ERGONOMIC ASSESSMENT OF UPPER EXTREMITY FORCE APPLICATION IN MANUAL TOOLS
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Date
2015
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
AGRICULTURAL ENGINEERING INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI
Abstract
A large number of agricultural equipment needs manual power for their
operation. Push and pull action are extensively used to operate most of the manual
tools involved in agricultural activities. The push pull strength varies significantly
with respect to work load, duration of work, physiological and postural parameters of
operator. Repetitive and continuous operation of these equipment results in postural
stress, which lead to musculoskeletal disorders in operators if used for longer period
of time. Hence the ergonomic assessment of hand tools is needed for drudgery
reduction and increase efficiency. This study was conducted to find out the best
forearm posture in ideal combination of muscles to optimize push/pull strength. An
experimental set up was fabricated to generate the push/pull task. Experiments were
conducted for seven forearm positions viz. neutral, pronation, dorsiflexion, palmer
flexion, radial deviation, ulnar deviation and supination. Ergonomic evaluation in
terms of heart rate, oxygen consumption, energy expenditure, body part discomfort
(BPDS) and overall discomfort score(ODS) were assessed for different forearm
position at different loads.
To conduct the experiment five subjects were selected from available
work force in ergonomic laboratory at Division of Agricultural Engineering ICARIARI
New Delhi. The subjects were in the age group of 30-45 years. Maximum
aerobic capacity of subjects were computed by extrapolation from calibration charts..
The relationships between heart rate (beats per minute) and oxygen consumption
(litre per minute) were found to be linear for all the subjects. The maximum aerobic
capacity (VO2 max) of the selected subjects varied from 2.05 to 2.35 l min-1
. Total
315 experiments were conducted on seven modes of forearm posture and three load
output conditions namely 45, 67 and 90 N. The working heart rate (beats min-1
),
oxygen consumption (l min-1
), energy expenditure (kJ min-1
), ∆HR (beats min-1
) ,%
VO2 Max, BPDS and ODS were highest for radial deviation and lowest for neutral
deviation of forearm postion. Higher load output condition under all the seven
ii
forearm position force application the ∆HR (beats min-1
) values exceeded the limit
for continuous performance level (40 beats min-1
).The observations reflect that these
can be short duration operations and must be continued with sufficient rest
allowance. The percent VO2 max value were much higher than the acceptable work
load for all modes of operations with higher load output conditions. This again
reveals that all mode of operation could not be performed continuously without
frequent rest. BPDS and ODS value were also highest for radial deviation for
forearm position signifying that this mode of operation was most uncomfortable and
strenuous whereas neutral position was quite opposite which is most comfortable and
least strenuous.
Based on the result in terms of maximum push pull strength and
ergonomic parameters, it was found that neutral forearm posture is the best mode of
force application. However there was similar push pull strength in the range of
handles orientation from 00
to 350
from the neutral position.
Description
T-9227
Keywords
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