As we know how important it is, for runners, to maintain optimal running form to maximize efficiency and to prevent injury. One method to optimize running form for injury prevention is to maintain and appropriate Z angle.
The Z angle is formed by analyzing running from side and measuring joint angles at your hip and ankle. 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 to find ‘z’ angle?
• Obtain a still photo of you running, shot from the either 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. ( 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.
Deviations and treatment :
If ankle of dorsiflexion is less, then athlet’s Z angle will show bigger angle at ankle than at hip. This means
• Gastro and soleus are tight, and
• Tebialis anterior is weak
The correction regime includes,
• Stretching of gastro and soleus, and
• Strengthening of tebialis anterior
If hip extension is less, this means
• Hip flexor and rectus femoris tightness and
• Hip extensors weakness
The correctional regime includes,
• Stretching of hip flexors and rectus femoris
• Glute strengthening.
free full text :
1. Ferber R, et al. Suspected Mechanisms in the Cause of Overuse Running Injuries: A Clinical Review. Athletic Training. 2009.
2. 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.
3. Schmitz A, et al. Do Novice Runners Have Weak Hips and Bad Running Form? Gait Posture. 40(1). 2014. 82-6.
image courtesy: capitalregionpt.com, flexible.com