Optimize Your Z Angle for Injury-Free Running

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Question: My physical therapist analyzed my running form using video gait analysis technology and she said I needed to work on my Z angle. What is the Z angle, and why is it important in running mechanics?

The Gait Guys define the Z angle as: "hip extension should equal ankle dorsiflexion and vice versa." (Hip extension is the direction of your hip moving towards the back of your body. Ankle dorsiflexion is the movement of your toes and ankle being flexed up towards your knee.) The Z angle is formed by the connection of your hip and ankle, and optimizing it may be the key to pain-free running and improved running efficiency.

Running and the Mystical Z Angle

If you are a runner, then you understand how important it is to maintain optimal running form to maximize efficiency and to prevent injury. Your physical therapist can analyze your running gait pattern and help you determine the best running form to keep you on the road and out of the rehab clinic.

One method to optimize your running form for injury prevention is to maintain an appropriate Z angle. This angle is formed by analyzing your running from the side and measuring joint angles at your hips and ankles. The Z angle is the angle formed by your hips and ankles when your foot is on the ground, just prior to a terminal stance.

How Do I Find My Z Angle?

Finding your Z angle is easy—if you have the right tools. Here's how to find your Z angle (you may need some help with this):

  • Obtain a still photo of you running, shot from the side. Your back foot should be on the ground, but just about to leave the ground in terminal stance. Your front leg should be up in the air and flexed in front of you. (The best way to obtain this photo is a video analyzing app like Dartfish. You'll need a friend or PT to take the video of you running on a treadmill.)
  • Once you have the photo, draw a line through your hip joint that is parallel to the plane of the top of your pelvis.
  • Draw a line along your stance leg extending down from your hip to your ankle.
  • Draw a line from your ankle joint, through your foot, and to your toes.

The three lines you have drawn should form the shape of the letter "Z." This is your Z angle.

The optimal Z angle should show that your hip extension range of motion is equal to your ankle dorsiflexion range of motion. Your letter Z should look like a symmetrical letter. If your letter Z is altered in any way, it could mean that you have some running gait deviations that may need to be addressed to optimize efficiency and to possibly prevent injury.

I Have My Z Angle—Now What?

Correcting your running form can be tough. We've all been running since our earliest days on the playground, and making a change now in your adult life can be difficult. But, if you perform the right exercises for your specific Z angle, you may be able to make slight changes that can optimize your running form. Your physical therapist should be able to analyze your specific Z angle and prescribe the best exercises for your Z angle deviations.

Start from the ground up by looking at your ankle position. If your ankle dorsiflexion range of motion is limited, your Z angle may show a bigger angle at your foot than at your hip. This may indicate your calf and soleus muscles are tight and your anterior tibialis is weak or inhibited. Exercises for you may include:

Next, turn your attention to your hip. If your Z angle indicates a lack of hip extension, as evidenced by a bigger angle at your hip than at your ankle, you may need to do exercises that may include:

These exercises help to improve your hip's ability to fully extend while you are running, keeping your hip, knee, and ankle in an optimal position and helping to propel you forward with maximal efficiency. Research also shows that optimizing hip strength may play a role in preventing knee pain in runners.

Putting It All Together

So you've seen your physical therapist and have analyzed your Z angle. You have some exercises to work on to make some changes. Now what? Keep running, do your exercises, and check in with your PT in a few weeks to see if there has been any change in your Z angle.

So will perfecting your Z angle prevent all injuries? Probably not. Your goal for optimizing your Z angle is to maximize your running efficiency. Research indicates that runners whose gait deviates significantly from the Z angle may have an increased risk of problems with Achilles tendonitis and tendinopathy, knee pain, or hip problems. Maintaining Z angle can simply keep things in the best position possible while running. This may prevent overuse injuries, but there is no guarantee that it will.

If you do develop pain while running, a good first step is to hold off on running and check in with your physical therapist. He or she can analyze your gait, check your range of motion and strength, and prescribe exercises to help correct any deficiencies.

Running can be a rewarding sport, but it can also lead to overuse and repetitive strain injuries. Take a moment to visit your PT to check your Z angle, and then take the steps necessary to correct your running form to optimize your Z angle and to maximize efficiency and (hopefully) prevent injuries.

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Article Sources
  • Ferber R, et al. Suspected Mechanisms in the Cause of Overuse Running Injuries: A Clinical Review. Athletic Training. 2009.
  • Kim S and Yu J. Changes of Gait Parameters and Lower Limb Dynamics in Recreational Runners with Achilles Tendinopathy. J Sport Sci  Med. 2015. 284-89.
  • Schmitz A, et al.  Do Novice Runners Have Weak Hips and Bad Running Form? Gait Posture. 40(1). 2014. 82-6.