HomeArticlesBack PainHip-Driven vs Trunk-Driven

Hip-Driven vs Trunk-Driven

This is Form and Function in action...

When we squat, our ankles, knees, and hips flex, as our pelvis and spine extend as seen in the drawing on the right. [1] When our lower limbs can function and flex, our hips drive the squatting motion as our upper body stays upright.

When our lower joints can’t flex, we make up for that “missing flexion” by flexing our pelvis and spine as seen on the left.

This puts us in a “trunk-driven” motion because we aren’t able to move the lower joints well anymore.

The function we have affects the position of our body, and the position of our body affects the way we function.

In 2016 a study was done to further learn how our trunk position affects our lower back, thigh, and butt muscles. The study had individuals squat with 3 different trunk angles, 0, 15, and 30 degrees. [2]

This study found that when the trunk leans forward, the thigh muscles are less active, and the lower back muscles become more active.

In a 30-degree forward trunk position, more like the drawing on the left, the lower back muscles contracted under length which exponentially increased the load and stress on the lower back muscles and greatly increased the pressure within the disc.  [2,10,20]

When the trunk position remained at 0 degrees, meaning it was upright as shown in the drawing on the right, the thigh muscles, mainly the rectus femoris, became more active while the lower back and hamstring work reduced to normal levels.

This study was effective in showing how position affects function, but it only looked for correlation, not causation.

All the participants had a capacity to squat with an upright trunk.

Most people currently only have the option to throw their trunk forward due to lack of function in the ankles, knees, hips, and pelvis, which increases the risk of a back injury and pain.

If your body functions more like the drawing on the left with limited joint motion so you have to recruit excessive movement and flexion from your pelvis and spine, then just back exercises or hip stretches won’t help much – if they help at all.

This squatting Trunk-Driven movement is a great example of showing why usually where we hurt is never where the real problem is.

If your back has to involuntarily hijack your movement in the first place due to the body not functioning well as a single unit anymore – the back isn’t the problem. It’s the victim, and the criminal is what the rest of your body is doing…

What I don’t want is for anyone to read this and force themselves upright – if your body could, it would.

Let’s look at why it isn’t naturally upright and work on things from there.

So if you’re someone whose squat just doesn’t feel “right”, or you experience pain while doing this motion – let’s not target what hurts. Let’s show your ankles, knees, hips, pelvis, spine, and shoulders how to work better together and watch what happens to how you’re moving and feeling while squatting now.

If you are interested in learning how to move and feel better, click through our website more – I recommend starting off by clicking How It Works in the navigation menu to learn more about how we can help before you enroll in our Online Program. 

Remember, if you join, you won’t find any area-specific pain exercises, because we aren’t here to teach you how to continue chasing symptoms – we are here to help you go after what’s creating symptoms in the first place.

[1] Palmitier RA, An KN, Scott SG, et al. : Kinetic chain exercise in knee rehabilitation. Sports Med, 1991, 11: 402–413.

[2]  Tae-Sik Lee, Min-Young Song, Yu-Jeong Kwon J, Activation of back and lower limb muscles during squat exercises with different trunk flexion. Phys Ther Sci. 2016 Dec; 28(12): 3407–3410. 2016 Dec 27.

2. Marín PJ, Santos-Lozano A, Santin-Medeiros F, et al. : A comparison of training intensity between whole-body vibration and conventional squat exercise. J Electromyogr Kinesiol, 2011, 21: 616–621.

3. Lötters F, Burdorf A, Kuiper J, et al. : Model for the work-relatedness of low-back pain. Scand J Work Environ Health, 2003, 29: 431–440.

4. Marras WS, Lavender SA, Leurgans SE, et al. : Biomechanical risk factors for occupationally related low back disorders. Ergonomics, 1995, 38: 377–410.

5. Xu Y, Bach E, Orhede E: Work environment and low back pain: the influence of occupational activities. Occup Environ Med, 1997, 54: 741–745.

