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The relationship between the change of trunk muscle thickness and landing technique in women volleyball players with Jumper’s knee

This study aimed to discuss the relationship between the change of trunk muscle thickness and the stability of landing movement of volleyball players with jumper’s knee. We studied a total of 14 women volleyball players. They were classified into the JK group consisting of 7 players with jumper’s knee and the CON group consisting of 7 players without jumper’s knee. We measured the transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) both at rest and in the plank position (PL) of the subjects, and figured out change rates of their muscle thicknesses by dividing the muscle thickness in the plank position by that at rest. We also measured flexion angle of trunk, hip, and knee at landing. We found that change rates of IO were significantly lower in the JK group than in the CON group (p<0.01), and that flexion angles of trunk was significantly greater in the JK group than in the CON group (p<0.01). In conclusion, our study clarified that players in the JK group have a lower change rate of trunk muscle contraction and increase the flexion angle. It also clarified that they make a compensa-tory movement by flexing knee joint and body truck to reduce the burden on knee joint.