Biomechanics: a Key Factor in Rehabilitation of Neurological Diseases

In the rapidly evolving modern world, technological advancements are allowing for more effective research and treatment of diseases, disorders, and injuries sustained by humans.  One of the foremost areas of current research in the biomechanics field is that of its role in treatment and rehabilitation of neurological disorders such as amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS).  According to the United Nations, as many as 1 billion people in the world live with neurological disorders.  This post will focus mainly on how biomechanics can aid in the treatment and rehabilitation of ALS and MS.  ALS is a fatal disease that causes degeneration of motor neurons leading to muscle atrophy and loss of motor skills.  MS is a nonfatal disease in which the body’s immune system attacks its central nervous system which can cause pain in movement and loss of motor function.  ALS and MS have no known cures; therefore, it is necessary that steps be taken in order to counteract the disabling symptoms of the diseases.  For ALS, rehabilitation can help to sustain motor function thus leading to an enhanced quality of life and perhaps a longer life expectancy.  For MS, rehabilitation can potentially allow for patients to regain motor function in areas where it may have been lost.

diagram showing example of how whole body function is determined by function of much smaller tissues
photo from Kulig & Burnfield, The role of biomechanics in orthopedic and neurological rehabilitation (2008)

 

Biomechanical research has led to breakthroughs in terms of understanding the root cause and resulting difficulties of movement caused by diseases such as MS and ALS.  Many people living with MS and ALS face challenges walking due to muscle weakness and the inability to balance.  Thanks to clinical gait studies, the abnormalities of the stride of people with MS and ALS can be thoroughly analyzed by comparison to the average stride of a human.  The root of these abnormalities can be discovered and addressed through rehabilitation exercises or biomechanical technology such as braces or implants that deliver medicine to muscles.

 

 

gait study participant equipped with surface electrodes, footswitches, and passive reflective markers walking on force plate sensors
photo from Kulig & Burnfield, The role of biomechanics in orthopedic and neurological rehabilitation (2008)

 

An article by Kornelia Kulig and Judith Marie Burnfield explains how clinical gait studies are performed using footswitches, passive reflective markers, force plates, and electrodes to record data on stride characteristics, full body kinematics, ground reaction forces, and muscle activity.  Footswitches enable initial detection of irregularities.  The kinematic data recorded by the passive reflective markers can then trace the irregularity to the source of the issue.  Ground reaction forces signify stress levels placed on various joints. Electrodes assist in distinguishing between movements that are a direct result of disability versus movements that are performed in order to make up for the lack of muscle function.

Clinical gait studies are just one example of how biomechanics research can improve rehabilitation techniques for those with neurological disorders.  Any basic muscular function lost to a neurological disorder (such as hand/grip function) is theoretically able to be treated through proper biomechanical research and rehabilitation.  It is a truly exciting prospect that diseases that were once permanently disabling are now becoming more and more treatable with the goal of a permanent cure in mind.

For additional information on the topic of neurological rehabilitation, visit this Wikipedia article.

 

Exciting Advance in ACL Repair

Anterior Cruciate Ligament (ACL) injuries are among the most common in sports, with nearly 100,000 tears annually. Additionally, the rate of pediatric tears has been increasing at a rate of 2.3% each year for the past 20 years. The high incidence of this injury is in part due to the structure of the knee complex, where the ACL is located. The ACL helps connect the two longest bones in the body and is responsible for rotation and transferring body weight to the ankle. Specifically, the primary functions of the ACL are to prevent the tibia from sliding too far in front of the femur and to provide rotational stability to the joint. This rotational motion, combined with a lack of muscle support at the knee, is why so many athletes tear their ACL. A recent paper looked into how a team of doctors led by Dr. Martha Murray at Boston Children’s Hospital have come up with a promising new approach to repairing the injured ligament.

