High-speed non-invasive measurement of tibial rotation during the impact phase of running

Several injuries to the lower extremity in runners have been linked to excessive rates of internal rotation of the tibia just after ground impact. This study presents an improved method of capturing internal/external tibial rotation, and investigates whether estimates of rates of internal tibial rotation during the first 50 ms of contact during running are influenced by the sampling rate and processing of tibial displacement data. A lightweight plate was moulded to the shape of each subject's right anterior-medial tibia. Nine male subjects ran barefoot (3.35 m(.)s(-1)) and the landing kinematics of the right leg were recorded at 1000 Hz. The group mean value for the total range of internal rotation of the tibia for the whole stance phase was consistent with the literature (15.4 degrees), but peak angular velocities (8.3 rad(.)s(-1)) were substantially higher than previously reported. The cut-off frequency of the low-pass filter influenced the peak angular velocity values obtained with the largest changes occurring between 15 and 40 Hz. Typically, researchers using lower sample rates have to filter around 10 Hz and consequently are likely to underestimate peak angular velocities. These findings have implications for obtaining a sound quantitative foundation for transient tibial motion before furthering our understanding of injury mechanisms.