International Journal of Human and Health Sciences Vol. 06 No. 01 January’22 108 Original article Three-Jaw Chuck Pinch Strength and Its Correlation with Hand Breadth in Electronic Technicians Shahnawaz Akter1, Moushumi Taher Asha2, Shamim Ara3, Segupta Kishwara4, Sunjida Shahriah5 Abstract Context: The three jaw chuck pinch refers to an act where placing the object between the pad of the distal phalanx of the thumb opposing the pads of the distal phalanges of both the index finger and the middle finger. Pinch strength is generally influenced by the  health status and level of physical activity of a person. Objectives: The present study was planned to measure the correlation of three-jaw chuck pinch strength with hand breadth in electronics technicians working in Dhaka Metropolitan City. The data obtained from the study used as a base line for other professions as well as for research in our country. Methods: A cross-sectional, analytical study was carried out in the department of Anatomy, Dhaka Medical College, Dhaka during the period of July’ 2015 to June’ 2016 with 100 adult male electronics technicians and 100 adult sedentary workers. Collection was done by convenient purposive sampling technique. Hand breadth was measured by digital slide calipers and pinch gauge was used to measure the three-jaw chuck pinch strength. Results: The mean three-jaw chuck pinch strength was significantly higher (P<0.05) in case group  than in the control group. Significant difference also observed between case group and  control group in the mean hand breadth (P<0.05). Mean hand breadth was greater in case  group  than  that  of  control  group.  Three-jaw  chuck  pinch  strength  showed  significant  positive correlation with hand breadth in case group. Case group was further subdivided according to their working experiences, the mean three-jaw chuck pinch strength and hand breadth was significantly higher (P<0.05) in more working experience group than  in less working experience group. Conclusion: Three-jaw chuck pinch strength showed significant positive correlation with hand breadth. Keywords: Three-jaw chuck pinch, Pinch, pinch gauge, hand breadth Correspondence to: Dr Shahnawaz Akter, Assistant Professor, Department of Anatomy, Marks Medi- cal College & Hospital, Mirpur-14, Dhaka, Bangladesh. Email: himupoly2005@gmail.com 1.  Assistant  Professor,  Department  of Anatomy,  Marks  Medical  College  &  Hospital,  Mirpur-14,  Dhaka, Bangladesh. 2. Assistant Professor, Department of Anatomy, Bashundhara Ad-din Medical College, Dhaka, Bangladesh. 3. Professor and Head, Department of Anatomy, Holy Family Red Crescent Medical College, Dhaka, Bangladesh. 4. Professor and Head, Department of Anatomy, Dhaka Medical College, Dhaka, Bangladesh. 5.  Professor  and  Head,  Department  of Anatomy,  Marks  Medical  College&  Hospital,  Mirpur-14,  Dhaka, Bangladesh. International Journal of Human and Health Sciences Vol. 06 No. 01 January’22 Page : 108-112 DOI: http://dx.doi.org/10.31344/ijhhs.v6i1.385 Introduction The human hand is a prehensile part of upper limb endowed with grasping and precision movements for skill works. Prehensile movements of the hand have been described as three basic forms of grip, namely precision, power and hook grips. In precision grip, an object is held by the pulp surface of the thumb and the fingers which  place themselves opposite to each other and small movements of the digits are carried out skillfully. Pinch grip is an example of precision 109 International Journal of Human and Health Sciences Vol. 06 No. 01 January’22 grip.1 Despite the technological advancements in many manufacturing industries, hands and fingers are still primary tools for high precision  manufacturing work.2 The human hand is one of the most sophisticated and complex anatomical structures in the body.3 It  is  not  a  fixed,  static  structure but a dynamic sensory motor organ.4To perform such sophisticated functions the human hand has been equipped with both mechanical and sensory capabilities.3 Non powered hand tool operation and manual assembly are the typical activities, in which pinching is usually applied.5 The human hand is capable of pinching, moving and placing objects without rough impact because of  the  softness  of  human  finger  tips.6 Pinch strength is categorized as isometric strength. 7 Pinch strength is the backbone of pinch grip. The majority of the inward force is generated by the long flexor tendon of forearm. This force is  balanced by one or more fingers of the same hand  applying a force back towards the thumb. Strength of the fingers is greatly influenced by the flexion  and extension of the wrist. 