Biomechanic Basics A beginner's guide to understanding the anatomy of lifting weights Ben Yanes Preface This book is my best attempt at answering the question "where do I start learning all of this biomechanics stuff"? This was the question that I always had when I first got into lifting, and there was never a simple answer. I tried to make this book a good middleground between diving in-depth enough so that any of you who have a solid foundation of knowledge would still be somewhat challenged (and maybe even learn something new or connect a few dots), but also so that anyone completely new to this information could begin to understand it, too. I hope that it serves as a good resource to refer back to, regardless of who you are. As an aside: I never thought I'd be writing an Ebook like this because I always hated learning in school. If you hated school too, cheers! I hope that you enjoy the book and get something out of it. If you don't, I'm terribly sorry, but there are no refunds. PHYSICS We all took a high school physics class that we hated, and even if we became personal trainers or discovered a passion in lifting weights, we probably never thought about the topic after we were forced to take a bunch of tests we didn't care about. More so than any other topic we can learn about, though, physics matters (see what I did there?); like, it matters a hell of a lot. Why does it matter? Because physics determines how we interact with the physical world. Physics is what connects us to our physical reality, whether or not we realize it. As you read these words, you're probably sitting in a position that's comfortable for you (I hope) - and that's determined by all of the tiny force equations at every segment through your spine, arms, hips, femurs and feet. This is even more relevant when we step into the weight room, where we're purposefully magnifying the amount of force on our bodies. We are, in a sense, magnifying all of the physics equations that we already interact with on a daily basis. We do this to create a desired outcome - one that we find meaningful in some way - and to achieve in this as efficiently as possible. So...physics determines how we interact with the world and it dictates the outcome of the exercises that we perform (I wouldn't say it's a stretch to assume that physics is pretty meaningful to you, then!). So what is physics, at a more fundamental level? Physics is (to repeat myself) how we interact with our surroundings. The basic unit of physics - as it relates to exercise - is force. If you google the definition of force, you'll see numerous results, most of which conclude something like: "force is an influence that can change motion". Force is the bridge between us and the objects that we touch. Force is what determines what moves, how it moves, and how it influences our bodies (and whether movement occurs at all!). Force is to the weight room as amino acids are to protein (forces are the building blocks of movement). Let's take this a step further now, so that we can understand how force actually provides influence in relation to you. Force is an abstract concept, meaning that there's no way to directly measure a force outside of looking at other properties of it. For example, we measure force through other proxies like mass and acceleration (that whole 'force is equal to mass times acceleration' thing). The units we use for force in the SI system are Newtons and Pounds in the US system (freedom units for the win). There are three major components to every force: the direction that the force is influencing an object, the magnitude with which it influences an object, and the application or location on which the force influences that object. In order words: direction, application and magnitude. When looking at the influence of any force on the body, we need to look at all three of these force components. Although there are other influences force, the scope of this book will mainly cover these three (if you're curious duration and frequency are also highly important, but won't be discussed here). Force interacts with our systems through something called a moment arm. A moment arm, by objective definition, is the perpendicular distance between an axis of rotation and a direction of force relative to that axis. In English: a moment arm is what determines a force's effect on an object, and how powerfully that force can create influence. It's the shortest distance between a line of force and where motion is occurring. An axis is a pivot point around which objects (levers) move. Your elbow is an axis for forearm movement, your door hinge is an axis for door movement, and your toilet bowl hinge is an axis for moving the seat up and down. So, let's take a look more clearly at what a moment arm is, what it actually looks like, and why it's essential in our understanding of exercise physics. To repeat myself: a moment arm is perpendicular distance. Perpendicular just means 90 degrees from (AKA, shortest distance), and distance is self-explanatory. Let's look at an example using the elbow joint: This is an individual doing a curl (hell yeah!). In order to understand the concept of a moment arm, we first need to determine what the major forces are in this equation, and what the direction of those forces are. Because the individual is using a free-weight implement (a bar), we know that (assuming no significant swinging during the curl) the forces imposed on the trainee's body are directly downward, in-line with the direction of gravity. All 'free weights' (DBs, plates, barbells, KBs etc.) are going to act this way. We can draw a line of force from the weight directly downward from the individual's hand: An important caveat here is that we need to make sure to draw the line of force from where the point of application of that object is, not just wherever the object is. Notice that I drew the base of the arrow slightly inward from where to end of the bar is (because the individual's hands are actually not in the same spot as the end of the bar from the perspective of this photo). After we determine the line of force from the point of application, we need to identify the primary moving axis of the exercise (we will dive in-depth on axes later). Note that, although many other axes are being influenced in this movement, the elbow is the one that is primarily being challenged. The red dot indicates the rough center of the axis of the elbow. These depictions do not need to be precisely accurate in order to understand the exercise (the axis will technically change slightly throughout the range of motion - but that's a discussion for another time!). Next (and last!) we can draw the moment arm using these two points. Remember that the moment arm is the perpendicular distance between the direction of force (which can change at varying points and with varying intents on the load) and the axis of rotation that we're looking at. Below, the green line represents the moment arm at this point during the exercise. We will soon talk about what this implies - don't worry! Let's do a few more examples before moving on. Repetition is important. This may be difficult at first to see immediately, but, with more practice, the relative moment arm lengths will become apparent without you having to draw them out on paper. Use the same process every time: begin by drawing the direction of the force (do this in your head before scrolling to the next page!). Did you get it right? Now, identify the primary working axis (assume that this individual is getting a sick biceps pump). Did you get it right? Next, draw in the line from the axis to where it meets the line of force at a 90-degree angle. I intentionally chose a picture where the line of force would not be already perpendicular to the forearm. The first photo that we used as an example is easier to see because the moment arm length was the same as the forearm's length. In the example below, the direction of force wasn't already perpendicular to the forearm, so the moment arm had to 'exit' the space of the body. Remember that the moment arm may be the same as the length of the forearm (in elbow examples), but, a majority of times it will not. Let's do one more for the upper body... this one will be tricky! Don't underestimate it. Start by drawing the line of force of