1. 我必须开始做健身运动了。

[ wǒ bì xū kāi shǐ zuò jiàn shēn yùn dòng le 。 ]

I've got to start working out.

2. 你为什么不去参加一个有氧健身班呢?

[ nǐ wèi shén me bù qù cān jiā yī gè yǒu yǎng jiàn shēn bān ne ? ]

Why don't you attend an aerobic class?

3. 上下楼梯可比什么健身器都要好。

[ shàng xià lóu tī kě bǐ shén me jiàn shēn qì dōu yào hǎo 。 ]

Walking up and down the stairs would beat any exercise machine.