Tag Archives: muscles

Packing a punch: Does strength indicate boxing performance?

Every sport has a different “ideal” body type, which is largely dictated by the muscle groups it focuses on training. Swimmers prioritize developing the muscles in their shoulders and backs, which allows them to propel themselves through the water with their arms. On the other hand, runners prioritize the hamstrings and quads in their legs, which allows them to generate greater force when pushing off of the ground. So, what is the ideal body type for boxing? Strength is clearly important when punching an opponent, but is it even the most important factor in boxing performance? Should either upper- or lower-body strength be prioritized over the other?

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Photo by Bradley Popkin for Men’s Journal.

The overall goal in boxing is to either knock out your opponent with a single punch or land more punches in the scoring area than your opponent. One of the best ways to achieve the latter is by wearing down your opponent with powerful strikes to reduce their ability to retaliate. Therefore, hitting your opponent, and hitting them hard, is crucial within the sport of boxing. 

First, let’s take a look at upper-body strength. Boxers execute punches by using muscular force to accelerate their arms, so it is easy to assume that arm strength is the most important factor in punch performance. However, this may not be the case. One of the most common upper-body strength exercises is the bench press, and research has shown that there is no significant correlation between the maximum weight a boxer can bench press and the force they deliver in a punch. While this may be surprising, the relationship between upper-body strength and punching actually comes down to speed rather than force. Based on data from both professional and elite amateur boxers, the maximum speed at which a boxer can bench press is indicative of improved punch performance. More specifically, professional boxers showed a strong relationship between the maximum velocity of their bench press and maximum punch velocity of their rear, or dominant, arm. 

If upper-body strength does not indicate punch force, then does lower-body strength? A study of amateur boxers found a positive correlation between maximum punch force and lower-body strength measures, including countermovement jump (see video below) and isometric midthigh pull. In contrast to the upper-body exercises, the maximum force generated in lower-body exercises is more important for increasing maximum punch force than the speed at which the exercise is completed.

Plot of countermovement jump force in Newtons versus punch force in Newtons. The data has a correlation of 0.683 and a p-value of less than 0.001. Plot of isometric midthigh pull force in Newtons versus punch force in Newtons. The data has a correlation of 0.680 and a p-value of less than 0.001.
Plots showing a strong, positive correlation between punch force and the lower-body strength exercises, countermovement jump, CMJ, (left) and isometric midthigh pull, IMTP, (right). Adapted from “Relationships Between Punch Impact Force and Upper- and Lower-Body Muscular Strength and Power in Highly Trained Amateur Boxers” by Emily C. Dunn, et al.
Video of how to execute the countermovement jump test by Training & Testing.
Kinetic Chain: Force is generated from the floor and transferred from foot to fist. Leg force, hip and torso rotation are key. Arrows show movement of force from foot, through the body, to fist.
Graphic of Kinetic Chain in a boxer from Boxing News.

When executing a punch, a boxer gains forward momentum by pushing off of the ground with their legs. Through a kinetic chain, force moves through a boxer’s body from the floor to the foot, then through the legs and torso, and finally, to the arm and hand. This phenomenon is what explains why lower-body force is crucial to a boxer’s maximum punch force. 

So, what does this all mean? How should boxers train in order to improve their punching performance? Most importantly, boxers should focus on their lower-body strength, as it is the most direct indicator of maximum punch force. While lower-body strength should be a primary training goal, exercising muscles within the upper-body, specifically while focusing on the speed of the movements, will also likely improve overall punch performance. We now know that developing strength is clearly beneficial in improving a boxer’s punch; however, brute force alone does not win a fight. Boxers should develop correct boxing technique through methods such as those suggested in this article, which will allow them to implement their new strength in the most effective manner.    

For additional information on the impact of strength on athletic performance click here and here.

Dolphin Magic or Dolphin Muscle?

Because of the film Bee Movie, many people at one point were intrigued by the idea that bumblebees should not physically be able to fly due to their large bodies and tiny wings. But, they fly anyway. Technology is advanced enough to study bee wing movement and determine that they produce enough lift to allow them to fly, disproving the previous notion. Similarly, Gray’s Paradox for a long time inferred that dolphins should not be able to swim nearly as fast as they do. But, they still consistently swim at speeds over twenty miles per hour. It was not until recent history that advancements allowed researchers to determine why they are able to reach such high speeds.

