Introduction. One of the major factors related to overuse injuries in runners is impact force resulting from the runner hitting the ground at heel strike. (Hreljac et al., 2000). This impact will increase and decrease based on the construction of the running shoe used as well as the type of surface being run on. The purpose of this research was to determine the effects that both midsole cushioning and surface stiffness have on this impact force.;Methods. Six recreation runners running at least 10 miles per week ran a 2.2 km course 3 times at a self selected pace. A variable cushioning running shoe (Adidas OneRTM) was used and set in a low cushioning, high cushioning, or self adjusting cushioning mode for each run. Accelerometers were attached at the leg and forehead to measure impacts and impact attenuation. Accelerometer data were sampled at 512 Hz. The course consisted of the following surfaces: cement, asphalt, dirt, gravel, woodchips, sand, grass, and a wooden suspension bridge. Cohen\u27s D formula was used to calculate effect sizes comparing each shoe and each surface. The values 0.5 and 0.8 were used to determine medium and large effect sizes respectively.;Results. The soft shoe setting had a medium effect (ES=0.66) compared to the hard shoe setting. No medium or large effects were found in head acceleration or impact attenuation between shoes. Sand had the largest leg accelerations of 7.8 g\u27s while the wooden bridge had the smallest (6.3 g\u27s). Large effects were found in leg acceleration with sand and 3 different surfaces. Gravel had the largest head acceleration of 1.58 g\u27s. Only medium effects were present between surfaces when comparing head accelerations. Sand had the highest impact attenuation of 83.8% while gravel had the smallest impact attenuation of 77.2%.;Discussion. Two of the softest surfaces (sand and grass) had the highest leg accelerations. This is believed to be due to changes made in kinematics while running on these two surfaces. Altering kinematics will change the effective mass of the body. The decrease in effective mass will increase leg accelerations even though the impact force may not have increased.
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机译：介绍。与跑步者过度使用伤有关的主要因素之一是跑步者在脚后跟撞击时撞到地面而产生的冲击力。 （Hreljac等，2000）。这种影响将根据所使用的跑鞋的结构以及所行驶的地面的类型而增加和减少。这项研究的目的是确定中底缓冲和表面刚度对这种冲击力的影响。六名每周至少跑10英里的休闲跑步者以自己选择的速度跑了2.2公里的路线3次。使用可变缓震跑鞋（Adidas OneRTM），并在每次跑步时设置为低缓震，高缓震或自调节缓震模式。加速度计安装在腿部和额头上，以测量冲击和冲击衰减。加速度计数据以512 Hz采样。该课程由以下表面组成：水泥，沥青，污垢，砾石，木屑，沙子，草和木制悬索桥。使用Cohen D公式来比较每个鞋子和每个表面的效果大小。值0.5和0.8分别用于确定中等和较大的效应大小。与硬鞋设置相比，软鞋设置的效果中等（ES = 0.66）。鞋子之间的头部加速或冲击衰减没有发现中等或较大的影响。沙子的最大腿加速度为7.8 g \ u27s，而木桥的腿加速度最小（6.3 g \ u27s）。发现在沙地和3个不同表面上的腿部加速作用很大。 Gravel的最大头部加速度为1.58 g \ u27s。比较头部加速度时，表面之间仅存在中等效果。砂的冲击衰减最高，为83.8％，而砾石的冲击衰减最小，为77.2％。最柔软的两个表面（沙和草）的腿部加速度最高。据信这是由于在这两个表面上运行时运动学上的变化。运动学的改变将改变身体的有效质量。即使冲击力可能没有增加，有效质量的减少也会增加腿部的加速度。
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