8 Pinch strength depends on factors such as occupation, grip span, position of the thumb, position of the elbow and position of the arm, torque directions, contact surface orientations, object shape and size. Manual labourers exert stronger three-jaw chuck pinch compared to sedentary and skill labourers.9 There are four types of pinch techniques such as three-jaw chuck pinch, pulp pinch, tip pinch and lateral pinch.6 In three- jaw chuck pinch the palm faced down, force was exerted between the pad of the index and middle fingers together and the pad of the thumb, through  the centre of the opposing pads .10 The muscles that contribute to pinch grips include both the intrinsic and extrinsic musculatures of hand and forearm. 11 Activities of daily living tasks require constant pinch strength. Workers in various occupations such as electronics technicians, rock climbers, musicians, dentists, carpenters use pinch techniques for their daily work.12According to Ager, cited by Ertem, et al, pinch strength increases from early childhood towards adolescence and with increasing age pinch strength decreases.13 Pinch strength exertions by males on dominant hand was found to be significantly higher.3 Electronics service technicians are responsible for installing and repairing home electronics equipment. They use pinch grip for high precision tasks, such as connecting or disconnecting wires, assembling small electronics parts. The present study aims to see the correlation of pinch strength and hand breadth between the electronics technicians of Dhaka Metropolitan City and sedentary workers of the same region. Materials and Methods A cross-sectional, analytical study, was carried out in the department of Anatomy, Dhaka Medical College, Dhaka during the period of July’ 2015 to June’ 2016 with 100 adult male electronics technicians (case group) and 100 adult male sedentary workers (control group), age ranging from 25-45 years both the groups residing in Dhaka Metropolitan City. 100 participants of case group was further divided into two subgroups according to their working experience. Among them 53 were in less working experience (5-10 years) group and 47 were in more working experience (11- 15 years) group. Electronics technicians should have minimum 5 years working experience were selected  from  different  electronics  repair  shops  of Dhaka, and they used tools like screwdrivers, impact drivers, tweezers etc for their work handling them using three-jaw chuck pinch. Sedentary worker had no prior experience in jobs which involve the use of tools requiring the use of three-jaw chuck pinch. After obtaining informed written consent from all the study subjects data were documented in a pre-designed data sheet. Prior to consent they were explained the aim and purpose of the research. The subjects were assured of the confidentiality of the study.  Exclusion criteria: 1. Congenital deformity of hand such as syndactyly, polydactyly etc. 2. Acquired hand deformity due to burn contracture, fracture or any surgical procedure of hand. After collection of data, statistical analysis was done by the software, SPSS (Statistical Package for Social Sciences) for Windows, Version 22.0. All data were expressed as mean ± SD (standard Deviation) as appropriate. Mean values of different  parameters were compared to see the differences  between two groups by using Student’s unpaired ‘t’ test. Correlation was done by Pearson’s Correlation Coefficient Test. The pinch strength measurements were recorded by a pinch gauge, which is inexpensive, easy to administer, and are considered to provide International Journal of Human and Health Sciences Vol. 06 No. 01 January’22 110 repeatable measurements, with the subject sitting on a chair with the elbow flexed at 90o and wrist in neutral position. Subjects were asked to exert his maximal voluntary contraction (MVC) on the pinch gauge and to hold that force for three second. To overcome the fatigue, subject was given one minute resting period between each exertion (figure: 1). Mean value of three exertion was taken  into account. Hand breadth was measured by slide calipers as a straight distance from the radial side of the second metacarpophalangeal joint to the ulnar side of the fifth metacarpophalangeal joint  (figure:2).  Fig: 1 photograph showing measurement of Three- jaw chuck pinch strength by using pinch gauge Fig. 2. Photograph showing measurement of hand breadth Results Mean three-jaw chuck pinch strength was 7.80±0.77 kg and 13.96±1.46 kg and mean hand breadth was 80.01±1.55 mm and 86.38±2.32 mm in control group and case group respectively (Table  1).  Significant  difference  was  observed  between control group and case group in the mean three-jaw chuck pinch strength and hand breadth (P<0.001) where mean three-jaw chuck pinch strength and hand breadth was greater in case group than that of control group. Mean three-jaw chuck pinch strength of less working experience group (5-10 years) and more working experience group (11-15 years) was 12.75±0.85kg and 15.32±0.47kg and mean hand breadth was 85.07±1.72mm and 87.86±2.01mm respectively  (Table  2).  