In boxing and other combat sports, the most feared fighters are often those who possess the most punching power. It might seem obvious that a heavyweight will usually deliver a more powerful punch than a lightweight, but boxing isn't called the "Sweet Science" for nothing, and body mass isn't directly proportional to knockout power.
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Measuring Punch Power
When measuring punching power, scientists use differing methods to collect their data. Often, researchers record both the force of the punch and the pressure relative to the surface area. Boxing dynamometers are sometimes used to record the force of punches, but motion capture technology can also be used to measure the speed at which the target moves when being hit.
Mass and Punch Power
Since mass plays a huge role in force, heavyweight fighters have a natural advantage in that department when it comes to developing knockout power. A heavyweight fighter will put more weight into each punch than a lightweight, but that doesn't necessarily mean he'll punch harder. In purely scientific terms, force is the product of mass and acceleration, so mass is only half of the equation.
Lightweights may lack the size and mass of heavyweights, but if they can't put as much weight into their punches, they more than make up for it with the speed they bring to the table. Additionally, punches can't be measured in strictly linear terms, so evaluating mass and acceleration exclusively won't give you an accurate measure of how hard a fighter can punch. Generally-speaking, a heavyweight fighter with twice the mass of a lightweight won't hit harder if the lightweight punches twice as fast.
Boxing historian Mike Casey claims that weight has little to do with punching power. He suggests that difficult-to-measure attributes such as snap, timing and leverage have more to do with developing knockout power than body weight. Professional boxing coach Steve Acuno admits that heavier boxers will usually have a slight edge in terms of power, but says the difference is exaggerated by most observers. At the end of the day, punching power comes down to a combination of mass, speed and technique.