Recently in ExPhysiology Category

Strength, as an isolated quality, can be defined and measured as the biological contractile potential of muscle--as how hard your muscles can contract to apply force. But from our perspective, Coach Glassman explains in this lecture excerpt, that is an incomplete definition and an isolated measure that doesn't really reveal much about its application to real-world functionality (just as VO2 max measurements alone tell us little about a person's capacity and athleticism).

True, useful strength is not merely the muscles' ability to generate force but a body's ability to productively apply that force.

The missing link in so much mainstream fitness programming, from bodybuilding to monostructural endeavors, is the neuromuscular piece--in particular, the development of coordination, accuracy, agility, and balance. We can sum these elements up as "technique." Omitting them from one's training necessarily results in only partial fitness, partial expression of one's genetic potential, and a decreased threshold of maximal capacity. To increase work capacity across broad time and modal domains (the goal of CrossFit), technique is the crucial connection--whether your goal is to win the game, protect your life, complete the mission, or just be fit for the demands of everyday life at any age.

Anyone who has watched CrossFit instructional videos and read CrossFit Journal articles focusing on lifting technique will know the importance of maintaining a straight torso with normal lumbar curvatures. This month I want to briefly discuss lumbar spinal anatomy and mechanics.

I believe that being able to express mechanical concepts (such as different postures during lifting) in numbers provides the strongest possible support for coaching points. Therefore, I have also included a quantitative analysis of the deadlift using a biomechanical computer model.

Mechanical terminology

The three directions in which forces are applied to human tissues are compression, tension, and shear (shown in figure 1). In case you are wondering, bending places one side of the object in compression and the other in shear, and twisting (torsion) is just a type of shear.

For this discussion on lumbar mechanics we do not need to focus on tension as it is as a force that tends to pull a tissue apart and is not relevant to our purposes. Our focus will be on compression and shear. Shear is defined as a force that acts parallel to a surface; in the spine, it can create sliding of one vertebra with respect to another.

Specifically Speaking

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Every single kind of exercise researcher and practitioner known to mankind has been indoctrinated with the concept of specificity of training. The idea is so well entrenched in the professional psyche that it even has an acronym, the S.A.I.D. principle--Specific Adaptation to Imposed Demand. In a lot of ways, it's pretty correct physiologically. We all remember Dr. Hans Selye and his General Adaptation Syndrome model, which explains how the body becomes stronger and fitter by adapting in response to physical stress. The S.A.I.D. principle fits nicely into that model. Training anaerobic exercise at the very edge of one's physical limits causes the body to adapt in a way that pushes out that boundary and increases the body's capacity for that kind of work. We believe this and we use this concept in exercise programming. Specificity does work.

Let's go a little further in our consideration of specificity though. Lots of coaches and trainers want to make their programs as specific to a trainee's sport or task as possible. To some extent, this is a physiologically sound idea. We wouldn't approach training a 100-meter sprinter the same way we would approach training a marathoner, since one relies on muscle contractile speed and stored and rapidly recycled adenosine triphosphate (ATP) and creatine phosphate for performance while the other relies on several metabolic pathways, carbohydrate availability, and cardiorespiratory efficiency.

Continuing with my theme of muscle mechanics (following my article two months ago on the stretch-shortening cycle), this month I would like to explain the rationale behind the plethora of variable resistance machines and training concepts that are so common. It isn't that designers of exercise machines and fitness programs do not understand muscle mechanics (although some clearly don't), but that knowledge is often applied in ineffective and/or illogical ways.

Take the torque production from a muscle-joint complex for example. As your limbs rotate, the line of action of the muscle force changes, as does the force a muscle can exert at varying lengths, and this results in changes in torque production. Torque is a simple concept that everyone inherently understands. Nobody tries to get out of room by pushing close to the hinge of a door as we all realize that a smaller force applied farther from the axis of rotation will get the job done (over at the handle!). This is torque: mathematically it is force multiplied by the perpendicular distance to the axis of rotation. When working with free weights you learn this fast: keep the weight close to your body--i.e., as close as possible to both the joint's axis of rotation and to the body's center of gravity--and despite the obvious fact that the weight is the same, the torque will be lower and the load will feel more manageable.

