question: How can martial artists break multiple bricks just by using their bare hands?
comment: Your friends are wimps. But, their hairline fractures are a start a making them tougher. As bones and tissue repair they become tougher. There are a lot of training techniques for "iron hands" starting with moving your hands through a wok of rice and graduating eventually too pebbles and rocks. Beginners in the martial arts spend a lot of hours hitting a padded board. This conditions the knuckles.
passages: USBA/WBA Founder Drew Serrano, producer of the documentary "Breaking All Records", encourages practitioners to gradually increase the difficulty and amount of a material to avoid injury. He suggests that beginners should start with wood boards and increase the amount as technical prowess increases. Once a level of comfort, both physically and mentally, is reached, harder materials such as concrete can be attempted.
   Generally, a martial artist engaged in breaking will practice by repeatedly hitting hard surfaces. Masutatsu Oyama, a famous breaker who was known for breaking the horns off bulls, would use trees. In karate, a device called a makiwara is used; this device has found more popular use by practitioners of other martial arts today. In the past, Shaolin and other earlier martial artists would use many different types of devices in order to condition themselves, not always for simply breaking, but using the same concepts used today. For instance, there is Iron Palm, Iron Shin, Iron Shirt, Iron Head, and other types of training which center around conditioning various parts of the body so they could withstand or give blows such as what is seen today in martial arts breaking. Many Chinese systems also are of the school of thought that "internal energy" or Chi is used when breaking, which is not dependent upon muscle strength and body weight.
   In ITF Taekwondo sparring competitions, using maximum force is not allowed due to the focus being on correct technique over technique effect. Breaking boards or bricks is therefore used as a way to test the power of the competitor. Taekwondo competition breaking may be roughly divided into two main categories:
  
  Power breaking. The power of a technique is measured by breaking single or multiple stacked boards. Stacked boards are commonly placed on raised supports on the ground.
   The original arm blocks were taught with palm up, wrist bent, to form a trapping motion as well as to block and/or strike with the radius bone.
  
  Beginners in Isshin-ryu are taught to use their forearms to block in order to strengthen their forearms while working toward becoming a black belt. When one attains a black belt in Isshin-ryu they understand the purpose for the block is to use the knuckles on the inside of an attacker's arm where are the soft tissue is emphasizing a hard strike to soft tissue. Therefore, there really are no blocks in Isshin-ryu.
   Section::::Uses.
  
  The Chinese martial arts can utilize a wide variety of open and closed hand strikes. Hardening the hands is also considered by some to supplement speed and strength lost through aging. Iron palm practitioners often demonstrate their abilities by breaking hard objects such as bricks, coconuts, stones and boards with their bare hands or in some cases hitting a steel object rapidly without sustaining injury.
  
  Section::::Techniques.
  
  Iron Palm also called Tie Zhang in Chinese utilizes 5 different striking techniques, they are as follows.
  
  BULLET::::1. Slapping - utilizes the whole palm
  
  BULLET::::2. Throwing - utilizes the back of the hand
   Breaking, the discipline of destroying inanimate materials such as wooden boards, bats, ice or bricks is a feature common to several Asian martial arts. It can be seen in its oldest form within some branches of Chinese Kung Fu such as Iron Shirt Chi Gung, where iron bars are smashed off the bare heads of martial arts experts, typically Shaolin monks.
   Though fundamentally different, the 4th kind of break — the "impulse break" — is often confused with a speed break (i.e. the first one of the 2 types noted above), because the striking implement often moves at a high velocity, despite the success of the break not depending on such speed. But moving your hand or foot or other body part very quickly, is where the similarity ends. The energy transmission from an impulse break derives not from mass displacement, but from wave transmission (e.g. as an ocean wave hits a beach). The mass of the hand/foot/etc. typically does not travel through the medium, but only goes as far as necessary to deliver the wave—this results in an extremely brief contact with the face of the brick or board and it's the wave itself that causes the striking surface to flex and buckle. The less flexible the striking surface, the more likely it is to break. An advanced aspect of this type of break can be seen where several bricks are placed on supports without spacers, and the person performing the break chooses which brick will break, e.g. breaking ONLY the middle brick of 3 stacked bricks, although the top or bottom brick could just as easily be targeted. This feat was demonstrated in China in the early part of the last century, by well-known qi-gong masters, many who performed it with 5 or 7 bricks or slabs of concrete, and the really talented masters could break two bricks, even if unconnected to one another (e.g. breaking the third and sixth bricks in a stack of 7).
   The film uses 1972 martial arts film "Crush" by Tu Guangqi, which tells the story of anti-colonialist revolt in Korea during the period of Japanese occupation, for its visuals which has been dubbed over by the filmmakers in an attempt at détournement. The concept and motivation of this film was to adapt a "spectacular" film into a radical critique of cultural hegemony and thus into tools of subversive revolutionary ideals.
   This kind of training is called "progressive resistance training"; see Weight training for more information. Often differences in body structure can be seen in the form of calcium deposits between a breaking practitioner and a non-practitioner. Mike Reeves, a champion breaker, advocates in his book the usage of a makiwara and knuckle push-ups. With knuckle push-ups, he recommends starting on softer floor material and working your way up to concrete.
   Can Dialectics Break Bricks?
  