Gray’s Paradox

All the way back in 1936, Sir James Gray observed the high speeds dolphins could reach in the ocean. He calculated an approximation of the amount of power the dolphins would need to produce to sustain these speeds, based on the drag force on the dolphin as it travels through the water. Gray compared this to the amount of power he expected the dolphin to be able to produce. In order to compute this, Gray used muscle power data from oarsmen. When he compared the muscle mass of these oarsmen compared to dolphins, he determined that the power dolphins could produce was only about one seventh what was needed to travel at the high speeds of which they are capable.

Force Diagram, showing that the same forces that the swimming mammal applies to water are applied back on it. Allows observation of max speed to determine these forces.
This diagram shows that the drag force, D, thrust force, T, and net axial force, Fx, must be equal for the swimmer and the fluid. The lateral velocity, u, can be used to determine the resulting drag force, allowing researchers to estimate how much thrust is needed. Credit: [2]

And now we have arrived at Gray’s Paradox. What allows dolphins to move so quickly? To Gray and other researchers for most of a century, this was a mystery. If the assumptions they had made were correct, that would mean dolphins have some way of travelling through water more efficiently than was thought to be possible. This sparked a large amount of speculation into how dolphin skin could reduce the drag force of the water, which was originally believed to be the way Gray’s Paradox would be resolved.

Answering Questions while Creating More

Finally in 2008, Timothy Wei’s research team was able to definitively disprove Gray’s Paradox. He set up an experiment that would allow the force that dolphins exert to be measured. This mainly consisted of having dolphins swim through a curtain of bubbles in a tank. By recording at high resolution the movement of these bubbles as the dolphins swam by, the researchers determined the speed of the water around the dolphin as it traveled. With this information, Wei’s team showed that dolphins are able to produce over 300 pounds of force at one moment, and over longer periods of time 200 pounds of force. This is approximately ten times more force than Gray estimated.

Wei’s findings resolve Gray’s paradox by showing that dolphins have the ability to produce sufficient power from their tail movement to overcome the strong drag force of the water as they move at high speeds. However, this does not explain how dolphins produce so much power with their amount of muscle mass, which is still being examined. One idea is that this is caused by anaerobic muscle fibers that behave in different ways than in humans, and allow more power to be generated than Gray expected.

Future Plans: Investigating Force Generation

Timothy Wei plans to continue examining force generation in the swimming of other marine animals. This has the potential to provide more understanding of how marine animals evolved in their swimming aptitude. On the level of microbiology, this research could improve understanding of how dolphin and other animal muscles can perform such high levels of power generation over sustained periods of time.

Additional Reading and Sources

Heads Up and Eyes Steady – The Optimized Mechanism for Human Running

In the insightful words of Bruce Springsteen, we as human beings were Born to Run. Humans have never been a sedentary species. The tendency to constantly relocate for survival purposes required skill in obtaining food efficiently, which heavily influenced early human evolution. Humans with optimal body mechanics for running ultimately held an advantage in hunting and gathering for food, and over time, the human body adapted to these survival requirements and developed a self-optimizing mechanism for running. This implies that initiating the act of running activates certain responses in the body to perform most efficiently.

Two aspects of the human body that the mechanism for running must account for, more so than other living species that depend on running for survival, is the bipedalism of humans and the disproportional size and weight of the head compared to other living species that run. For optimal locomotion, the head must remain stable while the body is in motion and experiencing the impacts of running not only to minimize the strain on the neck, but to allow for a steady gaze and safe navigation of the environment and potentially dangerous terrain. In order to achieve this, the human body has developed aspects within the mechanism for running that specifically protect against body pitching and head instability.

Plot title: Brain-to-Body Mass Ratio
X-axis: Body Mass (kg)
Y-axis: Brain Mass (kg)
where the ratio for humans is the largest compared to various other animals.
Image from Charlotte Swanson, Science World

The default mechanics of an individual’s natural stride minimize the shock through the body so that it may function as metabolically efficient as possible. This is true for most processes found in the universe; systems are constantly seeking a lower state of energy, and human beings are no different. Thus, as found in the research conducted by Michael A. Busa, Jongil Lim, Richard E. A. van Emmerik, and Joseph Hamill, the human body reacts to the external stimulus of running with a tendency toward an optimal stride frequency, which allows the head to be most stable during the motion.