Two side views of the knee joint, one showing a healthy knee and one showing a complete ACL tear.
Photo by BruceBlaus on wikimedia.org

Due to its environment, ACLs do not repair on their own like other ligaments do. The synovial fluid, which resides in the knee complex to reduce friction in the joint, limits blood flow to the ACL and PCL (posterior cruciate ligament). When injuries occur to these ligaments, the lack of blood flow prevents clotting. In most other ligaments, clotting would occur and would function as a “bridge” for the two ends of the torn ligament to grow and heal across. Due to ACLs not being able to undergo this process, the current method for repair is to take a graft from the patient’s hamstring or patella and replace the torn ACL with the new graft. While this method is typically successful, Dr. Murray’s team estimates that the re-tear rate is about 20% and up to 80% of patients develop arthritis in their knee 15-20 years after the surgery. To combat this, Dr. Murray drew inspiration from how other ligaments heal and developed Bridge Enhanced ACL Repair (BEAR). The premise of this technology is to take a “sponge” that is composed of proteins that are naturally found in the ACL, and insert it between the torn ends of the ACL.  Using sutures, the sponge is moved into position and the two ends of the ACL are pulled into the sponge. Blood is then drawn from the patient and inserted into the sponge. This environment acts as a blood clot and stimulates the ACL to repair itself. Clinical trials have shown that the sponge resorbs completely after 8 weeks, at which point the two ends of the torn ACL have begun to join back together. While the BEAR treatment is still relatively new, early results are encouraging with patients seeing similar results to patients that undergo traditional ACL reconstruction. Though it is difficult to predict the rate at which patients who receive BEAR treatment will develop arthritis, animal testing has shown lower instances of osteoarthritis development, which is promising news for those who suffer from this common injury.

For more information about the BEAR technology check out Boston Children’s Hospital website or this recent article. A short video detailing the technology can also be seen below.

Scleroderma and Raynaud’s Phenomenon: Cold Weather’s Influence on Skin

Anyone who is familiar with winters that are mainly at temperatures in single digit range knows how crucial gloves are to surviving the tough, frigid weather. If one was to go outside without them, their hands become extremely pale (or sometimes almost blue) and, once back inside, take a bit of time to get back to normal. It’s a tough life, I know, but people with a scleroderma have an even harder time surviving the winter. What is scleroderma, you ask? Scleroderma is an autoimmune disease that causes skin and internal organs to thicken, and if that wasn’t tough enough, a good chunk of people with it also experience secondary Raynaud’s phenomenon, which is an exaggerated vasoconstriction of arterioles in response to cold weather and causes a drop in blood flow. The main, visible outcome from this disease is how the skin whitens and swells. Problems must ensue from the combination of thick skin and lack of blood flow to the extremities, right?

Raynaud's Phenomenon in ring finger
Thomas Galvin [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
Modified from Balbir-Gurman, Denton, Nichols, Knight, Nahir, Martin, and Black, Annals of Rheumatic Diseases 2002

With the thickening of skin, certain properties of skin will noticeably alter when a person has scleroderma. In a recent study, researchers from multiple backgrounds used a new suction device to compare mechanical properties of skin of patients with scleroderma and healthy patients. In the experiment, the researchers used a modified Rodnan skin score to observe skin involvement. This way of testing focuses on how easy it is to pinch skin and witness how it folds. The skin was tested on 3 parts of the body including back, forearm, and shoulder in order to see how the skin not only differs between patients, but to see how different areas have different properties due to activity and use of those parts of the body. To test the skin of the patients, the new suction device used, the BTC-2000, also proved beneficial due to its non-invasive nature that could be used more frequently to produce data. The biomechanical properties of skin depend greatly on the dermis, or skin thickness, due to the properties being derived from witnessing skin response to pressure and stress. The study that these researchers performed supported the idea that mechanical properties of skin are altered negatively when a patient has scleroderma. The major properties that were observed were less extensibility, stretchiness, and a larger resistance to stress.

So the struggle to go outside in the winter is even bigger for people with scleroderma. But in their case, the damage brought on by cold weather is greater and typically more permanent. Similarly, if this is how the disease influences the mechanical properties of the outer skin, the potential impact on internal organs is intriguing.

Fish in Flight: The Science Behind Great White Breach Attacks on Cape Fur Seals

Great white shark employs vertical attack on prey decoy
Great white shark employs vertical attack on prey decoy – from Sharkcrew via Wikipedia Commons

If you’ve ever turned on Discovery channel during Shark Week, then you’ve probably seen the iconic footage of a 2.5-ton great white shark leaping out of the water to catch its next meal.  If you’re weird like me and you’ve ever tried to mimic one of these epic breaches in a backyard pool, then you realize just how difficult it is to generate enough momentum to jump even partway out of the water and therefore have a real appreciation for what it takes to pull off this incredible feat.

