Localized muscle fatigue (LMF) has been associated to many adverse effects on human performance and the risk of work-related musculoskeletal disorders (WMSDs). While the development of LMF can be dependent on several factors, the influence of cognitive demands is still uncertain. This study analyzed the influence of varying levels of cognitive load for a simple biomechanical system involving static exertions at a moderate level (25% of maximum voluntary capacity). Participants performed 1-hour sessions of intermittent isometric abductions of the index finger for four experimental conditions including passive rest and added cognitive load in the form of an arithmetic task. Both subjective and objective measures were recorded including measures of discomfort, muscle activity, physical and mental task performance, muscle capacity and task demands. All conditions with added cognitive demand showed better results compared to passive rest in terms of muscle activity, muscle capacity and physical demand. Moreover, moderate cognitive demand in concurrence with physical task showed most favorable results as subjects showed lowest perceived fatigue (1.66/10), physical demand (30/100), and muscle activity (0.184 volts) as well as highest muscle capacity retention (92.4%). Further addition of concurrent cognitive demand at a high level showed similar perceived fatigue (1.67/10) and physical demand (32/100) but demonstrated higher muscle activity (0.239 volts) and lower muscle capacity retention (89.9%). Meanwhile, some responses showed different trends for the two genders. Outcomes of this study can be used to develop guidelines for designing tasks for both genders under different occupational settings, to potentially reduce LMF and contribute towards reducing the risk and development of WMSDs, improving the performance, and for finding an “optimal” level of cognitive demand for different occupational setting to obtain most favorable results.

Library of Congress Subject Headings

Mental fatigue; Cognitive learning; Performance; Fatigue; Muscles--Diseases

Publication Date


Document Type


Student Type


Degree Name

Industrial and Systems Engineering (MS)

Department, Program, or Center

Industrial and Systems Engineering (KGCOE)


Ehsan Rashedi

Advisor/Committee Member

Esa Rantanen


RIT – Main Campus

Plan Codes