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Fatigue in the forearm resulting from low-level repetitive ulnar deviation
Jack Tigh Dennerlein1, Vincent M Ciriello, Kirsty J Kerin
1Department of Environmental Health, Harvard University, School of Public Health, 665 Huntington Ave., Boston, MA 02115, USA.
Summary
Repetitive work tasks can cause low-frequency fatigue (LFF) in the extensor carpi ulnaris (ECU) muscle, even at seemingly acceptable workloads. This muscle fatigue progresses throughout the workday, impacting worker health.
Area of Science:
- Occupational health
- Musculoskeletal research
- Human factors engineering
Background:
- Repetitive tasks are common in many industries.
- Understanding muscle fatigue is crucial for preventing work-related injuries.
- Low-frequency fatigue (LFF) is a significant concern in occupational settings.
Purpose of the Study:
- To measure LFF in the extensor carpi ulnaris (ECU) muscle during a repetitive ulnar deviation task.
- To assess the progression of muscle fatigue throughout a workday.
- To evaluate the effectiveness of psychophysical protocols in determining acceptable workloads.
Main Methods:
- A repeated measures design was used with 10 healthy women.
- Participants completed a repetitive ulnar deviation task at 20 and 25 repetitions per minute.
- Low-frequency fatigue was measured using the ratio of isometric force at 20 pps to 50 pps, with fatigue and discomfort self-reported.
- Measurements were taken eight times throughout control and workdays.
Main Results:
- Workdays showed lower force ratios compared to control days, indicating LFF.
- Muscle fatigue increased as the workday progressed.
- Psychophysically determined workloads, though not causing discomfort, were sufficient to induce LFF.
Conclusions:
- Repetitive ulnar deviation tasks at psychophysically determined workloads induce LFF in the ECU muscle.
- Muscle fatigue accumulates over the course of a workday.
- Current psychophysical methods may not fully prevent low-level muscle fatigue during prolonged repetitive tasks.