Electromyography (EMG) has been proposed as a method for determining muscle effort in repetitive upper limb tasks, which are often related to cumulative trauma disorders. EMG activity of the finger flexor musculature was investigated during a repetitive hand gripping task having 5 different cycle durations (2 to 6 s), various percentage of work time (and rest) within the work cycle (20% to 80%), and 3 different grip force levels. Thirty healthy adult participants each performed 27 randomly ordered 30-s repetitive hand gripping trials as well as 3 isometric contractions, which were used to normalize data from the hand gripping trials. There was a significant decrease in mean EMG as the duration of the work-rest cycle time increased. At each force level, EMG increased as the percentage of work time within the work-rest cycle increased, but to a greater extent at the highest force level. The results of this study suggest that overall muscle effort, and perhaps muscle fatigue, can be reduced most effectively by modifying the force requirements of the repetitive task. Other variables, such as the percentage of work time within a cycle and overall work cycle time have less effect on the EMG activity level. The results of this study have implications for developing strategies to reduce muscle fatigue during repetitive hand gripping tasks in an effort to reduce the effects of cumulative trauma disorders.
|Original language||English (US)|
|Number of pages||16|
|Journal||International Journal of Occupational Safety and Ergonomics|
|State||Published - Jan 1998|
Bibliographical noteFunding Information:
We thank Kelly Cary, PT, Laura Thune, PT, Jeff Wachter, PT, and Kelley Leach, PT, for their valuable assistance with the study. This project was supported, in part, by grants from the Center for Disease Control (CDC R49/CCR 703640-05) and through grants number U02/CCU308771 and U02/CCU312014 from the National Institute for Occupational Safety and Health. Correspondence and requests for reprints should be sent to John C. Rosecrance, # 158 I.R.E.H., University of Iowa, Iowa City, IA 52242-5000, USA. E-mail <firstname.lastname@example.org > .
- Cumulative trauma disorders
- Hand gripping
- Muscle force
- Work-rest cycle