Muay Thai originated during the migrations of tribes from China to Thailand in the 12th and 13th centuries, says Chad Boykin in “Muay Thai Kickboxing.” Training customs of this early era included shin bone conditioning, the practice of which entailed kicking the trunks of rubber, banana and palm trees, as well as rolling hard objects against the shins. Some practitioners still employ these traditional conditioning methods; however, nowadays most Muay Thai practitioners kick heavy bags and pads to strengthen their shins.
Wolff’s Law is a scientific theory that explains the process of bone adaptation. Just as muscles grow stronger as a result of the restoration of micro-tears in muscle fibres caused by exercise, so too do bones become denser when they repair after a break. When a bone breaks, the body essentially repairs it by filling the break with calcium, which turns into bone. Muay Thai fighters do not break their bones, though. Instead, they cause micro-fractures that fill with calcium and become denser and stronger over time.
Kicking objects that are harder than your shins can damage them, while kicking objects that are still hard but slightly softer than your shin bones will strengthen them slowly and safely. As such, the most-effective way to condition the shin bones is to constantly kick pads and bags, as opposed to tree trunks, according to Kru Tony Moore in his book “Muay Thai.” Harder or heavier pads and bags may strengthen your shin bones faster without damaging them, because they are still softer than your bones. However, they will be more painful to kick, especially during the initial stages of your conditioning program.
It is natural to experience pain and discomfort for a period following a conditioning session; after all, you are injuring your shins. Your body will repair these injuries over time, but you can assist it and speed up recovery time by applying ice to your shins. Fill a paper container with water and place it in a freezer. Once it's frozen, remove the container from the freezer and tear off a portion of the paper so that ice is exposed. Rub the ice against your shins until the pain subsides slightly. In addition, consume calcium supplements to assist your body in filling micro-fractures and creating denser, stronger bones.
Muay Thai conditioning methods are potentially harmful and may lead to permanent bone and nerve damage. Moreover, Muay Thai as a competitive sport places great emphasis on medium to full-contact combat and is therefore inherently dangerous. Do not attempt to condition your bones or participate in fighting bouts unless you have undergone extensive training with an accredited instructor.