Task selection for increased mechanical exposure variation: relevance to job rotation

Area of Science:

• Ergonomics and Occupational Health
• Biomechanics
• Human Factors Engineering

Background:

• Musculoskeletal disorders (MSDs) are often linked to repetitive mechanical exposure in manual tasks.
• Variation in mechanical exposure is widely believed to be beneficial for MSD prevention.
• Quantifying functional task similarity is crucial for designing jobs that minimize MSD risk.

Purpose of the Study:

• To develop and test an approach for quantifying the functional similarity between different manual tasks.
• To investigate the functional differences between three common handgrips: power grip (PG), pulp pinch (PP), and lateral pinch (LP).
• To assess the potential of alternating functionally different tasks to enhance exposure variation and prevent MSDs.

Main Methods:

• Isometric contractions at 30% of maximal voluntary contraction (MVC) were performed for 2-minute durations.
• Fifteen different combinations of handgrip tasks were tested on 25 participants.
• Changes in MVC forces were measured to quantify strength decrements after task performance.

Main Results:

• Significant functional differences were observed between the power grip (PG) and lateral pinch (LP).
• Alternating between PG and LP resulted in a strength drop to 85.1% MVC.
• Performing PG alone led to a more substantial strength drop to 59.3% MVC.

Conclusions:

• The power grip (PG) and lateral pinch (LP) are functionally distinct enough for their alternating use to increase exposure variation.
• Alternating functionally different manual tasks can contribute to reduced fatigue and increased work capacity.
• Understanding task differences aids in job design to better combine tasks and prevent musculoskeletal disorders.