Working spectacles for sorting mail.
BACKGROUND
Sorting mail into racks for postmen is visually demanding work. This can result in backward inclination of their heads, especially more pronounced for those who use progressive addition lenses.


OBJECTIVE
To evaluate the effects of customized working spectacles on the physical workload of postmen.


METHODS
Twelve male postmen sorted mail on two occasions: once using their private progressive spectacles and once using customized sorting spectacles with inverted progressive lenses. Postures and movements of the head, upper back, neck, and upper arms were measured by inclinometry. The muscular load of the trapezius was measured by surface electromyography.


RESULTS
With the customized sorting spectacles, both the backward inclination of the head and backward flexion of the neck were reduced (3°), as well as the muscular load of the right upper trapezius, compared to sorting with private spectacles. However, with the sorting spectacles, there was a tendency for increased neck forward flexion, and increased sorting time.


CONCLUSIONS
The reduction in work load may reduce the risk for developing work-related musculoskeletal disorders due to the positive reduction of the backward inclination of the head. But the tendency for increased neck forward flexion may reduce the positive effects. However, the magnitude of the possible reduction is difficult to predict, especially since quantitative data on exposure-response relationships are unknown. Alternative working spectacles with inverted near progressive lenses ought to be evaluated. They should still result in a positive reduced backward inclination of the head and may not cause any increased forward flexion.
Department of Design Sciences, Faculty of Engineering, Lund University, Lund, Sweden.
Hillevi
H
Hemphälä
Division of Occupational and Environmental Medicine, Lund University, Lund, Sweden.
Camilla
C
Dahlqvist
Division of Occupational and Environmental Medicine, Lund University, Lund, Sweden.
Catarina
C
Nordander
Department of Design Sciences, Faculty of Engineering, Lund University, Lund, Sweden.
Chuansi
C
Gao
Department of Design Sciences, Faculty of Engineering, Lund University, Lund, Sweden.
Kalev
K
Kuklane
Division of Ergonomics, School of Technology and Health, Royal Institute of Technology, Huddinge, Sweden.
Per
P
Nylén
Division of Occupational and Environmental Medicine, Lund University, Lund, Sweden.
Gert-Åke
GÅ
Hansson
D001132:Arm / Q000502:physiology; D001415:Back / Q000502:physiology; D005139:Eyeglasses; D006257:Head / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000502:physiology; D016272:Occupational Health; D011177:Postal Service; D011187:Posture; D064171:Superficial Back Muscles / Q000502:physiology; D013647:Task Performance and Analysis; D016526:Workload
EMG; Postmen; inclinometry; progressive lenses; work progressive spectacles