the object (a DB, in this case): Hopefully you remembered that the line of force starts from the point of application (his hand!) and NOT just on the DB. Draw that axis next! Finish by drawing the moment arm! But wait... The arrow doesn't go down far enough in this depiction! Alright, so I kind-of tricked you. In this instance, all you have to do is extend the line of force down further (yes, you can do that, because this is just about direction, not magnitude - more on magnitude later). Like this! Now there's a clear line for you to draw in that moment arm. Remember that the moment arm is always perpendicular in relation to force direction; just make sure you extend the lines of force when you need to! Like this! Now let's do a lower-body example where we'll look at two primary joints instead of one. Use the same exact thought process: direction of force; axis; extend the force if needed; moment arm(s). The next slide will show all of the answers for this photo. Notice that I drew the line of force with an application through the middle of the foot. This is somewhat arbitrary, but generally speaking, this isn't about being as precise as possible (and using specific numbers and math etc.) but more so about gathering general data to tell us more about the exercise. So, what does all of this moment arm stuff actually mean, and why is it important? To understand the answer to that question, we need to understand the idea of torque. From a mechanical standpoint, you can't 'torque' your knee like most people on social media are saying. Torque is a property of force, not a force on it's own. Forces alone can't 'twist' - they can only act in straight lines. In layman's terms: torque represents what a force's ability is to produce movement. Torque is equal to the product of a moment arm and the force (weight, in lifting) you're using (T=F x MA). Let's go over some real examples. Imagine you're doing a lateral raise with 10 pound DBs and that the primary moving axis is the shoulder. 10lbs 10lbs Now, go through the same process that we've gone through multiple times. Make sure to draw out the relevant axis, then the direction of force and moment arm to that axis. Below is the final product: 10lbs 3 ft Now, we can calculate the torque of the resistance (the DB) acting on the shoulder using the following equation (I am not including units as they are not hyper relevant to this discussion): T = F x MA 10 x 3 = 30 Now, let's compare the 30 units of force in the first example to the same exercise with the same 10-pound DB being used, but at a different point in the exercise: 10lbs Don't forget to 1ft extend that force direction both ways! 10lbs Let's assume the tiny green line is = 1ft here for the sake of easy math. Now calculate resistance torque: T = F x MA 10 x 1 = 10 Below represents the relative differences in moment arm (within the SAME EXERCISE) at both the bottom and top positions. Notice that the moment arm at the top position of the lateral raise (the longer moment arm) is about 3 times longer than at the bottom position, and that the outcome of resistance torque in each position is 3 times different (10 units of force compared to 30). So...within the same exercise, a 10-pound DB changed its impact of resistance torque on the shoulder by 3 times the amount! A 10-pound DB, therefore, is not just a 10-pound DB. How the DB influences you depends on all of the factors we've discussed so far. So far, we've discussed some of the basic physics concepts that help us determine what forces exist, which joints they're acting on, and what the significance of that influence on the body is. Now, we're going to continue to look into this idea of the moment arm, only inside of the body as opposed to outside of it. Up to this point, what we've gone over from a moment arm perspective has all been in relation to the objects that are external to the body: how the DBs, the machines and the barbells all act on us. Now, we're going to discuss how these concepts come into play INSIDE of the body: enter the internal moment arm. An internal moment arm is the same as an external moment arm in principle, but has opposite affects in terms of its application. Here's what I mean: When an external moment arm is longer (like at the top of a DB lateral raise compared to the bottom), the amount of resistance acting on us is HIGHER. When an internal moment arm is longer (like when a majority of muscles are in a mid-lengthened position), our capacity to produce force is higher. The longer that a moment arm gets (whether internal OR external), the more it increases the amount of torque (remember that T=F x MA) in a scenario; whether or not that works for or against us depends on internal or external circumstances. Here's a visual example: Think about the above image as two that are overlapping, both of which are of someone doing a curl (i.e. pretend that the person has a DB in their hand and that the direction of force is pointing downward toward the bottom of the page). Now, let's illustrate what the line of pull of the biceps are, in relationship to how they act on the bones they attach to. Notice that I also drew in the axis of rotation at the elbow, too. This process should look very familiar to you by now. Draw in the moment arm from the line of force that I already drew; the principles are the same, but now we've just applied them inside the body. The green line represents the moment arm that the biceps have to act on the forearm in the lower position of elbow flexion (i.e the lower version of the forearm in greater elbow extension): @ben_yanes Notice that, although there are two lines of force (one going from the forearm up, one from the shoulder down), the location I drew the moment arm is on the moving segment (the lighter segment of bone will be the one that moves much more significantly). Although the force on the shoulder is relevant, for the purposes of this discussion, we are focusing on the forces applied at the forearm. Below I've drawn out the direction of force from the forearm that's higher up (more elbow flexion) and also the moment arm in relation to that position. Notice how I've extended the line of force downward as shown in previous examples so that I could find a line perpendicular to the axis of the elbow. n_yanes #2 #1 The lines below represent the relative moment arm lengths of the biceps (pulling the elbow into flexion) in position #1 versus #2. Notice that the moment arm length decreases significantly from the first to second position, meaning that the biceps have LESS leverage to create elbow flexion the shorter that they become. This means that the biceps have a higher capacity to produce elbow rotation in their mid-lengthened position because their torque-producing capabilities (muscular torque capabilities) are higher toward position #1. #1 #2 Knowing what we know now about internal versus external moment arms, we can understand how changing joint position affects both the external influence of the weight on the individual as well as the torque-producing capabilities of the muscles acting around joints. External Moment Arms Internal Moment Arms I like to think about this relationship as a seesaw or tug-of-war between internal and external moment arms and the resultant resistance (external) and muscular (internal) torques that they produce. Every exercise that we choose in the gym can be seen this way: as a battle and balance between internal and external torques between objects, joints & the surrounding contractile tissues. Tom Purvis of RTS (I highly recommend checking out his work) likens this 'battle' between internal and external forces to a tugof-war; not only between muscles working around the same joint but also between those muscles and all forces externally. Internal Moment Arms + force External Moment Arms + force Torque These are pivotal concepts to grasp when attempting to understand the anatomy of lifting. Understanding this relationship will always change across exercises and even within the same exercise across different portions of the range of motion; which is why understanding these as principles and not fact across all scenarios is also of high importance. In the next chapter, we will begin the discussion of range of motion. RANGE OF MOTION: Are you #teamfullROM? Do you try to use as