Impact of Fatigue on Stride to Stride Variability of Sagittal Plane Joint Kinematics

Abstract

With recent improvements in motion-analysis, it has now become much easier to assess multiple distance running strides to determine how consistent a runner’s kinematics are. Thus, the impact of factors such as fatigue on running technique can now be evaluated. PURPOSE: To determine if stride-to-stride variability (SSV) of sagittal plane stance phase joint angles at the hip, knee, and ankle are altered by a 16-minute submaximal progression run. METHODS: Nineteen runners (18-45 yrs) participated in this study. Six Vicon Bonita cameras were used to collect kinematic data at 200 Hz. A Parvo metabolic cart was used to confirm the progression run caused fatigue. Baseline data were collected utilizing a 4 minute run at self-selected marathon race pace. After a 5-minute rest period the runners completed a 16-minute progression run, with increases in intensity at 4 minute intervals, which ended at marathon pace for the final data collection. Ten strides were used for SSV calculations. Stance phase joint angles were normalized to 101 data points. SSV was then determined for each joint by calculating the standard deviation (SD) across the 10 consecutive strides. The baseline and final SSV were compared using a 2-way ANOVA. RESULTS: The progression run increased the heartrate significantly (158.6±13.4 bpm to 169.6±14.3 bpm), thus confirming significant fatigue. Baseline and final SSV data were compared for the hip (1.23±0.37° vs. 1.17±0.37°), knee (1.47±0.39° vs. 1.51±0.44°), and ankle (1.20±0.50° vs. 1.21±0.40°). ANOVA and post-hoc testing revealed the knee to be the most variable joint overall. However, there were no significant increases in SSV between baseline and final measures. CONCLUSIONS: Despite experiencing metabolic and kinematic changes, the runners maintained the consistency of their running technique. Future research may want to evaluate SSV under greater to levels of fatigue to assess whether a fatigue threshold exists that will lead to an altered consistency of running technique.