Stretching is a major treatment for restoring the ankle range of motion while decreasing the ankle stiffness. An automatic stretching machine can provide long-term continual stretching at home. However, no commercial stretching machines are currently available, and therefore, no safety guidelines exist for them. In this study, we prototyped a stretching machine using a chassis from a commercial foot exerciser for preventing disuse syndrome, and then proposed three safety concepts as general requirements for stretching machines. The concepts were determined based on risk assessments, which included (1) preventing excessive force from being applied to the foot, (2) responding to the ankle stiffness and the range of motion of each different individual, and (3) preventing unintended operations by the user. The above concepts allowed us to develop a stretching machine taking into account safety measures. Further, the stretching effect of the prototype was tested on sixteen healthy young subjects ($$22.3 \pm 3.6\hbox { years}$$). We found that the passive resistance of the subjects at specific dorsiflexion angles decreased significantly after stretching the ankle using the prototyped machine.

中文翻译：

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脚踝背屈的气动拉伸机：涉及健康年轻受试者的安全概念和有效性测试

拉伸是恢复踝关节运动范围，同时降低踝关节僵硬度的主要方法。自动拉伸机可以在家中提供长期连续拉伸。但是，目前没有商用拉伸机，因此，没有针对它们的安全准则。在这项研究中，我们为拉伸机设计了原型，该拉伸机使用了商用脚踏训练器的底盘来预防废用综合症，然后提出了三个安全概念，作为拉伸机的一般要求。这些概念是根据风险评估确定的，其中包括：（1）防止对脚施加过大的力；（2）对每个不同个体的踝部僵硬和运动范围做出反应；（3）防止意外操作用户。以上概念使我们能够在考虑安全措施的情况下开发拉伸机。此外，在16名健康的年轻受试者上测试了原型的拉伸效果（$ 22.3 \ pm 3.6 \ hbox {years} $$）。我们发现，使用原型机拉伸踝关节后，受试者在特定背屈角处的被动抵抗力显着降低。