Influence of knee joint angle on muscle properties of paralyzed and nonparalyzed human knee extensors

Gerrits, Karin H., Maganaris, Constantinos N., Reeves, Neil D ORCID: https://orcid.org/0000-0001-9213-4580, Sargeant, Anthony J., Jones, David A. and Haan, Arnold de (2005) Influence of knee joint angle on muscle properties of paralyzed and nonparalyzed human knee extensors. Muscle and nerve, 32 (1). pp. 73-80. ISSN 0148-639X

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Abstract

Muscles of individuals with a spinal cord injury (SCI) exhibit an unexpected leftward shift in the force (torque)-frequency relationship. We investigated whether differences in torque-angle relationships between SCI and able-bodied control muscles could explain this shift. Electrically stimulated knee-extensor contractions were obtained at knee flexion angles of between 30 degrees and 90 degrees. Torque-frequency relationships were obtained at 30 degrees, 90 degrees, and optimum angle. Optimum angle was not different between groups but SCI-normalized torques were lower at the extreme angles. At all angles, SCI muscles produced higher relative torques at low stimulation frequencies. Thus, there was no evidence of a consistent change in the length of paralyzed SCI muscles, and the anomalous leftward shift in the torque-frequency relationship was not the result of testing the muscle at a relatively long length. The results provide valuable information about muscle changes occurring in various neurological disorders.