肌肉張力異常，例如痙攣(spasticity)、僵直(rigidity)等動作及運動疾病(motor and movement disorder)，一直是臨床人員或研究者關注的重點之一。肌肉張力異常經常困擾著病患、影響其運動功能的恢復以及日常生活的自主性。然而縱使臨床上有許多醫師或物理治療師能進行的治療方式，但對於其特性機轉的瞭解仍然不健全，更缺乏一個廣為接受的量化技術與設備。特性的探究與量化方法的設計一直是研究肌肉張力必需的一體兩面，本研究第一部份即針對痙攣及僵直兩種症狀對於速度因子的特性變化(velocity-related properties)，做一系統的研究。以自行研發的馬達驅動(motor-driven)的肌肉張力量測系統為基礎，研究中設計了四種牽張速度(40、80、120及160度/秒)對肘關節在垂直面上進行牽張測試，以了解痙攣、僵直與正常肌肉張力的速度相依特性(velocity-dependent property)。為了去除重力以及與速度較無關的肌肉張力部分(velocity-independent component)造成的影響，實驗設計了一個5度/秒的慢速牽張作為基準扭力(baseline torque)。在扣除基準扭力後，所得到的參數ASRT(Averaged speed-dependent reflex torque)便是速度相關的張力部分(velocity-dependent component)。同時觀察四種速度下得到的速度相關的張力部分，可以求出關節的速度相依程度，即VASRT(velocity sensitivity of ASRT)，作為研究速度相依(velocity-dependence)的參數。另外研究中將牽張的扭力依位置分為五個段落，以參數SASRT(segmental ASRT)來觀察牽張反應在不同位置下的變化情形。在12名中風痙攣病患、16名巴金森僵直病患以及12名正常受試者的測試中，結果顯示相較於正常肌肉張力，除了痙攣以外，僵直也顯現出速度相依的特性。在位置相關的肌肉張力變化上，結果顯示出三種不同的特性。即痙攣呈現出肌肉張力隨位置增加而漸增的模式，而僵直則在牽張位置中始終呈現一定的張力增強，正常肌肉張力則始終沒有張力增強出現。本研究建議速度因子也必須在研究或量化僵直時予以考慮，另外要區分痙攣與僵直，必須由位置相關的張力變化特性著手。
相較於馬達驅動系統，臨床所需的是可攜性高，使用方便且造價較低的評估肌肉張力設備。本研究的第二個部分，即發展出一套適合臨床使用的手持式肌肉張力量測系統(hand-held device)來量測手肘痙攣的程度。系統使用了氣壓式氣囊阻力感測器(air-bags with pressure sensor)及微型角速度偵測器(micro gyroscope)來量測手持牽張時的肌肉張力及位置變化。在馬達系統的基礎上，研究中進行了一系列的系統驗證(validation tests)與特性辨識(system identification)以確認系統的可行性。在臨床評估痙攣的使用上，本研究考慮了兩個重要且需控制的因子，即牽張範圍(stretch range)及速度(stretch velocity)。使用肘關節支架，可以使牽張範圍限制在60度；而藉由電子節拍器的協助，測試者可規律的以四種頻率(1/3、1/2、1及3/2赫茲)來做正弦牽張(sinusoidal stretch)。由於與速度相關的阻尼特性會造成阻力(resistance)與位置(displacement)間產生相位差(phase lag)，利用相位差及複合模數(complex modulus)大小，可以求得阻尼造成的肌肉張力部分(viscous component)，作為速度相依參數B(即BW1/3、BW1/2、BW1及BW3/2)。更進一步，根據B隨速度增加的程度，可以求得關節黏性大小(viscosity, 參數B)。本研究設計了三種基礎力學模型，即慣性(inertia)、阻尼(damper)及彈性(elastic)模型來測試驗證牽張方式及分析方法的可行性。另外，為了測試系統實際在臨床的可行性，研究中徵求了15位肘部痙攣的患者及15名肌肉張力正常的受試者來進行測試。根據馬達系統與手持式系統得到的數據比較，手持式肌肉張力量測系統在阻力與位置的量測上都有很好的準確度(相關性皆達0.9991以上)。另外力學模型顯示，此分析方法可以有效的將阻尼(即速度相依的部分)量測出來。實際臨床測試顯示以四種牽張頻率所得的速度相依參數B，在正常與痙攣肘關節間呈現出明顯的不同。與臨床評估方法的比較上，參數B與B呈現相當高的相關性(Rho>0.785)，顯示本研究的系統與實驗方法可提供給臨床一個有效量化肘部痙攣很好的選擇。

As a component of upper motor neuron syndrome, abnormality in muscle tone, including spasticity and rigidity, frequently draws attention of clinicians and researchers. Researchers have shown many characterized mechanisms and properties between spasticity and rigidity from electrophysiological and biomechanical aspects. Among these analyses, velocity factor is an important element to describe spasticity and rigidity. In first part of this study, we evaluated the velocity-related properties of muscle tone between hemiparetic spasticity and parkinsonian rigidity using a motor-driven system. Four preset constant-stretch velocities (40, 80, 120, 160 deg/sec) in a ramp-and-hold mode were applied to elicit the reactive resistance of elbow joint in a vertical position. To minimize the influence of gravity torque and velocity-independent component, a baseline torque was proposed as reactive torque measured at a selected low stretch velocity of 5 deg/sec. The averaged