Tibial acceleration is a surrogate measure for impact loading and lower limb fatigue injury in runners. Triaxial accelerometers may offer reliable and practical measurement of resultant peak tibial acceleration (PTA). With such potential in mind, this study examined variability and measurement reliability of tibial acceleration in 14 runners at baseline at one week, and eight of the runners again at six months. Triaxial accelerometers were attached to the distal tibiae of runners before they ran on a treadmill for two minutes each, at speeds of 2.7, 3.0, 3.3 and 3.7 m/s in standardised shoes. Resultant PTAs were calculated for each speed and session. Reliability outcomes were presented as percentage change and effect sizes. Variability outcomes included intraclass correlation coefficients and the typical error of the measurement. Smallest worthwhile change and performance/noise ratio were also calculated. While runners demonstrated marginally lower reliability and higher variability over six months, compared to one week, in all cases the measures of reliability and variability were of ‘good’ to ‘moderate’ reliability, and ‘small’ to ‘moderate’ variability using magnitude-based inferences. We can be confident that resultant PTA can be used with runners to assess and monitor their impacts throughout a six-month intervention.

Tibial acceleration is a surrogate measure for impact loading and might be useful for identifying lower limb fatigue injury in runners. The resultant tibial acceleration calculated from all three axes of a triaxial accelerometer provides a single metric that is independent of the sensor orientation. The purpose of this study was to investigate the relationship between resultant tibial acceleration and running velocity, and to establish a normative database of tibial acceleration profiles. Triaxial accelerometers were attached to the distal tibiae of 85 runners before they ran on a treadmill for 2 min each, at speeds of 2.7, 3.0, 3.3, and 3.7 m/s. Differences in resultant tibial acceleration were calculated using a one-way ANOVA, and the relationship between tibial acceleration and velocity was determined using a Pearson correlation coefficient and a multiple linear regression analysis. Tibial acceleration increased with higher velocities, with an average increase of 3.8 g (38%) between the slowest and fastest speeds. A moderate correlation was demonstrated between tibial acceleration and running velocity, and 19% of tibial acceleration was explained by velocity. While velocity influences tibial acceleration, individual variances to this relationship exist, highlighting the need for a personalised approach to understanding the response of each runner.