Effects of Running-Induced Fatigue on the Structure of Movement Variability in Novice Runners

Fatigue is a major issue in sports science, especially for endurance sports. Running is one of the most popular endurance sports worldwide. Consequently, there is a high number of people that start running without prior experience. On the other hand, novice runners were shown to be prone to injury, possibly because they lack an adequate running style or strength to deal with the loads acting on the body. On this basis, understanding the effects of fatigue in novice runners is crucial since fatigue may associate with injuries as well as with running economy. Nevertheless, studies analyzing the effects of fatigue in novice runners are rare. Previously, it was shown that running-induced fatigue does not affect spatiotemporal parameters in novice runners but influenced the center of mass (CoM) movement (1). Therefore, the aim of this study was to investigate how the movement variability structure stabilizing the CoM trajectory changes under running-induced fatigue in novice runners.
METHODS: Fourteen healthy male novice runners participated in the study. The experiment was conducted on a motorized treadmill (h/p/cosmos). After a treadmill familiarization protocol, the participants had two minutes to recover before running at a fixed speed of 13 km/h until subjective exhaustion. ... mehrKinematic data were recorded at 200 Hz using 16 Vicon cameras (Vicon Motion Systems, Oxford Metrics Group, Oxford, UK). The uncontrolled manifold (UCM) approach was applied to a 3D whole-body model using the joint angles as elementary variables, and the CoM as the result variable (2). The portion of variability that does not affect the CoM is referred to as UCM_par, whereas the portion that has effects on the CoM as UCM_ort. The ratio of UCM_par and UCM_ort (UCM_ratio) is used to operationalize the degree of stabilization (3). By using statistical parametric mapping (SPM), the differences between the PRE and POST fatigue conditions for three UCM parameters (UCM_par, UCM_ort and UCM_ratio) were analyzed.
RESULTS: The participants continued to run at 13 km/h for 6.18 ± 2.45 min. Their exhaustion was confirmed by a Borg-scale rating of 18.7 ± 1.0 (“very very hard“ (4)). The SPM results revealed significant increases in the UCM_ort but no significant effects on the UCM_par or UCM_ratio.
CONCLUSION: The increases in the UCM_ort after running-induced fatigue can be interpreted as decreased control concerning the CoM (5). However, based on the unchanged UCM_ratio, it can be suggested that the stability of the CoM was not affected by fatigue. To sum up, the running-induced fatigue increased the step-to-step movement variability in novice runners and decreased the level of control of their CoM.