筋 (jīn): กล้ามเนื้อ

I went to the gym to lift weights for the first time yesterday, and today the muscles in my arms hurt so much I can't lift them.

Grandma accidentally slipped in the kitchen and strained a muscle in her leg; the doctor told her to rest for two weeks.

Before running a marathon, you must warm up first and get all the muscles in your body moving, otherwise you can easily get injured.

He sits in the office for more than ten hours every day, and the muscles at the back of his neck are always tight; only after getting a massage did he feel a bit better.

Swimmers' muscles are especially flexible, so their movements when turning and kicking in the water are particularly smooth.