Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada.
Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milan, Italy.
Eur J Sport Sci. 2020 Jul;20(6):756-766. doi: 10.1080/17461391.2019.1664639. Epub 2019 Sep 24.
We sought to examine the effect of step length manipulation on energy absorption and impact attenuation during graded running. Nineteen runners (10F, 9M) ran on an instrumented treadmill at three step lengths (preferred and ±10% preferred) at each of five grades (0°, ±5°, and ±10°) while 3D motion data were captured. Speed was held constant at 3.33 m/s and step length was manipulated by syncing cadence to a metronome. Manipulating step length altered energy absorption ( ≤ 0.002) and impact attenuation ( < 0.0001) across all grades. Energy absorption at the knee joint was most responsive to step length manipulations [Δ range (±10%SL-PrefSL) = 0.076-0.126 J/kg, < 0.0001], followed by the ankle (Δ range = 0.026-0.100 J/kg, = 0.001) and hip (Δ range = 0.008-0.018 J/kg, < 0.006). Shortening step length reduced knee joint energy absorption at all grades with the smallest effect observed during uphill running (Δ ≥ -0.053 J/kg), while large reductions occurred during level (Δ = -0.096 J/kg) and downhill running (Δ ≥ -0.108 J/kg). Increasing step length resulted in greater knee joint energy absorption ( ≤ 0.037) across all grades of running. Impact attenuation was greatest at long step lengths (Δ = 2.708) and lowest at short step lengths (Δ = -2.061), compared to preferred. Overall, Step length influenced the energy absorption and impact attenuation characteristics of the lower extremity during level and graded running. Adopting a shorter step length may be a useful intervention to reduce knee joint loading, particularly during downhill or level running. Elongating step length placed a greater demand on the lower extremity joints, which may expedite the development of neuromuscular fatigue.
我们旨在研究在不同坡度的跑步过程中，步长改变对能量吸收和冲击衰减的影响。19 名跑步者（10 名女性，9 名男性）在坡度为 0°、±5°和±10°的五个坡度下，以 3.33 m/s 的恒定速度，使用节拍器同步步频，分别在三个步长（惯用步长和±10%惯用步长）下在装有仪器的跑步机上跑步，同时采集三维运动数据。改变步长会改变所有坡度下的能量吸收（≤0.002）和冲击衰减（<0.0001）。膝关节的能量吸收对步长改变最敏感[（±10%SL-PrefSL）的变化范围为 0.076-0.126 J/kg，<0.0001]，其次是踝关节（变化范围为 0.026-0.100 J/kg，=0.001）和髋关节（变化范围为 0.008-0.018 J/kg，<0.006）。缩短步长会降低所有坡度下的膝关节能量吸收，在爬坡时的影响最小（Δ≥-0.053 J/kg），而在平地（Δ=-0.096 J/kg）和下坡时的影响较大（Δ≥-0.108 J/kg）。增加步长会导致所有跑步坡度的膝关节能量吸收增加（≤0.037）。与惯用步长相比较，长步长时冲击衰减最大（Δ=2.708），短步长时冲击衰减最小（Δ=-2.061）。总的来说，在平地和分级跑步过程中，步长影响下肢的能量吸收和冲击衰减特征。采用较短的步长可能是减少膝关节负荷的有效干预措施，特别是在下坡或平地跑步时。增加步长会增加下肢关节的负荷，可能会加速神经肌肉疲劳的发展。