much range of motion as possible across every exercise? Do you think more range of motion is better? Or that more range is, in some fundamental way, more optimal for every goal? When it comes to range of motion, what we're really considering in the context of lifting weights is the range of the muscle or group of muscles that we're trying to train. Hopefully, whenever you're selecting an exercise, you have a general idea of what you're trying to accomplish with that exercise. It doesn't have to be as specific as what subdivision of every muscle and in what length it's being trained, but it should be something that vaguely resembles a train of thought related to the outcome. Let's use the example of the lateral raise that we pictured earlier to illustrate the idea of resistance torque and its importance. With the lateral raise, hopefully your primary goal is to train the middle deltoid. Before beginning to load any exercise, what I like to do first is determine which path of motion makes the most sense to load the tissue. Because this chapter isn't meant to be a thesis on middle delt mechanics, we'll assume (for now) that a lateral raise done in the scapular plane is an efficient exercise to train the middle deltoid. Consider the idea of torque again - more specifically, the resistance torque that the middle deltoid has to overcome when doing a lateral raise (recall that we determined the movement would be mechanically more difficult toward the top of the range of a lateral raise as compared to the bottom, assuming no weight tossing): 11ft ft 10lbs 10lbs 3 ft As we showed earlier, the resistance torque we need to overcome at the top of the range (around 90 degrees of flexion + abduction) was about three times more significant in terms of its magnitude of resistance as compared to at the bottom of the range. So what happens if we keep pushing the range higher? In your own head first, imagine someone with their arms over their heads like they're doing the YMCA; imagine the moment arm to the shoulder in that position, and ask yourself whether it would be greater, less than, or equal to the moment arms at lower angles of flexion. The following image will display the physics: Knowing what you know now - re-visit the questions posed on the first page of this section, and reflect on your answers before - your answers may be a bit different! The general point to be made around range of motion is this: more range of motion just for the sake of it is wasted time and energy. More range of motion isn't and shouldn't be the goal when it comes to actually training our muscles, because more range does not imply more stimulus - in many cases, it may imply the opposite. Take the example of the lateral raise - one done at the angles wherein the moment arms are longer (we'll say between 30-120 degrees of flexion + abduction) and one done with 'full range', where the arms come down all the way to the sides and then above the head in the most flexed position of the joint. Which do you think challenges the middle deltoid more? The version of the exercise where the resistance torque falls to nearly zero for half of the range, or the version where the resistance torque is constantly high? Don't take this to mean that the Y raise with dumbbells is inherently bad or evil - rather, this is simply one example to use that illustrates how 'more range of motion' can be deceiving when not looked at across specific contexts and individuals. If you took the path of motion of a Y raise and instead used cables or resistance bands, the outcome of that exercise could be completely different from the DB variation. Instead of having a moment arm of near-zero at the top of the range, you could set yourself up so that, at the top position, the resistance torque could be at its greatest - meaning that the moment arm could be longest at the top (whether or not you'd actually want to have the torque greatest at the top is part of a different discussion entirely). The goal (when it comes to training muscle) shouldn't be to train full range of motion, but rather full range of challenge. This is another concept I've taken from Tom Purvis (of RTS) which illustrates this idea of understanding and applying basic physics to exercise very well. If you're re-considering everything you've ever learned by this point, GOOD. That's what this book is here to do! Challenging your beliefs and being willing to change them at the presentation of new, more accurate information is what this information is ultimately meant to do. MACHINES Machines are a topic of contention in the fitness industry because people don't understand how they work. On one hand, they're either too simple to bother to analyze, and on the other, they're too 'non-functional, complex or unnecessary for the majority of people. Machines are tools that provide force to the body, much like any other tool in the gym; that's it. They're not good or bad without the context of the goal, who you're working with, and whether or not the individual is prepared for or set up for the motion that the machine provides. Although there are many different kinds of machines, all of them provide force through a foot plate, a handle, or a pad in order to load a specific plane or planes of motion (much more on planes later!). Some machines, like a leg-extension, for example, provide force through only one direction. Others, like a free-motion functional trainer (cable machine) can provide force through any plane relative to your body. Some machines also fall in the middle of this spectrum, wherein the specific plane loaded is limited in one sense but can be used in multiple ways. An example of this is in something like a leg press, where the machine only moves through one direction, but the individual using the machine can choose to vary their stance such that the motion at the hip (and subsequently muscular stimulus) is altered. Since we are just covering the basics in this book, I'm going to stick to general information about machines, how many of them function, and how we can alter their use to our advantage. We've all probably heard of the term 'resistance profile' at some point; but what is a resistance profile, and, more importantly, why is it important? Resistance profiles are the machine-equivalents of a strength curve. Technically speaking, a strength curve represents the amount of force that we can generate from a muscular standpoint throughout the range of a joint, and a resistance profile represents the same, just inside of a machine (and its force-producing effects on you). Every machine has a built-in resistance profile (some of which can be altered, many of which can't), whether you know it or not (many resistance profiles are built horribly and work against us). So why is a resistance profile important? A resistance profile is important because it's what determines how much force a machine produces against us throughout a range of motion. In other words, it determines how difficult an exercise is - be it a row, a curl, an extension, a squat etc. - at every point throughout that range for an individual. Many machines are built with pulley systems, just like you'd see in any cable machine. Credit: Google Images The moment arms produced by a rotating pulley work no differently than in any of the examples discussed thus far. In the image shown above, the pulley rotates clock-wise in such a way that allows for the resistance to 'drop off' as the individual moves through elbow flexion. Many pulleys are not shaped this way and are circular. The advantage of having an asymmetrical pulley (like the one above) is the fact that the machine accommodates for the amount of strength that the elbow flexors can produce at every point. Recall that, based on the strength curve of the biceps/elbow flexors, the amount of muscular torque that we are capable of producing will decrease as we approach full elbow flexion. In accordance with this: any well-designed preacher curl machine will alter its resistance against the individual as they move through the curling motion (the very bottom & top are deloaded relative to the middle, which is appropriate). The ability for an individual to match the strength of the machine and muscle is what creates a 'matched' resistance profile; i.e., an exercise wherein the amount of muscular