過去有許多關於握罐的研究，研究結果顯示出對於握罐而言，適當的力量調節是很重要的因素。當人們於日常生活中握一物體時，他們使用的握法是貼近於手部解剖構造的自然握罐方式，可是過去研究所用的儀器較著重於限制式的握罐。受限制的握罐方式即是五隻手隻頭皆在同一平面去握罐子。因此，本研究使用一個可調式的握罐模擬器，此握罐模擬器使用五個六軸荷重計，可以收取五隻手指施予罐身的力量及力矩。而在模擬器上放置三個反光球，使用攝影機以獲取模擬器在空間中的位置。受試者須使用此握罐模擬器完成兩個日常生活中較常見的動作－抬高罐子及倒水。
本研究第一個目的是比較每位受試者以自然握罐方式及受限制的握罐方式執行抬高罐子及倒水動作過程中之手指指力生物力學。此部分的結果顯示由於受限制的握罐方式會使手指關節呈現較不自然的彎曲角度，因此使用受限制的握罐方式時，受試者會用較大的手指力量及較為不穩定的手指施力去控制罐子。有趣的是，手指力矩結果顯示出在抬高罐子的動作，手指可以看成三個主要貢獻的角色：小指用以穩定罐身，食指、中指及無名指看為同一個群組相對於大拇指分別扮演協同與拮抗的角色。
人們在日常生活中為了達到手部的功能性動作，手部需要時間空間的動作控制以及在每隻手指之間需要適當的力量協調。過去研究顯示神經受損病人，對於其手部功能會有影響，但手部受傷病人也常見其損傷手部肌腱，但卻未曾有學者做此探討，因此本研究第二個目的是以個案探討的方式比較手部肌腱受損的病人與正常人使用自然握罐方式執行握罐及倒水動作時之手指力學表現。研究結果顯示每個病患由於受傷情形不同使得手指力學表現差異甚大，結果可看出病患手指施力有較不穩定的趨勢，而部分病人的指力超過正常受試者指力之範圍，顯示其使用過大的力量去平衡罐身。

There have been many studies investigating digits forces when holding a cylindrical object by grasping constrainedly on the same plane. However, due to the hand anatomy, the digits position was different among subjects during natural grasp. In previous studies, the pattern of digits force changed with different thumb positions. Nevertheless, there was no study to address the differences in force patterns during natural grasp and constrained grasp. Therefore, the objective of first part of this study is to compare the digits force pattern between cylindrical grasp in natural grasp (NG) and constrained grasp (CG).　
A custom cylindrical simulator with five force transducers was designed to record the applied digits forces and moments. Three markers were attached on the simulator to record the orientation of the simulator.
Results of this study indicated that digits exerted larger force in constrained grasp than that in natural grasp. Besides, the contributions of finger force were majorly exerted by index and middle fingers. For these results, digits created a discrepancy force between constrained grasp and natural grasp because constrained grasp manipulated cylinder with more digits flexion which would cause digits more perpendicular to the surface of load cell and affect digits strength. According to the moments of digits, digits could be divided into three main roles. Index, middle and ring finger could be considered as a group, which compared with thumb as agonist and antagonist. Besides, little finger is stabilizer.
To achieve a functional task, the proper force coordination among multi-digit and spatio-temporal control of hand motions are required. According to previous studies that patients with nerve injury will affect their digits force; however, force pattern of patients with tendon injury was unknown. Therefore, the objective of second part of this study is to compare the digits force patterns of patients with those of healthy control. Natural grasp is a proper way to collect digits forces and can be applied to patients with tendon injury to investigate their coordination ability. The results revealed that the force pattern of patients with tendon injury was differed with healthy subjects.

