Pir... is a title for a Sufi master or spiritual guide equally used in the nath tradition. They are also referred to as a Hazrat or Shaikh, which is Arabic for Old Man. The title is often translated into English as "saint" and could be interpreted as "Elder". In Sufism a Pir's role is to guide and instruct his disciples on the Sufi path. (Wikipedia)
I've seen many videos of what I think are Sufi gatherings, where the people are in near synchronous movements and are chanting/singing or in the act of dhikr. I'd see certain individuals go up to the Pir and touch them, or be touched by them, and this results in the sudden convulsion. What induces these convulsion?