torque-producing capability is matched by how much the machine is acting against the individual. Many people that utilize a machine with a wellmatched resistance profile report that the machine feels 'smooth', and this is because muscle is challenged appropriately relative to its strength-producing capabilities through every point in the range. Although not every well-designed machine will fit every person well, the ones that are designed to match the strength of the muscle(s) being challenged are typically the ones that feel best for most people. If you've ever used a machine that has an 'unmatched' resistance profile - i.e. a machine that acts against you with greater resistance torque when you're weaker and a lesser resistance torque when you're stronger - it feels 'clunky' and unnatural. Whenever using 'unmatched' resistance profiles, the individual has a greater tendency to cheat using inertial effects to move the weight (tossing it, generating momentum with other tissues etc.). The example of the preacher curl machine matching the strength-producing capabilities of the elbow flexors is a perfect example to use when discussing the concept of 'full range of challenge' discussed in the previous section. The easiest way to provide a full range challenge is to match the strength of a muscle against a resistance that is equally challenging at every point through the range. This provides the most efficient stimulus for the target tissue, as no reps (and no portion within them) are 'wasted'. If you've ever seen a machine that uses a weight stack (pin-loaded machines), pulleys are being used. Not all machines utilize pulleys exclusively, however! Machines like leg-presses, chest presses, rows and many others utilize plate-loading as the mechanism through which resistance is created. Although every machine is different in some way, all of them function off of the same physics principles that have been discussed so far. Pictured above is a plate-loaded pulldown machine made by Prime Fitness. If you take a look at the weight sleeve, you'll notice that there are three different locations that you can choose to add weight to the machine. Because plate-loaded machines utilize 'freeweight', we use gravity as our force-direction; i.e. we can analyze the resistance profile and how it would change based on forces pointing directly downard toward the floor below the machine. Picture someone adding plates to the highest weight sleeve, sleeve #3. Draw the line of force directly down from the sleeve and picture the moment arm as a result in the static bottom position. Use the exact same process that you used to draw out the moment arms in all previous examples (inside of the body and external to it): This is the axis Now, take note of that distance, and draw out the same moment arms for the other two sleeves, sleeves #1 and #2: Bonus info: as this machine moves, it will move in an arc, not a straight line. This makes drawing the moment arms slightly more complex, but the same in principle. If you're interested in this concept, google 'tangential forces' for more info. I felt a need to include this caveat for the sake of illustrating that this image is not in motion and is oversimplified to a degree. Take note of how different the moment arms are between each sleeve and where the entire lever is rotating around. The top weight sleeve provides a much longer moment arm to the pivot point in the bottom position. As the individual pulls on the handles, the machine will rotate up and back and that top sleeve will move closer to the axis of rotation. Because the sleeve will move closer to the axis, the moment arm will decrease. This effectively means that, if you put weight on the top sleeve, the load against you has a greater resistance torque in the bottom as compared to the top. Putting weight on the bottommost sleeve will do the exact opposite; picture how the pivot point and lowest weight sleeve would move farther away from one another as the axis rotates, making the weight gradually heavier as the individual pulls (this means it would become harder as the individual approached the short position). This conversation is not based on which load placement would be 'better' in absolute, but rather is meant to demonstrate how plate loaded machines with multiple options for loading can influence the outcome of the movement differently. Many machines that are plate loaded only have one sleeve to load, but all of the principles of moment arm and resistance torque remain the same when looking at those. Other machines, such as a 45° hyperextension, use the structure of the individual as the levers of the movement as opposed to something intrinsic to the machine. Of course, both the levers of the individual using the machine and the machine are important, however both should be looked at individually and analyzed individually before looking at the picture as a whole to understand how the two interact. If you want to figure out where a machine is heaviest, go to failure under control and you'll find out. :) Machines that have more adjustability are advantageous in being able to fit the structure of more total people. The problem with a greater amount of adjustability is that most machines are made to be in commercial gyms where general population individuals train. Most non-trainers (and many trainers themselves) aren't aware of how to use more adjustability. Many machines, for this reason, intentionally lack adjustability and attempt to fit the structure of the average person. Many machines won’t fit people perfectly without some degree of manipulation of the machine. This is true both from a structural standpoint and a path of motion standpoint. Because these structural considerations will change from machine to machine (and personperson!), we will not be able to get into the specifics of every machine. However, some general principles can be applied to commonly used machines: 1) Much like anything else, machines are neither good nor bad. They either fit the context of the goal, or they don’t. Some machines may work better for some people (for some goals) but you cannot call a machine good in absolute without the context of the greater picture (much like everything else we've discussed). Use the machine that fits you well (or that you can adjust to fit you well) only if it suits your goals and needs in training. 2) Align the path of motion of your arm or leg in the direction that is being loaded. When using any machine, you want to work within the range of the machine that the person can actively control without it. An easy way to figure this out is to reproduce the path of motion that the machine provides without actually contacting it. If you are comfortable working within this range using only your bodyweight while matching the path of motion of the machine, it is likely that you will be able to comfortably and progressively load the machine over time. If you find that performing the motion without any added load causes discomfort or too many secondary rotational mechanics (not loaded in the plane of the machine), then that particular machine may not be best to use long-term. This is not an absolute rule, but rather a general guideline to follow if you’re looking to analyze the mechanics of any machine and how they fit you. Adding handles to a row machine that are free moving can be extremely beneficial for this reason. 3) Although the resistance profile of every machine may not align well with the strength curve of the target muscle(s), there are ways to utilize inertial effects so that the muscular and resistance torques are more closely matched. For example, if you are using a row machine that gets harder as you pull (where you're weaker), it may behoove you to utilize a bit of momentum-based intent at the beginning of the pull, so that the short position becomes relatively easier. 