speed-dependent reflex torque (ASRT), defined as the measured torque deviated from the baseline torque, was used for quantifying the velocity-dependent response of hypertonia. Furthermore, velocity sensitivity of ASRT (VASRT) and segmented ASRT (SASRT), derived from the slope of the regression line among ASRT-velocity plots and from segmentations of reactive torque, respectively, are used to differentiate increased muscle tone of spasticity and rigidity with respect to velocity-dependence and position-related patterns. The results show that ASRT and VASRT were significantly higher in both spasticity and rigidity. SASRT analysis shows three different position-related patterns among spasticity, rigidity and normal groups. Spasticity exhibits progressively increasing muscle tension relative to position. Rigidity exhibits increased (relative to the norm) but constant muscle tone over the entire stretch range. As expected, the normal control shows a consistently low reactive torque for the entire range. Velocity-dependence analysis indicates that rigidity and spasticity exhibit approximately equal velocity-dependent properties. For differentiating these two hypertonias, position-dependent properties may be employed.
Compared to motor-driven systems, hand-held systems seem to have advantages in providing an on-line quantification of muscle tone, especially in clinical routine examination or in surgical room. Accordingly, in the second part of this study, we developed a portable device for hand-held evaluation of muscle tone in elbow joint. The portable system was designed for convenient use in clinical environment based on a pair of light air-bags with pressure sensor and small angular rate sensor. Reliability and validity tests of the portable system were performed based on our previous motor-driven system. Two important factors, including stretch range and stretch frequency, were controlled using a elbow limiter and a metronome for 60 degrees displacement and four stretch tempos(1/3, 1/2, 1 and 3/2 Hz). For evaluating the analytic method and clinical protocol, three simulation modules including inertia, damper and elastic modules were used. In addition, 15 spastic and 15 normal subjects were recruited for evaluating the feasibility of the portable device in clinically measuring spasticity. The tests show good reliability and high correlation in displacement and resistance measurements between portable and motor systems. Validity in modules testing also shows successful discrimination between damped and undamped properties. The results in clinical tests indicate that the portable system is useful in quantitative measurement of spasticity. Several factors affecting the recording accuracy of resistance during stretching movement are discussed.

1. Abbruzzese G, Vische M, Ratto S, Abbruzzese M, Favale E. Assessment of motor neuron excitability in parkinsonian rigidity by the F wave. Journal of Neurology 1985;232(4):246-9.
