INGENIEUR
of the neck , trapezius muscles on both sides of the upper back , the erector spinae muscles on both sides of the lower back , the anterior deltoid muscles on both shoulders and the brachioradialis muscles on both hands . Maximum Voluntary Contraction ( MVC ) for each muscle was recorded before the assessment proceeded . The muscles of each of the respondents were monitored continuously for 45 minutes without interruption .
Disposable electrodes ( 3M™ Red Dot™ Sensor ) were connected to the targeted muscles at an inter-electrode distance of 25mm . The bi-polar electrodes were connected parallel to the direction of the muscle fibres while the earth electrode was connected 20-30mm away from the bipolar electrodes . The electrodes were all connected to the 16 channel MegaWin ME6000 surface electromyography device . The data was processed using the MEGAWIN 3.0 Windows software . The EMG signals were band passed filtered at 20- 450Hz with a sampling frequency of 1000Hz . Fatigue , which is an indication of the change in Mean Power Frequency ( MPF ) was analysed using the software . The values were normalised with the Maximum Voluntary Contraction of each muscles expressed in hertz for the MPF .
Spine kinematic assessment The purpose of this intervention was to evaluate the occurrences of Low Back Disorder ( LBD ) while using the mechanical apparatus . The average probability of LBD risk using the mechanical apparatus was then compared with the traditional hand scoop method .
In this intervention , three respondents were recruited for the study . Participants were identified as healthy individuals without any back pain or injuries for the past 12 months related to the subjects ’ common physical activities . All respondents were required to sign an approved informed consent form before commencing the intervention assessment .
For spine kinematic analysis , all the work processes were simulated in a laboratory setup for both mechanical and traditional cockle harvesting . The spine kinematics were measured using the industrial Lumbar Motion Monitor ( iLMM ). The calibrated iLLM was attached to a harness worn by the respondents . All respondents were requested to follow the actual cockle harvesting technique and the continuous spine kinematics data was collected by the iLMM software using a wireless transmitter and a receiver system connected to and stored on a portable data recorder ( Microsoft Surface Pro 5 ). All of the collected data was analysed using Low-Back Motion software ( Ballet TM Version 3.1 Build 4 ).
RESULTS AND DISCUSSION
Development of the mechanical apparatus The manipulated weight design was selected for the study and was fabricated as shown in Figure 6 . The design and development of the pulley and cable system ( Figure 2 ), pulley and gear ( Figure 3 ), pulley and gear with steering ( Figure 4 ) were reckoned to take up to three times longer per effort than the manipulated weight design ( Figure 6 ).
scoop stand platform
Figure 6 : Prototype of the mechanical apparatus
The platform was used for better control of the apparatus during handling . Harvesting is done via a counterweight mechanism which works as a weight stabiliser . The scoop is connected to a rod and the operating mechanism is designed in such a way that when the person handling the apparatus stands on the platform and moves the rod counterweight down , the scoop moves up .
Ergonomic study : Muscle activity and spine kinematic assessment results Figure 7 shows the comparison of normalised data based on MVC from traditional and mechanical cockle harvesting operations . The value from every muscle shows a significant reduction in muscle contraction in the intervention assessment with the left erector spine muscles showing more than 43 % reduction of maximum contraction . A higher MVC was recorded in the left hand region with a 50 % muscle contraction followed by left trapezius and left erector spinae with 47 % and 44 % MVC
32 VOL 84 OCTOBER-DECEMBER 2020