The effect of a lumbar support pillow on lumbar posture and pressure is a topic of interest for people who suffer from back pain and those who work in positions where they sit for extended periods of time. This study examined the effect on posture and lumbar support provided by a bow pillow designed to maintain an ‘arch’ in the lower back when seated.
Back pain is a widespread problem with significant effects on quality of life, including physical function, mood states, and mental health. In fact, low back pain accounts for 12% of all disabilities worldwide. Studies have indicated that most cases of chronic low-back pain occur as a result of musculoskeletal problems and imposing prolonged sitting postures.
Postural muscles provide support to the spine and trunk. They maintain body segments in correct alignment and respond quickly when balance is threatened. Muscle fatigue can lead to poor postural control and may result in excessive load transfer through the back. The pelvis tilts forward and the lower lumbar spine hyper extends under compressive loading causing increased pressure on the intervertebral discs of the lumbar spine. It has also been shown that sitting for extended periods of time causes loss of lumbar lordosis resulting from shortening of hip flexor muscles. These changes contribute to low-back pain because it has been shown that back muscles are most efficient when loaded in a prolonged neutral standing position, rather than in flexion or extension.
Bow pillows
Bow pillows have been designed to support the bow-like arch of the spine. They allow for normal curvature while also maintaining an upright posture. Research on bow pillows is limited, but recent studies report bow pillows may be able to maintain lumbar lordosis and reduce muscle load.
A bow pillow has been shown to influence trunk muscle activity in patients with chronic low-back pain. A bow pillow provides increased load-bearing capacity by shifting the axis of the moment generated by body weight anteriorly, away from the lumbar spine. The bow pillow is particularly effective for maintaining upright posture when seated on a soft surface.
Methods
Subjects in this study were asked to sit on either an experimental bow pillow or a control cushion while they answered questions about their comfort and support during each phase of testing. Pressure distributions across subjects’ backs were measured using a pressure mapping sensor belt around the waistline. Electromyography (EMG) was used to record muscle activity from the subject’s back muscles during each session. Flexion, extension and rotation angles were determined using a digital inclinometer.
Participants
A convenience sample of 29 healthy adults (16 male and 13 female) between the ages of 18 and 50 voluntarily participated in this study. Subjects had no history of major lower-back injury or surgery, no acute or chronic pain at the time of testing, and were not currently taking medication that would affect their musculoskeletal system. Individuals who reported discomfort sitting on hard surfaces for extended periods were included in this study because bow pillows are designed to provide support while sitting on soft surfaces such as couches. The bow pillows used in this study were donated by Tempur-Pedic, a manufacturer of bow pillows.
Testing procedures
The bow pillows and control cushion height, width, length and density measurements were obtained from the manufacturer. The bow pillow tested has an average bow height of approximately 10cm, bow width of 28cm and bow length of 36cm. The research shows an original bow pillow model with dimensions labeled. The bow was designed for use with soft surfaces such as couches; therefore the experimental bow was not expected to provide large amounts of support while sitting on a hard surface. The control cushion has no bow; it is made up of two pieces of foam measuring 4cm thick, located inside a cotton pillowcase. The bow pillow and control cushion were placed on top of a Hardboard® platform to create a flat surface for the bow pillow. A digital inclinometer was used to measure flexion, extension and rotation angles while subjects were seated with their pelvis in a position of 0 degrees on the Hardboard platform.
Takeaway
The bow pillow tested in this study was effective for maintaining an upright posture when seated on a soft surface. A bow pillow with bow height of 28cm provided more support than the bow pillows designed by Tempur-Pedic. Bow width is most likely not as important as bow height because subjects evaluated their comfort using descriptors related to both size and shape of the bow, rather than bow width alone. The experimental bow was not expected to provide significant support while sitting on a hard surface; however, it was found that supporting the lumbar spine reduced muscle load compared to conditions without any cushion or control cushion.
Adam Mulligan did his degree in psychology at the University of Hertfordshire. He is interested in mental health and well-being.