2. Andrews CJ, Burke D, Lance JW. The response to muscle stretch and shortening in Parkinsonian rigidity. Brain 1972;95(4):795-812.
3. Artieda J, Quesada P, Obeso JA. Reciprocal inhibition between forearm muscles in spastic hemiplegia. Neurology 1991;41:286-9.
4. Marsden CD. Motor dysfunction and movement disorders. In: Asbury AK, Mckhann GM, McDonald WI, editors. Disease of the nervous system. Clinical neurobiology. Philadelphia: Saunders; 1992. p 309-18.
5. Ashworth B. Preliminary trials of carisoprodol in multiple sclerosis. Practioner 1964;192:540-2.
6. Aymard C, Katz R, Lafitte C et al. Presynaptic inhibition and homosynaptic depression - a comparison between lower and upper limbs in normal human subjects and patients with hemiplegia. Brain 2000;123:1688-702.
7. Bajd T, Gregoric M, Vodovnik L, Benko H. Electrical stimulation in treating spasticity resulting from spinal cord injury. Archives of Physical Medicine & Rehabilitation 1985;66(8):515-7.
8. Berardelli A, Hallett M. Shortening reaction of human tibialis anterior. Neurology 1984;34(2):242-5.
9. Berardelli A, Sabra AF, Hallett M. Physiological mechanisms of rigidity in Parkinson's disease. Journal of Neurology, Neurosurgery & Psychiatry 1983;46(1):45-53.
10. Bergui M, Lopiano L, Paglia G, Quattrocolo G, Scarzella L, Bergamasco B. Stretch reflex of quadriceps femoris and its relation to rigidity in Parkinson's disease. Acta Neurologica Scandinavica 1992;86(3):226-9.
11. Bohannon RW, Andrews AW. Correlation of knee extensor muscle torque and spasticity with gait speed in patients with stroke. Archives of Physical Medicine & Rehabilitation 1990;71(5):330-3.
12. Bohannon RW, Smith MB. Interrater reliability of a modified Ashworth scale of muscle spasticity. Physical Therapy 1987;67(2):206-7.
13. Boiteau M, Malouin F, Richards CL. Use of a hand-held dynamometer and a Kin-Com dynamometer for evaluating spastic hypertonia in children: a reliability study. Physical Therapy 1995;75(9):796-802.
14. Broberg C, Grimby G. Measurement of torque during passive and active ankle movements in patients with muscle hypertonia. A methodological study. Scandinavian Journal of Rehabilitation Medicine 1983;9(Supplement):108-17.
15. Brown RA, Lawson DA, Leslie GC et al. Does the Wartenberg pendulum test differentiate quantitatively between spasticity and rigidity? A study in elderly stroke and Parkinsonian patients. Journal of Neurology, Neurosurgery & Psychiatry 1988;51(9):1178-86.
16. Burke D. Critical examination of the case for or against fusimotor involvement in disorders of muscle tone. Advances in Neurology 1983;39:133-50.
17. Burke D, Andrews CJ, Lance JW. Tonic vibration reflex in spasticity, Parkinson's disease, and normal subjects. Journal of Neurology, Neurosurgery & Psychiatry 1972;35(4):477-86.
18. Burke D, Gillies JD, Lance JW. The quadriceps stretch reflex in human spasticity. Journal of Neurology, Neurosurgery & Psychiatry 1970;33(2):216-23.
19. Burke D, Gillies JD, Lance JW. Hamstrings stretch reflex in human spasticity. Journal of Neurology, Neurosurgery & Psychiatry 1971;34(3):231-5.
20. Calancie B, Broton JG, Klose KJ, Traad M, Difini J, Ayyar DR. Evidence that alterations in presynaptic inhibition contribute to segmental hypo- and hyperexcitability after spinal cord injury in man. Electroencephalography & Clinical Neurophysiology 1993;89(3):177-86.
