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Biomechanical effects of sitting with adjustable ischial and lumbar support on occupational low back pain: evaluation of sitting load and back muscle activity.

Makhsous M, Lin F, Bankard J, Hendrix RW, Hepler M, Press J - BMC Musculoskelet Disord (2009)

Bottom Line: The load and interface pressure on seat and the backrest, and back muscle activities associated with usual and this Off-Loading posture were recorded and compared between the two postures.It also significantly decreased the contact area on the seat and increased that on the backrest.These effects are similar in individuals with and without LBP.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL, USA. m-makhsous2@northwestern.edu

ABSTRACT

Background: Compared to standing posture, sitting decreases lumbar lordosis, increases low back muscle activity, disc pressure, and pressure on the ischium, which are associated with occupational LBP. A sitting device that reduces spinal load and low back muscle activities may help increase sitting comfort and reduce LBP risk. The objective of this study is to investigate the biomechanical effect of sitting with a reduced ischial support and an enhanced lumbar support (Off-Loading) on load, interface pressure and muscle activities.

Methods: A laboratory test in low back pain (LBP) and asymptomatic subjects was designed to test the biomechanical effect of using the Off-Loading sitting posture. The load and interface pressure on seat and the backrest, and back muscle activities associated with usual and this Off-Loading posture were recorded and compared between the two postures.

Results: Compared with Normal (sitting upright with full support of the seat and flat backrest) posture, sitting in Off-Loading posture significantly shifted the center of the force and the peak pressure on the seat anteriorly towards the thighs. It also significantly decreased the contact area on the seat and increased that on the backrest. It decreased the lumbar muscle activities significantly. These effects are similar in individuals with and without LBP.

Conclusion: Sitting with reduced ischial support and enhanced lumbar support resulted in reduced sitting load on the lumbar spine and reduced the lumbar muscular activity, which may potentially reduce sitting-related LBP.

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Related in: MedlinePlus

Average changes (in percentage Mean ± SE) of parameters of backrest interface pressure (total contact area "TCA", average pressure "AP", peak pressure "PP", vertical location of PP "PPZ" and "horizontal location of PP "PPY") induced by sitting posture change from Normal to Off-Loading posture for both Asymptomatic and LBP subjects.
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Figure 4: Average changes (in percentage Mean ± SE) of parameters of backrest interface pressure (total contact area "TCA", average pressure "AP", peak pressure "PP", vertical location of PP "PPZ" and "horizontal location of PP "PPY") induced by sitting posture change from Normal to Off-Loading posture for both Asymptomatic and LBP subjects.

Mentions: The average (Mean ± SE) values of TCA, AP, and PP in Normal posture are listed in Table 1. For both groups, changing from the Normal to the Off-Loading posture resulted in a significant increase in AP on the backrest (Figure 4). No significant interaction was found between the "group" effect and the "posture" effect and there was no significant group difference for the contact pressure on the backrest.


Biomechanical effects of sitting with adjustable ischial and lumbar support on occupational low back pain: evaluation of sitting load and back muscle activity.

Makhsous M, Lin F, Bankard J, Hendrix RW, Hepler M, Press J - BMC Musculoskelet Disord (2009)

Average changes (in percentage Mean ± SE) of parameters of backrest interface pressure (total contact area "TCA", average pressure "AP", peak pressure "PP", vertical location of PP "PPZ" and "horizontal location of PP "PPY") induced by sitting posture change from Normal to Off-Loading posture for both Asymptomatic and LBP subjects.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2654542&req=5

Figure 4: Average changes (in percentage Mean ± SE) of parameters of backrest interface pressure (total contact area "TCA", average pressure "AP", peak pressure "PP", vertical location of PP "PPZ" and "horizontal location of PP "PPY") induced by sitting posture change from Normal to Off-Loading posture for both Asymptomatic and LBP subjects.
Mentions: The average (Mean ± SE) values of TCA, AP, and PP in Normal posture are listed in Table 1. For both groups, changing from the Normal to the Off-Loading posture resulted in a significant increase in AP on the backrest (Figure 4). No significant interaction was found between the "group" effect and the "posture" effect and there was no significant group difference for the contact pressure on the backrest.

Bottom Line: The load and interface pressure on seat and the backrest, and back muscle activities associated with usual and this Off-Loading posture were recorded and compared between the two postures.It also significantly decreased the contact area on the seat and increased that on the backrest.These effects are similar in individuals with and without LBP.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL, USA. m-makhsous2@northwestern.edu

ABSTRACT

Background: Compared to standing posture, sitting decreases lumbar lordosis, increases low back muscle activity, disc pressure, and pressure on the ischium, which are associated with occupational LBP. A sitting device that reduces spinal load and low back muscle activities may help increase sitting comfort and reduce LBP risk. The objective of this study is to investigate the biomechanical effect of sitting with a reduced ischial support and an enhanced lumbar support (Off-Loading) on load, interface pressure and muscle activities.

Methods: A laboratory test in low back pain (LBP) and asymptomatic subjects was designed to test the biomechanical effect of using the Off-Loading sitting posture. The load and interface pressure on seat and the backrest, and back muscle activities associated with usual and this Off-Loading posture were recorded and compared between the two postures.

Results: Compared with Normal (sitting upright with full support of the seat and flat backrest) posture, sitting in Off-Loading posture significantly shifted the center of the force and the peak pressure on the seat anteriorly towards the thighs. It also significantly decreased the contact area on the seat and increased that on the backrest. It decreased the lumbar muscle activities significantly. These effects are similar in individuals with and without LBP.

Conclusion: Sitting with reduced ischial support and enhanced lumbar support resulted in reduced sitting load on the lumbar spine and reduced the lumbar muscular activity, which may potentially reduce sitting-related LBP.

Show MeSH
Related in: MedlinePlus