筋骨

duàn liàn jīn gǔ

锻炼筋骨

develop one's muscles

huó dòng jīn gǔ

活动筋骨

stretch oneself

tā kàn chu lai zì jǐ shì shòu le hǎo duō dàn shì shēn liang hái shi nà me gāo dà jīn gǔ hái nà me yìng bang tā fàng xīn le

他看出来自己是瘦了好多，但是身量还是那么高大，筋骨还那么硬棒，他放心了。

He could see that he was much thinner, but since he was as tall as ever and his muscles were still hard he was reassured.

bù shí de chōng fèn shēn zhǎn yī xià jīn gǔ yǐ fáng shēn tǐ biàn jiāng

不时地充分伸展一下筋骨，以防身体变僵。

Have a good stretch from time to time to prevent yourself getting stiff.