The Science Behind Triple Extension for Faster, More Efficient Running Form

Most runners have probably heard that hip extension is really important for running form and speed… but no one’s really explained why that’s the case. Naturally, it leads to a hunt for a detailed breakdown of all the “why’s” and “how’s”, and actionable steps towards achieving that optimal running form.

Well, hunt no further.

Not only will this article review the pivotal nature of hip extension, but it’ll also dive into a novel concept known as triple extension. It’s a necessary part of our biomechanics that allows us to jump, lift, and run effectively, yet it’s still something commonly overlooked (or left unexplained) in the athletic world.

So if you aren’t already familiar with it, lace up those shoes — this is going to be another fantastic addition to your arsenal of running-form knowledge.

What is Triple Extension?

Alright, let’s start with the basics.

The term “extension” refers to a movement that increases the angle between two body parts. Or, in a more visual explanation, picture one of your joints, like an elbow or a knee; when you straighten out the body parts connected to the joint (making the joint angle bigger), that’s extension.

It’s a super simple mechanic, but one that’s irrefutably vital in our everyday movement.

Now, when we talk about triple extension, you can probably infer from the name that it refers to extension times three, which is exactly what it is. But, more specifically, it’s the simultaneous extension of the three main joints in your lower extremities: the hip, knee, and ankle joints. 

Let’s think about it in regards to your running cycle. While running, triple extension should occur when the leg behind you pushes off the ground to propel you forward into your next step. This means that triple extension makes up 50% of your running cycle… so there’s no escaping the importance of this one, folks.

Triple Extension and Running Performance

To fully understand why triple extension is so vital for optimal running, it’s helpful to think of your running form in relation to the mechanics of a spring. 

The first half of your running cycle is like the compression of the spring — it’s all about absorbing shock. From the initial moment where your foot hits the ground to the middle of your gait cycle, all your joints are flexed (or bent) to absorb the impact of your step.

Shock Absorption

From that midpoint in your gait, your body will transition from absorbing shock to releasing it. With enough range of motion, strength, and tendon stiffness in your lower extremities, your body can “store” the energy from that initial shock absorption. When that energy is released, the force is exerted through the leg that’s pushing off the ground for your next step. And that “spring” action is what creates the motion of triple extension.

If the concept still feels a little abstract, take a look at the images here. As you can see, when your joints are flexed, they’re “compressed” and primed for shock absorption. In order for the spring to fully release, you need to achieve extension at your hip, knee, and ankle. If any one of these three joints don’t extend, it’ll ultimately decrease the power of the spring release, thus decreasing your ability to produce the most efficient energy use to propel you forward. (We’ll break down those power dynamics in a second.)

Additionally, you also want to be sure that all three joints are extending at the same time, otherwise you’ll decrease the amount of power generation in each step.

You can think of it this way: if one coil of a spring is bent, it won’t function as well. That same principle applies to your biomechanics, too! The more synchronized your joints are when they move into extension, the greater the power in your step. And, the more power you generate, the less energy your body has to use to push your body forward.

Now that’s efficiency.

Triple Extension and Injury Prevention

Before we dive into the science behind power generation, it’s also important to address the extra benefit of preventing future injury (or reinjury). 

Full triple extension is a vital piece of running form. Without it, you can experience the same issues as any other biomechanical deficiency — an increased likelihood of injury or overuse. If left unaddressed, it can ultimately lead to undue stress on your body over time and cause a plethora of common running injuries, such as:

A lot of room for injury, right? It’s not a fun realization, but it makes sense when you consider how triple extension involves a majority of your lower extremity. Improper form on this one movement can leave you prone to any of these pathologies as a result of poor shock absorption and increased impact forces (among other issues).

So, remember that optimizing your triple extension will not only improve your running performance, but also keep you injury-free and capable of running for decades to come.

Hip Extension and Running Form

Most research correlating triple extension with running speed and running economy primarily highlights two of the three joints: the hips and the ankles. Because each joint comes with extremely specific biomechanics and limitations, let’s take a moment (or several) to break things down in more detail for a true understanding of triple extension and running form, starting with the hip joint first.

As mentioned earlier, extension often involves straightening out the bend in a joint; but that can be a little hard to visualize when it comes to your hips. Instead, we can think of it relative to its opposite motion of hip flexion. Hip flexion occurs any time when you move your thigh closer to your chest — and that includes movement ranging from bringing your knee up to your chest to taking a tiny step forward.

Hip Flexion and Extension

Whenever your thigh moves further away from your chest (or moves behind the rest of your body), that’s hip extension. Extension can go as far back as the wind-up before kicking a soccer ball, or it can be as simple as standing up from a seated position. Check out the images exemplifying what hip flexion and extension look like in the context of a typical running gait. 