References

1. Li, L.M., V.M. Zatsiorsky, and M.L. Latash, Force sharing among fingers as a model of the redundancy problem. Experimental Brain Research, 1998. 119(3): p. 276-286.
2. Latash M.L., S.J.P., and Schöner G., Toward a New Theory of Motor Synergies. Motor Control, 2007. 11: p. 276-308.
3. Zatsiorsky, V.M. and M.L. Latash, Prehension synergies. Exerc Sport Sci Rev, 2004. 32(2): p. 75-80.
4. Zatsiorsky, V.M., F. Gao, and M.L. Latash, Prehension synergies: effects of object geometry and prescribed torques. Exp Brain Res, 2003. 148(1): p. 77-87.
5. Zhang, W., et al., What do synergies do? Effects of secondary constraints on multidigit synergies in accurate force-production tasks. J Neurophysiol, 2008. 99(2): p. 500-13.
6. Budgeon, M.K., M.L. Latash, and V.M. Zatsiorsky, Digit force adjustments during finger addition/removal in multi-digit prehension. Exp Brain Res, 2008. 189(3): p. 345-59.
7. Niu, X., M.L. Latash, and V.M. Zatsiorsky, Effects of grasping force magnitude on the coordination of digit forces in multi-finger prehension. Exp Brain Res, 2009. 194(1): p. 115-29.
8. Zhang, W., et al., Effects of carpal tunnel syndrome on adaptation of multi-digit forces to object weight for whole-hand manipulation. PLoS One, 2011. 6(11): p. e27715.
9. Lukos, J., C. Ansuini, and M. Santello, Choice of contact points during multidigit grasping: effect of predictability of object center of mass location. J Neurosci, 2007. 27(14): p. 3894-903.
10. Santello, M. and J.F. Soechting, Force synergies for multifingered grasping. Exp Brain Res, 2000. 133(4): p. 457-67.
11. Aoki, T., et al., Effects of friction at the digit-object interface on the digit forces in multi-finger prehension. Exp Brain Res, 2006. 172(4): p. 425-38.
12. Gao, F., M.L. Latash, and V.M. Zatsiorsky, Maintaining rotational equilibrium during object manipulation: linear behavior of a highly non-linear system. Exp Brain Res, 2006. 169(4): p. 519-31.
13. Lukos, J.R., C. Ansuini, and M. Santello, Anticipatory control of grasping: independence of sensorimotor memories for kinematics and kinetics. J Neurosci, 2008. 28(48): p. 12765-74.
14. Kuo, L.C., et al., The force synergy of human digits in static and dynamic cylindrical grasps. PLoS One, 2013. 8(3): p. e60509.
15. Shim, J.K., M.L. Latash, and V.M. Zatsiorsky, Prehension synergies: trial-to-trial variability and hierarchical organization of stable performance. Exp Brain Res, 2003. 152(2): p. 173-84.
16. Cuijpers, R.H., E. Brenner, and J.B. Smeets, Grasping reveals visual misjudgements of shape. Exp Brain Res, 2006. 175(1): p. 32-44.
17. Sartori, L., E. Straulino, and U. Castiello, How objects are grasped: the interplay between affordances and end-goals. PLoS One, 2011. 6(9): p. e25203.
18. Paulignan, Y., et al., Influence of object position and size on human prehension movements. Exp Brain Res, 1997. 114(2): p. 226-34.
19. Lederman, S.J. and A.M. Wing, Perceptual judgement, grasp point selection and object symmetry. Exp Brain Res, 2003. 152(2): p. 156-65.
20. Clayton, R.A. and C.M. Court-Brown, The epidemiology of musculoskeletal tendinous and ligamentous injuries. Injury, 2008. 39(12): p. 1338-44.
21. Preston, D.C. and B.E. Shapiro, Radial Neuropathy. 2013: p. 331-345.
22. Preston, D.C. and B.E. Shapiro, Median Neuropathy at the Wrist. 2013: p. 267-288.
23. Preston, D.C. and B.E. Shapiro, Ulnar Neuropathy at the Elbow. 2013: p. 298-318.
24. Monzee, J., Y. Lamarre, and A.M. Smith, The effects of digital anesthesia on force control using a precision grip. J Neurophysiol, 2003. 89(2): p. 672-83.
25. Nowak, D.A. and J. Hermsdorfer, Selective deficits of grip force control during object manipulation in patients with reduced sensibility of the grasping digits. Neurosci Res, 2003. 47(1): p. 65-72.
26. Hsu, H.Y., et al., Functional sensibility assessment. Part II: Effects of sensory improvement on precise pinch force modulation after transverse carpal tunnel release. J Orthop Res, 2009. 27(11): p. 1534-9.
27. Hsu, H.Y., et al., Establishment of a Proper Manual Tactile Test for Hands With Sensory Deficits. Arch Phys Med Rehabil, 2012.
28. Cole, K.J., C.M. Steyers, and E.K. Graybill, The effects of graded compression of the median nerve in the carpal canal on grip force. Exp Brain Res, 2003. 148(2): p. 150-7.
29. Dun, S., R.A. Kaufmann, and Z.M. Li, Lower median nerve block impairs precision grip. J Electromyogr Kinesiol, 2007. 17(3): p. 348-54.
30. Lowe, B.D. and A. Freivalds, Effect of carpal tunnel syndrome on grip force coordination on hand tools. Ergonomics, 1999. 42(4): p. 550-64.
31. Grip force adjustments evoked by load force perturbations of a grasped object. Journal of Neurophysiology, 1988. 60: p. 1513-1522.
32. Nowak, D.A. and J. Hermsdorfer, Digit cooling influences grasp efficiency during manipulative tasks. Eur J Appl Physiol, 2003. 89(2): p. 127-33.
33. Schenker, M., et al., Precision grip function after hand replantation and digital nerve injury. J Plast Reconstr Aesthet Surg, 2006. 59(7): p. 706-16.
34. Jenmalm, P. and R.S. Johansson, Visual and Somatosensory Information about Object Shape Control Manipulative Fingertip Forces. Neuroscience Research, 1997. 17(11): p. 4486-4499.
35. Sommer H. J. and B.F. L., Experimental determination of the instant screw axis and angular acceleration axis. In Proceedings of the 1990 Sixteenth Annual Northeast Bioengineering Conference 1990: p. pp. 141-142.
36. Li, L.M., et al., Motor redundancy during maximal voluntary contraction in four-finger tasks. Experimental Brain Research, 1998. 122: p. 71-78.
37. Rearick, M.P., A. Casares, and M. Santello, Task-dependent modulation of multi-digit force coordination patterns. J Neurophysiol, 2003. 89(3): p. 1317-26.
38. Latash, M.L., L.M. Li, and V.M. Zatsiorsky, A principle of error compensation studied within a task of force production by a redundant set of fingers. Experimental Brain Research, 1998. 122: p. 131-138.
39. Shim, J.K., M.L. Latash, and V.M. Zatsiorsky, Prehension synergies in three dimensions. J Neurophysiol, 2005. 93(2): p. 766-76.