4) Using a bilateral machine unilaterally can completely change the way that you interact with a machine. When doing a movement unilaterally, you gain the ability to adjust the orientation of your arm or leg much more easily than if you were to fix yourself into place with both hands or feet. Doing this is essentially the same as adding more degrees of adjustability to whatever machine you're using. An example of this that I often employ is using a row or press machine unilaterally while I adjust how I sit in the machine/how my torso or hips are oriented relative to my upper extremity. Making these seemingly minor adjustments to where you can comfortably pull/press/extend/flex can make the exercise a completely new one for you. Cable-only machines: Using regular cable pulleys - like a prime functional trainer - is a fantastic way to create more adjustability with a multitude of upper body exercises. Because the circular pulleys only redirect force (and don't make a separate profile on their own like the asymmetrical one earlier), it is incredibly easy to set up lines of force where you want them, relative to the joint angle that you want to load. Most pulleys also accommodate for minute changes in joint rotation because many pulleys rotate around two axes. Subtle rotations in internal or external motion, for instance, may be needed during presses and pulls. Most machines, on their own, do not account for these subtle rotations unless they have freemoving handles and/or adjustable paths of motion. One of the main drawbacks of using cables can be adding external stability in certain circumstances where it may be needed (like during heavy cable rows or presses). Using machines AND cables in tandem is a great way to extract the benefits of both modalities while not incurring too much of the downsides to either in isolation. This is yet another reason not to limit yourself to one or a few modalities. Often times, many modalities used together can optimize results most. JOINT STRUCTURE When we observe motion occurring from a superficial perspective, what we see moving are the levers of the body. Examples of these are the forearm, the femur, the tibia etc. all in different scenarios. This isn't where motion actually occurs, though. Enter the discussion of joints! Joints are the junctions of bones, where all movement is ultimately created. The primary joints that we'll be discussing are all synovial joints: lubricated pivots points that allow all of the major muscle groups (that we'll later discuss) to act around. Synovial joints are super cool. They're layered with a connective tissue called hyaline cartilage, which is primarily composed of a protein called collagen. This cartilage is incredibly smooth and allows bones to slide along one another (not with actual bone-bone contact) to provide a surface for smooth articular motion. Hyaline cartilage is what provides nutrition to the bone (when the joint gets compressed and decompressed) in tandem with the synovial fluid that's released into the joint capsule by the synovial membrane. This is an incredible mechanism that allows the body to lubricate and create its own nutrition to keep our joints healthy long-term. If you've ever heard the phrase "motion is lotion" - well, it quite literally is. Motion is what allows for the hyaline to release nutrition to the surrounding connective tissues, even though it itself is devoid of blood vessels and nerves. Joint Capsule Hyaline (articular) Cartilage Image Credit: Kenhub.com There are a few major synovial joint types that's we'll be discussing in this book: hinge, ball and socket, and pivot joints. There are multiple other kinds of synovial joints that we will not get into in this book, but just be aware that more exist. We are discussing these 3 because they are the joint-types that the major muscle groups we'll be discussing act around. For each joint, we'll discuss two major components: 1) Degrees of freedom that the joint has: how many planes of motion does the joint move in? We can imagine a plane of motion with an analogy: windshield wipers on a car have a point from with they pivot. The wipers themselves are the moving segments (bone) and the plane that the wipers move on is the glass itself. We can imagine this in relation to every single joint in the body. 2) Examples of the joint type. There will be multiple examples to draw upon for each joint type, although we'll focus on just one for each category. Keep in mind that all specific joints that fall under each category of joint type will move in a very similar way (i.e. the shoulder and hip are both ball and socket and their motion qualities are similar to some degree). Image Credit: Kenhub.com Hinge Joint: Degrees of freedom: 1 Example: tibiofemoral joint (part of the knee) The knee technically operates in two planes (google 'screw-home mechanism' if you're interested in that), but for all intents and purposes, the knee acts around the medial-lateral (side to side) axis. The structure of the knee does not allow for side-side movement and as a consequence it does not have contractile tissue that stabilizes it in the medial-lateral plane. The knee only pivots in one direction. Ball and Socket Joint: Degrees of freedom: 3 Example: glenohumeral joint (part of the shoulder complex) The GH joint operates with three degrees of freedom, meaning that it can move in the sagittal, frontal and transverse planes and combinations of all three of them (there are an infinite number of planes in reality!). This allows it to be a very mobile but not very structurally stable joint. Image Credit: Kenhub.com Pivot Joint Degrees of freedom: 1 Example: radioulnar joint Image Credit: Kenhub.com Pivot joints do exactly what they sound like they do, which is to pivot around an axis much like in the photo above. The radioulnar joint is probably the easiest to conceptualize this motion visually, and is what allows for pronation and supination of the forearm to occur (this is what visually looks like people turning their palms up and down as the arms are fixed). Now that we know the basic types of joints and their degrees of freedom, we need to talk about joint structure. Joint structure determines what ranges of mobility we have available to us. If you've ever heard the phrase 'structure determines function', this is what it's meant to illustrate; that there are structural constraints and physical bony limitations within which we all have an ability to contract. Let's look into a few examples. An obvious example to visualize are the end ranges of knee extension and flexion: When the knee bends fully, the constraints that the hamstrings and calves create (upon contact) stop the knee from flexing any more. We could consider this a structural endpoint wherein contractile tissue abuts. Image Credit: Kenhub.com Something similar may occur when the knee extends but for a different reason. In this instance, the joint end-range may be reached because the tibia can no longer continue to translate forward as it abuts the front/bottom of the femur. This is another example of a structural constraint in range that may be due more so to bony limitation as opposed to tissue that lies more superficial. Let's look at another example in the pelvis. Shown to the left is frontal plane abduction of the hip. Can you imagine what may stop this motion from occuring? Image Credit: Kenhub.com Image Credit: Kenhub.com Looking at the structure of the pelvis, take note of what bony landmarks stick out to you, and which ones will tend to abut one another with every joint motion. In the example of hip abduction above, the greater trochanter will at some point approximate the lateral aspect of the ileum bone (shown with arrows). This will provide a structural end range that is in bony contact rather than superficial tissues touching one another. Of course, both will play a role, but these are all just considerations to make in the context of observing joint range. Now let's consider the fact that every individual that trains is an N of 1, meaning that their structure (bony landmarks, the size of them, the shape of them, size of muscle tissue, structure of other soft tissues etc.) will be individual to them. Doesn't it seem silly now to think that everyone should be able to achieve certain arbitrary joint range standards? What if the structure prevents the individual from achieving 180 degrees of shoulder (overhead) flexion? What if, by attempting to increase these end ranges, we're actually creating more issues than we're solving? This is where I strongly question modalities like static passive stretching which are meant to increase joint range devoid of the contractile capabilities of the individual. If you or your client have specific structures