Reliability of Knee Flexion–Extension Lyapunov Exponent in People With and Without Anterior Cruciate Ligament Deficiency

in Journal of Sport Rehabilitation
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Objectives: The current study assessed the intrasession and intersession reliability of the knee flexion–extension Lyapunov exponent in patients with anterior cruciate ligament deficiency and healthy individuals. Study Design: University research laboratory. Methods: Kinematic data were collected in 14 patients with anterior cruciate ligament deficiency and 14 healthy individuals walked on a treadmill at a self-selected, low, and high speed, with and without cognitive load. The intraclass correlation coefficient, standard error of measurement, minimal metrically detectable change, and percentage of coefficient of variation were calculated to assess the reliability. Results: The knee flexion–extension Lyapunov exponent had high intrasession reliability, with intraclass correlation coefficients ranging from .83 to .98. In addition, the intersession intraclass correlation coefficient values of these measurements ranged from .35 to .85 regardless of group, gait speed, and dual tasking. In general, relative and absolute reliability were higher in the patients with anterior cruciate ligament deficiency than in the healthy individuals. Conclusions: Although knee flexion–extension Lyapunov exponent demonstrates good intrasession reliability, its low intersession reliability indicates that changes of these measurements between different days should be interpreted with caution.

Nazary-Moghadam and Zeinalzadeh are with the Department of Physiotherapy, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran. Salavati and Akhbari are with the Department of Physiotherapy, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Esteki is with the Department of Biomedical Engineering and Physics, School of Medicine, Shaheed Beheshti University of Medical Sciences, Tehran, Iran. Keyhani is with the Akhtar Orthopedic Hospital, Shaheed Beheshti University of Medical Sciences, Tehran, Iran.

Nazary-Moghadam (Nazary_salman@yahoo.com) is corresponding author.
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