Effects of cognitive loading and force on upper trapezius fatigue

Area of Science:

• Ergonomics and Occupational Health
• Neuroscience
• Physiology

Background:

• Musculoskeletal disorders (MSDs) are prevalent in the shoulder/neck, often linked to computer work and low-force exertions.
• Cognitively demanding tasks can increase muscle activity, yet the interplay between cognitive load, muscle activity, and fatigue remains understudied.
• Existing research lacks detailed investigation into the relationship between varying cognitive loads and resultant muscle fatigue.

Purpose of the Study:

• To quantify the impact of cognitive loading on upper trapezius muscle conduction velocity and isometric endurance.
• To determine how different levels of cognitive demand affect muscle fatigue markers.

Main Methods:

• Participants undertook isometric endurance tests of the upper trapezius at 20% and 40% of maximum voluntary contraction (MVC).
• Simultaneously, subjects engaged in computer-based tasks with three distinct levels of cognitive load (0, 1.59, and 3 Bits).

Main Results:

• Cognitive load significantly affected normalized conduction velocity slopes at 40% MVC, but not at 20% MVC.
• Endurance times for both exertion levels were significantly reduced with increased information load (P < 0.01).

Conclusions:

• High cognitive load tasks, when combined with static isometric exertions, lead to faster trapezius muscle fatigue.
• Findings are critical for modern workplaces with automation, decision-making, and extensive computer use, suggesting potential ergonomic risks.