Surface electromyographic analysis of the lower trapezius muscle during exercises performed below ninety degrees of shoulder elevation in healthy subjects
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The effect of an inclined landing surface on biomechanical variables during a jumping task
by
Hagins M, Pappas E, Kremenic IJ, Orishimo KF, Rundle A.
—
last modified
2009-10-09 15:17
Clin Biomech (Bristol, Avon). 2007 Nov;22(9):1030-6. Epub 2007 Sep 10.
BACKGROUND: Professional dancers sustain a high number of injuries.
Epidemiological studies have suggested that performing on inclined "raked" stages
increases the likelihood of injury. However, no studies have examined if
biomechanical differences exist between inclined and flat surfaces during
functional tasks, such as landing from a jump. Such differences may provide a
biomechanical rationale for differences in injury risk for raked stages. METHODS:
Eight professional dancers performed drop jumps from a 40cm platform on flat and
inclined surfaces while forces, lower extremity kinematics, and electromyographic
activity were collected in a controlled laboratory environment. FINDINGS: Dancers
landed on the laterally inclined surface with significantly higher knee valgus (4
degrees), peak knee flexion (9 degrees), and medial-lateral ground reaction
force (GR) (13.4% body weight) compared to the flat condition. The posterior GRF
was higher in the anterior inclined condition compared to the flat condition. In
the anterior inclined condition, subjects landed with 1.4 degrees higher knee
valgus, 4 degrees more plantarflexion at initial contact, and 3 degrees less
dorsiflexion at the end of landing. INTERPRETATION: Biomechanical variables that
have been suggested to contribute to injury in previous studies are increased in
the inclined floor conditions. These findings provide a preliminary biomechanical
rationale for differences in injury rates found in observational studies of raked
stages.