EFFECT OF STRETCHING EXERCISES ON TRAPEZIUS WORKLOAD USING MVIC AS AN INDICATOR

Abstract

The substantial increase in using the desktop in offices is directly
associated with Work Related Upper Limb Disorders
(WRULDs) where an average workload on trapezius of 4hours/-
day in females, is the main cause. Ergonomically inappropriate
work station may increase the static muscle load at bilateral
shoulder and wrist joint where keyboard is mostly responsible.
Intermittent rest periods and varying positions are found
significant during constant sedentary work. The aim of this
study was to determine the effect of active stretching on the
upper fibers of trapezius using desktop computer measured
by MVIC.
A 22 years old left hand dominated female typing with an
average frequency of 4 hours/day with 40 words/minute. An
adjustable VDU was placed with arm, wrist and foot support.
A word processing task was allotted for 20 minutes before and
20min after the stretching. The Root Mean Square (RMS) for
the EMG were collected at the intervals of 6th, 9th, 12th, 15th,
and 18th minutes during typing. Subject performed three
stretches of 20sec at the end followed by a rest period. The
results reveal that resting EMG of the dominant hand was
found to be 21% of MVIC where amplitude of EMG of the
dominant hand is higher than the non-dominant (more than
10% higher). Stretching exercises decreased the activity of
trapezius by 1.1% and the residual effect lasted for less than
12minutes. It is suggested that 20 seconds of static stretching
between the intervals were found to be effective in reducing
the workload for the students. Studies on larger scales should
be conducted for especially research and postgraduate
students and proper workstations should be recommended
for them.
KEYWORDS
MVIC (Maximum Voluntary Isometric Contraction), Work Related
Upper Limb Disorders (WRULDs), workload, trapezius,
stretching, EMG