6. Lee D, Lee S, Park J: Impact of decline-board squat exercises and knee joint angles on the muscle activity of the lower limbs. J Phys Ther Sci, 2015, 27: 2617–2619.

7. Lee TK, Park SM, Yun SB, et al. : Analysis of vastus lateralis and vastus medialis oblique muscle activation during squat exercise with and without a variety of tools in normal adults. J Phys Ther Sci, 2016, 28: 1071–1073.

8. Jang E, Heo H, Kim M, et al. : Activation of VMO and VL in squat exercises for women with different hip adduction loads. J Phys Ther Sci, 2013, 25: 257–258.

9. Kang MH, Jang JH, Kim TH, et al. : Effects of shoulder flexion loaded by an elastic tubing band on emg activity of the gluteal muscles during squat exercises. J Phys Ther Sci, 2014, 26: 1787–1789.

10. Hwang S, Kim Y, Kim Y: Lower extremity joint kinetics and lumbar curvature during squat and stoop lifting. BMC Musculoskelet Disord, 2009, 10: 15.

11. List R, Gülay T, Stoop M, et al. : Kinematics of the trunk and the lower extremities during restricted and unrestricted squats. J Strength Cond Res, 2013, 27: 1529–1538.

12. Mens JM, Vleeming A, Snijders CJ, et al. : Reliability and validity of the active straight leg raise test in posterior pelvic pain since pregnancy. Spine, 2001, 26: 1167–1171.

13. Hermens HJ, Freriks B, Merletti R, et al. : SENIAM 8: European recommendations for surface electromyography, deliverable of the SENIAM project. Enschede: Roessingh Research and Development, 1999.

14. Merletti R, Tonio P: Standards for reporting EMG data. J Electromyogr Kinesiol, 1999, 9: 3–5.

15. Hedrick A: Training the trunk for improved athletic performance. Strength Condit J, 2000, 22: 50–61.

16. Jamison ST, McNeilan RJ, Young GS, et al. : Randomized controlled trial of the effects of a trunk stabilization program on trunk control and knee loading. Med Sci Sports Exerc, 2012, 44: 1924–1934.

17. Iida Y, Kanehisa H, Inaba Y, et al. : Role of the coordinated activities of trunk and lower limb muscles during the landing-to-jump movement. Eur J Appl Physiol, 2012, 112: 2223–2232.

18. Kopper B, Ureczky D, Tihanyi J: Trunk position influences joint activation pattern and physical performance during vertical jumping. Acta Physiol Hung, 2012, 99: 194–2015

19. Bryanton MA, Carey JP, Kennedy MD, et al. : Quadriceps effort during squat exercise depends on hip extensor muscle strategy. Sports Biomech, 2015, 14: 122–138.

20. Rohlmannt A, Claes LE, Bergmannt G, et al. : Comparison of intradiscal pressures and spinal fixator loads for different body positions and exercises. Ergonomics, 2001, 44: 781–794.

21. Albayrak A, van Veelen MA, Prins JF, et al. : A newly designed ergonomic body support for surgeons. Surg Endosc, 2007, 21: 1835–1840.

22. Albayrak A, Richard HM, Snijders CJ, et al.: Impact of a chest support on lower back muscles activity during forward bending. Appl Bionics Biomech, 2010, 7: 131–142.

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15 thoughts on “Hip-Driven vs Trunk-Driven

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    1. Thank you for sharing! I did write a book more on the mental/emotional journey it takes and the lessons needed to navigate the road to restoring the body. I would love to write more on the mechanical aspects of function! It seems like there is a huge need for that content just based on the comments I’m reading on this. Thank you for sharing!

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  6. Great article! Brought back memories! My coach taught us to learn squat facing the wall! No weights allowed until full form was achieved with body weight.

    1. Now that was a great coach! My coaches back in the day just put weight on… and left the rest up to me. What sport did you play?

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