Butt wink

A common issue during squats- known as butt wink- is simply lower back flexion combined with a posteriorly tilting pelvis during a deep squat. This movement may not be the best option for the body, as it places unnecessary stress on the structures of the spine. Posterior pelvic tilt, coupled with lumbar spine flexion, results in compressive and shear forces occurring at the lower back. [1] [2] Maintaining a neutral spine while lifting is crucial for both spinal health and optimal power transfer throughout the body. [3]

For a proper squat, the spine and trunk must remain in a neutral position, with the heels in contact with the floor. When struggling with butt wink, many assume it’s due to a lack of hip flexion.

While hip flexion is important, a butt winked squat requires roughly the same amount of it as a standard one, so it’s not the determining factor. [4]

The key difference between a proper squat and a butt winked one, lies in the amount of ankle flexion. When ankle dorsiflexion is restricted, squat depth is restricted too. [5] Studies report that the average ankle dorsiflexion angle required for a proper deep squat is 38.5±5.9°. [6]

To understand why, let’s think of a squat as a balance exercise, where the goal is to keep the center of your body over the midfoot line. With good ankle flexion, people can bring hips closer to that midline, allowing the upper body to stay more upright.

When ankle range of motion or stability is limited during deep squatting, it can inhibit the performance of proximal joints. [7] Hips are forced backward, which, to prevent falling, forces your lower spine to compensate by bending as much as it can to help your upper body stay in the vertical line drawn from the midfoot (the green zone on the film).

By improving ankle flexion, the butt wink will disappear.

  1. Potvin, J. R., i in. „Trunk Muscle and Lumbar Ligament Contributions to Dynamic Lifts with Varying Degrees of Trunk Flexion”. Spine, t. 16, nr 9, September 1991, s. 1099–107. PubMed, https://doi.org/10.1097/00007632-199109000-00015
  2. Straub, Rachel K., i Christopher M. Powers. „A Biomechanical Review of the Squat Exercise: Implications for Clinical Practice”. International Journal of Sports Physical Therapy, t. 19, nr 4, s. 490–501. PubMed Central, https://doi.org/10.26603/001c.94600
  3. Long, Z. “The hip and Athletic Performance”. The CrossFit Journal, April 2015
  4. Kim, Sukbum, i in. „Relationships between physical characteristics and biomechanics of lower extremity during the squat”. Journal of Exercise Science and Fitness, t. 19, nr 4, October 2021, s. 269–77. PubMed Central, https://doi.org/10.1016/j.jesf.2021.09.002
  5. Kim, Si-Hyun, i in. „Lower Extremity Strength and the Range of Motion in Relation to Squat Depth”. Journal of Human Kinetics, t. 45, April 2015, s. 59–69. PubMed Central, https://doi.org/10.1515/hukin-2015-0007
  6. Hemmerich, A., i in. „Hip, Knee, and Ankle Kinematics of High Range of Motion Activities of Daily Living”. Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society, t. 24, nr 4, April 2006, s. 770–81. PubMed, https://doi.org/10.1002/jor.20114
  7. Butler, Robert J., i in. „Biomechanical Analysis of the Different Classifications of the Functional Movement Screen Deep Squat Test”. Sports Biomechanics, t. 9, nr 4, November 2010, s. 270–79. PubMed, https://doi.org/10.1080/14763141.2010.539623
anklebiomechanicsbutt winkexerciseshiplower backmobilitypelvic tiltpelvisspinesquat
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