Electromyographic and kinematic analysis of cutting maneuvers - Implications for anterior cruciate ligament injury

The objective of this study was to qualitatively characterize quadriceps an d hamstring muscle activation as well as to determine knee flexion angle du ring the eccentric motion of sidestep cutting, cross-cutting, stopping, and landing. Fifteen healthy collegiate and recreational athletes performed th e four movements while knee angle and electromyographic activity (surface e lectrodes) of the vastus lateralis, vastus medialis obliquus, rectus femori s, biceps femoris, and medial hamstring (semimembranosus/semitendinosus) mu scles were recorded. The results indicated that there is high-level quadric eps muscle activation beginning just before foot strike and peaking in mid- eccentric motion. In these maneuvers, the level of quadriceps muscle activa tion exceeded that seen in a maximum isometric contraction. Hamstring muscl e activation was submaximal at and after foot strike. The maximum quadricep s muscle activation for all maneuvers was 161% maximum voluntary contractio n, while minimum hamstring muscle activity was 14%. Foot strike occurred at an average of 22 degrees of knee flexion for all maneuvers. This low level of hamstring muscle activity and tow angle of knee flexion at foot strike and during eccentric contraction, coupled with forces generated by the quad riceps muscles at the knee, could produce significant anterior displacement of the tibia, which may play a role in anterior cruciate ligament injury.