Looking even further into the human body’s mechanism for running, a study was conducted by Andrew K. Yegian and Yanish Tucker investigating the involvement of neuromechanics. The researchers hypothesized that there was a neuromechanical connection between the biceps brachii and the superior (or upper) trapezius that served to provide stability for the head during running.

Biceps brachii highlighted in color on skeletal diagram.
Image from Wikipedia “Biceps Brcachii”
Sections of the trapezius muscle, upper or superior in orange, middle in red, and lower in fuchsia
Image from Wikipedia “Trapezius”

Although the activation of these two muscles is seemingly uncorrelated, the connection points on the shoulder are very close to once another and the line of action of both muscles is almost parallel. Both muscles are known to resist rotational impulses, and thus body pitching initiated by the significant weight of the head, during the foot’s contact with the ground during running.

In the study, the researchers observed human subject running on a treadmill and tracked muscle activity with electromyographic (EMG) sensors. They found the timing of muscle activation to be strongly coincident, and the magnitudes of both activation levels in both muscles were generally larger when mass was added to the runner’s head to further test the neuromechanical linkage. Due to the approximately parallel lines of action, the coincident forces from the biceps brachii and the superior trapezius, which act in opposite directions, directly support the stability of the scapula, which ultimately controls the stability of the head and upper body above the torso during running.

At this time, it is unknown whether the neuromechanical linkage between the biceps and the upper trapezius muscles to stabilize the head during running is direct or indirect, so further research is required to determine the mechanism that causes the muscle coordination.

For more general information about the biomechanics of running, visit this article found in Psysiopedia.

Muscle Loss Due to Aging

It is a well-known fact that as we get old, our bodies (sadly) deteriorate, leaving us unable to perform certain physical functions as easily as we could have when we were younger. In this article, the authors describe a study done to analyze muscle loss due to aging, primarily by examining two different age groups of humans. By conducting measurements on people over and under the age of 40 years, results show a clear difference in muscle mass and strength between the two.

Karsten Keller and Martin Engelhardt conducted their study on 14 adults under the age of 40 and 12 adults over the age of 40. They measured the circumference (size) of each leg of the participants in four different locations at 10 and 20 cm above the knee, and 10cm below it along with the largest circumference position below the knee. In addition, they conducted strength tests based on the motion of the leg at 30˚ and 60˚ from resting sitting position using the Dynamometer BIODEX® System 3.

Man Lifting Weights
Photo by Sopan Shewale on Unsplash

Results given in the article can be viewed in full here, but as a summary both the overall size and strength of legs was stronger in the younger participant group than in the older group. According to the authors, we as human beings generally are at our physical peak throughout the 20-30 year age range. From analyzing their own experimental results, Keller and Engelhardt conclude that our muscle mass generally begins to decline after about 40 years of age. The factors that contribute to the size and strength of our muscles declining due to aging is varied and complex, but one reason for our weakening is that as we age our muscle fibers decline in number. Once enough fibers are lost, our bodies experience apoptosis, or the destruction of cells. Anabolic hormone decrease, risk of disease, appetite loss, and declining of physical activity are all other large factors attributed to muscle loss in aging.

Maximum isometric strength of the left leg in 60° flexion of both groups.
Maximum isometric strength of the left leg in 60° flexion of both groups.

Maximum isometric strength of the right leg in 60° flexion of both groups.
Maximum isometric strength of the right leg in 60° flexion of both groups.

Human beings get old, and physically, it is not that great. Our muscle strength and size decline due to a number of factors. However, we can help ourselves fight physical aging by paying attention to our health, specifically maintaining some physical strength training and ensuring we receive nutrients to feed our muscles. The authors recognize the limitations of this study, including small sample size and desiring ages from every decade; however they are able to conclude by stating that their data shows that muscle declines after 40 years of age in a range from 16.6% – 40.9%. To learn more about some causes of muscle loss through aging, such as sarcopenia, inactivity, and physiological changes check out these articles.