  La dialectique peut-elle casser des briques ?, in English, "Can Dialectics Break Bricks?", is a 1973 Situationist film produced by the French director René Viénet which explores the development of class conflict through revolutionary agitation against a backdrop of graphic kung-fu fighting.
   In a 1995 interview to "Black Belt" martial arts instructor Ip Ching recalled a man skilled in the Eagle Claw style who around 1928 joined a martial arts school that was open to every style. The man claimed the title of chief instructor believing that "none of the instructors there had good kung fu" and told the others "your kung fu is rubbish". Ip Man was ultimately chosen to defend the others against the intruder.
  
  Section::::Zeke Shif.
   Martial Artists and breaking champions Craig and Paul Pumphrey demolish everything from boats and cars to houses using only their bare hands. For each challenge, they join forces with a team of experts in material science and engineering to review the object of their destruction from every possible angle before taking it apart, using physics and know-how to determine the most effective approach. The duo also enjoys a little friendly competition throughout the challenges. Each "Human Wrecking Balls" episode revealed the final outcome of the Pumphrey’s ripping and smashing, as well as the various experiments they put to the test.
   Johnson became friends with Bruce Lee, and the two did demonstrations of strength and speed together. “Bruce [Lee] was the only man who could ever ‘handle’ me - of course, he never knew Dr. Cheng.” Lee was quoted in Johnson’s book as saying, “All things are possible with the great Masters.”
   Breaking wooden boards with punches and kicks is part of the ATSD training as well as mandatory for Intermediate and Advanced belt testing. Some higher level black belts will also break concrete cinder-blocks, bricks, and blocks of ice, as part of their training regimen. To perform this level of breaking takes many years of dedicated training to achieve, and many years of toughening to the skin and bones of the body in order for the skin and bones of the practitioner not to break. This hardening regimen in known as Makiwara training and it can take decades to achieve.
  
  Section::::Belts/Ranks.
   The third method, "soft breaks", also known as "ki" breaks almost always involve the use of "flat hand" strikes; primarily the palm, as it's easier to accomplish a successful break with forward momentum, but sometimes the back of the hand (in a semi outstretched configuration) it utilized to exhibit the person's prowess, as this alternate method usually entails certain conditioning of the hand to endure the stress of impact (see note on Wolff's Law above) as well as using a less natural arm position when delivering the blow. The material is usually supported, horizontally, on two ends. The breaker raises their hand and lets it fall with no tension or significant flexing of the muscles, instead relying mostly on gravity, in order to palm strike the material. The material is broken by a complete energy transfer all the way through, in a direct line from the palm to the other side of the material. The impact also passes through a wider, more dispersed area and from a martial art perspective therefore causes more damage than other strikes, if delivered to a human adversary. This break is akin to striking a person with a slap, although more energy is transferred into the target than what is typically conveyed by a mere slap. Thus, such a palm strike can cause significant internal damage while leaving few signs of the damage externally (possibly a red mark but not much else), whereas a punch or similar strike, would tend to cause recognizably more external damage, such as bruising, swelling, etc., regardless of how much internal disruption was inflicted. Any person of any age, such as elderly people up to 80 and 90 years of age, can do this break with little injury to themselves. The most serious repercussions may be a palm that tingles afterward, should the break be unsuccessful. This method of break, even if utilizing more than one piece of material and additionally done with no spacers, is easily attainable by people of any age or gender, provided they have sufficiently practiced the technique. There are 2 reference videos at the bottom of the page: one shows Rudy Timmerman Sajanim, of the National Korean Martial Arts Association and the 9th degree Kong Shin Bup grandmaster, doing a multiple brick soft break, and another shows him teaching this unique soft breaking technique at a seminar.
   Breaking can often be seen in karate, taekwondo and pencak silat. Spetsnaz are also known for board and brick breaking, but not all styles of martial arts place equal emphasis on it or use it. In styles where striking and kicking are less important and there is an emphasis on grappling or weaponry, breaking is less prominent. Traditional Japanese martial art schools place little, if any, emphasis on board-breaking, although the art of breaking objects was known as "tameshiwari", while the similar practice of Tameshigiri or 'test cutting' is used in sword arts.
  