Muscles Used in Hip Extension

Now that you know the basics, let’s review a bit of the musculature behind the movement.

According to electromyography (EMG) studies on running form, the main muscles responsible for hip extension are the gluteal muscles and the hamstrings (your butt and thighs, respectively). These muscles actively stretch and store energy under load, which is what drives the hip into extension as they contract and pull your thigh bone backwards.

But it’s not just muscle contraction that allows for proper extension; you’ll also need a certain level of flexibility in the iliopsoas muscle (a primary hip flexor) in order for the hip to move into extension.

These elements will contribute to a greater range of motion in your hips’ extension capabilities, which is beneficial in more than one way. Not only will a greater range of motion improve your triple extension, but it can also lead to a greater stride length, which is an excellent method for increasing your cadence and running speed.

Common Limitations for Hip Extension

Unfortunately, while hip extension is an entirely natural and common piece of our everyday movement, we don’t practice it enough on our day-to-day to have extension optimal enough for powerful running. This results in it being one of the most common running form errors that increases runners’ risk of injury and prevents them from optimizing their speed and efficiency.

What’s even more frustrating is that there isn’t just one reason you may experience limited hip extension; there are a handful of usual culprits that countless runners have had to contend with.

But we’re not here just to be the bearer of bad news! Where there are problems, there are solutions — read on to figure out what common causes lead to limited hip extension and how you can sidestep them in your own running career.

Limitation #1: Tight Hip Flexors

Tight hip flexors are extremely common in runners, and it’s almost always a product of a sedentary work lifestyle. A majority of people have desk jobs where they sit for extended periods of time, leaving the hip flexor in a shortened position for hours on end. Day after day, week after week, the hip flexor adapts to this shortened length as its default position… and that’s all bad.

Running requires your hip flexors to move in the exact opposite posture as sitting; your hip flexors need to be flexible and capable of fully stretching and lengthening. (Not to mention, they have to do so under load for countless rapid, repetitive movements with every step you take!)

Hip Flexors

Without proper warm-up, stretching, and mobility work, your hip flexors will be far from prepared to take on the demands of running. This will create a direct barrier to proper hip extension, thus preventing proper triple extension as well.

Make sure you make time in your schedule to keep up with those essential hip flexor stretches on a regular basis (daily, in the most ideal situation). In tandem with active stretching, also find alternative working or living environments that can help you avoid sitting for prolonged periods of time.

Limitation #2: Poor Gluteal Strength and Activation

You’ve probably heard this in some form or another: weak glutes, inactive glutes, glutes that aren’t firing properly… the list goes on and on. Which is frustrating, because most people know it’s a problem, but they don’t necessarily know when it’s a problem (or why, for that matter).

The issue boils down to finding the right way to cue your brain to “turn on” your glute muscles properly. The most effective way to do so is by practicing specific drills and movements that prime these muscles for activity. Using resistance bands and gluteal-specific hip movements can retrain the body to focus on gluteal activation while running.

And that’s the real key here — activation. Yes, strengthening your glutes is important, but it won’t be nearly as effective without knowing how to properly activate the muscles to begin with. If you want to get the most power out of your glutes for optimal hip extension, focus on performing single-leg activation and strengthening exercises, as this will more accurately emulate the single-leg movements of running.

Limitation #3: Weak Hamstrings

The role of the hamstrings within hip extension is important, but it isn’t quite as prevalent as the hip flexors or gluteal muscles. (At least not for distance runners; it’s imperative for sprinters, but you otherwise don’t need to focus on your hamstrings as the main goal.)

Rather than go super in-depth with improving hamstring strength, we’ll primarily just advise that runners perform exercises in a similar fashion as gluteal strengthening: focus on single-leg hamstring strengthening drills to best mimic running biomechanics and get your muscle groups familiar with similar motions.

Ankle Plantar Flexion and Running Form

Hip extension aside, most studies on the relationship between triple extension and running performance focus on the biomechanics of ankle plantar flexion.

But before we dive into the specifics behind how the ankle contributes to optimal running, let’s first address the elephant in the room: what the heck is ankle plantar flexion?

Well, it’s actually just the lengthier, more-official terminology for ankle extension. Hence why it’s called “triple extension,” rather than “hip and knee extension, plus ankle plantar flexion.” (But also, no one has time to say that mouthful every time.) It occurs any time your foot moves away from your shin, like when you press on the gas pedal in your car or when you push your toes into the ground to stand on your toes.