 

High Heels: How They Can Affect You Even After You Take Them Off

Anyone who has worn high heels, or has even simply seen a person in high heels, knows that the foot is definitely not in its usual position in that kind of shoe – walking is more difficult and forget about even trying to run in high heels. Researchers from Manchester Metropolitan University and the University of Vienna wanted to investigate if frequent, long term use of high heels caused lasting changes in the calf, in addition to the normal discomfort experienced by high heel wearers. Previous studies have shown that muscles that are regularly used in unusual ways will often adjust to this new scenario to maintain functionality. These researchers, more specifically, investigated whether the regular wearing of high heels would result in physiological changes to the calf (gastrocnemius) muscle and Achilles’ tendon, and if these changes would then affect the normal functioning of the calf and ankle. In order to determine if and what changes occur, the researchers observed a group of women who regularly wore high heels and a control group who did not to compare their calves and ankles.

two women walking in stillettos
Modified Image by StockSnap on Pixabay

The calf muscle and Achilles’ tendon make up the top and bottom of the rear of the calf respectively. They play a crucial role in controlling ankle motion and in general mobility. Dimensions of the muscles, including length, were measured using ultrasound, and the cross sectional areas of the tendons were measured using MRI imaging. The torque and motion of the ankle were measured by an isokinetic dynamometer. From these values, the researches could determine other important characteristics of the tendon such as the force on it, the strain it experienced, the stiffness, and the modulus of elasticity. The strain value indicates how much the tendon is stretched from its relaxed position since it is the ratio of the change in length to the original length. The stiffness is the ratio of the force experienced to the amount of length change the tendon experienced. The modulus of elasticity, or Young’s modulus, is the ratio of how much force per area the tendon experiences to the strain.

muscles and tendons in the calf and ankle
Modified Image on Smart Servier Medical Art

MRI image of the side of two ankles with one having the foot on a wedge mimicking wearing high heels and one having the foot flat on the ground
From Csapo, Maganaris, Seynnes, and Narici, Journal of Experimental Biology 2010

 

The results of their analysis showed that people who regularly wore high heels had a resting ankle position that made the foot further from perpendicular with the leg than that of someone who did not regularly wear high heels. Additionally, generally the calf muscles of high heel wearers were shorter and the stiffnesses of their Achilles’ tendons were higher due to greater cross sectional areas of the tendons. The maximum strain in the Achilles’ tendon was lower in high heel wearers because of the reduction in length. However, no significant difference in the Young’s modulus of the tendon was observed. Similar torque-angle relationships were observed between the two study groups, so the researchers inferred that the body must have compensated for this new positioning. Additionally, these results explain the observation that high heel wearers had a reduced active range of motion in their ankles because of shorter, stiffer muscles and tendons. What the new normal ankle position means for regular high heel wearers is that their bodies are adjusting to shifts in gait, center of mass, and ground reaction forces if they wear high heels very often. The researchers infer that this physical change to the calf can also account for the discomfort women who regularly wear high heels experience when switching to flat shoes.

For additional discussion of this topic, take a look at Discover Magazine.

Gainz for Dayz: Conventional vs Sumo Deadlift

What’s the best way to pick stuff up and put it back down?

A large tattooed man deadlifting enough weight to bend the bar in the conventional form.
Photo by Alora Griffiths on Unsplash

By deadlifting, of course.  The deadlift is, arguably, one of the most important exercises a weight lifter can perform.  Although primarily thought of as a lower body exercise, the deadlift activates muscles throughout the entire body, and is one of the three all-important lifts for any lifting routine.  Although there are a variety of different deadlift form variations, two of the most prevalent are the conventional deadlift and the sumo deadlift.  The main difference between these two stiles is that in the conventional deadlift, the hands are placed on the outside of the knees, while sumo deadlifting places the knees outside of the hand.  The everlasting debate is therefore which form is the better one?

