Hamstrings contractile timing in anterior cruciate deficient subjects
Abstract
Anterior cruciate injuries are extremely debilitating injuries for active individuals. It is
estimated that 60 to 70% of all serious knee injuries involve damage to the anterior cruciate
ligament (ACL) (Brant. 1989). One of the functional roles of the hamstrings is to prevent the
anterior translation of the tibia, absorbing a portion of the anterior shear forces on the ACL
(Brant. 1989; Nordin & Frankel, 1989). Timing of the hamstrings contraction during gait
provides an important counter force to stabilize the knee. However, if the force occurs too early
or too late, stabilization is compromised. Electromyographical (EMG) research analyses
demonstrates that the hamstrings increase in actuation just before heelstrike (GaufBn & Tropp,
1992; Gronley & Perry, 1984; Phyllis, 1993; Johnstone, 1993). This response may be due to
training of the muscle to respond to spatial and temporal cues, causing a compensator)
contraction of the hamstrings (Schm idt 1988; Vlagill, 1989).
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- Retrospective theses [1604]