From: Spine (Phila Pa 1976). 2009 Oct 16

The effect of postural change on degenerative lumbar discs was quantified using novel kinematic magnetic resonance imaging. The purpose is to describe the bulging of degenerative intervertebral lumbar discs in vivo subjected to different postural loads using a novel kinematic magnetic resonance imaging.

Symptomatic lumbar disc degeneration is a leading cause of pain and disability throughout the world. Over 70% of US citizens will experience a debilitating episode of low back pain. Earlier reports of degenerative disc changes are cadaver studies or are performed with recumbent MRI that eliminates the functional effects of gravity and muscle power. Little data are available on the behavior of degenerative intervertebral discs in vivo under physiologic loads.

A total of 513 patients obtained kMRI. Disc bulging beyond the intervertebral space was quantified during upright neutral, flexion, and extension imaging. The degree of intervertebral disc degeneration was correlated using the Pfirrmann Classification. Moderately degenerated intervertebral discs (grade III and IV) demonstrated greater bulging than mildly degenerated discs (grade II). Severely degenerated discs (grade V) also showed a trend toward greater bulging, but this was not significant. Grade I discs at all levels moved posteriorly in flexion and anteriorly in extension when compared to neutral posture. However, mild to severe (grade II-V) degenerative discs behaved differently in response to postural loads. Extension resulted in significant posterior bulging, while flexion did not demonstrate obvious anterior derangement.

Disc bulging increases with the severity of disc degeneration. Grade I discs demonstrate the expected sagittal migration in response to postural load. However, more degenerative discs behave less predictably, and spine extension may result in significant posterior disc bulging. Degenerative changes in the intervertebral disc significantly affect the kinematic patterns under postural load in vivo. Kinematic magnetic resonance imaging is a useful tool to quantify the kinematic behavior of degenerative intervertertebral discs.

Tags: degenerative, lumbar, discs,, symptomatic, lumbar, disc, degeneration,, postural, load

From: Spine (Phila Pa 1976). 2009 Sep 14

An in vivo study of the effects of mechanical loading on transport of small solutes into normal human lumbar intervertebral discs using serial postcontrast magnetic resonance imaging (MRI) to investigate the influence of a sustained mechanical load on diffusion of small solutes in and out of the normal intervertebral disc.

Diffusion is an important source of disc nutrition and the in vivo effects of load on diffusion in human intervertebral disc remains unknown. Forty normal lumbar discs (on MRI) in 8 healthy volunteers were subjected to serial post contrast (Gadoteridol) 3 Tesla MRI in 2 phases. In phase 1 (control), volunteers were scanned at different time points – precontrast and 1.5, 3, 4.5, 6, and 7.5 hours postcontrast injection. In phase 2, 1 month later, the same volunteers were subjected to sustained supine loading for 4.5 hours. MRI scans were performed precontrast (preload) and postcontrast (postloading) at 1.5, 3, and 4.5 hours. Their spines were then unloaded and recovery scans performed at 6 and 7.5 hours postcontrast. In house software was used to analyze images.

Repeated-measures ANOVA and pairwise comparisons at different time points in the central region of the loaded disc compared to the unloaded discs revealed significantly lower signal intensity ratios indicating reduction in transport rates for the loaded discs. Signal intensity ratioscontinued to rise in loaded disc for 3 hours into recovery phase, whereas unloaded discs at the same time point showed a decrease.

Sustained supine creep loading (50% body weight) for 4.5 hours retards transport of small solutes into the center of human IVD and it required 3 hours of accelerated diffusion in recovery state for loaded disc to catch-up with diffusion in unloaded discs. The study supports the theory that sustained mechanical loading impairs diffusion of nutrients entering the disc and quite possibly accelerates disc degeneration.

From: Iowa Orthop J. 2009;29:97-9

This cross-sectional study examines whether there is an association between gluteus medius weakness in the presence of low back pain in pregnant women at any stage of gestation. Prevalence of low back pain during pregnancy is high, and identifying potential etiologies and targeted interventions is lacking. Thus, identification of an association between specific muscle weakness and pain would have clinical relevance. Initial pilot data suggests that weakness of the gluteus medius is strongly associated with the presence of low back pain during pregnancy.

Low back pain during pregnancy is considered a significant public health issue due to its high prevalence and associated health care costs. Prevalence ranges between 49-68.5% with up to one third of these women having pain that limits their ability to perform basic activities of daily living. Ten percent of women with chronic low back pain link the onset of their pain to pregnancy. Physical therapy literature and physical therapy clinical practice relating to low back pain in pregnancy has historically involved discussion of postural dysfunction, sacroiliac joint dysfunction, and “sciatica.” The authors of this proposal offer another possible correlation explaining back pain during pregnancy relating to gluteus medius performance.