Statistically  significant  difference  was  observed  between  less  working  experience group and more working experience group in the mean three-jaw chuck pinch strength and in hand breadth (P<0.001), where mean three- jaw chuck pinch strength and hand breadth was lower in less working experience group than that of more working experience group (Table 3). Table 1: Comparison of three- jaw chuck pinch strength and hand breadth between control group and case group Variable Control Group (n=100) (Mean ± SD) Case Group (n=100) (Mean ± SD) P value Three- jaw chuck pinch Strength In kg 7.80 ± 0.77 (5.90 – 9.20) 13.96 ± 1.46 (11.10 – 16.50) 0.001* Hand breadth In mm 80.01 ± 1.55 (74.23 – 84.10) 86.38 ± 2.32 (80.00 – 90.75) 0.001* Figure in parentheses indicate range.SD=Standard Deviation, Comparison between control and case was done by Unpaired Student’s ‘t’ test, ns= not significant,  *=significant, Control group = sedentary worker, Case  group = electronics technicians Table: 2 Comparison of three- jaw chuck pinch strength and hand breadth between different sub  group of case group Variable Less working experience group (n=53) (Mean ± SD) More working experience group (n=47) (Mean ± SD) P value Three- jaw chuck pinch Strength In kg 12.75 ± 0.85 (11.10 – 14.30) 15.32 ± 0.47 (14.50 – 16.50) 0.001* Hand breadth In mm 85.07 ± 1.72 (80.00 – 88.20) 87.86 ± 2.01 (81.50 – 90.75) 0.001* Figure in parentheses indicate range, SD=Standard Deviation, Comparison between different subgroup  of cases was done by Unpaired Student’s ‘t’ test, 111 International Journal of Human and Health Sciences Vol. 06 No. 01 January’22 ns=not significant, *=significant, Sub group of case  group was done depending on working experience in year, Less working experience group = 5 – 10 years, More working experience group = 11 – 15 years. Table 3: Correlation of three –jaw chuck pinch strength with hand breadth in control group and case group Variable Control Group Case Group r value p value r value p value Hand breadth +0.122 P=0.226 ns +0.629 P<0.001* Statistical analysis done by Pearson’s correlation coefficient (r) test, * = Significant, ns = not significant. Discussion Pinch  has  been  identified  as  a  basic  yet  crucial  skill for daily task performance, and is used to assess general strength in order to determine work capacity. Pinch strength is one of the most important parameters of hand function. Regular exercise improves pinch strength. Any deterioration in pinching ability can impair activities of daily living. In this study, correlation of three-jaw chuck pinch strength with hand breadth was discussed. Electronics technicians were selected for the present study on the basis of the observation that they regularly and repeatedly use pinch grip hundreds and thousands of times a day to get firm  hold  of  the  instrument  to  disassemble  and  reassemble equipment parts. Sedentary workers do not use the three-jaw-chuck pinch in their work. The results of the present study were compared with the studies carried out by Imrhan and Rahman, Didomenico and Nussbaum, Dempsey and Ayoub, Mohammadian et al., and Kaushik and Patra,P., In the present study, the mean three-jaw chuck pinch strength of control group and case group was 7.80±0.78 kg and 13.96±1.47 kg respectively. The mean three-jaw chuck pinch strength was significantly higher (P<0.0001) in case group than  in control group. Dempsey and Ayoub found 6.6±2.19 kg mean three-jaw chuck pinch strength.14 Mohammadian, et al. found 10.3±2.7 kg mean three-jaw chuck pinch strength.15 The mean three-jaw chuck pinch strength of case group in this study was significantly higher (P<0.0001) than the findings  of Dempsey and Ayoub and Mohammadian et al. In the present study, the mean three-jaw chuck pinch strength was recorded 12.75±0.85 kg in less working experience group (5-10 years) and 15.32±0.47 kg in more working experience (11- 15 years)group. The mean three-jaw chuck pinch strength was significantly higher (P<0.0001) in the  more working experience group than in the less working experience group. Kaushik and Patra reported 16.23±2.10 kg mean three-jaw chuck pinch strength in the group with 6-9 years working experience, 16 which was significantly higher (P<0.0001) than that for less  working experience group of the present study, and the researcher also recorded 13.42±2.43 kg mean three-jaw chuck pinch strength in the group with 10-14 years working experience which was significantly  lower  (P<0.0001)  than  that  of  the  more working experience group of the present study. The mean hand breadth was 80.01±1.55 mm and 86.38±2.32 mm in control group and case group respectively.  There  was  significant  difference  observed between control group and case group in the mean hand breadth (P<0.001). Mean hand  breadth was greater in case group than that of control group. In the present study three-jaw chuck pinch strength showed significant positive  correlation with hand breadth in case group (r=+0.629, P<0.001).  