21. Caligiuri MP. Portable device for quantifying parkinsonian wrist rigidity. Movement Disorders 1994;9(1):57-63.
22. Caligiuri MP, Galasko DR. Quantifying drug-induced changes in parkinsonian rigidity using an instrumental measure of activated stiffness. Clinical Neuropharmacology 1992;15(1):1-12.
23. Cantello R, Gianelli M, Civardi C, Mutani R. Parkinson's disease rigidity: EMG in a small hand muscle at "rest". Electroencephalography & Clinical Neurophysiology 1995;97(5):215-22.
24. Chan CW, Kearney RE, Jones GM. Tibialis anterior response to sudden ankle displacements in normal and Parkinsonian subjects. Brain Research 1979;173(2):303-14.
25. Cody FW, Richardson HC, MacDermott N, Ferguson IT. Stretch and vibration reflexes of wrist flexor muscles in spasticity. Brain 1987;110(Pt 2):433-50.
26. Crone C, Nielsen J, Petersen N, Ballegaard M, Hultborn H. Disynaptic reciprocal inhibition of ankle extensors in spastic patients. Brain 1994;117(Pt 5):1161-8.
27. Davidoff RA. Skeletal muscle tone and the misunderstood stretch reflex. Neurology 1992;42(5):951-63.
28. Day BL, Marsden CD, Obeso JA, Rothwell JC. Peripheral and central mechanisms of reciprocal inhibition in the human forearm. Journal of Physiology 1981;317:59-60.
29. Delwaide PJ. Electrophysiological analysis of the mode of action of muscle relaxants in spasticity. Annals of Neurology 1985;17(1):90-5.
30. Delwaide PJ, Oliver E. Short-latency autogenic inhibition (IB inhibition) in human spasticity. Journal of Neurology, Neurosurgery & Psychiatry 1988;51(12):1546-50.
31. Delwaide PJ, Pepin JL, Maertens de Noordhout A. Short-latency autogenic inhibition in patients with Parkinsonian rigidity. Annals of Neurology 1991;30(1):83-9.
32. Delwaide PJ, Schwab RS, Young RR. Polysynaptic spinal reflexes in Parkinson's disease. Neurology 1974;24(9):820-7.
33. Detrembleur C, Lejeune TM, Renders A, Van Den Bergh PY. Botulinum toxin and short-term electrical stimulation in the treatment of equinus in cerebral palsy. Movement Disorders 2002;17(1):162-9.
34. Diener C, Scholz E, Guschlbauer B, Dichgans J. Increased shortening reaction in Parkinson's disease reflects a difficulty in modulating long loop reflexes. Movement Disorders 1987;2(1):31-6.
35. Dietrichson P. Phasic ankle reflex in spasticity and Parkinsonian rigidity. The role of the fusimotor system. Acta Neurologica Scandinavica 1971;47(1):22-51.
36. Dietrichson P. Tonic ankle reflex in parkinsonian rigidity and in spasticity. The role of the fusimotor system. Acta Neurologica Scandinavica 1971;47(2):163-82.
37. Dietrichson P. The fusimotor system in relation to spasticity and parkinsonian rigidity. Scandinavian Journal of Rehabilitation Medicine 1973;5(4):174-8.
38. Dietz V, Quintern J, Berger W. Electrophysiological studies of gait in spasticity and rigidity. Evidence that altered mechanical properties of muscle contribute to hypertonia. Brain 1981;104(3):431-49.
39. Dimitrijevic MR. Spasticity and rigidity. In: Jankovic J, Tolosa E, editors. Parkinson's disease and movement disorders. 3rd edition. Lippincott: Williams and Wilkins; 1998. p 159-75.
40. Eisen A, Odusote K. Amplitude of the F wave: a potential means of documenting spasticity. Neurology 1979;29(9 Pt 1):1306-9.