It is the experience of the authors of this proposal that pregnant women routinely present to their physical therapy clinic with “radiculopathy” or “sciatica.” In fact, the incidence of herniated disc in pregnancy is actually quite rare (1%). Often, the physical exam does not reveal any neurologic findings indicative of radiculopathy, but instead reveals weakness and/or strain of the gluteus medius. Gluteus medius strain can present as low back pain either due to facet joint irritation relating to Trendelenburg gait, or can be referred pain from the gluteus medius itself. If a true neurologic weakness were present, one would expect to find both tensor fascia lata and posterior gluteus medius weak as they are commonly innervated (L5). Rather, in the authors experience weakness is specific to the gluteus medius. Foti et al. performed 3-dimensional gait analysis on 15 pregnant women during the second half of their pregnancy and again one year post-partum. Gait analysis includes both kinetic and kinematic parameters. The authors found significant changes in kinetic gait parameters during pregnancy, and offer this as an explanation for how
gait motion overall remains relatively unchanged. They found increased demand on the ankle plantar flexors, hip abductors, and hip extensors. Atrophied tissues, or weak muscles, are less tolerant of physical stresses applied. Pregnant women with weakness of the gluteus medius are therefore vulnerable for tissue injury—both because of the increased magnitude of stress applied (weight gain), and a decrease in stress tolerated before injury/strain.

Thus, the primary aim of this pilot study was to determine the association between weakness of the gluteus medius and the presence of low back pain during pregnancy.

As mentioned, prevalence of low back pain in pregnant women is high. Yet our knowledge is limited to descriptions of natural history. Unfortunately, most clinicians are limited in both work-up and treatment options due to the pregnancy. Often, women are advised to wait until after delivery for appropriate tests and treatment.

The rationale for postural change as a contributor to back pain during pregnancy involves increased lumbar lordosis with subsequent extension-related facet pain. Treatment is then guided toward improving posture, abdominal strengthening, and improved lumbopelvic stability. Lengthening of the abdominal muscles is a known consequence of a growing uterus, causing possible weakness of this musculature. It is thought that this lengthening and weakness contributes to poor lumbar stabilization and pain. Few studies exist showing a correlation between abdominal weakness and back pain in pregnant women. Fast et al. looked at rectus abdominus function in terms of ability to perform a sit-up. They found no significant difference between performance of a sit-up and incidence of back pain. Moore et al. performed a longitudinal study of 30 pregnant women and found the line of gravity, measured using special markers along the spinous processes, to be unaffected for the majority of women. Those who did experience a change, tended toward flattening of the lumbar spine. Other studies have found no correlation between postural patterns and the presence of low back pain.

Sacroiliac joint dysfunction is a much debated issue in the physical therapy literature. There is disagreement relating to whether the sacroiliac joints are mobile, and if so, to what extent. An excellent review by Walker documents review of multiple articles citing greater tendency toward fracture than joint displacement with high impact injury. This review also notes motion of the sacroiliac joint averaging about four degrees or three millimeters.
This brings into question whether this small amount of movement can be detected through physical exam alone. The discussion changes somewhat in the context of pregnancy, as there is known joint laxity around the pelvis. As the sacroiliac joint joint is not crossed by any muscle, we assume that stability is achieved through bony morphology and ligaments. During pregnancy, it is thought that the hormone relaxin contributes to the decreased strength
of collagen. There appears to be conflicting evidence relating to whether a correlation exists between relaxin levels, pain, and sacroiliac joint ovement/sympheseal distension. Specific provocative maneuvers to detect sacroiliac joint pain, as well as tests to determine symmetry/joint motion exist. However, at this time, reliability and validity of these tests does not appear sound, particularly in the case of detecting symmetry/abnormal joint motion.

Pregnant women with gluteus medius weakness were roughly 6 to 8 times more likely to have low back pain than those without weakness. There were no neurologic findings indicative of radiculopathy. This pilot data encourages us to continue this study with larger numbers. The authors also will consider a treatment trial looking to see if strengthening exercises prescribed at the first OB visit can reduce incidence of low back pain.

From: Gait Posture. 2009 Aug 31.

Postural adjustments following mechanical perturbations have been studied in healthy seated humans. However, little is known on the minimal intensity that should be used to provoke a reaction. This knowledge could be essential to assess seated postural deficits in some pathological populations. The goal of the present study was to identify a low-intensity perturbation that could elicit postural reactions in healthy seated individuals.

Six healthy participants sat on an adapted ergonomic chair fixed on a moveable support surface that was submitted to forward and backward translations. The head and trunk kinematics as well as the activity of sixteen neck and trunk muscles were recorded. The head, arm and trunk center of mass was computed using kinematics and standard anthropometric tables. The authors found that ramp displacements with an acceleration profile reaching a maximal value of 1.17m/s(2) elicited reliable kinematic and electromyographic reactions across participants. Head and trunk segments initially responded opposite to the direction of translation, then reversed direction. Median peak-to-peak angular displacements in the neck, head and trunk, respectively, reached 3.6 degrees , 7.0 degrees and 7.1 degrees for forward translations, and 4.0 degrees , 8.2 degrees and 7.0 degrees for backward translations.

For forward translations, neck and trunk flexor muscles were activated first, followed by the extensor muscles, whereas for backward translations, extensor muscles were activated first, followed by flexors. Although this perturbation is of low-intensity compared to those typically used previously to evoke postural reactions, this stimulus is sufficient to elicit a reliable response. We suggest that such a perturbation could be used to assess the physical condition of individuals with neck injuries.