Just like hip extension, it’s an extremely natural and common part of our everyday movement — but from a biomechanical perspective, it’s much more complicated and vital than we realize…

Muscles Used in Ankle Plantar Flexion

Although the extension occurs at the site of your ankle, the actual movement is a result of the power and mechanics generated by several muscles in your calves

Similar to how your gluteal muscles operate, your calf muscles elongate during the shock absorption phase of your running gait. This places them under eccentric load, meaning they can store a great deal of energy from that initial impact that will then be released during the push-off into your next step.

Plantar Flexion

Take a look at the images here; as you can see, when your ankle is flexed (more specifically known as dorsiflexion), your muscle is lengthened and under load during the shock absorption of your landing. Then, as you move into plantar flexion, the muscle contracts and releases the absorbed energy in that spring-like action.

Common Limitations for Ankle Plantar Flexion

Unfortunately, just as with hip extension, there are several common limitations that can impede your ankles from full plantar flexion — especially in the context of running.

This one may be a dead giveaway, but restricted range of motion in your ankle joint can be extremely limiting in achieving full plantar flexion. Most people tend to struggle with ankle range of motion as a result of external issues, such as previous injury, muscle stiffness, or other conditions such as arthritis.

Most people, however, tend to struggle more with insufficient calf muscle strength. Which is saying a lot, considering how the gastrocnemius (the main muscle of your calves) is unquestionably strong enough to easily lift your body weight during single-leg calf raises.

But that’s the difference: in running, you need enough calf strength to produce power and speed against forces that can add up to 3 times your body weight. And it’s important to remember that these forces occur with every step you take, so your calves require a significant amount of strength to generate enough power through the duration of a run.

It’s essential to perform single-leg calf strength exercises (i.e., calf raises off a step) on a regular basis to develop sufficient muscle strength and improve your running biomechanics. You can even consider adding weight during your exercises to “simulate” the forces of running to help familiarize your calf muscles with the repetitive and impactful nature of running.

How to Achieve Full Triple Extension

Alright, here’s the part you’ve been waiting for: actionable steps to actually get better.

The earlier sections touched upon a few key tips to ensure proper hip extension and ankle plantar flexion (like improving joint mobility in addition to stretching, strengthening, and activating muscles). Consistent training for each of these exercises will provide the necessary foundation for your range of motion and strength.

Which is all well and good… but it’s certainly not the end!

Once you’ve established that foundation for optimal muscle and joint biomechanics, you can focus on the next critical components of coordination, synchronization, and power.

You might be thinking that coordination shouldn’t be much of an issue; it seems intuitive that all three joints should extend simultaneously. But, more often than not, one or more of the joints extend asynchronously as a result of any of the foundational issues mentioned above.

Single-Leg Drill

Improving synchronization between all three joints requires deliberate practice — and that means loads of single-leg running drills with a position of emphasis (in other words, drills that move the body from peak shock absorption to triple extension). This will allow your lower extremities to adapt to the motion in a manner that best emulates running biomechanics.

While strengthening drills are key for muscle development and power generation, most of these exercises don’t put the hip in full extension. That’s why it’s imperative to include exercises specifically targeting the triple extension motion; certain drills like hip thrusters with a superband are a perfect match to your running form and provide ideal specificity in the motion.

Another means of improving your triple extension involves double- and single-leg power drills (i.e., box jumps, double- and single-leg bounding, and high skipping). Each of these drills involve a high amount of force over a short period of time and demand full triple extension for the most optimal results, making them perfect for enhancing that synchronized extension.


There you have it! The vital (yet often overlooked) element to generating enough power per step to improve your running performance, speed, and efficiency.

Keep in mind that, even though triple extension is a natural part of our biomechanics, there are a plethora of seemingly unrelated issues that can interfere with optimal results. As with most running-related training, it’s important to start with the basics (the mechanics and form of each individual joint!) before you dive into the big picture.

Once you master the entirety of your triple extension, say hello to better and faster running! So don’t hold yourself back from that extra power boost — go forth and train, fellow runner!

Triple Extension

By Dr. Kevin Vandi DPT OCS CSCS

Dr. Vandi is the founder of Competitive EDGE Physical Therapy — with his background in physical therapy, orthopedics, and biomechanics, he is a highly educated, compassionate specialist. Using state-of-the-art motion analysis technology and data-driven methodologies, Kevin has assisted a wide range of clients, from post-surgery patients to youth and professional athletes. When he isn’t busy working or reading research, he spends his time with his wife Chrissy and their five wonderful children, often enjoying the outdoors and staying committed to an active lifestyle.

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