The effects of hand force variation on shoulder muscle activation during submaximal exertions

Abstract

Upper limb injuries are highly prevalent in the workplace and new tools are needed to proactively design workstations to reduce injury risk. The objective was to characterize spatial, load and direction dependency of muscle activity for hand exertions in the upper limb workspace. Electromyographic signals were collected from 14 upper limb muscles during exertions for all combinations of 4 submaximal hand forces (20/30/50/60 N) in 6 cardinal (up/down/left/right/forward/backward) directions at 5 hand locations. Linear muscle activity increases accompanied increased hand forces. Total muscle activity increases between 20 and 60 N hand forces ranged by direction from 92% (downward) to 189% (right). Prediction equations for all muscles depended on hand force, and linear, quadratic and interaction permutations of hand location. Muscle activity associated with manual tasks is load, direction and spatially dependent. Equations developed to describe these complex relationships can be used to better design future and evaluate current occupational activities.

Keywords:

• electromyography
• upper limb
• work envelope
• hand force
• muscle

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Meghan E. Vidt http://orcid.org/0000-0002-8811-8569

Additional information

Funding

This work was partially supported through the Natural Sciences and Engineering Research Council of Canada (NSERC) [Discovery Grant 311895-2011 (CRD)]. Equipment used in the study was funded through combined support from the Canada Foundation for Innovation and the Ontario Research Fund.