From: BMC Musculoskelet Disord. 2009 Jul 7;10(1):82. [Epub ahead of print]

Among women, chronic pelvic pain is a highly prevalent (2% to 25%) clinical problem, with substantial costs as well as social and marital repercussions. Chronic pelvic pain is defined as continuous or recurrent pain in the lower abdomen or pelvis lasting at least six months, not related to pregnancy, and sufficiently severe to interfere with the habitual activities of the patient. Chronic pelvic pain excludes pain occurring exclusively in association with menstruation (dysmenorrhea) or during sexual intercourse (dyspareunia).

Although the etiology is often unknown, it may result from complex interactions among the gastrointestinal, urinary, gynecologic, musculoskeletal, neurologic and endocrine systems, as well as being influenced by psychological and sociocultural factors. To date, few therapeutic modalities have been effective in relieving the symptoms of chronic pelvic pain, particularly over the long term. An interdisciplinary approach has therefore been recommended, both to diagnose the presumed primary etiology, and to diagnose and control all the secondary factors associated with chronic pelvic pain.

In clinical practice, postural changes are frequently observed among women with chronic pelvic pain. Although this disease has been associated with musculoskeletal changes and particular postures, to date there have been no studies of the detailed postural evaluation of women with chronic pelvic pain, which can be performed by attending physicians, especially primary care physicians and gynecologists. Postural assessment can lead to early detection of uneven positions, shortenings, antalgic postures and tensions. Although these changes may not be the primary cause of the clinical condition, they can contribute significantly to the worsening of pain and tension. The authors therefore determined the frequency of postural changes in women with chronic pelvic pain, as assessed only by clinical examinations.

The authors observed statistically significant differences in the cervical spine and scapulae between women with chronic pelvic pain and control women. The authors believe that the changes observed in women with chronic pelvic pain resulted from a vicious cycle of pain and antalgic postures acquired over time. The mean duration of symptoms among women with chronic pelvic pain was about five years, and postural impairments over time can contribute significantly to the maintenance or worsening of pain. Nevertheless, the authors cannot conclude that women with chronic pelvic pain always show the same postural pattern. First, although the authors observed an association between chronic pelvic pain and postural changes, the control group, consisting of women who did not report any type of pain, also presented with several postural changes.

Additionally, the authors believe that postural changes among controls occurred because posture depends not only on pathologic condition, but on several other factors, including habits acquired by individuals throughout life, their work activities, and even their emotional and psychological states. Second, the authors study design did not allow them to determine whether postural changes were the cause or consequence of chronic pelvic pain. However, identifying postural changes is an important part of evaluating women with chronic pelvic pain because improvements in posture can contribute to improvement in chronic pelvic pain symptoms.

In this study, posture was assessed in a strictly clinical manner, with the examiners recording the static posture adopted by the women. This method of assessment was used because the authors wanted to determine the efficacy and reproducibility of this type of evaluation so that it might be incorporated into clinical practice in the evaluation of women with chronic pelvic pain. Because of its simplicity, this type of examination can be easily performed during ambulatory patient care at any level of assistance, thus minimizing factors that may worsen or perpetuate chronic pelvic pain and helping to refer these women to specialized services. However the authors recognize that, scientifically, more objective forms of postural assessment such as biophotogrammetry are necessary. However we believe that the method described here may be useful in assessing the effects of physiotherapy and/or advice to alleviate pain in women with chronic pelvic pain who have musculoskeletal changes.

The authors findings also support the importance of multidisciplinary care, involving physicians, physical therapists and psychologists, for women with chronic pelvic pain. In this series, musculoskeletal changes were associated with chronic pelvic pain in at least in 34% of the women in the chronic pelvic pain group, indicating that a more detailed assessment of women with chronic pelvic pain is necessary for better diagnosis and to provide more effective treatment for these women, including control of situations that may reduce the pain threshold.

Logistic regression showed that the independent factors associated with chronic pelvic pain were postural changes in the cervical spine and scapulae. Musculoskeletal changes were associated with chronic pelvic pain in 34% of women. These findings suggest that a more detailed assessment of women with chronic pelvic pain is necessary for better diagnosis and for more effective treatment

From this study the authors conclude that postural changes are seen more frequently in women with chronic pelvic pain. However, it is not possible to confirm if these changes are causes or consequences of chronic pelvic pain. Thus, more detailed assessments are necessary to obtain better differential diagnosis and, consequently, more effective treatment for these women.

From: Ergonomics. 2009 Jul;52(7):830-9

The aim of this study was to test the effect of a movable backrest on vibration transmission through the trunk during driving and on the physiological consequences thereof. Eleven healthy male subjects drove for about 1 h on normal roads with a movable and with a fixed backrest (back support) while surface electromyography (EMG) was measured at the level of the fifth lumbar vertebra (L5) and vertical accelerations were measured at the seat, backrest and at the spine at the levels of the second sacral vertebra (S2) and seventh cervical vertebra (C7). The movable backrest significantly reduced accelerations at C7 by up to 11.9% at the 5 Hz frequency band. The movable back support also significantly reduced the coherence and transmission between S2 and C7 accelerations, but not the differential motion between these sensors. EMG at both sides of L5 was on average 28% lower when using the movable backrest. Spinal shrinkage was unaffected by backrest type. It is concluded that a movable backrest reduces the transmission of vibration through the trunk and that it reduces low back EMG. Car driving is associated with the risk of developing low back pain and this may be related to exposure to whole body vibration. This study found an effect of a simple ergonomics measure on the transmission of vibration through the trunk as well as on back muscle activation.