41. Eklund G, Hagbarth KE, Hagglund JV, Wallin EU. The 'late' reflex responses to muscle stretch: the 'resonance hypothesis' versus the 'long-loop hypothesis'. Journal of Physiology. 1982;326:79-90.
42. Engsberg JR, Olree KS, Ross SA, Park TS. Quantitative clinical measure of spasticity in children with cerebral palsy. Archives of Physical Medicine & Rehabilitation 1996;77(6):594-9.
43. Fellows SJ, Ross HF, Thilmann AF. The limitations of the tendon jerk as a marker of pathological stretch reflex activity in human spasticity. Journal of Neurology, Neurosurgery & Psychiatry 1993;56(5):531-7.
44. Firoozbakhsh KK, Kunkel CF, Scremin AM, Moneim MS. Isokinetic dynamometric technique for spasticity assessment. American Journal of Physical Medicine & Rehabilitation 1993;72(6):379-85.
45. Fung VS, Burne JA, Morris JG. Objective quantification of resting and activated parkinsonian rigidity: a comparison of angular impulse and work scores. Movement Disorders 2000;15(1):48-55.
46. Gabel RH, Brand RA. The effects of signal conditioning on the statistical analyses of gait EMG. Electroencephalography & Clinical Neurophysiology 1994;93(3):188-201.
47. Galli M, Crivellini M, Santambrogio G C, Fazzi E, Motta F. Short-term effects of "botulinum toxin a" as treatment for children with cerebral palsy: kinematic and kinetic aspects at the ankle joint. Functional Neurology 2001;16(4):317-23.
48. Garcia Ruiz PJ, Pascual Pascual I, Sanchez Bernardos V. Progressive response to botulinum A toxin in cerebral palsy. European Journal of Neurology 2000;7(2):191-3.
49. Ghika J, Wiegner AW, Fang JJ, Davies L, Young RR, Growdon JH. Portable system for quantifying motor abnormalities in Parkinson's disease. IEEE Transactions on Biomedical Engineering 1993;40(3):276-83.
50. Gonce M, Delwaide PJ. Clinical neurophysiological assessment of Parkinson's disease. Advances in Neurology. 1984;40:365-73.
51. Gregoric M, Stefanovska A, Vodovnik L, Rebersek S, Gros N. Rigidity in parkinsonism: characteristics and influences of passive exercise and electrical nerve stimulation. Functional Neurology 1988;3(1):55-68.
52. Gresty M. Stability of the head in pitch (neck flexion-extension): studies in normal subjects and patients with axial rigidity. Movement Disorders 1989;4(3):233-48.
53. Hagbarth KE, Eklund G. The effects of muscle vibration in spasticity, rigidity, and cerebellar disorders. Journal of Neurology, Neurosurgery & Psychiatry 1968;31(3):207-13.
54. Hagbarth KE, Hagglund JV, Wallin EU, Young RR. Grouped spindle and electromyographic responses to abrupt wrist extension movements in man. Journal of Physiology. 1981;312:81-96.
55. Harburn K, Vandervoort A, Helewa A et al. A reflex technique to measure presynaptic inhibition in cerebral stroke. Electromyography & Clinical Neurophysiology 1995;35(3):149-63.
56. Hershler C, Milner M. An optimality criterion for processing electromyographic signals relating to human locomotion. IEEE Transactions on Biomedical Engineering 1978;25(5):413-20.
57. Hinderer SR, Lehmann JF, Price R, White O, deLateur BJ, Deitz J. Spasticity in spinal cord injured persons: quantitative effects of baclofen and placebo treatments. American Journal of Physical Medicine & Rehabilitation 1990;69(6):311-7.
58. Ibrahim IK, Berger W, Trippel M, Dietz V. Stretch-induced electromyographic activity and torque in spastic elbow muscles. Differential modulation of reflex activity in passive and active motor tasks. Brain 1993;116(Pt 4):971-89.
