Vocal overdoers typically have hefty vocal cord muscles and may also have a callus or swelling on the edge of the vibrating portion of the vocal cord. This swelling is typically in the very center of the cord and it stands out from the edge of the vocal cord. This protuberant swelling (or swellings) will touch first as the vocal cords are tensed and leave an opening both anterior and posterior to the swelling. Hence air will leak from in front of and behind the swellings.
Two vocal polyps, slightly different in size, touch before the vocal cords can completely close, allowing air to leak from in front of and behind them (arrows).