You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
workers with high levels of static contraction , prolonged static loads , or extreme working 
 postures involving the neck and shoulder muscles , are exposed to an increased risk of neck 
 and shoulder musculoskeletal disorders1 , 2 . repeated and sustained working with 
 elevated arms
is especially likely to lead to neck and shoulder pain3 , and a causal relationship has been suggested in several 
 systematic reviews4 . sustained or 
 repetitive activity of the neck and shoulder muscles is thought to cause compromised 
 circulation and mechanical pressure in the shoulder muscles4 . a long - term overhead working posture results in strain and fatigue 
 in the shoulder muscles because arm elevation is associated with shoulder muscular 
 fatigue5 .
wegner et al.6 suggested that a postural correction 
 strategy for the scapular position was helpful for patients with neck pain , restoring 
 muscular activation during computer work .
however , no study has investigated the influence 
 of overhead work on scapular position .
therefore , this study examined the changes in 
 scapular position after short - term overhead work .
twelve males , aged 2027  years and with a mean height and weight of 176.1  4.7  cm and 65.0 
  5.2  kg , respectively , participated in this study .
the subjects had no history of 
 musculoskeletal disorders or pain associated with the upper extremity in the past 6 months . 
 a palpation meter ( palm ; performance attainment associates , st .
paul , mn , usa ) was used to 
 measure the distance and inclination between two bony landmarks of the body .
the palm 
 consists of an inclinometer and two caliper arms ; the inclinometer has a semicircular arc 
 that moves within the range 030 in either direction from the midline at 1 intervals .
the 
 palm was used as a body - tool interface to combine the advantages of palpation with the 
 objectivity and reliability of caliper and inclinometer measurements .
the acromion angle was 
 determined using the palm as the value of the inclination angle between the acromion and the 
 c7 spinous process .
the scapular inferior distance was determined using the palm as the 
 distance from the inferior angle to the spinal process .
all subjects performed overhead work 
 with their arms during a scheduled work session of 20  min .
the overhead work was performed 
 at a height of 25  cm above the head of each subject .
the statistical package for social sciences ( spss , chicago , il , usa ) was used to 
 conduct statistical analyses . the significance of differences in the acromion angle and 
 scapular inferior distance before and after the overhead work was tested using the paired 
 t - test . the alpha level for statistical significance
the acromion angle was significantly decreased after the overhead work ( 10.6  3.3  ) 
 compared to before ( 14.8  4.5  ) ( p<0.05 ) .
the scapular inferior 
 distance was significantly increased after the overhead work ( 8.5  2.2  cm ) compared to 
 before ( 7.2  1.7  cm ) ( p<0.05 ) .
previous studies of overhead work requiring arm elevation and head extension have focused 
 on head extension , which leads to compression of the posterior elements of the cervical 
 vertebra7 .
more recently , the 
 relationship between upward rotation of the scapula and arm flexion has been reported as a 
 kinesiological chain , so studies are now examining the neck and shoulder muscle activities 
 and pain associated with overhead work8 , 9 . a change in the scapular position and 
 motion ,
in particular , changes in the lengths of muscles attached to the scapula , eventually 
 lead to shoulder pathology1 .
we found that the 
 acromion angle significantly decreased and the scapular inferior distance significantly 
 increased following performance of overhead work .
a decreased acromion angle indicates an 
 elevated shoulder posture , and an increased scapular inferior distance indicates an upward 
 scapular posture .
the upper trapezius is more active in shoulder abduction a in flexion up 
 to the horizontal position , after which it increases with arm elevation9 .
the shortening of the upper trapezius may result in 
 scapular elevation and upward rotation during arm elevation2 .
excessive and continuous scapular upward posture may also produce 
 overstretch weakness of the rhomboid , middle , and lower trapezius muscles ( activated by 
 scapular retraction)2 .
when this altered 
 activation is combined with weakness of the lower trapezius and tightness of the upper 
 trapezius and levator scapulae , this imbalanced musculature might contribute to dysfunction 
 of the scapulothoracic and glenohumeral joints10 .
the present study required subjects to perform short - term overhead 
 work of one hour duration . however , overhead work , even of this short duration , may present 
 a high risk of abnormal scapular position .
therefore , overhead workers must be provided with 
 modified job conditions or ergonomic devices for prevention of excessive upward scapular 
 rotation .
[ purpose ] this study investigated the changes in acromion and scapular position after 
 short - term overhead work . 
 [ subjects ] twelve males aged 2027  years , were recruited . 
 
 [ methods ] we measured the acromial angle and scapular inferior distance using a palpation 
 meter before and after overhead work . [ results ] the acromion angle was significantly 
 decreased after the overhead work compared to before . 
 the scapular inferior distance was 
 significantly increased after the overhead work compared to before . 
 [ conclusion ] even 
 though the overhead work was short - term work lasting less than one hour , it resulted in an 
 abnormal scapular position .