This article was contributed by David Liang, MD. You can follow him at@fightingdoc.
Let’s face it. Many of us first stepped into a martial arts school or gym after watching guys in cool uniforms break cement blocks with their hands, feet, and heads. You wanted to learn how to transform your body into an indestructible weapon.
But does board breaking and destroying cement blocks actually help for practical self-defense and sport purposes?
Many striking disciplines certainly seem to think so.
In Chinese Martial Arts / Kung Fu, certain styles incorporate Iron Shirt Kung Fu and Iron Palm training, such as Shaolin, or Praying Mantis Kung Fu.
Karate has Kote Kitae.
Muay Thai fighters spend time conditioning their shins.
Even boxers like the great Manny Pacquiao think body hardening is worthwhile.
I have never heard the man curse before watching this video.
The theories behind these exercises usually involve some combination of “deadening nerves” and “causing microfractures”. And it makes sense at first glance. But aside from anecdotal evidence, is this type of training actually supported by science?
Disclaimer:The following content was created for informational purposes and is not intended to serve as medical advice. Please seek the assistance of your medical doctor or another qualified healthcare provider if you have legitimate health concerns.
1. The practice of martial arts/combat sports will strengthen your bones by increasing your bone mineral density (BMD) as a whole.
There’s plenty of evidence for this in the literature. But what about targeting specific parts of the skeleton? We already know that bone is stimulated to grow when it is put under mechanical strain via muscle contraction (i.e. weight training), impact loading (i.e. plyometric jumps, which have been shown to increase BMD at the hip), or gravity. Benefits have also been noted from low-intensity/high-frequency strain (i.e. vibration exercises which may help bone health in women with osteoporosis).
For our purposes, we can look at the repetitive striking of heavy bags, Muk Yan Jong / Mu Ren Zhuang 木人樁 (Wooden Dummy), and Makiwara Boards as a form of impact loading exercise targeting whichever extremities are being used.
The great Ip Man (Bruce Lee's teacher) practicing with the Wooden Dummy. Note the impact he is placing on his radial forearm bones.
Research has shown that elderly Wing Chun practitioners have stronger radial bones compared to their non-training counterparts. There is also a Russian paper from the 1980s which documents “more intensive development” in certain hand and forearm bones of Karate practitioners compared to boxers and football players (unfortunately I was only able to access the English-language abstract). I was also able to find two studies that compared arm BMD between amateur boxers and non-boxers. Unfortunately, results here were inconclusive, as only one of the studies found a significant difference between the groups.
2. Too much of this type of training may not be the healthiest for you in the long run.
A common theory behind body hardening is that it causes small breaks in the bone which will then stimulate a repair process leading to stronger bones than before. Is this true?
Well, during the first weeks to months after you sustain a fracture, your body starts to create immature bone at the site in the form of a callus. This affords some temporary protection to a vulnerable bone but is still weak at this stage. Eventually, the final repaired product should theoretically be as strong as, or stronger than, the original bone. This is probably why we can see the types of adaptations mentioned previously.
However, the continued accumulation of this micro-damage may actually lead to decreased bone stiffness and strength down the line. As you continue to damage targeted areas of bone, you risk further destabilization as subsequent remodelling cycles will start taking away even the surrounding undamaged regions.
It is unclear exactly how long it would take for this process to occur in humans undergoing body hardening training. But as you can see from the diagram above, the balance between strain that is productive and damage that causes bone destabilization can be a tricky one. Bone micro-damage has also been linked to the development of osteoarthritis.
On that note, I did manage to find one interesting article (again from the 1980s) which found no X-ray evidence of arthritic changes in the hands of 22 karate instructors whose training consisted of Makiwara striking and daily knuckle push-ups. It goes without saying that newer studies looking at this would be welcome.
3. The real key to body hardening may be in your head.
Another common theory is that regular body conditioning “deadens nerve endings”. Let’s first take a step back here.
“Nerve endings” in this situation would refer to the small pain-sensing nerve cells located in your soft tissue called nociceptors. Pain signals are picked up by these cells and transmitted to the spinal cord, where they then travel up to your brain’s sensory processing region.
Techniques that attempt to dampen or desensitize these receptors are currently used by doctors to manage chronic pain. That’s part of the mechanism behind capsaicin cream, a medication which initially causes an unpleasant burning sensation before (hopefully) providing relief.
There is also evidence that norepinephrine, a hormone released when your body is in a “fight-or-flight” response, can inhibit pain. Perhaps this is what’s going on when Manny Pacquiao has his coach repetitively whack his abs with a bamboo stick.
Unfortunately, I was unable to find any studies establishing a solid connection between body hardening and long-term pain desensitization. More research will need to be done in this area... if they are able to find enough willing subjects, that is.
“Deadening nerves” can also relate to the thickening of skin and callus formation along striking surfaces of experienced martial artists and fighters. There is evidence that mature skin cells in a normal outer layer of skin are able to pick up and transmit pain signals. Calluses, on the other hand, are made up of immature/undifferentiated skin cells which may be less responsive to outside stimuli.
However, despite their intimidating appearance, calluses are less elastic than normal skin which makes them prone to tearing if they get too large.
In the end, the answer may just reside inside the mind of the martial artist. It’s known that practitioners and fighters have higher overall subjective pain tolerance than the general population. Perhaps this is due to increased pain thresholds as a result of tough physical training. However, the mental aspect of regular training also cannot be understated. Martial arts teaches mindfulness, proper breathing, and how to stay calm in stressful situations. All of these skills may then improve the ability to cope with pain.
Should you do body hardening training? There is plenty of reasoning behind it which certainly sounds good. But if you really look into it, the actual scientific evidence is limited. There are not many controlled trials out there that look specifically at targeted body conditioning exercises and whether they are associated with their intended effects. There is also evidence of potential long-term harm.
With that being said, a strong mind is arguably the most powerful weapon a superior martial artist or fighter can possess. If an individual truly believes that body hardening has produced an iron-clad physique without injury, and if that mentality subsequently gives him/her an edge in competition, then by all practical purposes that training has been effective.
However, my recommendation, especially for the newer practitioners, is to just focus on proper striking technique, controlled sparring/drilling, and overall conditioning.
You will be improving bone strength and pain tolerance throughout your entire body simply by practicing your art.