European Journal of Applied Physiology

, Volume 112, Issue 8, pp 2891–2902 | Cite as

Influence of mental workload on muscle endurance, fatigue, and recovery during intermittent static work

  • Ranjana K. Mehta
  • Michael J. Agnew
Original Article


Most occupational tasks involve some level of mental/cognitive processing in addition to physical work; however, the etiology of work-related musculoskeletal disorders (WMSDs) due to these demands remains unclear. The aim of this study was to quantify the interactive effects of physical and mental workload on muscle endurance, fatigue, and recovery during intermittent work. Twelve participants, balanced by gender, performed intermittent static shoulder abductions to exhaustion at 15, 35, and 55% of individual maximal voluntary contraction (MVC), in the absence (control) and presence (concurrent) of a mental arithmetic task. Changes in muscular capacity were determined using endurance time, strength decline, electromyographic (EMG) fatigue indicators, muscle oxygenation, and heart rate measures. Muscular recovery was quantified through changes in strength and physiological responses. Mental workload was associated with shorter endurance times, specifically at 35% MVC, and greater strength decline. EMG and oxygenation measures showed similar changes during fatigue manifestation during concurrent conditions compared to the control, despite shorter endurance times. Moreover, decreased heart rate variability during concurrent demand conditions indicated increased mental stress. Although strength recovery was not influenced by mental workload, a slower heart rate recovery was observed after concurrent demand conditions. The findings from this study provide fundamental evidence that physical capacity (fatigability and recovery) is adversely affected by mental workload. Thus, it is critical to determine or evaluate occupational demands based on modified muscular capacity (due to mental workload) to reduce risk of WMSD development.


Physical workload Cognitive demands Strength Muscle capacity Musculoskeletal disorders 


Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  1. 1.Departments of Cognitive and Learning Sciences and Kinesiology and Integrative PhysiologyMichigan Technological UniversityHoughtonUSA
  2. 2.Grado Department of Industrial and Systems EngineeringVirginia TechBlacksburgUSA

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