When the soul departs, the legs of the deceased body are positioned together in preparation for the burial rites. The term saq (literally “leg”) can also be interpreted metaphorically to signify a calamity. In this sense, calamity will be compounded for the soul of the departed sinner, as their earthly life has come to an end. Whether they wish it or not, they will now have to stand before the Throne of Judgment (Ali).
References:
Yusuf Ali, Abdullah. Translation and Commentary of the Quran. (surah 75 verse 29)