Great white breaks the ocean surface
Great white breaks the ocean surface – from Alex Steyn via Unsplash

So if a breach attack is so difficult to pull off, how are great white sharks able do it, and why do they do it?  As per usual, some basic physics can help us answer both these questions.

 

Great white shark mid-breach
Great white shark mid-breach – from Alex Steyn via Unsplash

According to a 2011 paper by Martin and Hammerschlag, who spent 13 years studying great white predation in South Africa, breach attacks allow great whites to play to their strengths and maximize stealth.

Millennia of evolution have left great whites with long bodies great for straight-line speed (can reach speeds  >11m/s) but not so great for agility. Additionally, roughly 95% of a great white’s muscle is white muscle, which allows for rapid contraction (e.g. speed bursts) but also results in poor endurance.  Considering these aspects of their physiological makeup, it’s in a great white’s best interest to attack swiftly, avoiding prolonged chases.  Martin and Hammerschlag report that the majority of great white attacks on seals are over within 2 minutes and that the longer an attack drags on, the less likely it is to be successful.

Great white shark chases decoy prey from behind
Great white shark chases decoy prey from behind – from Sharkcrew via Wikipedia Commons

As great whites are less agile than seals, maximizing stealth and minimizing the time seals have to react is imperative.  Having evolved to have a dark grey dorsal (top) surface, great whites are hard to distinguish from the coral on the ocean floor when viewed from above (seal’s perspective).  Additionally, since very little of the light entering the water is reflected back towards the surface, it is estimated that under even the best lighting conditions, a seal could only reliably distinguish a shark a maximum distance of roughly 5m below it, which explains why great whites attack from below rather than behind. Great whites need about 4m to reach top speed, so due to this acceleration distance and seal vision, Martin and Hammerschlag report that great white attacks generally start between 7m and 31m below the ocean surface, with the majority staring closer to 30m.  Looking at data for great white breach attacks ranging from vertical to 45 degree ascents, Martin and Hammerschlag estimate that it typically takes a shark between 2 and 2.5 seconds to go from initial acceleration to surface breach, and that when considering shark speed and average visibility conditions, a seal generally has only about 0.1 seconds to react if it spots the shark before contact is made.  Ultimately, due to the advantages it gives them, great whites are successful in over half their breach attacks when lighting conditions are ideal.

Schematic of geometry and optics of great white shark attacks on cape fur seals from Martin and Hammerschlag - not to scale
Schematic of geometry and optics of great white shark attacks on cape fur seals from Martin and Hammerschlag – not to scale

 

Sources & Further Reading:

Fallows, Chris & Aidan Martin, R & Hammerschlag, Neil. (2012). Predator-Prey Interactions between White Sharks (Carcharodon carcharias) and Cape Fur Seals (Arctocephalus pusillus pusillus) at Seal Island, South Africa and Comparisons with Patterns Observed at Other Sites

Martin, R. Aidan, and Neil Hammerschlag. “Marine Biology Research.” Marine Biology Research, vol. 8, no. 1, 30 Nov. 2011, pp. 90–94., doi:10.1080/17451000.2011.614255.

Egdall, Mark. “New Research Reveals Physics Behind Great White Shark Attacks.” Decoded Science, Decoded Science, 10 Dec. 2011, www.decodedscience.org/new-research-reveals-physics-behind-great-white-shark-attacks/7497.

Sloat, Sarah. “Shark Week: Here Is the Wild Physics of a Great White Leap.” Inverse, Inverse, 25 July 2018, www.inverse.com/article/47437-shark-week-great-white-jumps.

Madrigal, Alexis C. “The Physics of Great White Sharks Leaping Out of the Water to Catch Seals.” The Atlantic, The Atlantic Monthly Group, 9 Dec. 2011, www.theatlantic.com/technology/archive/2011/12/the-physics-of-great-white-sharks-leaping-out-of-the-water-to-catch-seals/249799/.

 

The Unfair Advantage: Prosthetics and Their Role in the Olympics

In 2012, the “Blade Runner” Oscar Pistorius became the first double amputee to compete in the Olympics. Ever since this historic occasion, the issue of whether prosthetics should be allowed in athletics has been a topic of controversy in the media. Do prosthetics give amputees an advantage over able-bodied athletes? Are athletes with prosthetics capable of running faster and performing better than able-bodied athletes?

