By LLCoolP: “Speed kills” will be a familiar phrase to any fan of boxing, whether that be as a participant, coach or avid fan. We hear it all the way up from the local amateur coach to Freddie Roach and we hear it regularly. Freddie Roach has often been quoted on his initial conversations with Alex Ariza when the latter joined team Pacquiao in 2008 as the boxers strength and conditioning coach saying “Don’t F**k up his speed!!!”
I am myself a big fan of the sport, have 12 years experience as a hospital medical doctor in a specialty that involves dealing with trauma management on a daily basis and have served as a ringside physician at several events.
Trauma or damage is broken down into 3 categories. 1) Penetrating injuries were a projectile penetrates the body e.g. a gunshot wound. 2) Blunt injuries were the injuring cause does not penetrate e.g. pedestrian hit by a car, and 3) Blast injuries were damage is caused by pressure waves e.g. explosions.
Boxing is mainly concerned with number 2 blunt injuries. In principles of physics and energy a punch obeys the same laws that any other form of blunt injury does whether that be by a car, a truck or falling from height, i.e. a landed punch combination can be thought of as being hit by a miniature car over and over.
One of the keys to being a successful boxer is causing damage to your opponent. Damage caused is directly related to the energy contained in the thrown fist and how much of that energy is transferred to the opponents body on impact. Several factors are involved. In terms of energy in the fist they are weight and speed and in terms of energy transferred they are impact time, plasticity/rigidity of the glove and surface area of the glove.
Lets firstly look at plasticity or rigidity and surface area. Reyes manufactured gloves while weighing the same as other manufactures e.g. Everlast ,as stipulated by boxing commissions, have more of their weight around the wrist and less padding on the fist, which equates to the impacting part of the glove being more rigid and a smaller punching surface area. Thus more of the energy contained in a given punch will be transferred to your opponent resulting in more damage. For example if a pedestrian is hit by a car made of rigid steel the damage is far greater than when a car of the same weight and speed but made of rubber hits them.
Turning now to energy in the fist, the factors are weight, speed and impact time. So why isn’t the phrase “weight kills”?. The energy contained in the fist is simple to work out and is called its kinetic energy or its movement energy. Kinetic energy or KE is calculated by the equation weight x speed x speed all divided by 2 or (0.5 x w x s2) The superscript 2 simply means that factor e.g. speed is multiplied by itself. For example 42 = 16( means 4×4 =16). Here s2 means speed x speed as said. One can see then that increasing the weight in the punch will increase its KE, which is why when a boxer chooses to cause maximum damage they put their whole body weight behind the punch and not just their arm weight in for example a jab.
Speed is counted twice though and weight only once meaning an increase in speed will result in more of an increase in energy than a similar size increase in weight.
An example serves well here. Our example boxer weighs 66kg or 145lbs.Take a punch thrown with half of the boxers weight (33kg) at a speed of 30 metres per second or KE= 0.5 x 33 x 302 = 14,850J (J= joules which is the unit of energy similar to metres being a unit of length). Now the boxers next punch he puts 5kg more weight into the punch so KE =0.5 x 38 x 302 = 17,100J. An increase of 2250J is seen. But what if the boxer kept his original weight behind the punch and threw it 5 meters per second quicker instead? So KE= 0.5 x 33 x 352 = 20,212.5J. Thus for it can be shown that the energy carried in the fist will be higher for a increase in speed compared to a relatively similar increase in weight.
The other minor factor of increasing speed concerns decreasing the impact time. Provided the same amount of energy is transferred to the opponent, if done over half a second as compared to 1 second because the boxer has retracted fist quicker, the former will do more damage.
While I hope the above goes someway to explain the scientific principle behind the phrase, it is not suggesting that all boxers should throw all their punches as fast as possible with all their weight at every opportunity wearing Reyes gloves. It is obviously up to the boxer and their team to decide the tactics to increase their chances of victory on the day.
Of note further reading on this topic will show the words mass to replace weight, velocity to replace speed, and the term potential energy being used. As this site caters for a group with wide age and scientific interest levels I have replaced some of the terms with more familiar words simply in an attempt to convey the essential principle of why “speed kills”.
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