The effects of running a 12-km race on neuromuscular performance measures in recreationally competitive runners

Background: The number of individuals participating in organised races is increasing, with few studies undertaken in ecologically-valid settings. Running involves cyclical movements and activation of lower-extremity muscles, with fatigue and foot-strike pattern proposed as factors contributing to running-related injuries. Research question: Our aim was to investigate the effects of running a 12-km race on plantar pressure distribution, postural balance, foot-strike pattern, and plantar-flexion strength. A secondary aim was to compare actual versus anticipated race finishing times and foot-strike patterns. Methods: Twenty-four recreationally competitive runners (15 males, 9 females) completed the following tests immediately before and after a 12-km race: (1) plantar pressure distribution in self-selected bilateral stance; (2) 30-seconds eyes-closed feet-together postural balance; (3) running foot-strike angle; and (4) peak plantar-flexion isometric force. In-race foot-strike angle and patterns were also assessed at 3 and 10 km. Results: Post-race left and right foot plantar pressure distribution, postural balance, and plantar-flexion force measures significantly differed from pre-race measures. These changes were associated with small to large standardised effects (absolute ES: 0.42 to 0.94). On average, the relative pressure under the left foot decreased by 3.2 +/- 5.0%; the centre of pressure path length and area of the 95th percentile ellipse from the balance test increased by 5.7 +/- 8.9 cm and 18.2 +/- 21.3 cm(2); and peak plantar-flexion isometric force decreased by 0.23 +/- 0.28 times body weight. Participants predicted their finishing times relatively well, but not their foot-strike patterns. No meaningful change in foot-strike angle or pattern was observed pre- to post-race, or between 3 and 10 km. Significance: Running a 12-km race influenced neuromuscular measures, confirming racing-induced fatigue in our recreationally competitive runners. However, these alterations did not lead to observable changes in footstrike pattern, indicating that this measure might not be appropriate for quantifying fatigue in recreationally competitive runners.