Interestingly, according to Ind Health. 2005 Jul;43(3):421-35

The addition of a back support causes stiffening of the body to limit the low frequency rocking motion of the upper body under x-axis motion, while considerable dynamic interactions with the backrest occur. The mean apparent mass (APMS) responses measured at the seat pan and the backrest suggest strong contributions due to the back support condition, and the direction and magnitude of horizontal vibration, while the role of seat height is important only in the vicinity of the resonant frequencies. In the absence of a back support, the seat pan responses predominate at a lower frequency (near 0.7 Hz) under both directions of motion, while two secondary peaks in the magnitude also occur at relatively higher frequencies. The addition of back support causes the seat pan response to converge mostly to a single primary peak, resulting in a single-degree-of-freedom like behavior, with peak occurring in the 2.7-5.4 Hz range under x-axis, and 0.9-2.1 Hz range under y-axis motions, depending upon the excitation magnitude and the back support condition. This can be attributed to the stiffening of the body in the presence of the constraints imposed by the backrest. A relaxed posture with an inclined backrest, however, causes a softening effect, when compared to an erect posture with a vertical backrest. The backrest, however, serves as another source of vibration to the seated occupant, which tends to cause considerably higher magnitude responses. The considerable magnitudes of the apparent mass response measured at the seat back under fore-aft motions suggest strong interactions with the backrest. Such interactions along the side-to-side motions, however, are relatively small. The results suggest that the biodynamic characterization of seated occupants exposed to horizontal vibration requires appropriate considerations of the interactions with the backrest.

From: Man Ther. 2009 May 6. [Epub ahead of print]

Pillow performance research has largely involved testing pillows of novel shape and design, comparing contour and noncontour shaped pillows and comparing contour pillows with the participants’ usual pillow. Shields et al. who undertook a systematic review regarding the effect of contour or cervical pillow use on neck pain, highlighted the methodological flaws in these studies and concluded that there was insufficient evidence to support the use of contour pillows in the management of chronic neck pain. Helewa et al. reported that contour pillows were ineffective in the management of chronic neck pain unless combined with active neck exercises.

The paucity of research has caused health professionals to provide patient advice regarding neck pillows based on the anecdotal suggestions of expert colleagues and professional associations. This advice has included the use of malleable pillows, a cervical roll, a contour pillow or a down or urethane pillow. Furthermore the range of marketing advice provided by pillow manufacturers is confusing for consumers, although details regarding this statement by the authors was not substantiated by evidence.

This paper reports the performance of commonly used type of pillows from specific manufacturers and their association with neck pain behavior. This pillow field trial was undertaken to:

Pillows used in this study were a polyester, synthetic fibre fill pillow, foam regular shape and foam contour shape pillows. It was stated that both foam pillows were molded from high density foam, although other details regarding the pillows were left to the reader to investigate via manufacturer name and website address. Details regarding manufacturer and website address were provided for all pillows used. Also provided was a latex rubber pillow and feather pillows which were purchased by the principal author.

The pillows varied in length from 70 to 73 cm and in width from 45 to 46 cm. The depth of the foam regular pillow was 120 mm (4.7 in), the foam contour pillow varied between 120 (4.7) and 142 mm (5.5 in) across the contour, the latex pillow was 115 mm (4.5 in), the feather pillow was 120 mm (4.7 in) and the polyester pillow was 118 mm (4.6). The study was conducted independently of any additional involvement of pillow manufacturers. Compression was not noted, however, one migh assume that a high density foam pillow has less compressibility than latex, therefore, one cannot be sure as to the properties of the foam pillows contributing to poor results. It should be noted that the latex pillow would be mid-range in compression between the high density foam pillows and the high compression of the feather pillow.

This study provides the first reports that pillow type can be recommended by health practitioners to alter the behaviour of neck pain for self reported side sleepers. It provides the basis for further investigation of pillow performance with specific groups of people (with known musculoskeletal problems or other sleeping positions) and a basis for evidence-based prescription of pillows for individuals suffering from regular waking pain, reduced pillow comfort or sleep quality.

The authors state, “The study findings are in direct conflict with historically held anecdotal advice regarding pillow selection in the management of cervico-thoracic symptoms.” This, in my opinion is not substantiated by the evidence presented. It is not known why pillows shown to decrease symptoms and improve sleep quality indicated in previous studies were not considered. Studies regarding water based pillows were not included in the references.

Subjects’ own pillow performed similarly to the polyester and foam pillows in terms of production of waking symptoms and maintenance of retiring pain. The authors state, “The shape of the foam pillow appeared to make no difference to waking pain or abolition of night pain. However the contour pillow was less comfortable and provided poorer quality sleep. Thus the contour pillow is less efficacious for these reasons.” This may have been the case for the particular contour pillow used, however, the conclusion cannot be generalized to all contour pillows as parameters like Density (lbs / ft3), Percent of Indent Force Deflection, Tear Strength (lbs/lin inch) and Elongation Pecentage vary considerably and greatly effect pillow performance. Contour shaped foam pillows were initially developed to support the cervical lordosis in the supine sleep position. Hence further investigation of the association between contour pillow shape and symptom behaviour in supine sleepers is indicated. Moreover, contour pillows of different heights require examination with respect to subject anthropometry, symptom behaviour, sleep quality and pillow comfort ratings.

