Reliability of Simple Reaction Time Measurement During Single-Leg Standing in Patients After Primary Anterior Cruciate Ligament Reconstruction

Objective Compared to healthy athletes, athletes who have undergone anterior cruciate ligament (ACL) reconstruction have been shown to have delayed reaction time (RT). However, the reliability of RT measurements after ACL reconstruction remains unknown, and no study has measured RT after ACL reconstruction in the single-leg standing position. This study aimed to validate the reliability of simple RT measurement in a single-leg standing position within a single session after ACL reconstruction. Materials and methods Participants who underwent ACL reconstruction were recruited for this study. A response-measuring instrument synchronized with a mat sensor measured simple RT in the single-leg standing position. The participant assumed the single-leg standing position on the mat sensor and lifted the sole off the mat sensor as soon as possible after the lamp lighting. The RT was defined as the time from the lamp lighting to when the sole left the mat sensor. The RT of each operative and nonoperative side was measured 10 times randomly. After confirming the normality of the data, the frequency effect on the 10 trials was confirmed by repeated measures analysis of variance. Results The mean of 10 RT trials in the single-leg standing position was 0.444 ± 0.072 s on the operative side and 0.436 ± 0.060 s on the nonoperative side. Repeated measures analysis of variance showed no significant difference between measurements for either the operative or nonoperative side. After the second trial, the intraclass correlation coefficient exceeded 0.900 for both the operative and nonoperative sides. The standard error of each measurement for the three trials was 0.006 s and 0.041 s for the operative and nonoperative sides, respectively. Conclusion The reliability of measurement within a single session of simple RT in the single-leg standing position after ACL reconstruction was acceptable.