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Written by Tristan Hulbert, Vivid.Care. Author of “The Healthcare Professional’s Complete Guide to Specialist Seating Assessments”. Last updated: 3 August 2026.
Deconditioning and pressure ulcers share a root cause: immobility. Getting patients out of bed helps with both, but sitting isn’t a free win. It concentrates load over the ischial tuberosities and sacrum across a smaller contact area than lying does, so long unbroken periods of sitting carry their own risk for anybody who can’t reposition themselves. The answer isn’t to choose between the two harms – it’s to plan chair and bed repositioning as one schedule.
Immobility drives both problems through mechanisms that overlap almost entirely.
| Mechanism | Contribution to deconditioning | Contribution to pressure damage |
|---|---|---|
| Reduced movement | Muscle unloading and atrophy. Kortebein and colleagues (JAMA 2007) measured around 0.95kg of lean leg mass lost over ten days of bed rest in healthy older adults. | Sustained loading of the same tissue without relief. Most of us shift position constantly, including in our sleep. Patients who can’t, don’t. |
| Loss of muscle bulk | The direct measure of deconditioning. | Less soft tissue padding over bony prominences, so the same external load produces higher internal tissue stress. |
| Poor nutritional intake | A protein and energy deficit prevents muscle being maintained. | Impairs tissue repair and tolerance. A well-recognised factor in every pressure ulcer risk assessment. |
| Reduced sensation and cognition | Less participation in mobilisation, and higher delirium risk. | Reduced awareness of discomfort, which is the normal trigger for repositioning. |
| Incontinence and moisture | Often a consequence of not being able to reach a toilet. | Moisture-associated skin damage compounds pressure damage. |
Which means a ward addressing one and ignoring the other is doing half the same job twice.
Sitting concentrates body weight over a smaller contact area than lying, mainly over the ischial tuberosities and the sacrum. For a patient who can’t reposition themselves, long unbroken periods of sitting are a genuine pressure risk.
This is why sitting time limits appear in seating guidance, and why a sit-out plan without a repositioning plan is only half a plan.
Three things make seated risk different from lying risk.
Fit. A mattress is a flat surface that accommodates more or less any body. A chair is not. Seat width, depth and height all have to match the individual, and people vary enormously in their dimensions and proportions. A seat that is too deep makes the patient slide forwards; too wide and they lean to one side; too high and the feet dangle, which pushes load back onto the ischial tuberosities. Getting the sizing right does more for pressure distribution in a chair than any cushion will, and it is the part most often skipped.
Shear. A patient who slides forwards in a chair, usually because the seat is too deep or the back angle is wrong, generates shear at the sacrum as the skin stays put and the skeleton moves. Shear damage goes deeper and shows less than direct pressure damage, and it’s a particular risk in seating.
Duration without relief. In bed, repositioning is a scheduled nursing task with a chart. In a chair it frequently isn’t scheduled at all, because the patient is recorded as being out of bed and therefore, by implication, fine.
| Element | What to do | Basis |
|---|---|---|
| One repositioning schedule | Count chair time and bed time together against a single repositioning interval, on one chart, owned by one person. | NICE CG179 recommends repositioning at least every six hours for adults at risk of pressure ulcers, and at least every four hours for those at high risk. |
| Sitting time limits for at-risk patients | Limit unrelieved sitting to around two hours per session for people who can’t reposition themselves, then check skin and tolerance. | International seating recommendations (EPUAP, NPIAP and PPPIA, 2019). |
| Pressure redistribution in the chair, not just the bed | A cushion matched to assessed risk, and a chair that supports posture so the patient doesn’t slide. | Guideline-supported as a principle. Note that no trial shows a specific chair cushion reduces ulcer incidence in acute wards. |
| Skin check at every transfer | Look at the sacrum and ischial tuberosities each time the patient moves between chair and bed. The transfer is happening anyway, so this adds seconds. | Established practice, and the cheapest surveillance available. |
| Fix the posture, not just the surface | Correct seat depth and back angle so the patient sits back rather than sliding forwards. A cushion under a sliding patient doesn’t solve shear. | Postural seating practice. See our ward chair specification page. |
This matters when you’re reading supplier literature, ours included.
The full set of questions to ask any supplier, us included, is on ward chair specification.
Pressure damage cost the NHS more than £3.8 million per day according to NHS Improvement (2018), based on 2015-16 data. Dealey and colleagues (Journal of Wound Care, 2012) modelled treatment costs of between £1,214 and £14,100 per ulcer by category at 2011 prices. Both figures are old, so state the data year – it stops the number being dismissed out of hand.
For the clinical basics of grading and treating pressure damage, see our post on pressure sores: grading, symptoms and treatments.
It can, for patients who can’t reposition themselves. Sitting concentrates load over the ischial tuberosities and sacrum across a smaller contact area than lying, and sliding forwards in a poorly fitting chair adds shear on top. That’s an argument for planning sitting time and repositioning properly, not for keeping people in bed, because immobility drives pressure damage too. International seating guidance (EPUAP, NPIAP and PPPIA, 2019) suggests limiting unrelieved sitting to around two hours per session for people at risk.