Oscar Pristorius strapped into a harness and being tested on a treadmill by Alena Grabowski's research team.
Photo by Jeff Fitlow/Rice, ScienceDaily 2008

In a recent article, physiology and biomechanics professor Alena Grabowski attempts to answer some of these questions. Grabowski was part of a research group that conducted a study to see if Pistorius’s prosthetics gave him any advantages after he was banned from competing in the 2008 Olympics. The group focused on comparing the abilities of Pistorius to those of able-bodied track athletes. The study involved testing Pistorius’ energy cost in running, his endurance, and his general running mechanics. In order to test for energy costs, the researchers measured breathing and metabolic rates of able-bodied runners who were similar in ability to Pistorius as they ran a series of short sprints. To test endurance, runners were placed on treadmills set at their max speed to measure how long they could maintain that speed. To test the running mechanics, each runner was asked to continue increasing their speed on a treadmill until they could no longer take eight consecutive strides on the treadmill without maintaining their position on the treadmill. Based on the study, the group was able to determine that Pistorius’ running abilities are very similar to able-bodied runners, thus allowing his ban to be lifted and for him to ultimately compete in the 2012 Olympics.

The three variations of prosthetics used in Alena Grabkowski's prosthetic parameters research.
Photo from The Royal Society Publishing 2017

After the initial research, Grabowski decided to conduct research of her own into prosthetics. Her study involved how changing key parameters in a prosthetic affected a runner’s abilities. In order to conduct the tests, she first modeled the foot as a spring system. This allowed her to pick the key parameters to change: stiffness, height, and speed of a prosthetic. Five participants were chosen to be tested. The study consisted of a participant using a set prosthetic to run on a treadmill, increasing the speed on each trial until they could no longer hold their position in the treadmill. This was repeated for different parameter changes in the prosthetics until enough data was collected to compare. From her study, Grabowski found that the length of the prosthetic had no overall effect on running speed. However, stiffness did appear to aid runners, but the effects were negligible at high running speeds. Thus, the advantages of having prosthetics come into play more for long distance running than for sprints. Based on her research finding, Grabowski hopes that future prosthetic development can be more tailored to match the specific wearers abilities before amputation.

The world of prosthetics opens up the door for many amputees to compete in an able-bodied society: from being able to complete just simple day-to-day tasks to competing alongside able-bodied athletes in the Olympics. Though many may still be skeptical of the use of prosthetics in competition—namely running, the evidence says that the effects are minimal or even no-existent in the case of sprinters. With the help of researchers like Alena Grabowski, more athletes like Oscar Pistorius are and hopefully will be making great strides in the future.

For more information on this story, make sure to read The Daily Beast, Scientific American, and The New York Times.

Artificial Turf: Game Changer or Game Ender?

Woman plays soccer on artificial turf field
Soccer player on artificial turf field
From Pixabay

Artificial turf fields were first introduced in the late 1960s and have grown tremendously in popularity since. Today, artificial turf fields can be found at all levels of sport, from youth league to professional, and across many different sporting disciplines. A major reason they are so popular is because they offer a consistent, low-maintenance, year-round green playing field in all weather conditions and climates. However, despite the benefits they provide, artificial turf fields are not without controversy. Even though artificial turf mimics grass in appearance, its properties are much different.

Of these properties, two are especially relevant to injuries sustained while playing sports, especially concussions and injuries to the knee and ankle. The first of these two is the field’s ability to absorb shock. Older artificial turf fields are often much harder than natural grass fields, which leads to greater impacts on athletes, which can then result in higher rates of concussions and other injuries. As artificial turf technology has developed, however, installation procedures and field composition have improved and greatly reduced the risk of injury.

The second of the two properties is the friction of the field, or how well an athlete’s cleats grip the turf. Because of their greater consistency and density, artificial turf fields can generate more friction than natural grass fields, allowing greater force to be generated at the contact point between an athlete’s foot and the ground. This is both a positive and a negative. Positively, the greater friction generated by athletic moves on artificial turf surfaces enable an athlete to perform at a higher level by enabling quicker changes in direction and more explosive movements. However, these greater forces can overload weaker parts of the anatomy, especially the ligaments in the knee, and cause injury. Numerous studies have found that rates of serious knee injuries, such as ACL (anterior cruciate ligament) tears, are found to be increased on artificial turf fields.

