The present study determined the effects of flexing and extending the head on the postural stability and mean anterior-posterior (A-P) center of mass (CM) position during upright stance in the elderly. To ensure visual input to stability was not a confounding variable, visual information was kept as constant as possible for all head positions. Twelve healthy elderly subjects (72.3±4.7 years) were asked to stand stationary on a single force-platform. Postural stability (assessed using the rms A-P excursion of the center of pressure (CP)) was determined for standing with the head erect, and with the head flexed and extended. The vestibular contribution to postural stability becomes increasingly important under challenging conditions, so to highlight the effects of vestibular system input, measurements of postural stability under conditions where visual and somatosensory inputs were disrupted were included. Changes in the mean A-P CM position when tilting the head were assessed by determining changes in the mean A-P location of the CP from standing with the head erect. Compared to standing with the head erect and looking straight ahead, postural stability was reduced when the head was flexed or extended (P<0.01). Changes in mean A-P CM position were only significant when standing with the head flexed (P<0.05). This suggests that increases in postural instability with the head tilted from the erect position may be in part due to mechanical perturbation rather than solely vestibular disruption.

Bakgrund Muskuloskeletala besvär i nacke och skuldra är vanligt förekommande arbetsrelaterade sjukdomar bland bildskärmsarbetare. Detta orsakar individuellt lidande med stora kostnader för samhället i storleksordningen 0.5% till 2% av ett lands BNP, men även för företag som utöver ökade omkostnader även riskerar sämre produktion och kvalitet. Det finns en oro att bildskärmsarbetande med progressiva glasögon arbetar med en ökad huvudextension och huvudprotraktion sk ”gamnacke”. Få jämförande studier har dock gjorts på HE respektive FHP vid användandet av progressiva glasögon, och ännu färre med subjekten i deras naturliga arbetsmiljö. Syfte – I denna studie undersöktes om det, i subjektens egen arbetsmiljö, föreligger ett samband mellan begreppet gamnacke och bildskärmsarbete vid användandet av progressiva glasögon avseende faktorerna FHP och HE jämfört med bildskärmsarbete utan progressiva glasögon. Subjekt –Datainsamlingen har skett på sju stycken olika företag i storstockholmsområdet under tidsperioden Mars-April 2017. Testgruppen bestod av 3 män och 7 kvinnor med en medelålder på 57,80 år (±8,18). Tid som de använt progressiva glasögon var 5,85 år (±5,59). kontrollgruppen bestod av 4 män och 6 kvinnor med en medelålder på 55,90 år (±3,60). Metod – Subjekten fotograferades med en smartphonekamera i ett stativ med horisontellt vattenpass, sittande vid sina skrivbord framför sina egna bildskärmar. Tre fotografier togs under 5 minuters tid på respektive subjekt. Subjekten var inte varse om exakt vid vilken tidpunkt fotografierna togs. En mobilapplikation användes för att ta ut vinklar för HE och FHP. Medelvärdena användes sedan för vidare analys med ett two-independent-sample test. Resultat – Testgruppens medelvärde för huvudets protraktion, TFHP var 42,20° (±7,15°). Testgruppens vinkel för mätning av huvudets extension, THE, hade medelvärdet 17,73° (±5,55°). Kontrollgruppens medelvärde för huvudets protraktion, KFHP var 40,87° (±7,53°). Kontrollgruppens medelvärde av huvudets extension, KHE var 11,53° (±7,42°). Korrelationen mellan progressiva glasögon och FHP var inte statistisk signifikant (p = 0,739), detta gällde även för korrelationen mellan progressiva glasögon och HE (p = 0,063). Konklusion – Resultatet av studien visade inget statistiskt signifikant samband gällande att bildskärmsarbetande i subjektetens naturliga arbetsmiljö med fullprogressiva glasögon hade en högre grad FHP eller HE än bildskärmsarbetande utan fullprogressiva glasögon i förhållande till lodlinjen respektive horisontallinjen, däremot sågs en tendens till en högre grad av HE hos gruppen med fullprogressiva glasögon i förhållande till horisontallinjen (p=0,063). / Introduction – Musculoskeletal disorders of the neck and shoulders are common occupational diseases among VDU operators. This causes individual suffering with high costs for society at around 0.5% to 2% of a countries GDP, as well as for companies, that besides high costs also risk a poorer production and quality. There is a concern that VDU operators with progressive lenses have an increased head extension and Forward head posture. However, Few comparative studies have been made on head extension and Forward head posture on subjects with progressive lenses and even fewer with subjects in their natural working environment. Aim – In this study, the aim was to, in the subjects own natural working environment, investigate whether there is a connection between the concept of poor posture in regards of FHP and HE, and VDU operators in the use of progressive lenses, compared to VDU operators without progressive lenses. Materials – The data was collected from seven different companies in the Greater Stockholm area during the period March-April 2017. The test group consisted of 3 men and 7 women with an average age of 57.80 years (± 8.18). The time spent using progressive lenses was 5.85 years (± 5.59). The control group consisted of 4 men and 6 women with an average age of 55.90 years (± 3.60). Method - The subjects were photographed with a smartphone on a leveled tripod, sitting at their own desks in front of their own monitors. Three photos were taken within 5 minutes on each subject. The subjects did not know exactly when the photographs were taken. A mobile application was used to extract angles for HE and FHP measurements. The mean values were then used for further analysis with a two-independent sample test. Results – The test group's mean head protrusion, TFHP was 42.20° (±7.15°). The test group's angle for measuring the head extension, THE, had an average of 17.73° (±5.55°). The control group's mean head protrusion, KFHP was 40.87° (±7.53°). The control group's mean of the head extension, KHE was 11.53° (±7.42°). The correlation between progressive lenses and FHP was not significant (p = 0.739), nor was the correlation between progressive lenses and HE significant (p = 0.063). Conclusion – The results of the study showed no statistically significant correlation that VDU operators in the subject's natural working environment with progressive lenses have a higher degree of FHP or HE than VDU operators without progressive lenses in relation to the vertical- and horizontal line respectively. On the other hand, they had a trend towards a higher HE than VDU operators without progressive lenses with a p-value of 0.063.