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Expect the Unexpected When You Cut and Run

It can happen in almost any sport. A player is running hard. No one hits her. But she suddenly stops or falls down, grabbing a leg. These noncontact leg injuries usually involve ligaments. Noncontact knee ligament injuries are especially common. But exactly why and how they happen is not well understood.

It is known that muscles surrounding the knee can absorb a lot of the stress and strain of running and cutting. In this way the muscles protect the ligaments from being overloaded. Much of this ability depends on the nervous system to control the muscles in the right way.

It is this muscle action that these authors studied. They tested the muscles around the knee in 11 male soccer players while running, cutting, and sidestepping. The soccer players had electrodes placed around the knee before going through two series of drills. In one series, they knew exactly when and where they needed to run, cut, and sidestep. This was called the "preplanned" series. In the second series, they had to react quickly during the test to change movements. This was called the "unexpected" series. Knee movement was also studied during both series.

The authors found that the muscles worked much differently in the two series. In the preplanned series, specific muscles contracted together to help protect the knee. In the unexpected series, the muscles contracted more randomly. The knee also went through much more rotation and stress during the unexpected series. The muscle contractions in the unexpected series were less efficient and less able to protect the ligaments of the knee. The nervous system simply didn't have enough time to activate the muscles to provide optimum protection for the knee.

Obviously, the unexpected tests were more like playing in a real soccer game. The authors wonder if training could be geared toward "preprogramming" the muscles to contract more effectively under unexpected conditions.

References: Thor F. Besier et al. Muscle Activation Strategies at the Knee During Running and Cutting Maneuvers. In Medicine & Science in Sports & Exercise. January 2003. Vol. 35. No. 1. Pp. 119-127.

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