What Are Biomechanics? (And Why Do They Matter?)

When you hear the word “biomechanics,” what’s the first thing you think of?

…Not the easiest question to answer, huh?

Perhaps it’s not something everyone can answer immediately, but it’s certainly something people have asked lots about. And rightfully so — the world of biomechanics is vast and complex, and there’s plenty to explore when it comes to truly understanding what it is and how it plays a role in our day-to-day lives.

That’s actually what inspired us to write this blog in the first place; many of our clients have come to us with questions, whether it be specific to physical therapy or about movement in general.

So, after hearing just how many questions have been floating around in people’s minds, we decided it was high time to write up a mini “glossary” of terms, definitions, and answers about all things biomechanics!

(Okay, not all things. But some of the most common things.)

Let’s get to learning!

What Are Biomechanics?

Before we get started with the nitty gritty terminology, let’s first review the basics and answer that very first question: what exactly is biomechanics?

You can sort of infer what it means if you break down the word; in the simplest definition, biomechanics are the mechanics of your body. (The original definition actually refers to biomechanics as the study and analysis of human movement.)

And more specifically, when we talk about the body’s mechanics, we’re talking about how the structures of your body function internally and how they respond to external forces in order to create movement. The functions of your muscles, tendons, ligaments, and bones all serve their individual purposes, but when combined with physiological responses and external stimuli, they result in specific mechanics that make up your athletic (and everyday) movement.


Take your muscles, for example. At their core, their primary function is to simply contract and relax, but that simple action alone powers multiple facets of our movement (like flexion and extension at our joints). But muscle contraction also leads to other vital, physiological functions like oxygen consumption or digestion.

It’s pretty nifty to think about how our anatomy and physiology are constantly working behind the scenes to keep our bodies moving; it’s certainly something that many people take for granted in their day-to-day.

But that shouldn’t be the case! Just because it’s something we don’t actively think about on a regular basis doesn’t mean that we shouldn’t.

And here’s why…

Why Do Biomechanics Matter?

Understanding biomechanics is the key to an in-depth approach to proper movement, whether it be for rehabilitation and injury prevention or improving your form and enhancing your performance. (And that goes for any kind of movement, not just sports-related ones!)

Sure, you could go your entire life without thinking about your biomechanics… But that’s ultimately why so many people deal with pain and injury. And really, it’s not anyone’s fault; you don’t exactly receive a crash course in biomechanics alongside PE. 

The body is a wildly complex system; more often than not, when you’re dealing with pain in one part of your body, it’s actually caused by an entirely different muscle (or tendon, or joint… or just about any other structure of the body). Plus, there are nearly endless ways our bodies can twist and bend and stretch. That alone is enough to impact how safely we move, and that goes doubly so when there are multiple external forces thrown into the equation.

But of course, all the (literal) moving pieces are difficult to notice in your own movement. And that’s where biomechanical data becomes your best friend.

Biomechanics and Physical Therapy

Having a base-level knowledge of movement is great, but it’ll only get you so far without the ability to analyze and apply that knowledge to your everyday life.

It’s not enough to simply move in a way that looks or feels right; the naked eye can only observe so much from the outside. Take squats, for example: plenty of people can perform a decent-looking squat, but not everyone’s glutes are firing as needed to actually gain benefit and maintain proper form.

Biomechanical Data

Taking the time to assess proper biomechanics goes beyond simply “moving in the correct way” — it encompasses the nuances behind all the different planes of movement, sufficient muscle activation and strength, proper alignment, control, and stability, and so much more.

Regardless of your athletic background (or lack thereof), seeking physical therapy backed by hard data is the key to empowering yourself to rehabilitate, adapt, and improve your movement for the long-term.

Technology for Measuring Biomechanics

Now, here’s another cool benefit to focusing on all this complex data: you get to work with elaborate technology in order to collect it.

Most people aren’t aware that this kind of technology is available, let alone what they actually do… But that’s why we wrote this blog! Check out below to read about some of our advanced technologies, what they do, and how we use them to provide insight into clients’ everyday and athletic movements.

Electromyography (EMG) Sensors

The name might sound daunting, but the purpose is actually quite simple — EMGs are little sensors that measure which muscles are turning on and how much they activate. It essentially allows you to see the connection between your brain and muscles during real-time physical activity.

As you can see in the image here, our physical therapists can place the EMGs on specific muscles or muscle groups to measure whether or not they’re activating properly while performing specific exercises. This allows us to directly see whether or not your muscles are functioning as they should, providing insight into other potential deficiencies in form and biomechanics.