Human Weapon System

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Video Article!

Robert Smith is an M.D. and the medical director of Direct Action Medical Network, a group of physicians providing medical training and support to organizations that work in high-risk, remote, and/or austere areas. In this video, he talks about the tactical and safety benefits that people working in such environments can gain from understanding the body as a human weapon system. There are significant advantages of training the whole human body in ways that engage natural abilities and hard- wired instincts, and these techniques are underutilized in most kinds of combat training. Thinking of the body as a human weapon system is about integrating medical and physiological knowledge into combative wisdom. It's about having faith in our physiology.

In any combat system, your equipment has to be properly tuned, and in this case, the equipment is the body. Tuning it means being prepared to utilize it optimally--being trained and conditioned to handle the unexpected, physically and mentally. You have to train the way you're going to fight: with intensity, and in accordance with the body's natural functions of perception, reaction, and response. The relevance to martial arts, self-defense, and athletics is obvious.

I recently overhead a new CrossFit trainee mention that the kipping pull-up he was being taught was "kind of cheating." This is a very common response that shows that many people are unaware that functional movements often require contributions of eccentric (lengthening), isometric (static), and concentric (shortening) muscle actions and that one very common power movement uses a stretch immediately prior to the muscle shortening. This pattern is called the stretch-shortening cycle, as the muscle is lengthened (while actively working) prior to shortening. Rather than cheating, kipping is just one example of an athlete utilizing this natural mechanical response. Cutting from right to left when playing a sport or performing a drop-down counter-movement before jumping are also examples of stretch-shortening cycles. Maybe I should quickly review some terminology. When a muscle is active but lengthening, the muscle action is called eccentric ("away from the center"). This is different from trying to lengthen a muscle while doing a stretch. In the latter case, the muscle is not actively trying to shorten; it is trying to relax. The opposite movement--the work of a muscle actively shortening, or contracting-- is called a concentric ("toward the center") contraction. When a muscle engages (tries to shorten) but does not change length (or produce motion) it is called an isometric contraction.

When you lower yourself slowly into a chair, your hip, knee, and ankle joints flex. Does this mean that your hip flexors, knee flexors (e.g., hamstrings), and ankle flexors (tibialis anterior) are contracting to produce this movement?

Genetic Potential

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I have kids. One, a six year old, Thomas, loves all things martial arts. Since he was four years old, he's been studying with Harley Elmore, a heavily credentialed and amazing instructor in Jeet Kun Do, Sayoc Kali, Muay Thai, and Silat. Why, as a little four-year-old, did he make a decision to study martial arts? I bet you can guess. TV. I'm not sure but I'll wager that there has been a large upturn in the traffic in any martial arts business with a good kids program due to two cartoons: The Avatar and Naruto. Both of these shows have engaging stories, interesting characters, and prominently feature fictionalized and/or magical martial arts forms rooted in Chinese and Japanese forms.

But this article isn't about martial arts, kids, and cartoons, it's about genetic potential. You'll see the connection soon. In Naruto, the title character, Naruto Uzumaki, lives in a community protected by a revered troop of Ninja warriors. His single-minded purpose in life is to complete Ninja school, become the greatest Ninja of all time, and ultimately become "Hokage," the leader of the Ninjas. To do so he must overcome his orphan status, prove himself in school and in the field, and learn how to deal with an occasionally active supernatural demon spirit that was purposely trapped in his body to save the world (OK, that last bit is weird but it's part of the story).

But the lesson I want to address here deals with not Naruto Uzumaki but with a couple supporting characters, Sasuke Uchiha and Rock Lee. Sasuke is the consummate "natural," possessing amazing abilities inherited from his family, and seems to effortlessly and intuitively perform combat skills without instruction or practice. Then there is Rock Lee, a Ninja nerd with absolutely no natural ability but a work ethic the size of Texas and an absolute commitment to never quitting, even if it kills him.

Athletes, coaches, and trainers familiar with CrossFit know that it works. However, I find that some are nonetheless hungry for more explanations of why it works.

