穿著專業的運動服裝在公園里走一圈，拍幾張自拍發朋友圈，然后就回家打游戲。大家都以為你在揮汗如雨地鍛煉，其實，你在家里躺著看片。你身邊有這樣的“假裝鍛煉族”嗎？

A workout impostor is someone who walks around in workout or gym-like clothing to give the effect that they have worked out or gone to the gym today or are planning to work out or go to the gym today when in reality they have not or are not going to.
Workout impostor指穿著體育鍛煉或健身的服裝四處走動，讓人感覺他們剛鍛煉完或者正準備去鍛煉，而實際上，他們根本沒有去鍛煉也沒有這個打算。我們可以說他們是“假裝鍛煉族”。

One usually does this to take a selfie and share it on social network or to make oneself feel better about their physique, while in reality they have done nothing to keep fit today.
他們這樣做是為了發個自拍到社交網站上，或者提振對自己身材的信心，其實，他們壓根就沒鍛煉或健身。

For example:

Look at that girl in the nike shorts, under armour shirt and asics sneakers with a pony tail. She is totally a workout impostor. I didn't see her at the track or the gym at all today.
看看那個女孩，穿著耐克短褲，安德瑪上衣，亞瑟士跑鞋，扎個馬尾。她其實就是假裝鍛煉，我今天根本沒有在操場或健身房看到過她。

（中國日報網英語點津 Helen）