  Section::::Types.
   Howard is now retired, but was a roofer by trade and is well known for apt demonstrations of smashing roof tiles. He has appeared on Ireland's most popular television show, RTE's The Late Late Show, on two occasions, most recently following his promotion, where he undertook a demonstration of tile breaking, and originally in 1976 where he famously broke his hand live on the show when he was undertaking a demonstration of block smashing.
  
  Section::::Early life.
   B. K. S. Iyengar, who founded Iyengar Yoga in the 1970s, introduced the use of yoga props including bricks and straps to assist his students towards correct alignment in the asanas. He recommended that yoga bricks be similar in size to a house brick, 9 x 4.5 x 3 inches (22.5 x 11 x 7.5 cm) in size. Iyengar yoga institutions sell unbranded props such as bricks, belts, bolsters and blankets.
  
  Section::::Considerations.
   Section::::Training.:Application.
  
  "Application" refers to the practical use of combative techniques. Chinese martial arts techniques are ideally based on efficiency and effectiveness. Application includes non-compliant drills, such as Pushing Hands in many internal martial arts, and sparring, which occurs within a variety of contact levels and rule sets.
   This is due to the way in which the two materials break. Wood, which is a natural fibrous matrix, flexes to a certain degree before it snaps at the target point. When unpegged, this allows for an entire stack of wood to flex upon impact, resulting in the break occurring in the order of furthest board from impact to the closest board (albeit a fraction of a second difference separates each board, making it appear instantaneous). This can be witnessed in many novice demonstrations where the rear board will break, but the remaining top boards are intact. When pegged, the gap between the boards necessitates each individual board to flex and snap before the next board is reached in succession. Bricks, on the other hand, are ceramic, and snap (or shatter) upon impact, with no flex action.
   The degree of Li force one can employ in kung fu depends on several variables such as resilience of muscles, strength of bones, speed and timing of attack and so on. An effective way to enhance the Li force is to exercise one's muscles and bones by applying increasing pressure on them (weight training, gym exercises, etc.). The stronger one's muscles and bones become, the more powerful and skillful the level of kung fu is.
   Both the speed and power breaks deliver the energy required to overcome the tensor and flexion forces of the board through "mass displacement", where the kinetic energy is given by 1/2 m*v. That is, either the speed of the striking implement (hand/foot/etc.) has to be high enough, or the striker must be strong enough to increase effective mass brought into the break (i.e. his or her body weight) to exceed the brick/board's threshold. For single boards, it is generally easy (as in the casual person has a sufficient reserve of mass) to reach this threshold through a power break.
   Starting with coloured belts Taekwondo students must learn breaking. As they progress through the ranks, the breaks they perform increase in difficulty as do the number of boards. As time goes on, the Taekwondo student's hands and bones become accustomed to breaking boards - repeated practice hardens bones, skin and tendons. Wolff's law states that the human skeleton will adapt to the stress it is put under, therefore the bones actually become stronger as a Taekwondo student advances in his martial arts career.
  
  ReferencesEdit
  
  Taekwondo Forms
  
  http://www.wtf.org/wtf_eng/site/about_taekwondo/poomsae.html
  
  http://www.kukkiwon.or.kr/viewfront/eng/data/technique_trunk2.jsp
  
  Self Defense Pressure Points
  
  Further readingEdit
   BULLET::::- Nine Block - This is a black belt leveled block and the first time it is usually used is around the black belt form.The person blocks their chest with one hand and stomach region with the other.The shape of the block forms a number nine when executed correctly.Both arms are bent at a 45 degree angle as well and it leaves little space open in the mid region of the defenders body.Your hand when this move is executed correctly should also be above your groin on the bottom and next to you opposite shoulder with the top hand.
   "Power breaks" are breaks where the striking object is supported. Either the break will employ human holders for horizontal, angular, or upward vertical strikes, or the break will require that the objects be stacked for downward vertical strikes. For a stacked break the object is placed on sturdy supporting objects, such as concrete blocks, that are placed on the ground. Many color belt (belts before black belt) promotion testing breaks are power breaks—it is substantially easier for an inexperienced person to muster sufficient energy to break a wooden board with a power break (Note, this is not true for all breaks). The vast majority of these employ human board holders. Often a stronger or more powerful striker may substitute some strength for technique and successfully accomplish the break. Most records that are catalogued are for power breaks. It is very common for black belt tests to use bricks, concrete patio blocks, or several boards stacked on top of supporting objects for challenging downward strikes.
  