The term "physiologic conditioning" refers to a planned program of exercise directed toward improving the functional capacity of a particular bodily system. There are four basic principles of physiologic conditioning that trainers and athletes must take into account:
individual differences

Although this model has existed in the athletic community for decades, I believe that it helps us understand some of the reasons behind the efficacy of CrossFit programming. And, furthermore, because CrossFit is such an effective example of the principles in action, it functions as a test--and confirmation--of the model's value.

For some people, hearing the words "the most powerful human" conjures up images of a spandex-clad superhero oozing muscles and capable of incredible feats of strength and speed. Or maybe it makes you think of a 248px-pound fullback driving through a mass of bodies to the goal line. In any case, it evokes a figure who is strong and can move fast. And this is where we begin our quest to understand the critical physical ability of TMPHBITEU, which is the combination of strength and speed--or, more precisely, power.

Power is an easily understood concept and it all begins with doing work. But work here is not the daily 9-to-5 grind, it is the application of a force to an object with a resulting movement of that object. We can quantify work by knowing the mass of the object moved and the distance it moves: work = weight moved × distance moved.

If I move ten pounds a distance of ten feet, I have done 100px foot-pounds of work. Pretty elementary. a time component. If I move that ten pounds ten feet in ten minutes, I have done the same amount of work as if I moved the ten pounds ten feet in ten milliseconds. Being able to do lot of work in a single effort is associated with being strong. Being able to do a lot of work in multiple repeated efforts is associated with having stamina. But how does work play into determining who the most powerful human is? Again we go back to our bag of physics equations and pull out the equation for power, which quantifies how much work we can do in a period of time: power = weight moved × distance moved

Last month I talked about rest periods during interval training and said I would discuss high-intensity sprint and peak power workouts further. One of the things I talked about is the need for relatively long rest periods during short-duration, peak-intensity work that lasts less than 10 to 15 seconds. I also noted that when it comes to sprint workouts that train short, maximal-effort running intervals, many CrossFitters--always trying to push the intensity envelope--seem to want to reduce the rest period as much as possible.

However, this changes the focus and stimulus of the workout--and not necessarily for the better. We have all heard of "adrenaline junkies"; these athletes are "lactic acid junkies," harboring the misconception that unless you are close to a visit from Pukie, you haven't worked hard enough. Wrong. As I stated last month, it depends on what you are working on. Pure strength workouts generally don't get you to the state of lying on the floor, gasping for breath, feeling absolutely wiped out and ready to throw up, and neither should a sprint workout where the focus is really on sprint technique and high power output.

When you work predominantly type-2b muscle fibers using the phosphagen system, little to no lactic acid is produced. So, when you work on low-rep Olympic lifts, train for the CrossFit Total, or do short sprint interval work, you should not produce much lactic acid.

Whenever the Workout of the Day on requires rest periods of unspecified duration between exercise bouts, there are always many questions about it on the comments page. This is understandable, as rest and recovery within a workout can be quite a complex issue, and the rest period should depend on the activity you are doing and the goal of the workout.

As many of you are aware, there are three systems that a human can draw on to produce the energy required to do physical work. These are the phosphagen, glycolytic, and oxidative systems (these are discussed in terms of sustaining maximum efforts in issue 10 of the CrossFit Journal).

A muscle must produce a chemical compound called ATP to fuel contraction. There is a very small amount of ATP already in the muscle, but the rest must be synthesized from other fuels in the body-- creatine phosphate (CP) stores, glucose, fat, or protein. The chemical processes that produce the ATP from these different fuels are different, and some also require oxygen to be available while others don't.

What is Meaningful

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To the objective observer, it should be fairly obvious that CrossFit methods of fitness training are proving themselves in the field. Out in the real world, the average Joe who sees results like those typically seen by their CrossFitting friends are swayed by success. This is why the CrossFit community is growing and thriving.

But there is always a cadre of exercise scientists and physicians who don't necessarily believe results from the field (after all, "there were no controls"). There is an adage in the sciences that "you can prove anything with a single case example," so anecdotal reports of success from the field are frequently assigned a merit and validity best suited for File 13 or Area 51. If the testing didn't happen in a controlled laboratory environment, the thinking goes, the results cannot be the product of an evidence-based system and therefore must be the worst kind of popular and faddish trash or fiction.

