| Description |
Tennis game is typical for high intensity, sudden changes of directions, rapid slow down, acceleration and running for the ball. These movements lead to intensive strain to lower extremities, which is connected with selective activation of muscle groups and their further adaptation. During the muscle adaptation, muscular dysbalances might occur, which can result in an increased incidence of injuries and can be the cause for the reduced ability to maintain a balanced body posture during the game. With regard to this fact, the aim of this study was to establish, the strength level of knee extensors and flexors and assessment of their unilateral and bilateral differences, further to examine the strength level in tennis players group - boys (TEN_M, n=10, aged 13.23 ± 0.51), girls (TEN_F, n=10, aged 13.34 ± 0.69) in comparison with groups of boys (CS_M, n=10, aged 13.04 ± 0.61) and girls (CS_F, n=10, aged 13.21 ± 0.55 let) who do not perform any sport activity. Diagnostics of knee joints strength was carried out by isokinetic dynamometry (Humac Norm CSMI, Stoughton, USA) under two angular velocities (180°/s and 300°/s). Significance of differences in mean values was assessed by using Cohen´s d. Data analysis proved that differences between TEN and CS groups concerning age, body height and weight were insignificant. Comparison of isokinetic strength level (180°/s) between TEN_M and CS_M group proved significantly higher strength level of knee extensors (d=0.75) and flexors (d=1.27) in tennis players dominant extremity. Also for non-dominant leg in TEN_M group, was found significantly higher strength level of extensors (d=0.68) and flexors (d=1.05). Assessment of bilateral differences in strength of knee extensors (d=0.11) and flexors (d=0.05) of dominant and non-dominant extremity in TEN_M group did not prove their significance. Neither in CS_M group was found significant bilateral strength differences between knee extensors (d=0.07) and flexors (d=0.15) of dominant and non-dominant extremity. Comparison of isokinetic strength level (300°/s) between TEN_M and CS_M groups proved significantly higher strength level of knee extensors (d=0.91) and flexors (d=1.48) of dominant extremity in tennis players group. Also in knee extensors (d=0.85) and flexors (d=1.05) of non-dominant extremity, was proved significantly higher strength level in tennis players group. Assessment of bilateral differences in strength of knee extensors (d=0.11) and flexors (d=0.01) of dominant and non-dominant extremity in TEN_M group did not prove their significance. Neither in CS_M group was found significant bilateral strength differences between knee extensors (d=0.10) and flexors (d=0.21) of dominant and non-dominant extremity. Comparison of isokinetic strength level (180°/s) of dominant extremity between TEN_F and CS_F groups did not prove significant differences in the strength of extensors (d=0.46) and flexors (d=0.45). Significant lateral differences in strength level in favour of TEN_F group were however proved in knee extensors (d=0.56) and flexors (d=0.73) on non-dominant extremity. Assessment of bilateral differences in strength of knee extensors (d=0.04) and flexors (d=0.24) of dominant and non-dominant extremity in TEN_F group did not prove their significance. Neither in CS_F group was found significant bilateral strength differences between knee extensors (d=0.12) and flexors (d=0.05) of dominant and non-dominant extremity. Comparison of isokinetic strength level (300°/s) between TEN_F and CS_F group proved significantly higher strength level of knee extensors (d=0.63) of dominant extremity in tennis players group, while the significance of difference was not proved in flexors (d=0.48).
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