and/or osteoarthritic changes that actually make pushing more range a potential danger to the system, then you're violating the joints that you're trying to take care of in the first place. We are not meant to move around like cartoons in every way imaginable. We have specific structural end-ranges that are build into the frameworks of our bodies. This is why improving range of motion should not be a goal, but rather a consequence of the individual's ability to work within what they can actively control and tolerate on any given day. Attempting to give yourself or your client more range of joint mobility just for the sake of it is not doing anyone any favors. This topic alone could comprise an entire chapter in this book, but for now, I'll leave it at that (and maybe finish that thought in an additional book :)). Joint Motion Now that we've gone over some of the basics as it relates to joint structure, let's talk about motion. Recall that every joint is the origin of motion and not the surrounding bony levers. Although it may appear that the levers that we translate force through are doing the moving (such as a an upper leg, upper arm or forearm etc.), where motion actually occurs is around an axis that lies somewhere close to the middle of the joint (there are exceptions to this). Before we look into some visuals, let's cover a bit of terminology. Terminology is an important aspect of specificity. Specificity is crucial when it comes to describing motion because there are many different ways to describe similar things. For example, I could say "abduct your hip" and you could do 10 different things. You could abduct it from a standing or a seated position, from a standing position but somewhere slightly out in front of the body or behind it etc. Anyways - enough rambling! Axis of rotation: the point around which bones pivot. An axis is technically a line that goes through a specific plane, as shown below: Image Credit: Kenhub.com We could also use the term fulcrum, which is meant to describe a fixed point around which rotation can occur. If you wanted to only draw the fulcrum on the image to the right, you'd simply remove the green line and keep the circle. I use fulcrum and axis interchangeably because using the two separately creates confusion at no benefit to understanding. I like to use plane of motion to illustrate where axes are in different motions because it's easier to understand intuitively (as mentioned earlier - recall the windshield wiper analogy). Plane of motion: from a technical standpoint is the line perpendicular to the axis of rotation. If it's complicated to visualize, picture the windshield analogy again. The 'axis' of the wipers would be going directly through the glass (entering it at 90 degrees), almost as if it were a pole crashing through the glass. Another way to think about plane of motion is to equate it with the direction of motion. Flex and extend your knee and you'll see that the plane of motion is parallel with the leg and that the axis of rotation is perpendicular to that, going straight through the sides of the knee. Image Credit: Kenhub.com Let's look at a few examples now, starting with hip adduction in the frontal plane. Notice first the green dots that represent the axis of rotation for this motion (again, technically a fulcrum, but axis works just fine) and the plane of motion which would be perpendicular to that. Before reading on below, try to visualize the plane of motion. The plane of motion here would be the direction your screen is facing. If I could draw a line going directly through the screen (entering the screen at 90 degrees), that would represent how the axis of rotation would actually extend. Let's look at another example: Image Credit: Kenhub.com Shown again in green is the axis of rotation for movement at the knee, which would technically be going through the screen at 90 degrees if I could extend it that way. The plane of motion of this movement being flexion and extension of the knee would dictate that that plane of motion would be a line that sits as the screen does (put your hand on the screen, and that's the plane!). Hopefully the repetition helps with this. It can be tricky to see at first, but once you get it, you get it. Something I would highly recommend is downloading an app like Complete Anatomy '22 and going through all of the joint motions of there to see things in 3D. Let's briefly go over what we've talked about so far (in no particular order) before we get into the fun stuff - muscles! 1) Moment Arms - external and internal moment arms (recall perpendicular distance) 2) Levers - bones! Recall structure as the bedrock of range of available joint motion/mobility 3) Force (or influence) and its three major components: direction, magnitude or amount (which we did not cover extensively), location/point of application 4) Torque (T= force x moment arm) and the tug-of-war of internal and external moment arms and forces 5) Basic Machine Mechanics - pulleys, plate loaded machines, linear machines 6) Joint Structure - recall structure as the foundation for function and motion, and that this differs significantly between individuals (N is always =1) 7) Joint Motion - axes of rotation, planes of motion, fulcrums, levers 8) Types of joints - degrees of freedom, planes of motion MUSCLES: We live in a day and age where information about every muscle in the body is somewhere on some fitness influencer's page. How many of you think that those influencers have taken the time to learn all of the physics concepts we've discussed? How many of you think that they've sat down and learned about joint structure before making a post about doing leg extensions sideways? Now that we've got a solid foundation of understanding of the aforementioned topics, we're now able to dive into muscles. Muscles don't come first (even though they have for many); physics and structure do. Notice that we didn't start off this book by talking about the fiber orientation of the lateral head of triceps or the angle of pull of the medial hamstrings; we talked about all of the things that are the foundation for being able to look at and answer questions about those topics on your own. Too many people today start trying to learn about muscle action without understanding all of the physics and joint-related concepts. I was one of those people too (*sigh*), which is partially why I'm writing this E-book in the first place - to be able to give people more of a truly foundational starting point. It's unfortunate that this is the state of the industry and how people learn, but makes perfect sense given that a majority of people are getting most of their information from social media. In principle, all of the topics we've discussed so far should give you most of the answers you want as it relates to looking at muscular function and how to train them - all it takes is repetition of those concepts applied to different tissues! In theory, training for strength and hypertrophy (which, if you're not a powerlifter, are pretty much the same things FYI), is pretty simple: 1) Take every muscle you train through its stretched position and then shorten it under load. Use various exercises to do this. 2) Repeat step #1 with enough volume, exertion and food. But in application, it's much trickier than this. Why? Because to understand all of the elements of how a muscle acts, we need to understand the physics and structure concepts, which a majority of people in this industry (including well-known coaches, trainers and athletes) do not. So let's dive into some application (now that I've gotten that out of my system)! Fiber Direction: Fiber direction is pretty easy to understand intuitively. Every muscle is oriented in such a way that, when it pulls on the bones it attaches to, it influences those bones in a manner that differs from every other muscle. Fiber direction is influenced by a number of things, to include (but not limited to): direction of fibers attaching to origin, direction of fibers attaching to insertion, other muscles that share similar origins and or insertions, total length of the tissue, moving bones between origins and insertions, non-moving bones between origins and insertions and many more. In application, what's most important to recall is that forces only act in straight