In attempt to answer this, tracking data was used to employ a biomechanical analysis of these two forms of deadlifting. One of the biggest differences they found was in the distance that the bar had to travel from the beginning of the lift to the completion of the lift.  In the sumo deadlift, the significantly wider foot stance results in a 19% decrease in the distance the bar must travel, decreasing the amount of work that the lifter needs to use.  It therefore seems that the conventional deadlift, if it requires more work, is the better form, right?  Well, maybe.  The researchers also found that the sumo deadlift conveyed a biomechanical advantages compared to the conventional deadlift.  This was mostly due to a more upright trunk at the beginning of the lift, resulting in less trunk extension being required to complete the lift, although it consequently may require more flexibility to perform.  This in turn decreases the moments of the bottom two vertebrae and shear forces on them, and the sumo deadlift therefore seems to have a safety advantage over the conventional deadlift.

The postures of athletes performing the conventional and sumo deadlifts as determined by tracking body points through video footage.
Modified from McGuigan and Wilson, Journal of Strength and Conditioning Research 1996

But what about muscles?  What should you do if you want to gain strength by pushing your muscles to work harder?  As the study showed, the conventional deadlift needs an increased amount of energy to complete, but are all the muscles used in the two forms the same?  Researchers at Duke University Medical Center decided to use electromyography (EMG) to find out.  They found that the wider stance assumed in the sumo deadlift, besides conveying the safety advantages mentioned above, also resulted in an increased recruitment of some of the lower body muscles.  Namely, the vastus lateralis, the vastus medialis, and the tibialis anterior, or the outer (and strongest) and inner thigh muscles as well as the shin muscle.  The conventional deadlift recruited only the medial gastrocnemius (inner calf) significantly more than the sumo deadlift.  The recruitment of the vastus lateralis and vastus medialis make sense, since having your feet placed more directly under you in conventional deadlift would tend to recruit the more central thigh muscles.

With all of the above, it looks like sumo be the better option: it decreases stress on the back, recruits more lower body muscles, and indirectly places a focus on flexibility.  However, if you’re not convinced, Men’s Journal, BarBend, and Starting Strength provide some additional commentary comparing these two methods.

For the following video provides a better explanation of the differences in form between the two styles of deadlift.

 

Why your Muscles Hurt after a Workout

How often do we cut our overly ambitious workouts short because of exhaustion or muscle soreness? Probably more than we care to admit. But have you ever stopped to ask yourself why your muscles hurt, especially a day or two after your workout? The simple answer is, you’ve put so much strain on your muscles that you aren’t used to, so they tore, and now your body has to repair the tears and build up more muscle, so the same thing doesn’t happen in the future.

Normal muscle tissue in the arm versus strained muscle tissue
Fitness Science, 2015

When your muscles become sore after a strenuous workout, that is called Delayed Onset Muscle Soreness, or DOMS. Matthew Ely, a graduate employee in the Department of Human Physiology at University of Oregon states that DOMS occurs often when you are doing a new workout or using muscles that you typically don’t utilize. What happens then, is that since these muscles are not accustomed to enduring so much stress, they tear. On a microscopic level, what is happening is that after these muscles have torn, local cells begin to work together to repair the muscle fibers. Correspondingly, tissue cells, immune cells, and proteins migrate to the torn ligaments to remove the damaged proteins and repair and replace them with new ones. This process is ultimately the soreness we feel. As the proteins and muscles build up, that exercise that made us sore no longer does as we’ve gotten stronger with visible muscle growth. While this pain ultimately supports the saying “no pain no gain”, this pain shouldn’t last longer than a few days. If it does, the damage could be more serious and require medical attention.

Damaged muscle torn across the fibers
Total Cheer Performance, 2018

Since 2010, a group of Japanese neurologists have been studying DOMS and nerve damage. Ultimately, their findings don’t show us too much more than what is already known.

Inflammation of muscle fibers due to over exertion
Physio4fight, 2014

Their research essentially suggests that the pain we feel is nerve growing pains. However, after examining the effect of DOMS in rats, the Japanese were able to begin working on a “cure” for DOMS, meaning they thought they were able to completely suppress this soreness. So far, though, cryotherapy, stretching, homeopathy, ultrasound, and electrical current modalities have not proven to be entirely fruitful.

