Department of Life Sciences, University of Roehampton, London, United Kingdom.
Gait Posture. 2020 Feb;76:327-333. doi: 10.1016/j.gaitpost.2019.12.019. Epub 2019 Dec 24.
When stepping down from a raised surface, either a toe or heel contact strategy is performed. Increased vertical momentum is likely to be experienced during a step descent, yet the extent to which these descent strategies influence the development of load at the ground and knee has not been examined.
Does descent strategy influence ground and knee joint loading? Does the contribution from leading and trailing limb joint mechanics differ between descent strategies?
Twenty-two healthy male participants (age: 34.0 ± 6.5 years, height: 179 ± 6.3 cm, mass: 83.5 ± 13 kg) walked along a raised platform, stepped down from a 14 cm height utilising either a toe (n = 10) or heel (n = 12) initial contact, and continued walking. Vertical ground reaction forces and knee external adduction and flexor moments were extracted for the duration of the braking phase. Joint work was calculated for the ankle, knee, and hip in both the leading and trailing limbs.
Waveform analysis of the loading features indicated that a toe-contact strategy resulted in significantly reduced loading rates during early braking (1-32% of the braking phase) and significantly increased magnitude in late braking (55-96% of the braking phase). Individuals performing toe landings completed 33% greater overall work (p = 0.091) in the lead limb and utilised the lead limb ankle joint as the main shock absorber (79% of total lead limb work). Concurrently, the trailing limb performed 29% and 21% less work when lowering the centre of mass and propulsion, respectively, compared to a heel landing.
A toe-contact strategy results in reduced limb and knee joint loading rates through greater utilisation of the lead limb ankle joint. A heel-contact strategy, however, can reduce loading during late braking by utilising the functionality of the trailing limb.
从高处表面下来时，会采用脚尖或脚跟接触策略。在下降阶段，很可能会经历增加的垂直动量，但这些下降策略对地面和膝盖的负荷发展的影响程度尚未被研究。
下降策略是否会影响地面和膝关节的负荷？领先和滞后肢体关节力学在不同的下降策略中是否有不同的贡献？
22 名健康男性参与者（年龄：34.0±6.5 岁，身高：179±6.3cm，体重：83.5±13kg）沿着一个凸起的平台行走，从 14cm 的高度用脚尖（n=10）或脚跟（n=12）初始接触下降，并继续行走。在制动阶段提取垂直地面反作用力和膝关节外展和屈肌力矩。计算了领先和滞后肢体的踝关节、膝关节和髋关节的关节功。
加载特征的波形分析表明，脚尖接触策略导致早期制动（制动阶段的 1-32%）的加载率显著降低，并且在后期制动（制动阶段的 55-96%）的幅度显著增加。采用脚尖着地的个体在领先肢体中完成了 33%的整体功（p=0.091）增加，并利用领先肢体踝关节作为主要减震器（79%的总领先肢体功）。同时，与脚跟着陆相比，在降低质心和推进时，滞后肢体的工作分别减少了 29%和 21%。
脚尖接触策略通过增加领先肢体踝关节的使用，降低了肢体和膝关节的加载率。然而，脚跟接触策略可以通过利用滞后肢体的功能来减少后期制动的负荷。