lines (remember that whole conversation around torque and how you can't torque an object?), they don't act in arcs of motion as is visibly represented in motion. If a group of muscle fibers is distorted in such a way wherein the belly of the tissue is 'twisted', when it contracts, it will attempt to create the shortest distance that it can between attachment sites. This is synonymous with saying that the fibers of a particular muscle will attempt to shorten into a straight line if effectively recruited. Let's look at a few examples now. Note that the long head of triceps (red arrow) has an origin that lies medial (closer to the spine) to the insertion and that, if you look closely, the fibers wrap inward/downward in an oblique direction as they insert into the olecranon. What does this imply? Image Credit: Kenhub.com If we look at the long head of the triceps from a different angle, this oblique fiber direction becomes more clear. This is why I mentioned earlier it's important to learn these things in 3D! Because the fibers insert down toward the elbow at an angle, if only the long head were to contract, the arm would be pulled like this: Image Credit: Complete Anatomy '22 If we picture what that line of pull would do to the upper arm: the long head can function as a shoulder external rotator (not really in practice, but in principle it could). Now, would it be reasonable to say that ONLY the long head could contract if I extended by elbow? Of course not - but what this illustrates is that, even though the fibers appear to be pulling in a 'curved' direction, their influence - like all other forces - acts in a straight line. In this particular example, if I maintained that externally rotated position, those distal fibers of the long head would move more parallel to the bone, making the arrangement of fibers such that they're as close to being a straight line as possible. Practically speaking, then, if I wanted to 'bias' the long head of the triceps with an elbow extension movement, I'd put my shoulder into an externally rotated position and then I'd hold that position as I worked through elbow flexion and extension against load (like in a single arm cable pushdown). This is effectively how all biases are created: the brain chooses the solution that most efficiently solves the problem. Assuming that you're talking about the muscles on the correct side of a joint you're trying to train, your brain will contract the tissue that's aligned in the straightest possible orientation between its attachment sites. Of course, forces also need to be set up properly, but that's specific to each exercise. An analogy I like to think of to teach this: imagine that you're driving a couple of miles to the grocery store. You have the option to take two different routes; one that takes you 2 miles north and then one mile east, or one that takes you 2.5 miles northeast. Which one would you take? I'll let you decide :) Let's look at another example in the upper extremity in the rear deltoid. Image Credit: Kenhub.com The arrow above points roughly to the middle of the rear deltoid, of which there are 3 subdivisions. Imagine moving the humerus from this static anatomical position and raising it out into frontal plane abduction (straight out to the sides). How would fiber orientation shift? Pictured below is frontal plane abduction of the arm in a degree of external rotation. Check out what happens to the rear delt: Image Credit: Complete Anatomy '22 Straight line (more efficient) fibers *Imagine doing a DB row with your arm out to the side like this. This is what would Bending (less efficient) fibers preferentially be recruited with forces specficic to that scenario. Observe now how the fiber orientation changes and which portion of the highlighted segment would be more efficient at pulling the arm directly back from here. It would be the fibers that have more of a straight-lined orientation (the ones that are more lateral on the scapula)! Now picture in your head how that orientation would shift with a shoulder position that was more adducted (closer to the body). Hopefully you can imagine how the more medial portions of the rear delt would be more efficient at pulling the arm back if the arm moves closer into the body. Now, be careful with the application of this information. These specifics aren't trying to tell you that you should be so myopic and nuanced about your training that you should train every division of every muscle with a different exercise (impossible to do anyways!); rather, these examples are purely meant to illustrate visually how different portions of a muscle can 1) be biased over others and 2) how fiber orientation functions to align the length of the muscle in as straight a line as possible between attachment sites (and how all muscles will look to do this). Let's look at an example in the lower body to illustrate a different point. Take the quads, for example. Note that all of the different fiber orientations are oriented in an oblique (diagonal) direction, much like the long head of the triceps toward the distal end of the upper arm. Image Credit: Kenhub.com The quads are a muscle group that is multipennate, which is a fancy way of saying they're oriented diagonally relative to the length of the bone (femur) they lie on. This allows more fibers to be packed into the same amount of space as if those same fibers were running parallel to the bone. But how are they going to act on the knee to pull it in a straight line? The answer is in resultants. A resultant is the net force of two or more forces acting on an object. I purposefully didn't put this in the introductory section so that I could introduce it here with a visual example. Because the knee is a hinge joint with (practically speaking) one degree of freedom in the sagittal plane, both the medial and lateral aspects of the quads will pull on the patella to create a resultant force (along with the intermediate quads along the middle of the femur) that goes directly sagittal. Can you picture that in your head before I draw out the diagram? Try to visualize it on your own before scrolling. Here's what it looks like: Image Credit: Kenhub.com The net forces from both the medial and lateral aspects of the quads (within the muscles themselves) are drawn in red, and the resultant arrow is drawn in bright green. Let's look at another example of this in the upper body. Of course, the upper, middle and lower traps could all act preferentially, but to illustrate the concept of resultants, let's assume that you're doing something similar to a row, where the scapulae need to move inward toward the spine. What would the resultant look like? Image Credit: Kenhub.com Keep in mind this is an over-simplified illustration meant to demonstrate the point. The upper traps insert on the clavicle too, but what I illustrated here were net forces of all of the upper portions of the trap pulled toward the head and all of the lower portions pulling down toward the lower thoracic spine. The outcome of these two (very theoretical) lines of pull would be something similar to the green resultant as shown above. Now that we've got a solid understanding of fiber direction and lines of influence, we can understand - at least, in theory - how to fully stretch and shorten any muscle, or any subdivision of any muscle: orient the fibers so that they're arranged in a way that creates the most efficient solution for the brain to choose upon contraction, and then move within that arc of motion to train the tissue. In Layman's terms: put the muscle into a straight line, and then stretch and shorten it under load. This is much easier said than done in application, but in the specific muscle sections, we'll be diving into the basics of most of the major muscle groups. Moment Arms: We discussed early on the concept of a moment arm: what it is, why it's important and the basics of its relation to exercise. Now, we're going to talk more specifically (and give more examples) about the internal moment arm. Recall this idea of torque, and how it functions as a property of force; one that determines the effectiveness of a force on you, or - in the case of this section - the effectiveness of a muscle in its ability to move the bones that it attaches to. Because torque is the product of force and