59. Ivanhoe CB, Tilton AH, Francisco GE. Intrathecal baclofen therapy for spastic hypertonia. Physical Medicine and Rehabilitation Clinics of North America 2001;12(4):923-38, viii-ix.
60. Jankovic J. Botulinum toxin in movement disorders. Current Opinion in Neurology 1994;7(4):358-66.
61. Jankovic J, Tolosa E, editors. Parkinson's disease and movement disorders. 3rd edition. Lippincott: Williams & Wilkins; 1998.
62. Ju MS, Chen JJ, Lee HM, Lin TS, Lin CC, Huang YZ. Time-course analysis of stretch reflexes in hemiparetic subjects using an on-line spasticity measurement system. Journal of Electromyography and Kinesiology 2000;10:1-14.
63. Katz RT. Management of spasticity. American Journal of Physical Medicine & Rehabilitation 1988;67(3):108-16.
64. Katz RT, Rovai GP, Brait C, Rymer WZ. Objective quantification of spastic hypertonia: correlation with clinical findings. Archives of Physical Medicine & Rehabilitation 1992;73(4):339-47.
65. Katz RT, Rymer WZ. Spastic hypertonia: mechanisms and measurement. Archives of Physical Medicine & Rehabilitation 1989;70(2):144-55.
66. Katz R, Pierrot-Deseilligny E. Recurrent inhibition of alpha-motoneurons in patients with upper motor neuron lesions. Brain 1982;105(Pt 1):103-24.
67. Katz R, Pierrot-Deseilligny E, Hultborn H. Recurrent inhibition of motoneurones prior to and during ramp and ballistic movements. Neuroscience Letters 1982;31(2):141-5.
68. Kearney RE, Hunter IW. System identification of human triceps surae stretch reflex dynamics. Experimental Brain Research 1983;51(1):117-27.
69. Kearney RE, Hunter IW. System identification of human joint dynamics. Critical Reviews in Biomedical Engineering 1990;18(1):55-87.
70. Lakie M, Walsh EG, Wright GW. Resonance at the wrist demonstrated by the use of a torque motor: an instrumental analysis of muscle tone in man. Journal of Physiology. 1984;353:265-85.
71. Lamontagne A, Malouin F, Richards CL, Dumas F. Evaluation of reflex- and nonreflex-induced muscle resistance to stretch in adults with spinal cord injury using hand-held and isokinetic dynamometry. Physical Therapy 1998;78(9):964-75.
72. Lance JW. Pathophysiology of spasticity and clinical experience with Baclofen. In: Feldman RG, Young RR, Koella WP, editors. Spasticity: disordered motor control. Chicago: Year Book Medical Publishers; 1980. p 185-203.
73. Lance JW. Symposium synopsis. In: Feldman RG, Young RR, Koella WP, editors. Spasticity: disordered motor control. Chicago: Year Book Medical Publishers; 1980. p 485-94.
74. Lance JW. Disordered muscle tone and movement. Clinical & Experimental Neurology 1981;18:27-35.
75. Lee RG. Pathophysiology of rigidity and akinesia in Parkinson's disease. European Neurology 1989;29(Supplement 1):13-8.
76. Lee RG, Tatton WG. Motor responses to sudden limb displacements in primates with specific CNS lesions and in human patients with motor system disorders. Canadian Journal of Neurological Sciences 1975;2(3):285-93.
77. Lehmann JF, Price R, deLateur BJ, Hinderer S, Traynor C. Spasticity: quantitative measurements as a basis for assessing effectiveness of therapeutic intervention. Archives of Physical Medicine & Rehabilitation 1989;70(1):6-15.
78. Levin MF, Hui-Chan C. Are H and stretch reflexes in hemiparesis reproducible and correlated with spasticity?. Journal of Neurology 1993;240(2):63-71.
79. Lossius R, Dietrichson P, Lunde PK. Effect of diazepam and desmethyldiazepam in spasticity and rigidity. A quantitative study of reflexes and plasma concentrations. Acta Neurologica Scandinavica 1980;61(6):378-83.