Inertial Measurement Units (IMUs)

Ah, yes, another big term attached to a tiny piece of tech: Inertial Measurement Units!

IMUs (for short) are also small devices that can be attached to your body; but rather than acting as sensors that focus on your muscle activation, IMUs measure their position in space relative to each other. This allows the devices to calculate specific joint angles, posture, and movement patterns as you perform different activities.

And if that alone wasn’t cool enough, IMUs are also capable of simulating a skeletal avatar of your real-time movements! In the video below, you can see a clear visual of what this avatar looks like and how it tracks your movement (as well as the complex data of the forces and angles of your activity to the left-hand side).


This one is as cool as it sounds; in its simplest definition, a dynamometer is a device that helps accurately measure muscle strength.

…Which is actually kind of all there is to it!

Dynamometers provide much more insight into muscle strength compared to a manual muscle test; rather than simply assessing how your muscles hold up against controlled resistance, dynamometers measure the actual force output generated during muscle contraction. (Usually, the force output is measured in newtons, but it’s totally possible to convert it into pounds for us American folk.)

One of the most common versions is a hand dynamometer, where you can measure muscle force with different kinds of gripping forces. Our particular version, however, allows you to measure the force output from any muscle, meaning you can track specific progress with strength gains or pinpoint muscle weakness that may lead to biomechanical deficiencies.

Force Plates

In-ground force plates accurately measure the various forces and stressors on the body during movement. Individuals can perform an array of exercises or movements on a force plate to measure how much force is generated, as well as the direction in which that force is moving.

Force Plate

This comes in handy when trying to assess a variety of significant mechanics in sport-specific movements: body alignment, jump height, reactive strength, stability, and explosiveness.

Defining Muscle and Movement

Now that you understand some of the behind-the-scenes processes for collecting biomechanical data, we can start to review some common questions (and misconceptions) around how muscles function and respond during specific kinds of movement or exercise.

Chances are, if you’ve ever Googled what kind of exercises are best for certain types of training plans or performance benefits, you’ve likely encountered some terminology that left you scratching your head — and that’s what we’re here to break down for you. So let’s get into it.

What are Isometrics?

At first mention of strength training, many people picture a default scenario of performing common exercises like squats or bench presses, or maybe they imagine using weight machines at the gym.

Which is certainly well and good… but pretty much the exact opposite of what isometrics are.

Isometrics are static strength work that challenge you to flex your muscles and keep them flexed. And by that, we mean your muscles are activated and working while under load without undergoing any additional lengthening or shortening via movement. Think wall sits, plank holds, or glute bridge holds, to name a few. The image here is an example of an isometric calf hold.

Isometric Calf Hold

If you’re thinking that static workouts don’t sound like the most effective way to build strength, you’d be right! Isometrics aren’t meant to improve your strength so much as they’re supposed to act as maintenance for the gains you’ve been making through your other training. (Technically, isometric exercises are capable of helping you build strength, but not by much; they certainly won’t be the most effective approach if your goal is to make significant progress with strength.)

Eccentric vs. Concentric Contractions

On the topic of muscle mechanics, let’s talk specific types of muscle contraction. (Yes, you heard us right — there’s more than one.)

There are a handful of variations behind how muscles can contract, but the two most commonly known are as mentioned above: eccentric and concentric.

It can be a little tricky to fully grasp either concept, so here’s a loose example to help…

Imagine the classic bicep curl. (It’s not our favorite exercise, but it’s a solid visual for the purpose of understanding eccentric and concentric contraction, so bear with us.) When you initially pull your hand up towards your chest, your bicep is contracting concentrically; the muscle shortens and generates a certain amount of tensile force to hold your muscles in that position.

Eccentric Loading

And when you lower your arm back down, that’s eccentric contraction; your bicep is still staying under control while lowering the weight, but this time, the muscle is lengthening. Eccentric contraction typically occurs when the tensile forces in your muscles are overcome by greater resisting forces.(And, if you stopped with your elbow at 90 degrees and held it, that’s an isometric hold!)

So any time you read or hear about eccentric exercises, that’s what they’re referring to! Any exercise that places load on your muscles while they’re still elongated. (Think of many exercises that require you to lower your body with elongated muscles: push-ups, squats, crunches, calf-raises, single-leg squats, etc.)

What are Plyometrics?

