Samenvatting

Introduction
Nowadays, humans are used to sit a lot during daily activities. Most of the time this happens in a relaxed way. This position is also called ´slouching´ or ´slouched posture´. In the slouched posture the pelvis and the lumbar spine are flexed and places the muscle spindles, muscles and ligaments in a lengthened position. This position seems to effect muscle spindle activity, and therefore influences the proprioception of the lower back. The proprioception is considered important for the (dynamic) stability of the lower back. Moreover, a good stability seems to be an important preventing factor in development of lower back pain.
Aim
The purpose of this study is to investigate the effect of the sitting slouched posture on the proprioception of the lower back. The following hypotheses were investigated:
1. Slouching decreases the dynamic stability.
2. The slouching posture decreases the proprioception of the lower back.
Method
In this study, 18 healthy persons, both male and female, participated. Centre of pressure (CoP) velocity (sway velocity) was measured after 30 minutes of slouching, and after 15 minutes of activating exercises. The group of participants was randomized in either starting with slouching, or starting with exercises. The CoP velocity measurement took 75 seconds, containing 15 seconds of vibration of the lower back muscles at the L4/L5 level. The results evaluate the measurements from 15 until 30 seconds and from 30 until 45 seconds (vibration period).
Results
A significant difference (p= 0.03) of sway velocity was found after comparing the slouching and activation condition, during the 15-30 seconds interval.
There was no significant difference (p= 0.81) between the two conditions during the vibration period (30 - 45 seconds interval).
Conclusion
The results show that slouching effects the dynamic stability, but does not effect the proprioceptive input of the lower back in healthy subjects during this test. These results may suggest a difference in visco-elasticity of soft tissues and/ or difference in motor control.