Foam or Knuckles—Navigating the Illusion of Safety
If you really want to understand how gloves contribute to the safety of our athletes, especially when it comes to their brains, take a closer look at the physics behind taking a punch with a bare fist or a glove.
Large Surface Area
The surface area of a boxing glove is obviously much larger than a bare fist, but it is difficult to appreciate the magnitude of the difference without first doing some experimentation. I made some measurements of my own fists in action to help shed some light on these differences, but I encourage you to try it out yourself, using your own fists and your own gloves.
The method I followed was relatively simple, but a little tedious in practice. First, I attached a paper towel to a body opponent bag (any punching bag or "realistic" target will do). Next, I applied a coat of red acrylic paint to my hand using a sponge to apply the paint evenly, and punched the target at full force.
I repeated this process ten times with bare knuckles, boxing gloves, and MMA gloves (I measured a bunch of other strikes as well, primarily for the sake of my own curiosity). I also threw some punches at a hard wood floor so I could see the difference between a hard and soft target. After all the punching was done, I took a picture of the imprinted paper towels with a ruler in the shot for reference.
Punching the hardwood floor resulted in an imprint of the first two knuckles (1.7 square inches), which aligns with our own visualization of a punch when we throw it, but the introduction of a soft target resulted in a full imprint of the fist (8.8 square inches, including some of the thumb). The boxing glove covered a surface area almost three times larger than the fist (23.6 square inches), but the MMA glove was only larger by about 20% (10.3 square inches).
These results are interesting, but they should be considered rough estimates and not hard data. Every fist and every glove is a little different, so I encourage you to test your own at home. Additionally, we should remember that humans are a combination of hard and soft targets, so even though MMA gloves have a 20% larger surface area when compared to a right cross on a soft target, the surface area of the MMA glove would be six times higher than a right cross to a hard surface.
These measurements are important to us because differences in surface are tied directly to the amount of damage done by a strike. The energy of a strike is responsible for the structural damage done to the surrounding tissue, and the momentum of a strike determines how much you can move your opponent (or your opponent's head). Surface area has no effect on momentum, but it is incredibly important when it comes to energy. The sharp side of a knife has a very small surface area, which can cause devastating local damage to your tissue, but the flat side of the knife has a large surface area, which is relatively harmless. This implies that gloves with large surface areas should be relatively effective at reducing the type of superficial injuries associated with local tissue damage, so we should expect to see more cuts, bruises, black eyes, and swelling during an MMA match than we would during a boxing match.
The compression of padding in boxing gloves and MMA gloves requires energy. When this energy is spent compressing foam, it is no longer available to compress your opponent's face. Much like the surface area, we would expect this to result in a reduction in localized tissue damage, but the foam will have no effect on the momentum transfer. You can test this personally by pushing a friend or a punching bag with your bare knuckles, and then doing it again with a glove on. The primary noticeable difference in the pushes comes from the slight change in the length of your reach.
Gloves with large surface areas disperse energy and gloves with lots of padding absorb energy as the pads compress. Both reduce the frequency and severity of cuts, bruises, swelling, black eyes, etc. Momentum transfer is unaffected, which means padding provides no protection from diffuse axonal injury to the brain.
Padding Increases Surface Area
When you punch your opponent on the chin while wearing boxing gloves (and to a much lesser extent, MMA gloves), the padding in the glove compresses around the chin, and the outer shape of the glove conforms to the shape of your opponent's face. Not only does this greatly increase the surface area, but it also allows for the transfer of momentum from a punch that might have otherwise been deflected. Angles can be used to break up force and momentum into two different parts, and some of the most effective blocks employ steep angles so that most of the momentum of an incoming punch is lost. When it comes to boxing gloves, the shape of the glove changes to push your opponent's face instead of just deflecting away, and that makes it easier to transfer your punch momentum to his head.
Benefits of Covered Fingers
The tips of your fingers have a very small surface area, and when that small surface area meets the soft tissue of the eye, it takes very little energy to do serious damage. Boxing gloves provide a serious advantage here because all of the fingers are fully contained in the glove. Even though MMA rules forbid eye gouging, accidental eye injury is still very common. Some athletes have complained that the flat shape of the padding in MMA gloves naturally extends the fingers when the hand is at rest, which may make MMA gloves more prone to eye injury than bare fists. The UFC is currently looking for a solution to this problem, but for now, this remains an outstanding issue with MMA gloves. Gloves with covered fingers significantly reduce the rate of eye injury.