The feather pillow was a consistent poor performer in all outcome measures and therefore cannot be recommended as an alternative should subjects request a pillow which is better than their own. However the rubber pillow performed consistently well, and was a better performer than subjects’ own pillow in all outcome measures and should be recommended as an alternative should subjects seek a better performing pillow than their own. Again, specific qualities are not mentioned, however, manufacturer and website address are detailed. Like other studies, the relationship to the manufacturer must be suspect. Future studies should refrain from noting specific manufacturers and should address specific features of the materials as stated previous for the foam pillows.

The authors note, seven days appears to be a suitable period for a pillow trial as all drop-outs occurred before the fifth trial day. The ‘washout period’ of own pillow use for seven days between pillow trials also appeared to be appropriate to reduce trial pillow symptoms, to catch up on sleep from poor quality sleep from the trial pillows and to retain the interest of the study sample.

The authors further state, “The fit of pillow-to-human form has not been reported in the literature, and was not investigated in this study. Anthropometric studies may thus provide useful information regarding if, and what, anatomical parameters will ensure a comfortable, symptom free union between person, mattress and pillow.” The authors should be aware of studies like, Prediction of Optimal Pillow Height by Anthropometric Parameters, Pei-Te Huang, Alice M.K., in IFMBE Proceedings 15, pp. 222-223, 2007, where an actual formula based on anthropometrics is presented.

The authors note several limitations in this study including an inability to completely blind subjects for pillow type, reliance on daily self-report measures of pain occurrence and duration, sleep quality and pillow comfort, and a lack of information on subjects’ own pillows. There was a surprisingly high number of waking pain reports on subjects’ own pillows, questioning our assumption that these were the most comfortable pillows ever used by subjects. Although there was no difference in subject reports of known reasons for waking pain between the trial pillows, there was a noticeably high percentage on subjects’ own pillows in the first trial week. This could lead to questions such as ‘Did this occur because subjects were anxious about the trial, or perhaps more aware of waking pain?’ If this is so, it must be considered that reports of cervical waking pain on the trial pillows may well have been related to known reasons other than the pillow, but were perhaps ascribed to the pillow itself, in error. The potential for over and under reporting of symptoms during the trial pillow weeks must be considered.

For reasons stated, these types of studies are very difficult and the authors should be praised for their efforts. The authors conclude, “This study provides evidence to support recommendation of rubber pillows in the management of
waking cervical pain, and to improve sleep quality and pillow comfort.” It should be noted that the only conclusion that can be reached is that the specific rubber pillow performed better in the parameters studied than the specific foam and specific contour pillow used in the study, and that the specific feather pillow was least effective for unspecified or evaluated neck pain. To use a specific pillow and assume all pilllows made of the base material are the same is not warranted. To note the manufacturer name and website address brings into question the reasons for choosing specific pillows, relationships among manufacturer to study participants, and these studies are additionally noted to be used by the specific manufacturer as marketing materials.

From: J Manipulative Physiol Ther. 2009 Jun;32(5):352-7

Throughout the course of the day, the spinal intervertebral discs display viscoelastic creep properties that determine an individual’s overall stature. These properties were demonstrated by Tyrrell et al who used in vivo stadiometry measurements to detect 19.3 mm (1.1% of stature) variation in height between first arising and the end of the day.

Contributions to the total diurnal stature loss from structures other than the intervertebral disc are minimal. Kanlayanaphotporn et al used stadiometer measurements to assess the contribution of soft tissue structures below the sacrum and concluded that these structures accounted for 19% of the height change during the first 5 minutes of sitting. Based on these findings, stadiometry is considered to provide an accurate measure of spinal height changes after various loading conditions.

The 2 primary methods of measuring spine height changes are magnetic resonance imaging (MRI) and stadiometry. Stadiometry has been shown to be a valid and reliable tool to assess spinal height when compared to objectifiable measures made from MRI. Stadiometry assessment has advantages over MRI in terms of costs, use in clinical setting, as well as the ability to measure subjects that simultaneously sustain compressive loads of the trunk.

Several authors have assessed the effects of postures and different compressive loads on spinal height using stadiometry. Kourtis et al used stadiometry to identify increased height associated with prolonged hyperextension in lying, where a gain in intervertebral disc height after this activity was confirmed using MRI. The mean disk height gain from intervertebral discs T11 to L5 measured by MRI after extension lying was 2.1 mm, whereas the average total spine height gain measured by stadiometry was 5.2 mm. The results consistently demonstrated an increase in participant height when measured using MRI and stadiometry after a position of extension lying that followed a seated loaded position. Similar findings were reported by Magnusson et al who indicated sustained extension lying of 20° for 20 minutes provided the optimal impact on the increase of spine height.

Although previous studies have assessed the effects of extension postures on spine height, no previous investigation has assessed the effects of flexion postures. Therefore, the purposes of this study were 3-fold: (1) to determine if the authors test protocol using a commercially available stadiometer demonstrated findings consistent with prior laboratory-based protocols; (2) to determine if hyperextension in the prone position and trunk flexion in the supine position caused increased spine height after sustained loading; and (3) to compare the effects of hyperextension in the prone position and trunk flexion in the supine position on spine height changes after a period of sustained loading.

