Running gait kinematics are reproducible at the beginning and end of two different intensity, energy expenditure matched runs, using either discrete points or functional data analysis.

Introduction: The aims of this study were to examine reliability of treadmill running kinematics: i) during two different intensity, energy expenditure matched, runs ii) at two time points within each run iii) using two different methods of statistical analysis. Methods: Twenty healthy club distance runners performed two high intensity interval runs (HIIT) and two medium intensity continuous runs (MICR). Kinematics during ground contact were analysed in all three planes of motion at the ankle, knee, and hip. Maximum angle and range of motion were identified and for Functional Data Analysis (FDA) all of the collected data was utilised. Reliability was established from both discrete points and FDA using intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimum detectable change (MDC). In addition, coefficient of variation (CV) was calculated for discrete points, however, this was not possible for FDA. Results: Both discrete point analysis and FDA showed acceptable reliability in all three planes of motion. Only three variables produced SEM values higher than 5.0 degrees while ICC values ranged from poor to excellent. Discussion: There were no differences in reliability between the start and end of the runs for HIIT or MICR. Gait kinematics during treadmill running were reliable across intensities, run type and time frames.