In contrary, Imrhan and Rahman recorded 80.0±4.0 mm and Didomenico and Nussbaum reported 88.0±5.0 mm mean hand breadth.17,10 The mean hand breadth of Didomenico and Nussbaum was significantly  higher  (P<0.0001)  and  mean  hand  breadth of Imrhan and Rahman was significantly  lower(p<000.1)  than  the  findings  of  the  present  study. Dempsey and Ayoub found 83.7±6.4 mm and Mohammadian, et al. recorded 89.9±4.4 mm mean hand breadth.14,15 The mean hand breadth of Mohammadian, et al. was significantly higher  (P<0.0001) and the mean hand breadth of Dempsey  and Ayoub was significantly lower (p<000.1) than  the findings of the present study. The researchers  also  found  nonsignificant  positive  correlation  between the three-jaw chuck pinch strength and hand breadth (r= +0.493, P<0.05) and significant  positive correlation between the three-jaw chuck International Journal of Human and Health Sciences Vol. 06 No. 01 January’22 112 pinch strength and hand breadth (r= +0.16, P<0.05) respectively.  Conclusion In this study, the three-jaw chuck pinch strength was significantly higher in electronics technicians.  Significant  positive  correlation  between  three-  jaw chuck pinch strength and hand breadth in electronics technicians was found. In case group, the more experienced subgroup had significantly  higher three-jaw chuck pinch strength than the less  experienced  subgroup.  Besides,  significant  difference in hand breadth was observed between  the  sub-group.  The  study  findings  suggest  the  repetitive work increases three-jaw chuck pinch strength. The cause of increase hand breadth needed to be evaluated by further study. Conflict of interest: None declared. Funding statement: No Funding. Ethical approval issue: Ethical clearance has been taken from the Ethical Review Committee (ERC) of Dhaka Medical College, Dhaka, Bangladesh. Author contributions: Conception and study design: SA, SA; Data collection, compilation and analysis: SA, MTA; Manuscript writing, literature review, revision and finalizing: SA,MTA, SA, SK, SS.  References: 1. Salmons S. Muscles. In: Williams LP. ed. Gray’s Anatomy, 38th ed, London: Churchill Livings Stone, 1995; 733-889. 2. Ng  KP,  et  al.  The  effects  of  size  on  pinch  force.  International Postgraduate Conference on Aerospace, Manufacturing and Mechanical Engineering. 2015;1(1):1-10. 3. Dianat I, Feizi H, Hasan-Khali K. Pinch Strength in Healthy Iranian Children and Young Adult Population. Health Promotion Perspectives, 2015;5(1):52-8. 4. Shim HJ, et al. Normative Measurements of Grip and Pinch Strength of 21st Century Korean Popution. Arch Plast Surg. 2012;40(1):52-6. 5. Shih C, Chen L, Huang S. The Effect of splints on  Peak Strength, Sustaining Time, and Total Force Generation  at  Different  Pinching  Types.  Journal  of the Chinese Institute of Industrial Engineers. 2005;22(2):134-42. 6. Ng KP, et al. A review of different   pinch techniques.  Theoretical Issues in Ergonomics Science. 2014;15(5):517-33. 7. Chandra MA, et al. A Comparative Assessment of the  Impact  of  Different  Occupations  on  Worker’s  Static Musculoskeletal Fitness. International Journal of Occupational Safety and Ergonomics (JOSE). 2007;13(3):271-8. 8. De S, et al. Age and Sex Related Variation of Pinch Strength among Adult Bengalee Population. Developments in Agricultural and Industrial Ergonomics. 2005;1(1):1-11. 9. Ng KP, et al. Pinch Effort Variations with Torques,  Shape, Size, Sensation and Technique. J. Applied Science. 2014;14(5):401-14. 10. Didomenico, A. and Nussbaum, A.M. Measurement and  prediction  of  single  and  multi-digit  finger  strength. Ergonomics. 2003;46(15):1531-48. 11. Ng KP, Saptari A. A review of shape and size consideration in pinch grips. Theoretical Issues in Ergonomics Science. 2014;15(3):305-17. 12. Jansen SWC, et al. Measurement of Maximum Voluntary    Pinch    Strength:  Effects    of    Forearm   Position and Outcome Score. J Hand Ther, 2003; 16(4): 326-36. 13. Ertem K, et al.   Effects of dominance, body mass,  index and age on grip and pinch strength. Isokinetics and Exercise Science. 2003;11(4):219-23. 14. Dempsey GP, Ayoub MM. The influence of gender,  grasp type, pinch width, and wrist position on sustained pinch strength. International Journal of Industrial Ergonomics. 1994;17(3):259-73. 15. Mohammadian M, et al. Investigation of grip and pinch strengths in Iranian adults and their correlated anthropometric and demographic factors . Work. 2015;53(2):1-9. 16. Kaushik A, Patra P. Upper extremity and neck disability in male hairdressers with concurrent changes in pinch strength: an observational study. Healthline. 2014;5(2):46-52. 17. Imhran NS, Rahman R. The effect of pinch width on  pinch strengths of adult males using realistic pinch- handle coupling. International Journal of Industrial Ergonomics. 1994;16(2):123-34.