Test-retest reliability of the OptoGait system for the analysis of spatiotemporal running gait parameters and lower body stiffness in healthy adults

Despite the widespread use of the OptoGait photoelectric cell system for the analysis of running spatiotemporal parameters, its reliability has not been proved. Consequently, this study intends to determine the test-retest reliability of the system when applied to treadmill running spatiotemporal parameters and lower body stiffness at a constant velocity. Amateur endurance runners (n = 31; age: 34.42 +/- 9.26 years; height: 171.54 +/- 9.15 cm; body mass: 66.63 +/- 11.3 kg) voluntarily consented to participate in this study. Data for each participant were recorded twice per session across two testing sessions. The intra-session and inter-session reliabilities of spatiotemporal parameters and lower body stiffness were determined through test-retest analysis. Although mean comparisons revealed significant differences between measurements in spatiotemporal running gait characteristics and lower body stiffness for intra-session (p < 0.05 in all parameters), the effect size was always small (<0.4). Moreover, the relationship between measurements was very large for spatiotemporal parameters and lower body stiffness (r > 0.7). The intraclass correlation coefficients revealed an almost perfect correlation between measurements (intraclass correlation coefficients >0.81), except Kleg with substantial reliability (intraclass correlation coefficient = 0.788). The inter-session reliability revealed some significant differences in contact time (p = 0.009) and Kleg (p = 0.013), although Cohen's d indicated small effect size (<0.31). The relationship between sessions was very large for spatiotemporal parameters and lower body stiffness (r > 0.8), and the intraclass correlation coefficients revealed an almost perfect inter-session association (intraclass correlation coefficients >0.881). The results found here show that the OptoGait system can be used confidently for running spatiotemporal parameters analysis and lower body stiffness at a constant velocity for healthy adults.