Is it permissible to pray in clothes known as a "tracksuit," and can someone wearing it lead people in prayer?

If the garment is loose, covers the 'awrah (intimate parts), and does not define them, then there is no harm in wearing it or praying in it. The prayer of one who wears it is valid, and his imamate (leading the prayer) is valid if he meets the other conditions for imamate. However, if it reveals the skin of the 'awrah, prayer performed in it is not valid. If it covers the 'awrah but defines its size due to its tightness, wearing it and praying in it is disliked, although the prayer itself is valid. The imamate of one who wears it is also valid. However, the one who leads the prayer should be the most complete among the congregation in terms of recitation and jurisprudence, and this includes having good attire. One who wears tight clothing is not among the best dressed people. If there is someone else who wears loose, concealing clothing and fulfills the other conditions of imamate, he would be more deserving of leading the prayer.