A major reason for this is because the knee is a hinge joint, meaning that it only allows straightening and bending motion while resisting rotation. Within the knee, tendons attach muscles to the tibia/fibula and the femur so that the knee can be bent voluntarily, four major ligaments attach the femur to the tibia/fibula to stabilize and restrict the knee’s motion, and a variety of cartilage and fluid sac structures ensure smooth and consistent motion. While robust together, each individual component in the knee is susceptible to injury if it is subjected to a force in an unusual or extreme way, which could happen while changing direction rapidly, incorrectly landing a jump, or during a collision. On an artificial turf field, the risk of damaging ligaments, cartilage, or other structures in the knee is increased because greater forces can be generated from the ground and because the foot may stick in the turf while changing direction and cause inadvertent rotation in the knee.

Nevertheless, even these risks can be somewhat mitigated by taking steps to avoid injury like the one recommended by The Polyclinic.

 

 

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.

Walk [Under] Water: The Benefits of Underwater Running

Just because you can’t walk on water doesn’t mean you shouldn’t run under it!

Aqua-jogging. Hydro-running. Water-treadmills. Have you ever heard some combination of these terms and wondered what the hype is?

Running underwater offers benefits for people throughout their fitness journey. Underwater running has proven useful for a variety of focuses, including recovery after injury, cross training, and even improved gait. This article includes a video showing a Runner’s World coach tries out a Hydrotrack and discusses some of the benefits!

So, why does it work?

Three basic water properties: hydrostatic pressure, buoyancy, and viscosity.

Hydrostatic pressure is the force that the water exerts on a submerged point. Hydrostatic pressure acts all around the point. However, since hydrostatic pressure is proportional to the weight of liquid above the point, it increases with increased water depth. This means that your feet would experience greater hydrostatic pressures than your knees. While running, this pressure helps support your body and decrease impact forces. In addition to helping prevent injuries through a decreased risk of falling, it also helps decrease swelling and promote cardiovascular health. This article talks about the specifics of pressure with swelling and the cardiovascular system.

Diagram showing hydrostatic forces. Magnitude of the hydrostatic force is larger as it goes deeper below the surface.
Hydrostatic pressure acts on all sides of a point. The pressure increases with depth. Created in Microsoft PowerPoint.

Buoyancy is the hydrostatic force applied to an object with volume (rather than just a point). Since they are at the same depth, all the horizontal forces cancel out. Since the bottom of the object is deeper than the top, the net buoyant force on the object pushes up. The difference between the buoyant force and the weight of the object submerged determines if the object will rise, sink, or stay in place. Thus, the more submerged a person is, the more of their weight is supported. This research article explains how this support can help make gait analysis more effective to further prevent injury. When water reaches the person’s navel, 50% of their weight is supported. This weight bearing capability of water decreases forces on joints and can even help improve range of motion. This allows physical therapy to begin sooner and, overall, take less time out of the patient’s normal routine. This allows shorter rehabilitation times without sacrificing quality of care or recovery.

 

Diagrams showing how the hydrostatic force varies around the submerged object due to depth. The side forces cancel out at equal depth leaving a net buoyant force acting upward against the downward force of the object weight.
Buoyant forces cancel out on the sides leading to the second image showing the net buoyant force and the weight of the object. Created in Microsoft PowerPoint.

Viscosity is a fluid property that affects the resistance that an object encounters during motion. In the case of underwater running, viscosity explains why you move significantly slower in water than on land. It also can offer resistance up to 15 times the amount of resistance on land. Forcing your limbs through the water strengthens muscles that are not typically used out of the water and even burns more calories!

As noted above, viscosity can help strengthen muscles as shown in this study on deep water running (DWR) in a community of elderly women shows how viscosity affects overall strength training. It showed that the women who participated in DWR increased their muscle strength (measured through power) and performed better in various tests, including ones that involved sitting down and getting up. The study showed that deep water running helped to mitigate some of the negative muscular effects of aging.

Overall, running underwater offers some great benefits. The basic properties of water (hydrostatic pressure, buoyancy, and viscosity) provide scientific background for why hydro-running provides benefits for all.

 

 

 

 

 

 

 

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.