The authors clinically applicable protocol using a commercially available stadiometer confirmed the findings of previous research by Kourtis et al that reported loss of trunk height associated with loaded and unloaded sitting. Kourtis et al used MRI to measure changes of intervertebral disc height associated with loading and unloading of the spine. The research methods of the current study matched the methodology and population of Kourtis et al who reported mean changes (−5.03 mm) in spinal height similar to the changes recorded in this study (−3.24 mm). These findings are consistent with previous investigations including 4.28 mm height loss, 3.07 and 3.55 mm height loss, and 3.85 mm height loss recorded after 5 minutes of sitting in young adults.

This is the first reported investigation to assess the effect of trunk flexion in the supine position on spine height using a stadiometer measurement protocol. Magnusson et al suggested that increased lumbar intervertebral disc hydration occurred as a result of load transfer from the lumbar intervertebral disc to the zygapophyseal joints during lumbar extension postures. The authors findings suggest that trunk flexion in the supine position provides similar increase in spine height as those obtained through extension postures. Therefore, controlling the effects of gravity on the intervertebral diskc through unloading the spine seems to bear greater influence on increased spine height and hydration of the discs than the directionality (flexion or extension) of the position of the spine.

No significant differences were found between sexes for any of the experimental conditions, suggesting that sex and body frame were not associated with variability in spine height changes. These results are in agreement with previous findings, which indicated no effect on spine height changes associated with sex, suggesting that trunk height changes associated with various recovery positions can be generalized for both sexes in asymptomatic young adults.

Spine height measurements, using stadiometer protocols, are largely dependent on lumbar intervertebral disc hydration. Kourtis et al using both stadiometer and MRI to assess the effects of various positions on trunk height, reported similar results for extension recovery positions under both techniques. This reflects the intervertebral discs’ ability to imbibe fluid during periods of unloading and lose water with loading, translating into trunk height changes detected using stadiometer measurements. Under normal conditions, the lumbar intervertebral disc is able to imbibe large quantities of water. With intervertebral disc degeneration, the ability to bind water and maintain hydration is diminished. Positions that temporarily aid in the recovery of spine height may help offset these consequences and provide ergonomic applications.

Therapeutic interventions for the management of low back pain can be assessed in terms of intervertebral disc hydration level reflected through spine height changes. This includes the evaluation of various positions and exercises to prevent or treat back pain, the use of traction and manual therapy techniques as well as exercises in the aquatic setting. Future studies should include patients with various conditions such as nonspecific low back pain, lumbar radiculopathy, and lumbar intervertebral stenosis. Determining if a correlation exists between intervertebral disc hydration levels reflected in spine height measures using stadiometer protocols and patient symptoms may provide additional management strategies for the management of low back pain.

These abstracts are from: Work. 2009;32(3)

Effect of backpack load placement on posture and spinal curvature in prepubescent children

From: Work. 2009;32(3):351-60

Parents, educators and researchers have expressed concern about the long term impacts of children carrying excessive loads in their backpacks on a daily basis. Although many researchers have investigated appropriate weight limits for children’s packs, little research has been conducted on the design of children’s backpacks. The purpose of this study was to evaluate the changes in children’s trunk forward lean, cranio-vertebral angle and spinal lordosis angle that occurred with high, medium and low load locations during standing and walking. Ten-year-old children (n = 15) completed a repeated measures designed study while carrying 15% of each child’s body weight in a typical backpack with only shoulder straps. A special instrumented backpack was designed that allowed the weight to be placed in the proper location and continuously measure changes in spinal curvature. Trunk forward lean and cranio-vertebral angle postures were captured on digital video at five intervals including: standing without a backpack prior to a 1000 m walk; standing with a backpack at the beginning and end of a 1000 m walk; and walking with a backpack at the beginning and end of a 1000 m walk. Results indicated that significant changes occurred in trunk forward lean and cranio-vertebral angle when the backpack was loaded to 15% body weight. The low load placement in the backpack produced fewer changes in cranio-vertebral angle from the initial standing baseline measure than the high and mid placements. When all measures were assessed collectively, there were fewer changes in spinal lordosis angle in the low load placement. These findings indicate that future backpack designs should place loads lower on the spine in order to minimize children’s postural adaptations.

Backpack load limit recommendation for middle school students based on physiological and psychophysical measurements

From: Work. 2009;32(3):339-50

The load of student’s backpacks has raised questions over the safety and health of schoolchildren everywhere. The purpose of this study is to use electromyography (EMG), posture evaluation, heart rate, and ratings of perceived exertion and perceptions of pain to find an acceptable backpack load limit for middle school students. Twenty middle school students aged 11 to 14 (10 female and 10 male) volunteered for the study. The subjects completed two tests, standing stationary and walking on a treadmill, where they carried 5% incremental loads from 0% body mass to 20% body mass. The study indicated that the Borg-CR10 ratings and trunk flexion angle for the walking trial indicated a possible load limit of 10% body mass due to the non-significant difference between 0 and 10% body mass and the significant difference between 10 and 15% body mass.

