Low-level ezperimental accommodative/vergence load and trapezius muscle activity
This experimental study induced different levels of oculomotor load by instructing subjects to focus a blurred point target with both eyes while the trapezius muscle activity was measured with bipolar surface electromyography (EMG). Twenty-eight subjects with a mean age of 29 (range 19-42, std 8) viewed a high-contrast fixation target for four 5-minute periods through: (i) 0 diopter (D) lenses; (ii) -3.5 D lenses; (iii) individually adjusted prism D lenses (1-2 D base out); or (iv) +3.5 D lenses. The fixation target was placed close to the individuals age-appropriate near point of accommodation in conditions (i-iii) and at 3 m (0.33D) in condition (iv). Each subjects ability to nullify the added lens blur was extracted via infrared photorefraction measurements. A bitwise linear regression analysis was conducted on individual measures of eye-lens refraction on the x-axis and normalized trapezius muscle EMG (％RVE) on the y-axis. The model estimated a constant level for x-values indicating that the incurred defocus had not been compensated for by a change in ocular accommodation/vergence, and a line coefficient for the other x-values. The average eye-lens refraction value and the 50th percentile EMG level was strongly correlated in the -D (ii; p < 0.001) and the +D blur (iii; p < 0.001). During prism blur this association did not reach significance (p=0.06). During no blur there were no signs of relationships. These results are directly attributable to a distinctive and directional engagement of the eye-lens accommodative system and in all likelihood reflect sensorimotor processing along the reflex arc of the accommodative system. It is concluded that sustained accommodation/vergence at near, through an eye-neck/scapular area functional linkage, may increase muscle activity levels, and therefore represents a risk factor for trapezius muscle myalgia when an uncorrected visual error is present. These findings also add to the current understanding of eye-neck/scapular area functional linkages that may arise during strenuous near-work conditions when no visual error is present.
Richter, H.O. B(a)nziger,T. Abdi, S. Forsman, M.
Centre for Musculoskeletal Research, University of G(a)vle, Sweden The Bernadotte Laboratories, St Eric’s Eye Hospital, Department of ClinicalNeuroscience, Karolinska Division of Occupational and Environmental Medicine, Department of Public Health Sciences, Karolinsk
国际会议
17th World Congress on Ergonomics(第十七届国际人类工效学大会)
北京
英文
1-9
2009-08-09（万方平台首次上网日期，不代表论文的发表时间）