PT3 - The Spine and Pelvis In Sitting Flashcards
What influences the way we sit?
- task
- environment
- organism
- coordination + control sits in the centre of these 3
What is the pelvis position during standing
- ischial tuberosities posterior to hip joint
What is the position of the pelvis in sitting?
- pelvis must be rotated posteriorly for ischial tuberosities to be vertically below centre of gravity of trunk
- results in reduction in lumbar lordosis in erect sitting
What happens to the lumbar spine in sitting?
- forces experienced by joint in lumbar spinal in sitting and standing are below traditional tissue damage ranges
- prolonged static loads can result in fatigue injury = low prolonged muscle contraction/prolonged flexed postures of spine => accumulated damage to posterior annulus
- standing = good rest from sitting => reduction in passive tissue forces
- constant loading + reduced dynamic movement in sitting + standing => reduced rest/change for muscular activation levels or low back loading
What happens to intradiscal pressures in sitting?
- sitting on stool with normal straight back => similar pressure to standing (0.45-0.5)
- actively straightening + extension of back => increased pressure (0.55)
- bending forwards + elbow support (relaxed) => reduced pressure (0.43)
- pressure decreased when leaning backwards (armchair) => reduced pressure (0.37) + increase lumbar flexion
Describe the structure of the intervertebral disc
- nucleus pulposis = semi fluid material
- deforms + resists compression
- on compression exerts radial pressure => braces + stiffens annulus => prevents buckling
- anulus fibrosus = collagen fibres in concentric rings + thicker anteriorly + laterally
- vertebral end plates = cartilage => strong attachement to AF + NP; less than vertebral body
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What is the effect of prolonged sitting and physical activity on thoracic spine mobility?
- sitting is damaging on thoracic spine mobility
- physical activity is beneficial
What is the influence of different sitting postures on head/neck posture and muscle activity?
- different sitting posture affect head/neck posture + cervico-thoracic muscle activity
- importance of thoracolumbar spine postural adjustment when training head/neck posture
What happens in sitting posture to the chest wall shape and motion with breathing?
- changes in sitting posture in a single plane alter motion of chest wall in 3 dimensions + distribution of volume when breathing
Mr Smith is back to playing regular tennis without any low back pain. He would now like some advice on what he could do to keep himself healthy at work given that he works at a desk most of the week.
What adaptations might you expect to see in his spinal posture and tissues?
- tightness in hamstrings due to ischial tuberosities coming underneath the hips from siting
- posterior pelvic tilt due to lumbar spin lordosis removal
- lumbar lordosis may have been removed by sitting
- prolonged static loads from sitting may result in muscle contraction from postural muscles leading to damage of posterior component of annulus
- vertebral end plates becoming worn due to increased pressure from muscular contraction, pressing down onto annulus, which braces and fluid from annulus contacts spinal column => resulting in radiculopathy
Mr Smith is back to playing regular tennis without any low back pain. He would now like some advice on what he could do to keep himself healthy at work given that he works at a desk most of the week.
What practical advice might you give Mr Smith?
- move regularly to assist in reducing compressive forces from prolonged periods of sitting on annulus fibrosis + nucleus pulposis
- will also assist in moving facets and ligaments in posterior column reducing tension forces
- head and neck position can have an impact on chest wall and breathing, so would advise doing some breathing exercises
- movement through thoracic-lumbar spine to decrease activation of cervico-thoracic muscles
