Is practicing boxing for self-defense and physical fitness haram?

Practicing boxing as it is known today is not approved by Islamic law or by reason, due to the harm and damage it entails. However, if it is merely for strengthening the body and self-defense, without causing harm to oneself or others, and without falling into a Sharia-prohibited act such as neglecting prayer or exposing one's 'awrah, then there is no objection to it. It is stated in the book "Islamic Jurisprudence and Its Proofs" that free wrestling, boxing, and similar activities are forbidden due to the harm they cause, but they become permissible if there is no harm to either party, or if they involve accustoming a person to strength, combat, and self-defense, citing as evidence the wrestling of the Prophet, peace and blessings be upon him, with Rukanah and his victory over him.