Reliability of quadriceps twitch muscle properties and explosive voluntary contractions at different knee joint angles

Background: Measures that assess muscle strength and its development, either voluntarily or involuntarily, are important in the clinical and research context. The main aim of this study was to verify the inter day reliability and the minimum detectable change (MDC) of the knee extensors muscles torque using evoked contractions and explosive voluntary contractions (EVC), across 6 different joint angles.
Methods: 20 participants, 16 men and 4 women (26.5 ± 6.6 years; 174.5 ± 11.1 cm; 73.7 ± 11.3 kg) participated in this study. Evoked twitch contractions and voluntary explosive contractions of the knee extensors were performed in 2 days (test-retest) at 20, 40, 70, 90, 105 and 115 degrees.
Results: The most reliable twitch parameters were peak torque (PT), contraction time (CT), half relaxation-time (½ time), total impulse and peak rate of torque development (RTDPeak), with coefficient of variation (CV) ranging from ~8% at 20o to 5% at 115o angle. It was verified that CT and ½ time become more reliable as the knee angle changed from 20 to 115 degrees, from shorter to longer muscle lengths (7.3 to 2.7% and 8.8% to 4.0%, respectively). The more reliable parameters for voluntary contraction were PT, RTD250ms, RTDPeak and impulse250ms (CV from around ~8% at 20o/115o and 5% at 70o/ 90o). For voluntary contractions, all measures performed at 70o angle were more reliable compared to the other angles.
Conclusion: It was concluded that for the knee extensor muscles, evoked twitch contractions presented greater reliability across knee angles, with lower CV values when compared to the voluntary measures for the same time windows. Specifically, for the evoked twitch contractions, angles from 70 to 115-degree proved to be highly reliable. On the other hand, for the voluntary contractions, the central angles (70 and 90-degree) were the most reliable.

This is an Accepted Manuscript version of the following article, accepted for publication in Measurement in Physical Education and Exercise published by Taylor & Francis: Zimmermann, H. B., Knihs, D., Sakugawa, R., Bishop, C., & Pupo, J. D. (2024). Reliability of Quadriceps Twitch Muscle Properties and Explosive Voluntary Contractions at Different Knee Joint Angles. Measurement in Physical Education and Exercise Science, 28(4), 377–390. https://doi.org/10.1080/1091367X.2024.2370533 . It is deposited under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way