Intra-rater reliability and criterion-related validity of using an accelerometer to measure the impact force and knee joint sway during single-leg drop landing

[Purpose] This study aimed to clarify the reliability and validity of the impact force and knee joint sway measurement during single-leg drop landing by using a motion sensor with two built-in accelerometers. [Participants and Methods] Ten healthy college students (4 males and 6 females) who joined a basketball club participated in this study. Peak vertical acceleration, time between initial contact and peak vertical acceleration, and knee joint mediolateral sway were measured using the accelerometer during the landing motion. Reliability of the measurement with the accelerometer and the criterion-related validity between the accelerometer and force plate data were examined. [Results] The intraclass correlation coefficients indicated a peak vertical acceleration of 0.88, time between initial contact and peak vertical acceleration of 0.96, and knee joint mediolateral sway of 0.62. The magnitude and timing of the peak values between both measurement instruments showed high validity. [Conclusion] The measurement method using a motion sensor for the evaluation of the impact force and knee joint sway during landing has a moderate to high reliability and criterion-related validity. A motion sensor measurement might be a useful and easy method for evaluating landing impact force and knee joint stability.