There are several reasons that the Japanese and other researchers have proven fruitless in their efforts of understanding this topic, primarily, the early stage in history that DOMS are even being studied. While many remedies have been created to combat diseases, athletic injuries and musculoskeletal research are in their earlier stages of study. The second reason is that DOMS have proven to be more complicated than originally thought. The basic theories tend to prove to be false. But the most accepted theory for DOMS is that when the muscles tear, they swell up and push on nerves which sends a message to our brain that we are in pain, similar to more basic injuries from cuts or broken bones.

In the end, muscle soreness is not a bad sign that you’ve damaged your body like simple injuries. As far as research has shown, muscle soreness is the response your brain receives when too much stress has been placed on an unused muscle so that it tears and swells. When the swelling pushes on nerves, we feel pain. As our bodies repair the damage by replacing proteins, the swelling goes down and the muscle gets larger so it can compensate for the stress it now knows it must overcome when we do that specific exercise. This process would then repeat as we push ourselves further every time we work out.

DOMS – What is it and what to expect

 

Are Muscle Loads During Irish Dance Unsafe?

Do you think your ankle can bear loads more than 14 times your body weight? Can you look graceful while doing it?

This question is one of great importance for many athletes participating in high-impact sports. Dancers of all kinds have strived, for years now, to perfect the balance of athleticism and grace that their competitive markets demand. Achieving this balance is no simple feat, and many dancers fall victim to injuries during their countless repetitions of high impact leaps and landings, and Irish dancers are no exception. Researchers have recognized the need for biomechanical analysis of muscles and joints of Irish dancers, and created a model to do just that.

The method for one such study by James M. Shippen and Barbara May assumed an Irish dancer’s body to be a composition of discrete rigid bodies, each having a unique mass and set of inertial properties that dictate its motion. Joints connect these segments, and muscles that cross numerous sections exert forces between those segments.  The study analyzed 196 muscles, which in turn generated 53 torques on various joints. A least-squares regression minimized muscle activation, which is a physiologically sensical model, as lower muscle activation decreases fatigue. The solution for the model was subject to three logical conditions: muscle torques are equal to the sum of the external and inertial torques at each joint, the muscle loads must be positive (as muscle contraction only allows for pull), and the load must be smaller than that which the muscle can maximally generate. The finalized model represented 35 joints, each constrained in accordance with its anatomical analog (i.e. the human hip joint is spherical, so the hip joint in the model has equivalent degrees of freedom.)

Researchers attached optical tracking markers to the test subject dancers (similar to the image on

Optical trackers attached to a walking test subject
Photo from Advanced Real Time Tracking

the right) to analyze motion at 250 frames per second; force plates were mounted into the ground to measure reaction forces at 24,000 samples per second. 5 Irish dancers performed the rock step (video), among other common Irish dance moves, during which the dancer uses one ankle to push the other to the ground (see video below for example of rocks).

Muscle activation in the gastrocnemius and soleus during the rock step
Shippen & May, Journal of Dance Medicine & Science 2010

The relevant components analyzed during the rock step were the Achilles tendon and attached soleus and gastrocnemius muscles. Shippen and May’s calculations yielded forces of 2700N on these ankle muscles and tendon.  Normal muscle forces due to walking are in the range of 500-1430N for worthwhile analogy. The figure on the left shows the activation of the two relevant muscles during the rock step, and it is evident that the gastrocnemius reaches an activation of 1.6, far above the maximal isometric force activation of 1.0.  This is demonstrative of the risk associated with this specific move, and why the loads can be unsafe.

Componentized contact forces in the right ankle during the rock step
Shippen & May, Journal of Dance Medicine & Science 2010

The figure on the right shows the contact forces in the right ankle componentized into external loads (reactions forces with the floor) and forces generated internally (from muscles acting at the joints). The maximum load for this dancer was about 14 times her body weight, with the great majority of that coming from muscle forces.

This study demonstrated the risk associated with the rock step in Irish dance. It also is helpful for future research, as it suggests that emphasis should be placed on reducing the internal muscle loads that work to stabilize the ankle, as opposed to modifying ground reaction forces, which have a smaller margin for success.

The mathematical model developed in this research can be applied to many other athletes and examples of human motion in the future to understand internal forces and reduce risk of injury in athletes.

For more research on biomechanical models of the human body and their applications, read about this humanoid robot and human sitting posture for driving.