他感到身体僵硬，可能是久坐的原因。

Tā gǎndào shēntǐ jiāngyìng, kěnéng shì jiǔzuò de yuányīn.

He feels stiffness in his body, perhaps due to prolonged sitting.

他的表情看起来有些僵硬，似乎不太自然。

Tā de biǎoqíng kàn qǐlái yǒuxiē jiāngyìng, sìhū bù tài zìrán.

His expression looks a bit stiff, as if not very natural.

在寒冷的天气中，手指容易变得僵硬。

Zài hánlěng de tiānqì zhōng, shǒuzhǐ róngyì biàn de jiāngyìng.

In cold weather, fingers can easily become stiff.