What movement do we do more than any other these days? It’s sitting. We sit in the car, at our desk, and probably on the couch in front of the TV. Sitting is something we probably do for more hours than any other activity, possibly even more than sleeping. According to one reference, those in Western cultures typically sit for 8-11 hours per day, yet we probably haven’t considered its impacts. So what effect does all this sitting have on our body? What happens, anatomically, when we sit? Can we sit better? In this article, we’ll explore some answers to these questions and look more closely at sitting through the lens of anatomy.

Anatomy of sitting posture

There is one thing that’s true anatomically for all the ways that we sit. We remove the legs from the job they do in supporting us when we switch from standing to sitting. The pelvis becomes our base. In order to do that, we flex our hip joints. If we’re standing or lying on our back, our hip joints are in roughly what we describe as neutral. That is, they’re not flexed and making the angle at the hip joint smaller. Neither are the hip joints extended, making the angle at the hip joint larger.

Photo	Title	Buy
	Comfytemp Cordless Heating Pad with Massager for Back FSA Eligible HSA Gift

Slumping

However, not surprisingly, much of what happens to our body anatomically when we sit depends on how we sit. The biomechanics of what happens in our lumbar spine, for example, change depending on whether we’re slumped, either in a chair or on the floor, or whether we are sitting tall and erect on the edge of a chair or stool. If we slump, we typically roll onto the posterior part of our ischial tuberosities, or even behind them, and flex our lumbar spine. Then, in order to get our eyes gazing back out to the horizon, or computer screen, we make additional compensations along our thoracic and cervical spines to lift our head. 

Sitting tall

In contrast, when we sit tall and erect in a chair or on the edge of a stool, we are sitting on the anterior portion of our ischial tuberosities, with our lumbar spine slightly extended. While we may still make creative compensations with the thoracic and cervical portions of our spine, it is generally easier to stack our torso and head over our pelvic and lumbar base if we have our pelvis and lumbar spine in this position.

Issues with sitting

Negative effects of being sedentary

Why does sitting get such a bad rap these days? There are really two separate issues with lengthy periods of sitting. One is that if we’re seated for a long period of time, obviously, we’re sedentary. And, regularly spending long stretches of time being sedentary has negative consequences for our health, regardless of what position our body is in. There are many problems associated with increased hours of being sedentary. Significant sedentary time is correlated with negative effects on cardiovascular and metabolic health, and is even associated with negative effects on cognitive function.

Problems with sitting posture

Separately, the issue is the posture of sitting itself. Sitting is not necessarily a bad posture per se, but specifically how we sit may be more or less ideal. Often, our choice of sitting posture is less biomechanically ideal. We slouch in chairs or lounge on couches. We stop training our body to hold itself upright when we sit.

All of the postural adaptations to a lengthy session in a slumped seated position can add up to aches and pains. Negative effects of the many variations of slumping postures include increased back and neck pain, other body aches and pains, and increased muscle fatigue, even for daily functional tasks. Poor sitting posture specifically can also increase pressure on the lumbar vertebral discs and exacerbate issues with the low back.

Photo	Title	Buy
	TENS 7000 Digital TENS Unit with Accessories - Muscle Stimulator Machine for Back Pain Relief, Sciatica, Neck, Nerve, Shoulder, Hip, Elbow, Muscle Pain Relief

Finally, there is the effect of maintaining any one posture for hours each day, a sitting posture in this case. If we want to do a desired activity, like run a marathon, for example, we typically need to train. If we spend many hours running every day, maintaining that one posture will affect our body. Some muscles will get tighter, making it easier to run long distances or run faster. But it will also make it harder to do other things, like reach into a deep forward fold in yoga. When we electively choose an activity, we probably accept its pros and cons. However, we likely haven’t thought much about how best to train our body to sit.

Ideal sitting posture

Can we sit better? The answer seems to be yes. The effects of being sedentary for long stretches, associated with prolonged sitting, may remain. However, anatomically, it seems that we can sit better and reduce some of the problems associated with sitting posture. Tom Myers of Anatomy Trains describes proper balance in sitting as maintaining an appropriate amount of the lordotic and kyphotic curves that should appear in our spine, and give it some of its strength and resiliency. Ideally, there is a balance between the tissues on the front and back of our body, holding us up.

We can look for that balance in sitting posture by establishing our pelvic base on the anterior part of our ischial tuberosities. Several references suggest that we aim for an angle of 135 degrees between the thigh and spine when sitting on the edge of a chair or a stool. Then, with your spine in extension, stack the torso, head, and neck comfortably over one another. Optimally, our torso, head, and neck are not significantly in front of or behind the acetabulum of the hip joints. Arranging our body with this orientation and relationship lets gravity help us keep these heavy parts of our body resting over one another. 

Reducing the negative effects of sitting

The obvious way to reduce the negative effects of sitting is to sit less. But we don’t always have a choice about how much we have to sit, especially in our work environments. So, the next best option is twofold. First, take frequent breaks from sitting during the day. Interrupt your time sitting as frequently as is practical by getting up to stretch, take a walk, or work from a different position. If sit-stand work stations are available in your work space, that’s one option for breaking up the long stretches of sitting and varying your position. Finally, when you do sit, practice using a more anatomically ideal sitting posture.

Conclusion

Many of us have to sit for hours every day, and often, some of the sitting we do is not optional. We may have little choice about how long we sit at work, for example. But we do have control over how we sit, and we can incorporate more frequent breaks to interrupt longer stretches of sitting. Incorporating just these two changes can help reduce the negative impacts of sitting posture. 

References

Chaitow, L. and J. DeLany. 2011. Chapter 4: The Close Environment. In Clinical Application of Neuromuscular Techniques – The Lower Body. Volume 2 (Second Edition). New York, NY: Churchill Livingstone Publishing.

Cho, M., J.S. Han, S. Kang, et al. 2023. Biomechanical effects of different sitting postures and physiologic movements on the lumbar spine: A finite element study. Bioengineering (Basel). 10(9):1051.

Kallings, L.V., V. Blom, B. Ekblom, et al. 2021. Workplace sitting is associated with self-reported general health and back/neck pain: a cross-sectional analysis in 44,978 employees. BMC Public Health. 21(1):875.

Lurati, A.R. 2018. Health issues and injury risks associated with prolonged sitting and sedentary lifestyles. Workplace Health Saf. 66(6):285-290.

Myers, T. W. 2014. Chapter 10: Anatomy Trains in Training. In: Anatomy Trains. (New York: Churchill Livingstone). p.224-225.

Ten Broeke P., B. Gardner, D.G.J. Beckers, S.A.E. Geurts, and E. Bijleveld. 2023. Why do people sit? A framework for targeted behavior change. Health Psychol Rev. 17(4):641-654.

Latest Posts