80. Lossius R, Dietrichson P, Lunde PK. Effect of clorazepate in spasticity and rigidity: a quantitative study of reflexes and plasma concentrations. Acta Neurologica Scandinavica 1985;71(3):190-4.
81. Marsden CD. The mysterious motor function of the basal ganglia: the Robert Wartenberg Lecture. Neurology 1982;32(5):514-39.
82. Marsden CD, Merton PA, Morton HB. Servo action in the human thumb. Journal of Physiology. 1976;257:1-44.
83. Matthews PB. Evidence from the use of vibration that the human long-latency stretch reflex depends upon spindle secondary afferents. Journal of Physiology. 1984;348:383-415.
84. Mauritz KH. Gait training in hemiplegia. European Journal of Neurology 2002;9(Supplement 1):23-9.
85. Miglietta OE, Lowenthal M. Measurement of the stretch reflex response as an approach to the objective evaluation of a spasticity. Archives of Physical Medicine & Rehabilitation 1962;43:62-8.
86. Milanov I. A comparative study of methods for estimation of presynaptic inhibition. Journal of Neurology 1992;239(5):287-92.
87. O'Brien CF, Seeberger LC, Smith DB. Spasticity after stroke. Epidemiology and optimal treatment. Drugs & Aging 1996;9(5):332-40.
88. Panizza M, Balbi P, Russo G, Nilsson J. H-reflex recovery curve and reciprocal inhibition of H-reflex of the upper limbs in patients with spasticity secondary to stroke. American Journal of Physical Medicine & Rehabilitation 1995;74(5):357-63.
89. Patrick SK, Denington AA, Gauthier MJA, Gillard DM, Prochazka A. quantification of the UPDRS rigidity scale. IEEE Transactions on Neural System and Rehabilitation Engineering 2001;9(1):31-41.
90. Pierrot-Deseilligny E, Katz R, Morin C. Evidence of Ib inhibition in human subjects. Brain Research 1979;166(1):176-9.
91. Pinter MM, Helscher RJ, Nasel CO, Riedl E, Schnaberth G. Quantification of motor deficit in Parkinson's disease with a motor performance test series. Journal of Neural Transmission - Parkinsons Disease & Dementia Section 1992;4(2):131-41.
92. Pisano F, Miscio G, Del Conte C, Pianca D, Candeloro E, Colombo R. Quantitative Measures of Spasticity in Post-Stroke Patients. Clinical Neurophysiology 2000;111(6):1015-22.
93. Powers RK, Campbell DL, Rymer WZ. Stretch reflex dynamics in spastic elbow flexor muscles. Annals of Neurology 1989;25(1):32-42.
94. Powers RK, Marder-Meyer J, Rymer WZ. Quantitative relations between hypertonia and stretch reflex threshold in spastic hemiparesis. Annals of Neurology 1988;23(2):115-24.
95. Price R, Bjornson KF, Lehmann JF, McLaughlin JF, Hays RM. Quantitative measurement of spasticity in children with cerebral palsy. Developmental Medicine & Child Neurology 1991;33(7):585-95.
96. Priebe MM, Sherwood AM, Thornby JI, Kharas NF, Markowski J. Clinical assessment of spasticity in spinal cord injury: a multidimensional problem. Archives of Physical Medicine & Rehabilitation 1996;77(7):713-6.
97. Prochazka A, Bennett DJ, Stephens MJ et al. Measurement of rigidity in Parkinson's disease. Movement Disorders 1997;12(1):24-32.
98. Relja MA, Petravic D, Kolaj M. Quantifying rigidity with a new computerized elbow device. Clinical Neuropharmacology 1996;19(2):148-56.
99. Robinson CJ, Kett NA, Bolam JM. Spasticity in spinal cord injured patients: 1. Short-term effects of surface electrical stimulation. Archives of Physical Medicine & Rehabilitation 1988;69(8):598-604.