Whereas isometrics are all about maintaining muscle strength through static loading, plyometrics focus on leveraging both speed and strength through dynamic, higher-intensity motions. Alternatively known as jump training, plyometrics might be closer to what you first imagined when you thought about strength training. 

Plyos are intentionally demanding workouts: your muscles will be placed under high loads in quick bursts of movement, like box jumps or squat jumps. The goal here is to familiarize your muscles with proper shock absorption as you work at maximum effort for a series of intervals.

You can think of it in the context of jumping (since that’s one of the main mechanics used in plyos to begin with): when you land a jump, your lower extremities experience multiple impact forces from hitting the ground. As your muscles adapt to properly and efficiently absorbing shock, they can store that energy and release it once you start to push off the ground into your next movement. It’s analogous to the mechanics of a spring, where your contracted muscles are like the compression of a spring; after placing the coils under load, you release the energy to allow the spring to “bounce back” with more power.

What Is the Difference Between Strength and Power?

This is definitely a confusing one; plenty of people aren’t even aware that there’s a difference between the two! Strength and power are often used interchangeably because of how interconnected they are (but trust us — there’s a huge difference).

Let’s tackle this one at a time…

Strength training is the workout that most of us are accustomed to, where you work your muscles under load to build up your muscle mass. The key for strength training is that extra load: added weight or tension introduces a level of resistance to your workout, and the muscle mass develops as your body repeatedly learns to overcome that resistance. Anything that adds extra weight or resistance to your workout likely constitutes some form of strength work (i.e., deadlifts, bodyweight exercises, banded resistance exercises).

Power, on the other hand, is kind of like a subset of strength. Your gains are still focused on your body’s ability to overcome resistance, but with the added element of speed. This roughly translates to performing your strength work in the shortest amount of time possible (without hurting yourself, of course). Think exercises like plyometrics where you’re recruiting the strength of your muscles, but the primary goal is to build explosive power by ensuring speedy execution.

Granted, you can also perform power workouts with extra weight, just probably not as much as you would during a straightforward strength session. After all, the name of the game for power training is all about that speed (and fast work combined with excessive weight can be a tricky thing to execute well).

What Is the Difference Between Flexibility and Mobility?

Similar to the confusion between strength and power, the concepts of flexibility and mobility are often used interchangeably… and incorrectly.

But just like before, it’s a completely understandable mistake; flexibility and mobility are both correlated to your range of motion, just in different ways. (They’re also heavily interconnected when it comes to fluid movement, so it’s no surprise they get confused all the time.)

The primary difference is between the anatomical roles of each.

Flexibility typically refers to how your muscles lengthen through range of motion, whereas mobility focuses on how your joints and ligaments function through range of motion. Or, to put it more plainly, it’s about how your muscles stretch versus how your joints rotate, bend, or extend. (Think of static stretching versus swinging your leg all the way forwards and backwards.)

What’s tricky is that you can excel at one and completely lack the other — which can actually be a recipe for disaster if left unchecked. 

Lots of resources tend to praise individuals with high flexibility, but there is such a thing as being too flexible. With too much flexibility, your muscles are capable of lengthening, but they aren’t necessarily in control. That’s why mobility is a key factor for keeping your muscles in check; having sufficient control over your joints and ligaments will help ensure that your body doesn’t get too carried away with its newfound flexibility.

And the same applies vice versa; in order to achieve good mobility, you also need good flexibility, it’s just not the only aspect you need to train. The real sweet spot, though, is to master full joint mobility with flexibility, strength, and stability. (But that’s a topic for another time!)

Final Thoughts

So, how are we feeling about biomechanics now??

Informed? Excited? Amazed? (All of the above, we hope!)

Of course, as mentioned before, this is far from an exhaustive list of what constitutes biomechanics technology and terminology… But, it’s a fantastic start! What’s important is that you took the time to tackle an extremely complex topic for the sake of bettering your own understanding of movement.

And what’s even better is that there’s still SO much more to unveil in the world of biomechanics, movement, and physical therapy! (You may just have to stay tuned for a part 2 for even more knowledge!)

Biomechanics and Physical Therapy

By Megumi Kamikawa

Megumi is a graduate from San Jose State University with a degree in English, Creative Writing. Previously, she has worked as a Writing Specialist, where she served hundreds of peers in the SJSU community with her knowledge of English pedagogy. In addition to her experience with academic, creative, and professional writing, she has experience with creating visual and informational resources for various audiences. She has enjoyed taking courses on anatomy and basic physiology, and continues to educate herself in the world of health and wellness through her work with Competitive EDGE.

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