Here is the first article of the series “The Science of Martial Arts” published in this month’s Masters Magazine.

There is a classic story of David, the young shepherd boy, who defeats the nine-foot tall giant, Goliath. However, in real life a simple question remains: Could a trained lightweight fighter defeat an untrained heavyweight street brawler. The street brawler has the mass advantage and his strikes would certainly produce significant damage but what about the lightweight? Could the lightweight’s speed, agility and technique overcome his adversary’s brute force? In the first article of this series, we will explore the principles of physics to arrive at our conclusion.

The fundamental concept in physics is center of gravity. Throw off an opponent’s center of gravity and you can knock down even the strongest of opponents. The simplest definition of center of gravity is the point around which an object’s weight is equally distributed. The center of gravity is always found towards the heavier end of the object. Thus, men with their broad shoulders tend have a slightly higher center of gravity than women. Interestingly, this makes it slightly harder for men to do a standard pushup then women.

Center of gravity can be stabilized by lowering the body or widening the stance. However, this increased stability comes at the cost of decreased mobility. Thus, a horse-stance may be extremely stable but would be very impractical in a fight. Likewise, an opponent in motion will be the least stable and this would provide the ideal time to initiate or counter an attack. If our untrained heavyweight had a large gut, this would provide him with an advantage as it would lower his center of gravity.

The next fundamental physics concept is momentum. Momentum can be mathematically described as the mass of an object times the velocity. For simplicity, let’s use weight instead of mass and speed instead of velocity. The heavyweight fighter would appear to have the upper hand with this concept given his massive size. However, the lightweight fighter could compensate by increasing the speed of his strikes. Although momentum may appear to be a great property, it is a double edged sword.

In 1687 Sir Isaac Newton published the book called “Philosophiae Naturalis Principia Mathematica.” Even today this is considered to be the most influential text in the history of science. In it, Newton wrote his famous three laws of motion. His first law was that an object in motion or at rest will stay in that state unless acted upon by an external force. This is often referred to as inertia. Thus, our heavyweight brawler requires a lot more energy to start moving and once he is moving it is also much harder for him to stop. This gives our lightweight fighter the ability to outmaneuver and outlast his heavyweight counterpart. The lightweight fighter can also use the concept of Newton’s first law in that he can use combinations on every strike. Remember, it takes a lot more energy to launch the first punch then to keep punching.

So far the heavyweight street brawler has the advantage of both center of gravity and momentum. This isn’t looking very good for our lightweight fighter. But we saved the best for last. This is the concept of Kinetic energy or the energy of motion. Kinetic energy equals one half mass times velocity squared. In another words, doubling the mass of the fighter’s strike will double the kinetic energy, however, doubling the speed of his strike will increase the kinetic energy by a factor of 4. This gives the fast lightweight the ability to do more damage with each strike than the heavyweight. Just think about the damage a 115 gram 9mm bullet can do traveling at over 1000 feet per second versus a brick weighing 2.7 kilograms traveling a few feet per second. Thus being a fast lightweight can actually give you the power advantage. So unless you are looking to knock somebody over or to use your weight in grappling, weight does not necessarily do a lot of damage. Speed on the other hand certainly does.

So understanding these concepts, lets return to our original question of whether the best lightweight fighter can defeat the untrained heavyweight street brawler. The answer is a resounding YES! While mass adds significantly to force, the heavyweight has inertia working against him. He needs a lot more energy to start and stop a movement. The lightweight can produce the same force in his strikes as the heavyweight by increasing the speed (velocity) of his strikes. Looks can be deceiving and while the heavyweight may look tougher, the lightweight may surprise you. In the end, the fighter with the best combination of mass, speed, and technical skill will always be victorious.