En gjennomgang av hvordan sitteposisjon og holdning påvirker kroppen.
In order to assess the loads placed on a spine during various positions, Rohlmann, et al. (2011) looked at various seating positions.4 They found the implant force increased 48 percent for 15 degrees flexion and decreased 19 percent for 10 degrees extension of the trunk. Placing the hands on the thighs reduced the loads by 19 percent, on average, compared to having arms hanging at the sides.
Dreischarf, et al. (2010) also found that reduced spinal load during sitting can be achieved by supporting the upper body with the arms.5
A study by De Carvalho, et al. (2010) compared lumbar spine and pelvic posture between standing and sitting via radiologic investigation. Lumbar lordosis and sacral inclination decreased by 43 and 44 degrees, respectively.6 This shows that with respect to sitting posture, to goal should be to maintain or prevent a reduction of the lumbar lordosis.
One study found 40-percent higher cervical extensor activity in the slouched posture. More neutral sitting postures reduce the demand on the cervical extensor muscles.7 Education on maintaining a neutral sitting posture can offset the detrimental effects.
A study by Caneiro, et al. (2010) showed that slumped sitting was associated with greater head / neck flexion, and increased muscle activity of the cervical erector spinae.9 Adjustments to seat angle and lumbar roll can also significantly effect head and neck posture.
A study by Horton, et al. (2010) found that the degree of angulation of the backrest support of an office chair, plus the addition of a lumbar roll support, are the two most important seat factors that will benefit head and neck postural alignment.10
A study by Bullock, et al. (2005) looked at how sitting posture can affect range of motion and pain for those with shoulder impingement.11 An erect posture appeared to increase active shoulder flexion, although there was no difference in shoulder pain between an erect and slouched posture.
Finley, et al. (2003) found that an increased thoracic kyphosis from a slouched posture can significantly alter the kinematics of the scapula during humeral elevation.12
And Kebaetse, et al. (1999) found that a slouched posture is associated with a 16.2 percent reduction in arm horizontal muscle force.13
A recent study by Dunk, et al. (2009), out of the University of Waterloo, evaluated whether the intervertebral joints of the lumbosacral spine approach their end ranges of motion in a seated posture.15 In upright sitting, the L5-S1 intervertebral joint was flexed to more than 60 percent of its total range of motion. In a slouched posture, each of the lower three intervertebral joints approached their total flexion angles. This shows an increased loading of the passive tissues (time-dependent «creep»), which may contribute to low back pain from prolonged sitting.
A study by Reeve, et al. (2009) assessed the thickness of the TrA in various postural positions. Thickness was significantly greater in standing and erect sitting than in a slouched or sway-back standing position.16 The authors concluded that lumbopelvic neutral postures have a positive influence on spinal stability compared to equivalent poor postures.
A study by Claus, et al. (2009) looked at the effect of various postures on regional muscle activity.17 For the deep and superficial fibers of lumbar multifidus muscles, the least muscle activity occurred during a flat posture, which was similar to a slump posture. The most activity occurred in a short lordosis position; there was also more activity in the obliquus internus.
A study by Dolan, et al. (2006) provided evidence that a slouched posture of 5 minutes’ duration can increase reposition error.18 Proprioceptive control is known to be valuable in spinal stability. The fact that reposition error can occur within as little as 5 minutes of «slouched» posture suggests the importance of postural education in decreasing proprioceptive loss and injury.