Computer use in school: Its effect on posture and discomfort in schoolchildren

From: Work. 2009;32(3):321-8

The aim of the study was to investigate the posture and musculoskeletal discomfort of secondary school students while working at computers in school. Students (n = 40) were observed while working at a computer during their designated computer class. The Rapid Upper Limb Assessment Tool was used to assess posture. A Body Discomfort Chart and Visual Analogue Scale were used to record the area(s) and intensity of musculoskeletal discomfort, if any, experienced by the students at the beginning and end of the computer class. None of the students’ posture was in the acceptable range (Action Level 1) according to Rapid Upper Limb Assessment Tool. The majority (65%) were in Action Level 2, 30% were in Action Level 3, and 5% were in Action Level 4. There was a statistically significant increase in reported discomfort from the beginning to the end of the computer class. Longer class length (80 minutes) did not result in greater reporting of discomfort than shorter class length (40 minutes).

A comparison of posture and muscle activity means and variation amongst young children, older children and young adults whilst working with computers

From: Work. 2009;32(3):311-20

Children and young adults are the most frequent users of computers. Whilst guidelines for adults have been based on research, available guidelines for children have had to assume children and adults are similar due to limited research evidence derived specifically from children. This study aimed to compare the posture and muscle activity of children with young adults. Thirty six adults aged 18-25 years, 24 children aged 10-12 years and 18 children aged 5-6 years participated in a series of laboratory studies. Upper body postures were measured using a 3D motion analysis system. Muscle activity of bilateral cervical erector spinae and upper trapezius muscles was assessed. Mean and variation were examined, the latter using both amplitude range and Exposure Variation Analysis matrix standard deviation. Mean postures assumed by children tended to show more spinal flexion and spinal asymmetry than adults. However children also tended to show more variation in posture and muscle activity. These findings suggest that whilst there may be differences in how children and adults use computers, basic principles of encouraging appropriate postures and variation should apply for both children and adults.

Computer-related posture and musculoskeletal discomfort in middle school students

From: Work. 2009;32(3):275-83

In recent years, there has been an increasing concern over the association between computer use and reports of discomfort, aches and pains in students. It is suggested that the physical set-up and individual styles of using interactive media has an influence over this discomfort. As children grow up, they will interact and use computers throughout most of their life. Healthy computing may be vital to preventing/reducing the incidence of discomfort/pain associated with interactive media. This research paper will describe a study, which has collected health and comfort data on the incidence and prevalence of self-reported computer-related musculoskeletal discomfort/pain among 6th and 7th grade students in three middle schools in New England. General base line data from this three-year study is reported

Why do children think they get discomfort related to daily activities?

From: Work. 2009;32(3):267-74

Children commonly report musculoskeletal discomfort related to different activities such as computer use, playing electronic games, watching TV, reading, and performing physical and hand intensive activities. Discomfort can result in disability and is a strong predictor of future discomfort in adulthood. Adult beliefs regarding discomfort can affect the level of disability and are modifiable. Children’s beliefs regarding discomfort could potentially be modified to minimise disability related to musculoskeletal disorders. The aim of this study was to describe children’s beliefs about why they experience musculoskeletal discomfort, both in general and related to specific activities. Eighty eight school children completed questionnaires on frequency and usual duration of nine activities, whether they had felt discomfort and what they believed was the cause of any discomfort in relation to those activities. The most common activity was TV watching, and most activities were performed for 1 hour or shorter. Bad posture and doing too much of a certain activity were the most common beliefs regarding reasons for discomfort. This study shows that children are developing beliefs that tend to reflect scientific knowledge about risk factors. These beliefs could be incorporated into preventative health interventions.

From: Ind Health. 2009 Apr;47(2):183-8

Poor posture is a common finding in physical therapy evaluations of patients with musculoskeletal complaints. The upper spine has been of particular interest to physical therapists treating disorders of the cervical and thoracic spine, the shoulder, and the temporomandibular region. Many studies have attempted to identify head and neck postures that would reduce the risk of developing musculoskeletal pain of the neck and trunk.

The effects of the head and neck posture depend on the characteristics of a task. Visual display terminal (computer screen) work typically involves remaining for a long time in a fixed position. Sezto et al. found that individuals increase their forward head posture during computer screen work, which involves an excessive anterior position of the head in relation to the theoretical plumb line perpendicular to the body’s center of gravity, and can be considered similar to a protracted position of the cervical spine in which the lower cervical vertebrae are flexed in a forward glide and the upper cervical vertebrae are extended. This causes a shortening of the posterior cervical and suboccipital muscles, lengthening and weakness of the anterior neck muscles, weakness of the scapula retractor muscles, and increased stress on the ligaments. The imbalances created by this position decrease muscular efficiency, and extra muscular action is needed to hold the head and neck in a stable position. Fredriksson et al. reported that neck and shoulder pain was associated with computer screen work in both men and women.

The head and neck posture of an individual can influence soft-tissue relationships in the cervical region. Neck postural changes can lead to neck pain via associated changes in cervical movement patterns, so it is necessary to evaluate cervical spine kinematics in both normal subjects and in patients with neck pain. Reductions in the cervical range of motion (ROM) have implications for the safety and efficiency of functional activities and lead to a loss of corrective or protective reactions, which contribute to a loss of balance in the soft tissue extensibility around a joint. A study has also shown that a decreased cervical ROM is associated with poor sitting postures, such as forward head posture. ROM losses can occur from inactivity and structural changes of the tissues in the cervical spine, and result in an increase in connective-tissue density, shortening of collagen tissue, and muscle fibrosis.

