11.man and machine the measurement of range of movement of the wrist
Advances in Physics Theories and Applications www.iiste.orgISSN 2224-719X (Paper) ISSN 2225-0638 (Online)Vol 4, 2012 Man and Machine? The Measurement of Range of Movement of the Wrist Imaekhai Lawrence* Department of Materials and Production Engineering, Ambrose Alli University, Ekpoma. Nigeria Email: firstname.lastname@example.orgAbstractThis paper documents a pilot study undertaken to compare the effectiveness and efficiency of manuallymeasuring the range of movement at the wrist using both a traditional goniometer and a motion capturetechnique (using a CODA system). Fifteen subjects, male and female 18-22 years old were measured usingboth techniques. The results indicate a variation of adduction and abduction values at the wrist, beyond thatstated in existing references. The manual goniometric data collection was quicker than using the CODAsystem. A longer time period was spent in preparation and post processing of the result from the CODAsystem into a spreadsheet. However, the CODA system provided a more detailed description of the ROM ofa wrist, highlighting the compound angle made by the wrist during the measurement of adduction andabduction which is not shown through manual goniometry.Keywords: ergonomics, man, machine, wrist, effectiveness.1. IntroductionIt has been established that position of forearm, wrist and hand during manual handling or manipulativetasks can affect an individual’s ability to grip an object (Pryce, 1980). However, the authors do not know ofany work being undertaken to investigate the relationship between wrist mobility and an individual’s abilityto perform a manual handling task. This investigation is part of a programme of work to define thecharacteristics and performance of the hands using a sample of the Nigeria population, sponsored by theNigeria Population Commission.The tests documented within this paper describe the use of two methods of goniometric measurement,conventional goniometric measurement by an operator using a goniometric, and the angular measurementtaken using a motion capture machine. The aim of this trial was to review the effectiveness and efficiencyof the motion capture machine, Cartesian Optoelectronic Dynamic Anthropometer (CODA), in recordingRange of Motion (ROM) at the wrist, against manual measurement of the same angles. It was also toidentify any relationships between conventional measurements of hand characterizes anthropometrics andgrip strength. The evaluation of how appreciate is it to use a motion capture system to recordanthropometric characteristics of a subject within a trial is also discussed.Measurements were taken from a population of 157 first year undergraduate students, (of which 76 werefemale), from the department of Materials and Production Engineering, Ambrose Alli University and theDepartment of Industrial and Production Engineering, University of Ibadan. They were aged betweeneighteen and twenty-two years, old. No student had any impairment or abnormality in his or her hands. Thetrial ran between January and June 2011.2. MethodThe subjects were invited to take part in the trial which was undertaken in two phases, measurement ofanthropometric data, followed by measurement of other aspects of hand performance such as grip strength,finger compliance and finger friction, detailed in previous references (Torrens and Gyi, 1999). The series ofmeasurements to be taken were discussed with subjects and their writer approval given before taking part inthe trial. All measurements to be taken were discussed with subjects and their written approval given beforetaking part in the trial. All measurements were taken in a room with ambient temperature, humidity andaway from direct sunlight. In phase one; anthropometric measurements were taken from all 157 subjects.The measurements taken were of the right hand only, for speed of measurements, and the subject’sdominant hand recorded. BS 7231 (1990) was used as a guide to method of anthropometric measurement.In phase two, grip strength, finger friction, finger compliance and ROM measurements were taken from 9
Advances in Physics Theories and Applications www.iiste.orgISSN 2224-719X (Paper) ISSN 2225-0638 (Online)Vol 4, 2012thirty-five subjects, fourteen of whom were female. Finger friction and compliance were also measured butare not discussed in this paper. Thirty-five subject from the sample population had the ROM of their wristsmeasured and were chosen to be reprehensive of the anthropometric percentile range of the population. Twooperators processed subjects in groups of five. Due to time constraints, each measurement was taken onlyonce, manual and machine measurements were taken in the same order each time and by the same operator.A consultant ergonomist who was experienced in taking anthropometric measurements was one of theoperators. Data was recorded by hand. The finger friction and compliance measurements required a restperiod of at least five minutes between each measurement and so the wrist goniometric (ROM)measurements were done between each finger test. Grip strength measurement followed the protocoldescribed by Mathiowetz et al, 1994 and Torrens and Gyi, 1999.ROM of the hand about the wrist was measured using a modified conventional clinical joint motionprotocol (Rowe et al, 1965). The flexion and extension of the hand about the wrist were measured with thehand in a mid-supinated (or neutral) position, i.e. at 900 to the horizontal. The authors were aware thiswould make the comparison of collected data with existing ROM references difficult, but would not affectthe validity of the comparison between manual and machine measurement of the same subject. The chair inwhich the subject sat was fixed to avoid the need to adjust the CODA field of view for each new subject. Itwas necessary to constrain the limb position. A single CODA system was used and so the positioning of thearm in relation to the field of view of the CODA scanner was critical to ensure all the markers remained inthe field of view.Each subject sat upright in a conventional steel contract chair, (seat height 400mm), with their right forearmheld at a right angle, horizontal to the floor. The subject was shown the sequence of hand movementsrequired. These were flexion (into the body), extension (away from the body), adduction (upward), andadduction (downward). All hand movements were performed with the subject keeping their arm resting onthe goniometer. The operator asked each subject to hold their maximum comfortable hand movement ineach direction whilst they took the measurement from the back of the hand, (for flexion/extension), and theaxis of the forearm