I know of saints as youths who engaged in corporal mortification of the kind exhibited here.
One does not have to be of any significant level of holiness to do these things, far from it. Some kind of bodily mortification is quite necessary to make progress from the start.
In truth, all that matters, is that it is done properly, and that the interior motivations are correct, at any age past the age of reason.
*‘We give our youth to the devil, and the remains of our life to the Good God, who is so good that He deigns to be content with even that. . . but, happily, everyone does not do so. A great lady has been here, of one of the first families in France; she went away this morning. She is scarcely three-and-twenty, and she is rich-very rich indeed. . . She has offered herself in sacrifice to the good God for the expiation of sins, and for the conversion of sinners. She wears a girdle all armed with iron points; she mortifies herself in a thousand ways; and her parents know nothing of it. She is white as a sheet of paper. Hers is a beautiful soul, very pleasing to the good God, such as are still to be found now and then in the world, and they prevent the world from coming to an end.’
St. Jean Marie Baptiste Vianney, the Cure of Ars*
In the Rule of St. Benedict, corporal discipline is prescribed as a punishment for both youths and the aged. The scriptures say, ‘spare the rod and spoil the child’
So there is no general reason why anyone of any age cannot engage in it. Now there will be individual cases of course, where certain kinds of it cannot be entered into, for example, because of ill health, etc. These are as always only individual exceptions…
Sometimes these exceptions can be overcome as the soul makes progress, sometimes they are lasting and cannot be.
Some kind of bodily mortification can always be practiced, but not all kinds can always be practiced.
Given one of the poster’s here’s previous comments against these practices, or making it only symbolic, I am wondering from the latest comments if some slight conversion hasn’t occurred here. I certainly hope that is the case.
In the beginning I believe good starts are eating foods you find highly distasteful, striking your breast quite heartily and painfully while saying, ‘Lord have mercy’, and the various traditional practices, such as sleeping on a hard bed, showers with water of a temperature not preferable, the use of a bamboo cane, painful belts, etc. all these things can be used to do not the slightest real harm but be quite discomforting or temporarily painful and so penitential.
In Singapore caning is still given as punishment for criminals. I can only think if the U.S. still believed in punishment for crime, there would be far less crime. Crime without punishment, with only rehabilitation, denies too much justice, it is not a mercy.
We cannot only wait for purgatory to pay the price for sins, we have to do penance in this life. Without penance there is no salvation.
People go to boxing matches and watch the boxers have a great time in a fight, and enjoy watching the battle. Boxing is quite painful, but the participants themselves love it. We excuse it utterly.
How unfair of the world to then cast painful spiritual pursuits always in a negative light. I can only see the devil at work there, with such an effeminate reaction. We need courageous holiness, and true penitential spirits aware of the need to make some sign of reparation to divine justice.
Ascetical practices of painful mortification can be easily understood for the sake of penance and for the sake of overcoming the body’s too great control of our life.
It takes some hedonism to see all pain as evil, and only pain, and all pleasure as good.
*‘Let us read the lives of the saints; let us consider the penances which they performed, and blush to be so effeminate and so fearful of mortifying our flesh.’
St. Alphonsus Maria de Liguori
*
This is practice that I don’t understand much. 
