Muscle fatigue in relation to forearm pain and tenderness among professional computer users

Gert F Thomsen¹^,2 , Pete W Johnson³ , Susanne W Svendsen¹ , Ann I Kryger⁴ and Jens Peter E Bonde¹

¹Department of Occupational Medicine, Aarhus University Hospital, Noerrebrogade 44, building 2 C, 8000 Århus, Denmark

²Department of Occupational Medicine, Ribe County Hospital, Oestergade 80, 6700 Esbjerg, Denmark

³Department of Environmental and Occupational Sciences, School of Public Health, Seattle, USA

⁴Department of Occupational and Environmental Medicine, Copenhagen University Hospital, Bispebjerg Bakke 23, 2400 Copenhagen NV, Denmark

author email corresponding author email

Journal of Occupational Medicine and Toxicology 2007, 2:17doi:10.1186/1745-6673-2-17


Published:	8 December 2007

Abstract

Background

To examine the hypothesis that forearm pain with palpation tenderness in computer users is associated with increased extensor muscle fatigue.

Methods

Eighteen persons with pain and moderate to severe palpation tenderness in the extensor muscle group of the right forearm and twenty gender and age matched referents without such complaints were enrolled from the Danish NUDATA study of neck and upper extremity disorders among technical assistants and machine technicians. Fatigue of the right forearm extensor muscles was assessed by muscle twitch forces in response to low frequency (2 Hz) percutaneous electrical stimulation. Twitch forces were measured before, immediately after and 15 minutes into recovery of an extensor isometric wrist extension for ten minutes at 15 % Maximal Voluntary Contraction (MVC).

Results

The average MVC wrist extension force and baseline stimulated twitch forces were equal in the case and the referent group. After the fatiguing contraction, a decrease in muscle average twitch force was seen in both groups, but the decrease was largest in the referent group: 27% (95% CI 17–37) versus 9% (95% CI -2 to 20). This difference in twitch force response was not explained by differences in the MVC or body mass index.

Conclusion

Computer users with forearm pain and moderate to severe palpation tenderness had diminished forearm extensor muscle fatigue response. Additional studies are necessary to determine whether this result reflects an adaptive response to exposure without any pathophysiological significance, or represents a part of a causal pathway leading to pain.