But does it really matter what exercise scientists say? The disregard some academics have for practitioners is a two-way street. Most exercise scientists know that the research reports or theoretical papers they publish are completely ignored by actual practitioners. In a very recent conference keynote speech, Dr. William Kraemer, putatively one of the most recognizable and respected figures in exercise research, said "Coaches don't listen to sports scientists."

Putting Out Fires


Honolulu Fire Department, Hawaii; Orange Country Fire Authority and Oakland Fire Department, California; Woodinville Fire and Life Safety District, Washington; Marietta Fire Department, Georgia; Parker Fire District, Colorado. What do all of these fire departments have in common?

You’ve probably already guessed part of the answer: They use CrossFit, officially or unofficially, to prepare for the rigors of their profession. But there’s more. In firefighter competitions around the country, it seems that whenever CrossFit-trained personnel enter, they end up at the top of the field. We might even say that fire companies like those above dominate the competition.

For those of us familiar with CrossFit and its results, this success is not terribly surprising. However, we have observed a phenomenon in these competitions that is curious indeed. In the parts of the competitions that require contestants to use oxygen tanks, CrossFit-trained firefighters consumed less from their oxygen bottles than other competitors. At first this seems odd—winners using less oxygen? The conventional understanding is that the more fit you are, the more oxygen you can consume (i.e., the greater your VO2 max), the higher levels of exertion you can sustain, and the faster you can get the job done.


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This article was originally written specifically about the role of perception in alpine skiing. It was written by my father, George Twardokens ("Dr. T.," as he is known), and was published in the journal Professional Ski Instructors of America. We wanted to bring some new concepts and prescriptions to the CrossFit community to get "black boxed" and refined. This article uses some of the words of my father’s article verbatim and removes most of the skiing specifics to discuss the importance of perception in training for all types of athletes, as well as soldiers, police, firefighters and others who depend on their physical readiness.

Athletes looking to improve their skills often concentrate on how they move, but they'd be wise to focus also on which movements they select and how quickly they respond. Training to reduce response time through enhanced perception—as if by instinct—can make for better performance on demand.

Perception is a topic that's generating wide general interest these days. In his bestselling book Blink: The Power of Thinking Without Thinking, Malcolm Gladwell examines what happens inside a person’s brain during the nanosecond between when it receives stimuli and then prompts decisions and actions the person isn’t even aware of. Gladwell scrutinizes the way the brain absorbs information immediately and then generates responses that we often consider to be intuition but that, in reality, are part of a complicated process of neural actions and reactions.

In last month's CrossFit Journal, I explained why you shouldn't pay for expensive tests such as gas analysis to measure your VO2 max. Simple tests repeated often will show your improvement (or decline) and how steep the trend curve is. Expensive tests can be accurate, but if you want to know how your fitness is progressing, an expensive test, measuring one component of fitness once per year, isn't going to give you that information. The most common request I get from students, athletes, and the general public is to measure percent body fat. Most people get the same reply I give regarding a gas analysis for VO 2 max: "Save your money."

However, the reasons behind that same reply are not identical. There are two main reasons I do not like to measure someone's percent body fat:
1. I can't do it very accurately and neither can anyone else (despite their sales pitches).
2. It is not a component of fitness and is more than likely not a causative factor in poor health (despite what the media and medical literature say).

If you get a body composition test done and you are told your percent body fat is, for example, "12%," you are being given only part of the results. The accurate information would be something like "12% body fat with a standard error of estimate of 3%." What that means is that approximately two-thirds of the people getting this result would actually be between 9% and 15% body fat. The other third would be outside this range.

The most fundamental concept in exercise is adaptation, the response of the human body to physical stress. And the most fundamental concept in exercise programming is the way adaptation varies among athletes at different levels of training advancement. The only thing hard to understand about them is why these two perfectly obvious principles go largely ignored by the vast majority of people who practice within the field of exercise programming. Strength coaches and personal trainers, exercise physiologists, physical therapists, and athletic trainers routinely "plan" exercise programs for people with no regard for these most logical and obvious derivatives of the basic nature of animal physiology. This must stop. We will stop it.

