmetry magnitudes did not change significantly with youth tennis players' maturity offset over a 3-year period.

Morphological and functional asymmetry in elite youth tennis players compared to sex- and age-matched controls.

Besides examining upper and lower limb morphological and functional asymmetry magnitudes, this study examined the relationship between lean mass and functional asymmetry in terms of magnitude and direction in 41 youth tennis players versus 41 controls. Asymmetry magnitude was determined using anthropometric measurements (circumferences, widths), bioelectrical impedance analysis (lean mass) and a test battery (handgrip strength, seated medicine ball throw, plate tapping, single leg countermovement jump, single leg forward hop test, 6 m single leg hop test, 505 change of direction). ANOVAs compared the dominant (overall highest/best value) against the non-dominant (highest/best value of opposing limb) result. Linear regressions explored the relationship between lean mass and functional asymmetry magnitudes. Kappa coefficients examined asymmetry direction consistency between the limb displaying the highest lean mass value and the limb performing dominantly across tests. Significant asymmetry magnitudes (p < 0.05) were found for all upper and lower limb outcome measures. No significant relationship was apparent between lean mass and functional asymmetry magnitude (r-value = -0.283-0.262). Despite finding (almost) perfect consistency in asymmetry direction (k-value = 0.84-1.00) for the upper limb, poor to slight consistency (k-value = -0.03-0.15) was found for the lower limb. Therefore, lean mass and functional asymmetry should be examined independently.

Bioelectrical impedance analysis as a means of quantifying upper and lower limb asymmetry in youth elite tennis players: An explorative study.

This study aimed to examine side-to-side differences in phase angle (PhA) in both upper and lower limbs of youth elite tennis players. Among other outcomes, PhA was directly determined using segmental multifrequency bioelectrical impedance analysis (BIA) in 26 tennis players (11.6 ± 1.1 years, 54% boys) and compared against a sex- and age-matched reference population. Significant upper limb asymmetry in PhA (p < 0.001), with a higher value on the dominant side of the body, was observed in the tennis players. At lower limb level, the tennis players showed a tendency towards a significantly higher PhA in the contralateral compared to the ipsilateral limb (p = 0.089). Using vector analysis (BIVA), a significant degree of PhA asymmetry (p = 0.002) was only reflected in the tennis players' upper limb. Additional segmental outcomes also demonstrated a significant degree of upper limb asymmetry in terms of tennis players' lean mass (p < 0.001), total segmental water (p < 0.001), fat mass (p < 0.001), extracellular water (p < 0.001) and extracellular water ratio (p < 0.001), whereas lower limb asymmetry was only observed in tennis players' fat mass (p = 0.037) and extracellular water (p = 0.001). This is the first study to report significantly more pronounced BIA-based side-to-side differences in youth elite tennis players compared to a non-athletic reference population at the upper limb level, whereas no significant between-group differences in the lower limbs were found. This explorative study should trigger future research to further scrutinize the role of BI(V)A as a promising field-method in monitoring bodily asymmetries in youth elite tennis players in view of sport performance and athletic health.HighlightsBioelectrical Impedance Analysis is a promising field-method to monitor side-to-side asymmetry in youth elite tennis players.Youth elite tennis players displayed a more pronounced degree of BIA-based side-to-side differences compared to a non-athletic reference population at the upper limb level, whereas whilst between-group differences appeared to be less evident in the lower limbs.Future research is warranted to scrutinize whether and to what extent these degrees of segmental bodily asymmetry may be related to injury risk (prevention) and athletic development of (pre)adolescent tennis players.