through the centre of the wrist to the envisaged line running through the centre of thethird digit (middle finger) for adduction/abduction.Motion capture measurements were taken using a CODA mpx30. This system uses infrared emitters(markers) attached to the body, via surgical double-sided tape, and stereo sensors within a scanner unit todefine an anatomical location on the body. Each subject was fitted with five markers to locate theanatomical references of the hummers (marker one) at its proximal point, ulnar (marker two) and radial(marker three), next to the wrist processes. The proximal side of the metacarpophanangeal joints of thesecond (marker four) and fifth digits (marker five) were also marked.With the markers in position, the subject was asked to follow the sequence of movements previously shownto them. The CODA system had been set to sample at 200Hz over a ten second period. Earlier pre-trial testshad shown that this was a sufficient amount of time within which the movements could be completed.The goniometric data from each motion capture was reviewed and the maximum angles taken from a graphgenerated by the CODA system software that enables windows-based views. The data was manuallytransferred on to a spreadsheet following completion of the trial. Only complete sets of data were processedin full. The data sets within the completed spreadsheet were compared through correlation. Analysis anddescriptive statistics. Correlation analysis was used to help identify where the measurements takenmanually and by machine were comparable. This form of comparison also highlighted the interrelationshipsbetween each measurement for further evaluation. Due to the small number of subjects, no furtherevaluation was undertaken on the data.3. Results and discussionOnce processed, fifteen complete sets of data from nine males and six females provided the basis forcorrelation analysis. The lost data was due to operator and compute error. The data gathered from subjectsdocumented in Table1. Shows the statues of the subjects ranged from 1922mm (subject 4, males) to1522mm (Subject 11, female). The final sample group was not fully representative of largest percentilestature in the original sample population, but did include the smallest female percentile. Weight rangedfrom 87.7Kgs (Subject 8, male) to 51.5Kgs (Subject 11, female). These results correspond to equivalent 10
Advances in Physics Theories and Applications www.iiste.orgISSN 2224-719X (Paper) ISSN 2225-0638 (Online)Vol 4, 2012existing data sets for a Nigeria population accessed using the computer-based anthropometric databasePEOPLESIZE (Open Ergonomics, 1999). Grip strength ranged from 58Kgs/569N (Subject 2, male) to23Kgs/226N (Subject 15, female). There were strong correlations between stature and limb lengthsegments.The ROM results, shown in Table 2, highlighted discrepancies between adduction and abduction values andthose published (Rowe et al, 1965). Whilst reviewing the motion capture flies, through the CODA software,it was noted that subjects did not hold their wrists vertically during the motion performance and that theangle made between the forearm, wrist and hand was a compound angle even when the hand appeared to bein line with the forearm. A reason for the high abduction value of the female subject 11, shown in Table 2,may be seen in the motion recording. Analysis of her wrist using a graph plot and stick-figure diagramshowed that he wrist had rotated over 36% to the vertical, giving the motion a component of extensionrather than adduction alone. There were strong negative correlations between abduction and anthropometricvalues in female group that was not significant in the male correlations within the male group.4. ConclusionFollowing the completion of this study the authors and Chamwood Dynamics Limited have each developedmethods to avoid laborious location of makers on to anatomical references on a subject that shouldsignificantly reduce preparation time and increase repeatability. The authors are experimenting with a glovewith makers attached, Chamwood Dynamics Limited have developed a software solution where the makersare grouped to define body segments. Manual goniometric measurement of wrist motion seems the mostcost-effective method of data collection, however, using the CODA system has highlighted a number ofissues such as reducing the compound angle between hand, wrist and forearm during measurement whenusing a manual goniometric. Taking multiple measurements of the whole upper limb at same time wouldgreatly reduce the overall time taken when compared with undertaking the individual goniometricmeasurements manually. The relationships between measured hand characteristics highlighted in this pilotwarrant further study.ReferencesBritish Standards Institute (1990), BS 7231, Part 1, Body measurements of boys and girls from birth up to16.9.Mathiowetz, V., Kashman, N.,Volland,G.,Weber, K.,Dowe, M., Rogers, S (1985), Grip and Pinch Strength:Normative Data for Adults. Archives of Physical Medicine and Rehabilitation, 66, 2Open Ergonomics Limited (1999) PEOPLESIZE software, Loughborough.Pryce JC (1980), The wrist position between neutral and ulnar deviation that facilitates the maximumpower grip strength. Journal of Biomechanics, 13, 505-511.Rowe CR, Heck CV, Hendryson IE (1965), Joint Motion: Method of measuring and recording. AmericaAcademy of Orthopaedic Surgeons, United States of America.Torrens GE, Gyi D (1999), Towards the integrated measurement of hand and object interaction. 7thInternational Conference on Product Safety Research, European consumer Safety Association, U.S.consumer Product safety commission, Washington D.C., p 217-226 ISBN 90-6788-251-8. 11
Advances in Physics Theories and Applications www.iiste.orgISSN 2224-719X (Paper) ISSN 2225-0638 (Online)Vol 4, 2012Table 3, A summary of issues when using manual and motion capture techniques for goniometricmeasurement. manual Goniometry Motion captureCost £100 plus operator training £80,000 plus operator training.Preparation None Scanner and computer set up 30 minutes, 15 minutes to place markers per subject.Measurement 5 minutes per 40 seconds per subject. SubjectAnalysis of motion Single measurement value. Multi-angle analysis possible, variable view Dependent upon skill of operator. stick figure for orientation during analysis. Replay facility. Dependent upon skill of operator in maker placement.Post processing Manual data input to spreadsheet Analysis of stick figure diagram, graph plot and 2 minutes. transfer to spreadsheet 15 minutes.Portable Yes Yes, but can only be used under artificial lighting and requires an power supply. 13
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