Document Title: Colby-AJSM-Mar00.shtml
Article Title: Electromyographic and kinematic analysis of cutting maneuvers: Implications for anterior cruciate ligament injury
Authors: Scott Colby; Anthony Francisco; Bing Yu; Donald Kirkendall; et al.
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: Mar/Apr 2000
Volume 28, Number 2, pages 234-240

(Figures included. Reference-denoting numbers appear in the same point size as the document text.)

This fascinating study looks at the muscle-firing patterns underlying various cutting-type movements. Given that roughly 70% of ACL injuries occur in the context of sports, an improved understanding of the biomechanical/kinematic precursors to ACL injuries offers the potential to engender improvements in athletic training. One method that greatly reduces torque at the knee during cutting-type manoevres entails learning to pivot on the front portion of the foot (rather than planting the entire shoe sole). Such a technique is especially worthwhile for athletes with knee-injury histories. Colby et al. also provide a good description of the stride and stance phases of walking and running.

ABSTRACT

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

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