Complex sentence: Perhaps the most common foul committed is the grabbing of the opponent's hair as, as it is tied up in a form of "chonmage" it is possible for a hand to become inadvertantly tangled in it during a bout.
Split into simpler sentences: Perhaps the most common foul committed is the grabbing of the opponent's hair. Since it is tied up in a form of "chonmage" one's hand can become inadvertantly tangled in it during a bout.