Institute of Sport Sciences, University of Lausanne, 1015, Lausanne, Switzerland.
Research and Development Department, Volodalen Swiss Sport Lab, Aigle, Switzerland.
Sci Rep. 2023 May 22;13(1):8236. doi: 10.1038/s41598-023-35345-8.
The aim of this study was to examine how running biomechanics (spatiotemporal and kinetic variables) adapt with exhaustion during treadmill runs at 90, 100, 110, and 120% of the peak aerobic speed (PS) of a maximal incremental aerobic test. Thirteen male runners performed a maximal incremental aerobic test on an instrumented treadmill to determine their PS. Biomechanical variables were evaluated at the start, mid, and end of each run until volitional exhaustion. The change of running biomechanics with fatigue was similar among the four tested speeds. Duty factor and contact and propulsion times increased with exhaustion (P ≤ 0.004; F ≥ 10.32) while flight time decreased (P = 0.02; F = 6.67) and stride frequency stayed unchanged (P = 0.97; F = 0.00). A decrease in vertical and propulsive peak forces were obtained with exhaustion (P ≤ 0.002; F ≥ 11.52). There was no change in the impact peak with exhaustion (P = 0.41; F = 1.05). For runners showing impact peaks, the number of impact peaks increased (P ≤ 0.04; [Formula: see text] ≥ 6.40) together with the vertical loading rate (P = 0.005; F = 9.61). No changes in total, external, and internal positive mechanical work was reported with exhaustion (P ≥ 0.12; F ≤ 2.32). Results suggest a tendency towards a "smoother" vertical and horizontal running pattern with exhaustion. A smoother running pattern refers to the development of protective adjustments, leading to a reduction of the load applied to the musculoskeletal system at each running step. This transition seemed continuous between the start and end of the running trials and could be adopted by the runners to decrease the muscle force level during the propulsion phase. Despite these changes with exhaustion, there were no changes in either gesture speed (no alteration of stride frequency) or positive mechanical work, advocating that runners unconsciously organize themselves to maintain a constant whole-body mechanical work output.
本研究旨在探讨在以 90%、100%、110%和 120%最大有氧速度（PS）的跑步机上跑步时，随着疲劳的增加，跑步生物力学（时空和动力学变量）如何适应。13 名男性跑步者在装有仪器的跑步机上进行最大递增有氧测试以确定他们的 PS。在每次跑步的开始、中间和结束时评估生物力学变量，直到达到自愿性疲劳。随着疲劳的增加，四种测试速度的跑步生物力学变化相似。在疲劳时，功量因子和接触与推进时间增加（P≤0.004；F≥10.32），而腾空时间减少（P=0.02；F=6.67），步频保持不变（P=0.97；F=0.00）。随着疲劳的增加，垂直和推进峰值力减少（P≤0.002；F≥11.52）。随着疲劳的增加，冲击峰值没有变化（P=0.41；F=1.05）。对于显示冲击峰值的跑步者，随着疲劳的增加，冲击峰值的数量增加（P≤0.04；[公式：见正文]≥6.40），垂直加载率增加（P=0.005；F=9.61）。随着疲劳的增加，总、外部和内部正机械功没有变化（P≥0.12；F≤2.32）。结果表明，随着疲劳的增加，垂直和水平跑步模式趋于“更平滑”。更平滑的跑步模式是指发展出保护调整，从而减少每个跑步步施加到肌肉骨骼系统的负荷。这种过渡似乎在跑步试验的开始和结束之间是连续的，跑步者可以采用这种过渡来降低推进阶段的肌肉力水平。尽管随着疲劳的增加会发生这些变化，但跑步速度（步频没有改变）或正机械功没有变化，这表明跑步者无意识地组织自己以保持恒定的全身机械功输出。