moment arm, we can say that, in relation to external torque, the force is the resistance you're holding or contacting (i.e. a DB, a barbell, machines, cables etc.). The forces internally - and in relation to internal torques - are how much tension lies between the muscle belly and wherever it attaches to. Knowing the precise numbers of these forces are not what's relevant in this section, however (or really anywhere besides research and the application thereof). What IS relevant in this section are the internal moment arms we'll be discussing and their effect on what we're going to call muscular torque. So, to summarize in brief: external torque we can define as resistance torque, and internal torque we can define as muscular torque. This section is dedicated to elaborating on what enhances or diminishes muscular torque: the internal moment arm. Recall the illustration early on in the physics section of an elbow and how we drew out the internal moment arms at various points throughout the range of contraction: @ben_yanes Also recall how this internal moment arm from the insertion of the biceps to the axis of rotation at the elbow changes as the elbow continues to flex: And finally how we made a comparison between the two internal moment arms to show how, in the more elbow-extended position, we had a greater internal moment arm, which meant a greater ability to produce muscular torque around the elbow joint: #2 #1 #1 #2 (torque = F x MA - moment arm #1 being about 30% longer could potentially mean producing close to 50%+ more muscular torque) Hopefully that served as a good refresher for the concept of internal moment arms. Let's dive into some other examples! Everyone wants to bench press with a really wide grip, but let's look into why that's not advantageous from a pec-training perspective (hint: it's because of internal moment arm!). First, draw out the internal moment arms for any tissue you're looking it. The angle at which you look at them will differ based upon location and structure of the muscle. Because the pecs are a fan-shaped muscle that wraps around the ribs, it's easiest to see moment arms from a sagittal viewpoint. For simplicity's sake, in this example, we're just going to choose to look at the sternal division of the pec. Image Credit: Complete Anatomy '22 If you need a refresher on the steps to identify the internal moment arms, see the introductory section again on basic physics before proceeding. Take note of the moment arm shown (in green) above. Now let's look at an image that shows the arm in the 'guillotine' position as many gym bros call it: Image Credit: Complete Anatomy '22 (apologies for the faded deltoid that's in the way) Not too great of a moment arm in the moreabducted position, huh? Let's compare the internal moment arms below (scaled appropriately): Wide Narrow In this instance, we can conclude that the pecs (generally speaking) have greater internal leverage in a relatively adducted position, where the arm is closer to the side of the body - as compared to a more abducted position, where the arms are out wide close to 80+ degrees of abduction. Internal moment arms are half of what determines leverage (T = F x MA). Let's look at another example, but in the lower body. As discussed previously, the quads are a multi-pennate muscle that act on the knee joint. Although their fiber direction appears to pull the patella in several different directions (medial/lateral), the net forces will (under normal, healthy circumstances) translate the patella in the sagittal plane as the knee is meant to flex and extend. Let's take a look at internal moment arms throughout the range of knee flexion and extension: Let's first look at the quadricep's leverage for knee extension with a knee bent around 90 degrees (keep in mind that this is not full knee flexion for most people!): Image Credit: Complete Anatomy '22 And now in a more relatively knee-extended position (not fully extended for most!): Image Credit: Complete Anatomy '22 And now let's compare the two moment arms scaled the same way: More extended knee More flexed knee Although not drawn perfectly in any of these pictures, I hope that these moment arm illustrations are starting to make sense across the board. We can see clearly that the moment arm for knee extension decreases significantly the shorter that the quadriceps become. This is what is responsible for the decreasing amount of muscular torque you're able to produce as you straighten your knees (amongst a few other things such as exercise selection, execution, muscle length etc.). Now that we've discussed both fiber direction and internal moment arms, it's time to start diving specifically into the major muscle groups that we look to develop in the weight room. Specific joint structures will be discussed in greater depth in the following sections as is necessary to understand each muscle's function, which is why there hasn't been an in-depth section up to this point on it. I've put a lot of thought into how I wanted to present the muscle mechanics information and settled on making videos where I could actually talk and show things in real time. Plus, you're probably tired of reading at this point, so it makes sense anyways. For every major group, I made a corresponding video that goes over the specifics of each tissue in tandem with some information about the joints they surround. Keep in mind these are meant to illustrate the basics of a lot of these tissues and that each video on its own probably could've been an hour (or more) each. I tried to keep rambling to a minimum and hopefully everything is concise. Below you will find all of the links to each of the major groups as hyperlinks. Simply click on whichever group you want to see and you'll be taken to an unlisted YouTube upload. I advise going in order from top to bottom because there are a number of concepts that I introduce in earlier videos that I assume as prior knowledge in later ones. I hope you enjoy. Calves & Tibialis Quads Hamstrings Glutes Trunk Muscles Hip Flexors & Adductors Pecs & Lats Delts Arms & Forearms Upper Back Hopefully that all was much easier to see and hear in real time as opposed to me trying to describe (in text) all of the minutia that I wanted to cover for each group. I recommend going over these videos again at various points or prior to training sessions of your own so that you can visualize and feel the motions for yourself and see where your own ranges align well for each tissue. Notice that I didn't get into many specific exercises for each of the groups, other than listing a few generally and making reference to them when discussing relative length biases. This book is not meant to function as some cookie-cutter program that's just going to give you all of the answers to generalized questions like "what are the best exercises for XYZ muscle group?". Rather, this book is meant to function as a means of providing the tools that you can practice using on your own. The old adage of 'teach a man to fish' has high application to these topics in particular, because once you've honed in your own thought process on all of this information, you can use it and apply it to any scenario to accomplish whatever you want. Once you've got a good grasp of this information, you'll be able to set anything up in a way that's appropriate for yourself or anyone that you're going to train. You'll quickly come to realize that every scenario you encounter will be slightly different in some way, but that that's ok because it's part of solving the puzzle of each client or of each exercise within your own training. Honing the tools here long-term will be where the results really start to manifest themselves. I hope this makes sense; and if it doesn't now, it will eventually with enough repetition. If you enjoyed this short Ebook or my content in general and want to support me so that I can continue to create in this way, please refer it to friends or share it to your platform so that more people can pick it up. I ask that you please not share the PDF with those who haven't actually purchased it, as these thoughts took a long time to consolidate and articulate. I really think so many of the issues we face as an industry as it relates to exercise comes from not understanding these fundamentals. Thank you :)