title: Sex differences in the shoulder joint position sense acuity: a cross-sectional study.
abstract: BACKGROUND
  Work-related musculoskeletal disorders (WMSD) is the most expensive form of work disability. Female sex has been considered as an individual risk factor for the development of WMSD, specifically in the neck and shoulder region. One of the factors that might contribute to the higher injury rate in women is possible differences in neuromuscular control. Accordingly the purpose of this study was to estimate the effect of sex on shoulder joint position sense acuity (as a part of shoulder neuromuscular control) in healthy individuals.
  
  
  METHODS
  Twenty-eight healthy participants, 14 females and 14 males were recruited for this study. To test position sense acuity, subjects were asked to flex their dominant shoulder to one of the three pre-defined angle ranges (low, mid and high-ranges) with eyes closed, hold their arm in that position for three seconds, go back to the starting position and then immediately replicate the same joint flexion angle, while the difference between the reproduced and original angle was taken as the measure of position sense error. The errors were measured using Vicon motion capture system. Subjects reproduced nine positions in total (3 ranges × 3 trials each).
  
  
  RESULTS
  Calculation of absolute repositioning error (magnitude of error) showed no significant difference between men and women (p-value ≥ 0.05). However, the analysis of the direction of error (constant error) showed a significant difference between the sexes, as women tended to mostly overestimate the target, whereas men tended to both overestimate and underestimate the target (p-value ≤ 0.01, observed power = 0.79). The results also showed that men had a significantly more variable error, indicating more variability in their position sense, compared to women (p-value ≤ 0.05, observed power = 0.78).
  
  
  CONCLUSIONS
  Differences observed in the constant JPS error suggest that men and women might use different neuromuscular control strategies in the upper limb. In addition, higher JPS variability observed in men might be one of the factors that could contribute to their lower rate of musculoskeletal disorders, compared to women.
  
  
  CONCLUSIONS
  The result of this study showed that shoulder position sense, as part of the neuromuscular control system, differs between men and women. This finding can help us better understand the reasons behind the higher rate of musculoskeletal disorders in women, especially in the working environments.
authors.affiliation: School of Physical and Occupational Therapy, McGill University and Interdisciplinary Research Center in Rehabilitation (CRIR), 3654 Promenade Sir William Osler, Montreal, QC, H3G 1Y5, Canada. Amir.vafadar@mail.mcgill.ca.
authors.forename: Amir K
authors.initials: AK
authors.lastname: Vafadar
authors.affiliation: Department of Kinesiology and Physical Education, McGill University and Interdisciplinary Research Center in Rehabilitation (CRIR), 475 Pine Avenue West, Montreal, QC, H2W 1S4, Canada. Julie.cote2@mcgill.ca.
authors.forename: Julie N
authors.initials: JN
authors.lastname: Côté
authors.affiliation: School of Physical and Occupational Therapy, McGill University and Interdisciplinary Research Center in Rehabilitation (CRIR), 3654 Promenade Sir William Osler, Montreal, QC, H3G 1Y5, Canada. Philippe.archambault@mcgill.ca.
authors.forename: Philippe S
authors.initials: PS
authors.lastname: Archambault
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D011434:Proprioception; D016059:Range of Motion, Articular; D011984:Sensory Receptor Cells / Q000502:physiology*; D012737:Sex Factors; D012785:Shoulder Joint / Q000294:innervation*; D055815:Young Adult