Short Interventions to Prevent Trapezius Muscle Fatigue in Computer Work
Condition: Muscle Fatigue; Trapezius Muscle Strain
MeSH terms: Fatigue
Study type: Interventional

Summary: 
      This study is expected to demonstrate that during experimental days of seated computer work
      sustained and focalized low-level muscle activity contributes to the development of
      long-lasting fatigue effects (and thus possible disorder). On days with and without frequent
      interruptions, signs of fatigue and the activity pattern of the trapeze muscle are registered
      and compared using electromyographic registrations of the trapezius muscle.
    

Detailed description: 
      30 healthy adults without chronic neck pain participated in a laboratory study designed to
      simulate two full workdays of computer work. Within each session, participants performed five
      50-min working activities separated by 10-min breaks: i) Use a computer keyboard to type a
      text presented on the left side of the screen; ii) do the typing task with the desk height
      set10 cm above elbow height; iii) play the computer game Spider Solitaire implemented in
      Windows 10; iv) Stroop test (This test consists of reading the name of a color whose text is
      in a color different from the name. The color name was then selected from a multiple-choice
      panel displaying color names; v) the same online puzzle game was presented to all
      participants. Assembling the puzzle was performed by drag and drop actions. The work periods
      were not disrupted (on the "control day") whereas two short interruptions of 5-min were
      introduced at 1/3 and 2/3 of each working period on the "intervention day". During these
      interruptions, participants were asked to perform "muscle disrupting/relaxing" activities.
      For each experimental session a 30-min lunch break took place between the third and the
      fourth work periods. The specific sequence of work activity type and disrupting/relaxing
      activities was randomized across participants; however, for each participant the order of
      work activities remained the same for the two experimental sessions (control and intervention
      days). The order of control and intervention days was also randomized between participants.

      A set of six measures were performed at specific time intervals during each experiment:
      before the first work activity, before and after lunch, immediately and 1 hour after the
      fifth (last) work activity: i) upper trapezius activation, assessed through the temporal EMG
      profile recorded by a single bipolar signal; and ii) through the spatio-temporal distribution
      of EMG activity detected by a 2D array of electrodes (64 channels); iii) muscle fatigue,
      quantified by changes in electrically induced muscle twitch force signals, iv) isometric
      performance, v) dynamic performance; iii) cognitive and physical load and stress level. In
      addition, personality traits (anxiety level), perceived workload and musculoskeletal symptoms
      were evaluated as covariates.
    

Intervention name(s): interruptions of work tasks
Intervention type(s): Behavioral
Intervention description(s): During each activity two interruptions/breaks were selected randomly from a set of ten predetermined actions:
Active break types:
Move shoulder and upper back
Swing arms near the body
Three slow but forceful elevations of the shoulders, a relaxation exercise based on the principles developed by Jacobson
Stand up and stretch
Slowly turn head in all possible directions.
Passive break types:
Tell a couple of jokes
Stand up and have a drink
Relaxing the trapezius
Questions on actual posture and feelings of comfort / discomfort.
A short rest on the couch
Intervention model: Sequential Assignment
Intervention model description: Randomized controlled laboratory experiment. 30 subjects are randomly assigned to two full day experiments either starting with the conditions including additional short interventions or without them.
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: muscle fatigue; work-related disorders; trapezius myalgia; sustained working task; high-density EMG