The term "stress" is quite familiar to those of us with a job, responsibilities that are sometimes difficult to fulfill, or three girlfriends. In physics, stress is the force that causes deformation in a system, and the deformation is referred to as "strain." The stress may be the force of a snatch dropped on the platform from overhead, and the strain may be a bent Eleiko bar (but wait, that just cannot happen). In physiology, stress is that which causes an adaptation in a system. The adaptation to the stress of a shovel handle might be calluses where the handle rubs. But blisters might also form, which would indicate a stress that exceeds the capacity for adaptation. Notice that neither calluses nor blisters form on the other side of the hand--stress, and the adaptation to it, are specific.gist of the paper is that when stress is applied to a viable physiological system, the response is either adaptation through supercompensation (calluses when the stress is of a magnitude that can be adapted to) or a failure to adapt (blisters where the calluses would have formed if you weren't so pig-headed about insisting on wearing your gloves). In dire circumstances, failure to adapt means the death of the organism. For athletes, it usually just means overtraining, a mere inconvenience in the grand scheme of things unless an endorsement or a pro contract is lost in the process.

CrossFit makes my brain hurt. Coach Glassman has established a training model for developing fitness that works, and works well. However, the program and its results cannot be easily analyzed with a superficial examination. The system of training is innovative. Conventional exercise science thinking cannot explain why it works as it does. We have to dig deeper to solve this puzzle of human adaptation. The first piece of the CrossFit science puzzle for me was figuring out how VO 2 max gains were being driven by the interval-type training that is inherent in the system, since the conventionally wise could not fathom how these unconventional methods were developing exemplary endurance.

But as in all good scientific inquiry, answering one question spawns new questions. So a second piece of the CrossFit puzzle, a real poser, emerged, and it concerns the coexistence of strength and endurance training in a single workout. One of the observed benefits of CrossFit training is a simultaneous improvement in strength, endurance, and mobility.intended to improve strength lest there be interference in achieving optimal fitness gains. The thought is that typical endurance training will reduce the amount of strength gain achieved if the two types of training are included in the same workout or are done sequentially. So why can CrossFit-trained people get strong and aerobically fit when they regularly do strength-enhancing and VO 2-max-enhancing work in the same workout? (Dramatic pause while I take a couple of naproxen.)

An Aerobic Paradox

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Have you ever thought about what it is exactly that drives improvement in aerobic work capacity? If you are like most people you probably haven’t really felt compelled to ponder this. Even though I am trained pretty extensively in cardiovascular physiology and training theory, I am an anaerobe and a musclehead. What makes muscle work, become stronger, bigger, or more powerful is my interest.

That means that I hadn't, until recently, considered the question either. In fact, if I had been asked that question two years ago, I probably would have pulled an answer out of some old aerobic dogma buried in my brain somewhere, obtained from reading texts and research journals or from sitting in a lecture hall somewhere. I accepted fairly unquestioningly (albeit with a few exceptions in programming issues) the conventional wisdom of aerobic training physiology. I was a happy camper. I didn’t know I actually cared about a higher level of understanding pertaining to aerobic fitness.

In my article on exercise science in last month's CFJ, I highlighted the difficulty of scientifically determining optimal training methods. Most often, it is coaches working hands-on using a trial-and-error methodology that actually push the science ahead. Eventually, scientists notice that most coaches are doing a particular thing with success and then design a study However, coaches' practical, field-tested insights and clinical experience don't necessarily translate into the realm of scientific testing and study design.

I was recently contacted by a coach working with the Canadian National wrestling team. One of the wrestlers was competing in the 62 kg class, but the coaches thought that if he could drop down a weight class he would be able to medal at the Olympics. They wanted him to drop from 62 to 55 kg, but realized that he was, understandably, concerned about how he would perform after dropping over 11 percent of his body weight. So they wanted him to get a few weight-cutting practice trials in before he actually had to do it in ompetition. He was to act like it was a wrestling meet and cut down for weigh-in at 6 p.m., rehydrate overnight, and then go through some physiological fitness tests in the morning.

What About Recovery?

