Postures
No clear definition of ‘posture’ can be
found in ergonomics literature. It may
be regarded as the configuration of the
body’s head, trunk and limbs in space
or as a quasi-static bio-mechanical
alignment, depending on whether the
particular context in which it is used is
anatomical or bio-mechanical. In any
work situation, functional, geometric
and bio-mechanical aspects are as
integral to the concept of posture
as they are to the consequences for
performance and comfort.
Pilot study data of laboratory
experiment supports the hypothesis
that extreme and/or complex
postures correlate negatively with
task performance. Sewing machine
separation task can be characterized
by “low force exertion, but with
high speed manipulation, frequent
repetition of hand movement and
long duration of continuous work
under a constrained body posture”.
An awkward sitting posture can
be influenced by the interaction of
several factors, including work place
layout (e.g. seat and table height and
inclination), task location (task height,
distance and direction), and manual
and/or visual requirements of the tasks
and the anthropometric characteristics
of the seated worker. The tendency
of operators to work in the hunched
posture suggests a potential conflict
between workstation geometry
and operator dimension. Analyses
indicate, most commonly, operators
position the chair away from the work
surface in order to allow a knee angle
of 110 ° or greater. Factors limiting
operator access to the workstation
was the location of the treadle, which
is too close to the proximal edge
and of various obstructions (motors,
pneumatic equipment, and machine
guards) beneath the work surface.
While typical recommended knee room
averages about 46 cm, the presence of
these obstructions, in some cases, limit
available space to less than 26 cm.
An increase in task distance and
increase in trunk forward flexion,
results in decrease in head/neck
flexion. As the task height moved
HAZARDOUS BODY POSTURES
WRIST
Extremes of ulnar deviation;
Extremes of radial deviation
This represents the movement
of wrist towards little finger
or thumb. It is advisable not to
exceed the extremes, of 30 ° for
ulnar and 20 ° for radial deviation.
SHOULDER
Shoulder flexion
Shoulder flexion should not
exceed 90 ° . It pertains to
movement of hand from shoulder
point towards front.
OTHER BODY
PARTS
FINGERS – Lumbrical
and pinch grasps
Pinch grip involves
lifting of item with the
help of thumb and one
Extremes of wrist
flexion; Extremes of
wrist extension Extremes of wrist
supination; Extremes
of wrist pronation
“Wrist should remain
straight,” this is the ideal
position for wrist. The extension
should not be more than 65 °
whereas flexion should not
exceed 75 ° . Wrist should remain as close
to neutral as possible during
much of the work cycle as
possible. Pronation and
supination at about 90 ° can
give harmful effects.
Shoulder abduction and
rotation lateral shoulder rotation along
with 15 ° -20 ° of shoulder abduction
can cause traumas.
Shoulder abduction should not
exceed 18 ° -20 ° . Abduction reflects
movement of hand from shoulder
point towards lateral side.
Greater than 5 ° -10 ° of medial or
finger only, whereas
lumbrical grasp is a
fatiguing posture for the
small muscles of the hand,
causing ache of the palm.
This is a posture where the
fingers are straight except
the thumb and grasp is done
by the thumb.
Hyperextension of shoulder
Hyperextension is extension
of abduction towards back. It
should not exceed 40 ° .
NECK – Greater than 20 ° of
neck flexion
Neck should not be more than 20 °
flexion from its normal position.
LOWER BACK –
Leaning or bending of lower back
beyond 18” for females, 22” for
males is a hazardous posture.
www.apparelresources.com | MAY 2017 | Apparel Online Bangladesh
53