Good Friday, or Viernes Santo, is one of the days which my wife dreads whenever we stay in Pangil, Laguna during Holy Week, which she labels as the "Penitencia" Capital of Laguna owing to the number of men (and sometimes women) performing the rites.
"Penitencia" or penitence is the act of hitting oneself with a "panghampas" consisting of wooden pegs attached to a rope and hitting the bloodied back from side to side.
People try to avoid the penitents walking along the roads not out of fear but to avoid the penitents' blood from staining their clothes and since the odor of the drying blood is not really good.
The ritual is performed apparently as a "panata" or promise for an answered prayer or to atone for one's sins. The Catholic church frowns upon the said ritual. Bishop Iniguez, of the Catholic Bishops Conference of the Philippines, said that devotees should go beyond such practices and adds that what is important is to carry one’s daily cross and face challenges of life in faith and guided by God’s grace. (http://www.journal.com.ph/index.php?issue=2008-03-23&sec=4&aid=53459)