Gait variability and fatigability during a simulated 10-km running race in trained runners

Purpose: Fatigue is an inevitable phenomenon during distance running, leading to the adoption of altered gait patterns by runners. Therefore, the aim of this study was to investigate the changes in gait variability and fatigability in distance runners over a 10-km running race. Methods: For this aim, 12 runners (36.5 ± 5.4 y) completed a simulated 10-km running race. Throughout the trial, heart rate (HR) and rate perceived exertion (RPE, CR-10) were analyzed. In addition, kinematic/kinetic measurements: contact time (CT), flight time (FT), step length (SL), stride time (ST) leg (kvert) and vertical (kleg) stiffness, were recorded. Gait variability including phase coordination index (PCI) was calculated for each 2-km segment. Results: HR increased (from 88.46 ± 5.84 to 93.87 ± 6.48 %HRMAX, P < 0.05) as well as RPE (6.58 ± 0.47-8.96 ± 0.40 a.u., P < 0.001) as the distance increased. Conversely, no differences between running segments for the kinematic/kinetic data (CT-FT-SL-ST-kvert-kleg) were observed over five 2 km. However, there was increase (P < 0.05) in gait variability (PCI), over the course of the running race. Furthermore, the determination coefficient (R2) was found as strong and very strong when compared five (0-10 km) and four (4-10 km) running segments between HR-RPE and PCI (R2 = 0.623-0.845). Conclusion: These results suggest that the gait variability is one mechanical determinant in assessing the neuromuscular output when the fatigability increases during a running race.