Punches are Complex Actions
Your fist, if you chopped it off at the wrist, weighs about a pound (16 ounces). An MMA glove might weigh about 4 ounces including the hand wraps, and a boxing glove might weigh between 10 and 16 ounces. This means that the mass of the fist can be doubled when wearing a glove. If punching was as simple as throwing your fist at your opponent, we would expect double the mass to result in half the speed, but punches are complex actions involving much more of the body than just the fist.
In order to better understand the effect of gloves on punch speed, I performed a simple experiment, which I encourage you to try. First, I recorded myself punching without gloves as fast as possible (without sacrificing technique) for fifteen seconds, and then watched the video frame by frame and counted the punches. I repeated the process for MMA gloves (4.5 ounces) and then for boxing gloves (15.5 ounces). I evaluated three different punching techniques in order to get an idea for the full spectrum of the effect of glove weight on punches.
First, I tested Wing Chun style "chain punches," which involve a square stance, relaxed shoulders, and a vertical fist down the center. Almost all of the action for these punches comes from the arm, and the emphasis is on speed, rather than putting a large effective mass behind the punch. My punch speed started at 7.2 punches per second, dropped to 6.5 with MMA gloves (9% reduction in speed), and then dropped to 5.1 with boxing gloves (30% reduction in speed).
I also tested "brawler" punches, which involves a square stance and planted feet, but almost all of the motion comes from the shoulders and turning the torso, with very little flexing and extending of the arm. These are horizontal punches and they come in from either side, almost like alternating hooks. My punch speed started at 4 punches per second, and remained unchanged with the addition of MMA gloves or boxing gloves (actually, it went up to 4.2, but this is possibly just random fluctuations). This is because the motion behind this type of punch is all torso and shoulder movement rather than arm movement, and adding a few ounces to your body weight is negligible.
The last set of punches I tested was the jab-cross combination from a boxing stance, which involves arm extension, hip and shoulder rotation, and pushing off of the back foot. This took the longest time between punches, at 2.9 punches per second, but it also showed no change with the addition of gloves to the fists (there was an increase to 3.3, but this is possibly random fluctuations as well). Even though these punches involved extension of the arm, the execution of the punch involves the entire body, and a few ounces on the fists are not enough to slow the whole process down.
Of course, "punches per second" is not the same thing as "miles per hour." It might be the case that the actual fist velocity of the right cross is reduced by 30%, just like the chain punches, but because twisting the body takes so long, the number of punches per second will remain unchanged. Either way, the result of the weight of the glove is to reduce the speed of arm movements, but not the movements generated by the body.
The added weight from wearing gloves may provide some small increase in momentum, but this effect is negligible for strikes involving body mass. The added weight also significantly reduces the speed of the arm, but not for motions involving the whole body. This will make high-energy strikes more difficult, but high-momentum strikes will be unaffected.
Boxing gloves and MMA gloves are effective at absorbing and dispersing the energy of impact, which causes local tissue damage, but we have no reason to believe that any gloves are able to reduce momentum transfer. In fact, thanks to the excellent hand protection gloves provide, fighters are able to punch with greater momentum than they would with bare knuckles, and they are able to attack hard targets like the head more often. This means gloves do a great job of reducing the types of injuries associated with structural tissue damage (cuts, bruises, swelling, black eyes, and broken bones), but they also lead to an increase in the frequency and intensity of momentum transfer to the brain, which is directly related to diffuse axonal injury and CTE (Chronic Traumatic Encephalopathy).
Fifty years ago, before we had a firm understanding of CTE, the choice was clear: use padded gloves to protect from injury. Today, we need to think a little harder. A cut, a broken hand, or an eye injury might stop a fight or even end a fighter's career, but brain injury can take away a fighter's ability to function as a human being, both in and out of the ring.
The above excerpt is from Fight Like a Physicist: The Incredible Science Behind Martial Arts by Jason Thalken, Phd.