Extension and flexion torque variability in ACL deficiency

Area of Science:

• Biomechanics
• Orthopedics
• Neuromuscular control

Background:

• Anterior cruciate ligament deficiency (ACLD) often leads to altered knee function and strength deficits.
• Previous research indicates reduced knee extension torque in ACLD legs, but the impact on torque variability remains unclear.
• The role of visual feedback and muscle length in modulating torque variability in ACLD is not well-established.

Purpose of the Study:

• To investigate differences in knee extension and flexion torque variability between anterior cruciate ligament-deficient (ACLD) and healthy legs.
• To determine if muscle length and visual feedback influence torque variability in ACLD.
• To explore potential deficits in submaximal isometric torque variability in ACLD.

Main Methods:

• Evaluated isometric knee extension and flexion torques in 13 untrained men with unilateral ACL rupture.
• Assessed torque variability at specific knee angles (90°, 120°, 140°) and with/without visual feedback.
• Utilized coefficients of variation (CV) and permutation entropies (PE) to quantify submaximal isometric torque variability.

Main Results:

• Healthy legs demonstrated significantly greater isometric knee extension torques at 90° and 120° compared to ACLD legs.
• No significant differences were found in torque variability (CV) for knee extension or flexion between healthy and ACLD legs, with or without visual feedback.
• Permutation entropy (PE) of knee extension torque was significantly higher in healthy legs at 90° and 120° knee angles.

Conclusions:

• While ACL deficiency did not significantly affect linear torque variability (CV), it reduced the complexity (PE) of submaximal knee extension torque.
• Assessing ACLD requires evaluating not only maximal isometric torque but also torque variability and complexity using nonlinear methods.
• Nonlinear analysis of submaximal isometric tasks may provide a more sensitive measure of functional deficits in ACLD.