100. Robinson CJ, Kett NA, Bolam JM. Spasticity in spinal cord injured patients: 2. Initial measures and long-term effects of surface electrical stimulation. Archives of Physical Medicine & Rehabilitation 1988;69(10):862-8.
101. Rothwell JC, Obeso JA, Traub MM, Marsden CD. The behaviour of the long-latency stretch reflex in patients with Parkinson's disease. Journal of Neurology, Neurosurgery & Psychiatry 1983;46(1):35-44.
102. Schmit BD, Dewald JPA, Rymer WZ. Stretch Reflex Adaptation in Elbow Flexors During Repeated Passive Movements in Unilateral Brain-Injured Patients. Archives of Physical Medicine & Rehabilitation 2000;81(3):269-78.
103. Schmit BD, Dhaher Y, Dewald JPA, Rymer WZ. Reflex Torque Response to Movement of the Spastic Elbow: Theoretical Analyses and Implications for Quantification of Spasticity. Annals of Biomedical Engineering 1999;27(6):815-29.
104. Shefner JM, Berman SA, Sarkarati M, Young RR. Recurrent inhibition is increased in patients with spinal cord injury. Neurology 1992;42(11):2162-8.
105. Sinkjaer T, Andersen JB, Nielsen JF. Impaired stretch reflex and joint torque modulation during spastic gait in multiple sclerosis patients. Journal of Neurology 1996;243(8):566-74.
106. Sinkjaer T, Hoffer JA. Factors determining segmental reflex action in normal and decerebrate cats. Journal of Neurophysiology 1990;64(5):1625-35.
107. Tatton WG, Lee RG. Evidence for abnormal long-loop reflexes in rigid Parkinsonian patients. Brain Research 1975;100(3):671-6.
108. Teravainen H, Tsui JK, Mak E, Calne DB. Optimal indices for testing parkinsonian rigidity. Canadian Journal of Neurological Sciences 1989;16(2):180-3.
109. Thilmann AF, Fellows SJ, Garms E. Pathological stretch reflexes on the "good" side of hemiparetic patients. Journal of Neurology, Neurosurgery & Psychiatry 1990;53(3):208-14.
110. Thilmann AF, Fellows SJ, Garms E. The mechanism of spastic muscle hypertonus. Variation in reflex gain over the time course of spasticity. Brain 1991;114(Pt 1A):233-44.
111. Tsai CH, Chen RS, Lu CS. Reciprocal inhibition in Parkinson's disease. Acta Neurologica Scandinavica 1997;95(1):13-8.
112. Vodovnik L, Bowman BR, Hufford P. Effects of electrical stimulation on spinal spasticity. Scandinavian Journal of Rehabilitation Medicine 1984;16(1):29-34.
113. Walsh EG. The measurement of muscle tone. Paraplegia 1992;30(7):507-8.
114. Walsh EG. A review of some measurements of muscle wasting, tone and clonus in paraplegia. Paraplegia 1993;31(2):75-81.
115. Wang RY, Tsai MW, Chan RC. Effects of surface spinal cord stimulation on spasticity and quantitative assessment of muscle tone in hemiplegic patients. American Journal of Physical Medicine & Rehabilitation 1998;77(4):282-7.
116. Watts RL, Wiegner AW, Young RR. Elastic properties of muscles measured at the elbow in man: II. Patients with Parkinsonian rigidity. Journal of Neurology, Neurosurgery & Psychiatry 1986;49(10):1177-81.
117. Webster DD. Rigidity in extrapyramidal disease. Journal of Neurosurgery 1966;24(Supplement II):299-304.
118. Wiegner AW, Watts RL. Elastic properties of muscles measured at the elbow in man: I. Normal controls. Journal of Neurology, Neurosurgery & Psychiatry 1986;49(10):1171-6.