free contraction

例句：

1. 1. Thefree contraction of the muscle is akey factor in determining its strength.
   肌肉的自由收缩是决定其强度的关键因素。
2. 2. During thefree contraction phase, the cell membranes are more permeable to substances.
   在自由收缩阶段，细胞膜对物质的通透性更高。
3. 3. Free contraction isoften observed during the formation of newtissues, such as blood vessels or nerves.
   自由收缩现象常在形成新组织时观察到，如血管或神经。