Thinking about running form? Here’s why your arm swing matters

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In the context of running, much of our attention is put on the lower half of our bodies with respect to what we’re doing with our feet, legs, and hips. But, there are actually some important things happening on our upper bodies that — with a little attention and help — could improve our running economy and enhance performance. In our last post, we discussed running and posture; here, we’ll talk about the importance of arm swings and how it affects our balance and stability. (hint: it actually still has a lot to do with your posture).

Arms vs. Legs

Let’s consider the human body as a well-oiled machine and think back to Physics class and Newton’s Third Law of Motion: “for every action, there is an equal and opposite reaction”. Putting this in the context of running, your arm swings are both the reaction and action to your legs’ motion, and thus, balances out the momentum to help create stability in your form.

Related: Why you should swing your arms when you run

Think of it this way: when taking a step with your left leg, your pelvis, core, and shoulders are naturally inclined to rotate slightly to the right (unless you have perfectly flexible hip flexors). To counter this, your left arm ideally swings straight back to help keep your core facing in the forward direction and avoid excess rotation from side to side. If both your legs and arms swung in the same direction, you’ll find that your body will rotate side to side much more.

Luckily, we are naturally hard-wired to swing our arms and legs in opposite directions, so this isn’t something you have to go out of your way to account for. However, what is common amongst runners and should be avoided are cross-over arm swings.

Cross-over arm swings are when your hand and arm swing across your midline into the opposite side of your body. This causes and reinforces excess pelvic rotation which wastes a whole lot of energy to return yourself to a neutral pelvis.

Taking a step back to Newton’s Third Law; if our arm movements are counter movements to our legs — you guessed it — cross-over arm swings often come hand in hand with cross-over steps, and vice versa. In other words, poor form on our upper body influences your form on the lower body. In terms of correction, this raises an interesting question: which came first? The cross-over arm swing or cross-over step?


The Ideal and Correction

Here’s this for a twist: the cause for cross-overs — either arms or legs — is likely from a weak core and poor posture. These flailing extremities we call arms and legs are at the very end of our kinetic whip, and movement problems here can likely to fixed at the root of the problem — your core. Your core is the source of power for all of the movements that fuel the mechanics of running, so a weakened power source results in poor posture and undesirable movement patterns on our limbs; putting you at risk for injury and inhibiting your performance.

The ideal arm swing for long distance running is a clean, straight swing back past your hips — as if you were reaching for something in your back pocket. Your hands should make a slight fist like you are holding an egg shell between your thumb and fingers; your elbow should be at a comfortable 90-degrees; your shoulders should be relaxed, pulled back, and down; and your scapula — shoulder blades — should be pulled back together as if you were crushing an imaginary cookie between the blades. However, as we talked about earlier, our bodies are naturally inclined to swing back to counter the movement of our legs, so the main focus shouldn’t be on over-swinging, but rather setting your upper body up for success by maintaining good, upright posture as you run. This gives your arms the opportunity and ability to swing back correctly and reduce the chances of cross-over steps and excessive pelvic rotation.


Exercises and Drills

Poor upper body posture usually plagues the average runner as fatigue sets in. As we tire both mentally and physically, we tend to slump over and forget to engage our core to maintain good, upright posture. They key here is to strengthen your core and back muscles, specifically around the scapula, so that good posture becomes second nature and the stage is set for your arms to swing straight back and out. Here are some drills and exercises you can do:


Line Drills

On your running path, find a thin line and run with one foot on each side of the line — this line will represent your midline. As you run along the path, make sure that neither your feet nor your arms cross over this line. This will help you avoid cross-overs swings and steps, and reduce your pelvic rotation.


Foam Rollers

Foam rollers are great tools for stretching and exercises for posture. Here’s a collection of exercises you can do with a foam roller to release built up tension in your back.



Corner Wall Push

This is a Lumo favorite for practicing tightening the scapula muscles. Find a corner in a room and stand in front of it facing where the two walls meet. Place your palms against each wall, and place one foot in to the corner. Hold this position for 30 seconds, switch your feet and repeat.





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Ellie Kulick

About Ellie Kulick

Ellie specializes in all things content and communications at Lumo BodyTech. Her passions are in tech, writing and in health. She loves to create and share content that is useful and easily digested by the reader. BS in Psychology, Northeastern University. Find Ellie on Twitter.

1 Comment

  • Richard Diaz
    Richard Diaz

    I would agree on the front end of your post. Your arms and legs are tied and entrainment is the result of flaws that are reflected from one to the other and they must be be corrected to have a successful gait. However, your core only has influence once you are in contact with the ground. If your arm swing crosses your boy as you over stride, your core is put into a compromised position that no amount of core training can rebuff. A good arm swing and a solid contact with the earth near center of mass with time will correct a weak core because the entire kinetic chain is engaged in proper recruitment and loading. Its a matter of the chick before the egg.

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