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For the record, my bad attitude towards any established corpus of recovery information stems from several quirks of my intellectual temperament and the nature of my clinical practice. It has been my professional experience that successful training protocols present themselves over time through superior performance among their adherents.

Repeatedly over my career exceptional performance has been easily and quickly rooted out and attributed to the particulars of the performer’s training regimen. A natural process of question and answer mines more potent strategies quickly: "Where does this guy come from; he learns so quickly?" "He’s a gymnast." "Why are these guys so much stronger than the others?" "They powerflifted for years." How did she get so lean so quickly? "By cutting her intake of high glycemic carbohydrate."

By watching, learning, asking, and experimenting we have been able to build a successful program whose methods were harvested entirely from elite performers. I want to ask, someday, "Who are those amazing athletes?" to which the answer comes, "the new resters."

Effective coaching requires efficient communication. This communication is greatly aided by coach and athlete sharing a terminology for both human movement and body parts.

We've developed an exceedingly simple lesson in anatomy and physiology that we believe has improved our ability to accurately and precisely motivate desired behaviors and enhanced our athletes' understanding of both movement and posture.

Basically, we ask that our athletes learn four body parts, three joints (not including the spine), and two general directions for joint movement. We cap our A&P lesson with the essence of sports biomechanics distilled to three simple rules.

We use a simple iconography to depict the spine, pelvis, femur, and tibia. We show that the spine has a normal "S" shape and where it is on the athlete's body. We similarly demonstrate the pelvis, femur, and tibia.

We next demonstrate the motion of three joints. First, the knee is the joint connecting tibia and femur. Second, working our way up, is the hip. The hip is the joint that connects the femur to the pelvis. Third, is the sacroiliac joint (SI joint), which connects the pelvis to the spine. (We additionally make the point that the spine is really a whole bunch of joints.)

We explain that the femur and tibia constitute "the leg" and that the pelvis and spine constitute "the trunk." That completes our anatomy lesson - now for the physiology. We demonstrate that "flexion" is reducing the angle of a joint and that "extension" is increasing the angle of a joint.

Metabolic Conditioning

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In the second issue of CrossFit Journal, “What is Fitness?” we explored the nature of metabolic conditioning, or “cardio,” and highlighted some of the qualities of and distinctions between aerobic and anaerobic exercise, and touched on interval training. In this issue we’ll reexamine metabolic and interval training in a little more detail.

Let’s begin with a review of metabolic training. Metabolic training refers to conditioning exercises intended to ncrease the storage and delivery of energy for any activity. There are three distinct biochemical means by which energy is provided for all human action. These “metabolic engines” are known as the phosphagen pathway, the glycolytic pathway, and the oxidative pathway.

The first, the phosphagen pathway, provides the bulk of energy used in highest-powered activities, those that last less than ten seconds.

The second, the glycolytic pathway, dominates moderate-powered activities, those that last up to several minutes.

The third, the oxidative pathway provides energy for low-powered activities, those that last in excess of several minutes.

Metabolic Conditioning Glossary

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V02 max: Maximum amount of oxygen that can be used continuously divided by body mass. Long the gold standard of aerobic fitness, the slight advantage that endurance athletes have over anaerobic athletes in V02 max can be attributable to the low body mass of endurance
athletes. I can use a similar definition of strength – by dividing lifts by weight - to show that little guys are stronger than big guys.

The Problem

The most powerful forces that can be generated by the human body are initi- ated, controlled, and dominated by the hip. Unfortunately, in the majority of trainees, some degree of hip dysfunc- tion creates postures and mechanics that reduce power and stability and are generally unsound. The faulty mechanics arise from inadequate training and insuf- ficient practice of critical hip move- ments. We've named this widespread fault "muted hip function" or "MHF."

Who's Got It?

MHF is evident to some degree in all but the most accomplished athletes or those who've trained to avoid it. We tell our best athletes that it will typically take three to five years to fully develop the hip's explosive capacity where there are no sign of MHF postures or tendencies.

The Mechanics

MHF is, ultimately, the postures resulting from the legs compensating for the hip's failure - specifically, and foremost, using leg extension to compensate for weak or nonexistent hip extension. MHF is squatting where hip extension is retarded while leg extension is not.


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