Effects of postural and visual stressors on myofascial trigger point development and motor unit rotation during computer work

Depiction of three experimental conditions (from left to right, VL/PL, VH/PL, VL/PH).

Placement of surface electrode array (14 channels) over trapezius muscle. Channel 7 records EMG data directly over the trigger point location, as determined by myofascial specialist.

EMG analysis and FFT processing illustration to calculate the running means of the median frequencies. FFT=Fast Fourier Transform.

Average median frequency cycles (across all spatial locations combined) as a function of condition. Whiskers=1 standard deviation. Results showed that all three conditions were significantly different from one another.

Average median frequency cycles (across all subjects) as a function of muscle spatial location (relative to MTrP). Location highlighted in red represents the MTrP location. Green (lighter) locations represent locations that are significantly different from MTrP location (p<0.05). Grey discs indicate electrode placement while the dotted lines represent muscle striation lines.

Mean VAS scores for neck/backache (post–pre) as a function of condition. Whiskers=1 standard deviation. Results showed that VL/PL and VL/PH conditions were significantly different; however, VH/PL condition was not significantly different from the other two conditions.