Edwards W Brent, Taylor David, Rudolphi Thomas J, Gillette Jason C, Derrick Timothy R
Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, IL 60612, USA.
Clin Biomech (Bristol). 2010 May;25(4):372-7. doi: 10.1016/j.clinbiomech.2010.01.001. Epub 2010 Jan 22.
Stress fractures are dependent on both loading magnitude and loading exposure. Decreasing speed is a potential mechanism of strain reduction during running. However, if running speed is decreased the number of loading cycles will increase for a given mileage. It is unclear if these increased loading cycles are detrimental despite reductions in bone strain. The purpose of this study was to determine the effects of running speed on the probability of tibial stress fracture during a new running regimen.
Ten male subjects ran overground at 2.5, 3.5, and 4.5m/s. Force platform and kinematic data were collected synchronously. Inverse dynamics and musculoskeletal modeling were used to determine joint contact forces acting on the distal tibia. Peak tibial contact force served as input to a finite element model to estimate tibial strains. Stress fracture probability for each running speed was determined using a probabilistic model based on published relationships of bone damage, repair, and adaptation. The effects of speed on stress fracture probability was compared using a repeated measures ANOVA.
Decreasing running speed from 4.5 to 3.5m/s reduced the estimated likelihood for stress fracture by 7% (P=0.017). Decreasing running speed from 3.5 to 2.5m/s further reduced the likelihood for stress fracture by 10% (P<0.001).
Runners wanting to reduce their risk for tibial stress fracture may benefit from a decrease in running speed. For the speeds and mileage relative to the current study, stress fracture development was more dependent on loading magnitude rather than loading exposure.
应力性骨折取决于负荷大小和负荷暴露时间。降低速度是跑步过程中减少应变的一种潜在机制。然而，如果跑步速度降低，在给定里程内的负荷循环次数将会增加。目前尚不清楚尽管骨应变有所降低，但这些增加的负荷循环是否有害。本研究的目的是确定跑步速度对新跑步方案期间胫骨应力性骨折概率的影响。
10名男性受试者在地面上以2.5、3.5和4.5米/秒的速度跑步。同步收集力平台和运动学数据。采用逆动力学和肌肉骨骼模型来确定作用于胫骨远端的关节接触力。胫骨峰值接触力作为有限元模型的输入，以估计胫骨应变。使用基于已发表的骨损伤、修复和适应关系的概率模型来确定每种跑步速度下的应力性骨折概率。使用重复测量方差分析比较速度对应力性骨折概率的影响。
跑步速度从4.5米/秒降至3.5米/秒，应力性骨折的估计可能性降低了7%（P = 0.017）。跑步速度从3.5米/秒降至2.5米/秒，应力性骨折的可能性进一步降低了10%（P < 0.001）。
想要降低胫骨应力性骨折风险的跑步者可能会从降低跑步速度中受益。对于与当前研究相关的速度和里程，应力性骨折的发生更多地取决于负荷大小而非负荷暴露时间。