Goniometer-based systems such as the CROM can reliably measure uniplanar cervical spine movement and the Spin T is a three-dimensional goniometer with demonstrated accuracy and reliability for measuring cervical spine mobility. Norton and Ellison also obtained good reliability and validity for Metrecom measurements on inanimate objects with known dimensions. The head and neck posture when performing computer work has been commonly evaluated in the sagittal plane based on two-dimensional posture or movement.

The association between forward head posture and neck pain has not been clearly defined, but a mechanism for the development of neck pain from habitual postures has been demonstrated. Studies of the effect of sustained forces have indicated that a single posture should not be sustained for longer than 1 h). McGill and Brown have shown that 20 min in a position of sustained loading can induce creep in soft tissues, with recovery taking longer than 40 min. Sustained forces produce time-dependent deformation and adaptations in soft tissue). Short duration stretching produces temporary deformation of soft tissues, but 1 h of stretching might be sufficient for long-term soft-tissue adaptations. Therefore, a longterm habitual posture can result in abnormal loading of ligaments and muscles that might ultimately contribute to a reduction in the cervical ROM and to the development of neck pain. Yoo et al. suggested that it is necessary to frequently change the sitting posture when performing long-term computer screen work.

Examining the active cervical ROM forms an important part of patient evaluations and has been studied in primary researches of work-related neck and upper-limb disorders. Therefore, primary studies need to investigate the association between cervical ROM and poor habitual posture. The purpose of this study was to elucidate the relationship between the active cervical ROM and changes in cervical posture after continuous long-term computer screen work.

A previous study found that workers using computer screens had increased forward neck flexion compared to those with relaxed sitting postures. Increased forward neck flexion may result in increased tension in posture-stabilizing muscles as well as increased compressive forces in the articulations of the cervical spine, resulting in a higher risk of work-related musculoskeletal disorders. Slumping over documents and staring all day at a computer screen screen do great damage to muscles, exacerbating tension and tightness around neck and shoulders.

This study was designed to identify the relationship between the active cervical ROM and the changes in the mean craniocervical and cervicothoracic angles after computer screen work. The authors hypothesis was that these parameters are significantly correlated. This study showed that the active neck extension angle was negatively correlated with the mean craniocervical angle and that the active neck flexion angle was negatively correlated with the mean cervicothoracic angle. This shows that, after long-term computer screen work, subjects with a more limited ROM of neck extension would exhibit a change in the craniocervical angle and those with a more limited ROM of neck flexion exhibit a larger change in cervicothoracic angle. The authors also suggest that treatments for poor cervical posture should focus on recovering the normal ROM of neck flexion and extension. The significant correlations between the upper trapezius muscle activity and head-neck angles found in studies represent important evidence of a link between muscle activity and postural control. The authors propose that the change in craniocervical angle would be related with shortening of the scalenus muscles in deep muscles, because shortening of scalenus muscles can cause limited range of motion in neck extension. The change in cervicothoracic angle would be related to shortening of the levator scapular muscle in deep muscles, because shortening of the levator scapular muscle can cause limited range of motion of neck flexion.

Jull et al. found that patients with neck pain put higher demands on their superficial neck muscles than do healthy people, to compensate for weakness of the deep muscles. The role of deep muscles for maintenance of cervical posture was verified in a computer model, which showed regions of local segmental instability if only the large superficial muscles of the neck were stimulated to produce movement, particularly in a ideal posture. Specific postural re-education exercise, initiated with the formation of a neutral lumbopelvic posture, should therefore be viewed at this time as a component of rehabilitation, providing a simple means for the patient to recruit the deep postural muscles of the cervical spine in a functional way regularly throughout the day. Postural patterns are maintained by a complex arrangement of input modified by habits. Poor postural patterns eventually result in chronic pain symptoms, which have been shown to be predictably caused by limited range of motion or shortening or lengthening of muscles. The authors suggest that an effective treatment program should include individually determined exercises based on postural muscle balance.

Only left lateral flexion in lateral flexion angles was negatively correlated with the change in cervicothoracic angle. All subjects were right-handed. Generally, they spend the majority of their day sitting at desks testing or studying. These tasks usually involve right-handed mouse work. It is possible that the constant use of this work causes shortening of muscles such as the upper trapezius. Habitually shortened muscle length, with the individual not moving through a complete range of motion on a daily basis, might cause adaptive changes in muscle length with a habitual forward head posture. The length/tension relationship of a muscle will adapt to the new resting length. Head posture will affect cervical range of motion in normal individuals as well as in individuals with neck pain.

The authors found that the active neck extension angle was negatively correlated with the mean craniocervical angle and that the active neck flexion angle was negatively correlated with the mean cervicothoracic angle. The authors suggest that treatments for poor cervical posture should focus on recovering the normal ROMs of neck flexion and extension. Also, the cervical ROMs of neck extension and flexion could be useful data for predicting changes in the head and neck posture after long-term computer screen work.