上肢的累積性傷害在體育活動及工作環境中很常發生，不良姿勢、重複性與用力的動作都是可能的危險因子。如肱骨外上髁炎，此問題在新手網球打者的盛行率很高，過去研究指出可能與新手使用不適當的單手反拍姿勢有關。過去有研究探討手腕在不同角度下伸腕肌群所能產生的力量，然而這些研究皆侷限於矢狀面之手腕活動的靜態收縮與向心收縮表現。且市售的手腕測力儀僅提供手腕於矢狀面與冠狀面的活動，與生活中的斜向功能性手腕活動有所不同。此外，也仍缺乏不同腕關節角度下伸腕肌群的活化表現的相關研究。
故本研究利用客製化手腕等速測力儀，比較伸腕肌群於斜向平面與矢狀面的手腕活動表現，其中斜向平面動作以模擬網球反手拍活動為例，並觀察斜向平面下不同腕關節角度的伸腕肌群表現。實驗過程配合表面肌電圖儀來探討伸腕肌群活化情形。實驗共徵召三十位健康受試者，執行斜向平面下伸腕肌群最大用力之等長、向心與離心收縮，其中十二位受試者也執行矢狀面下的相同測試。實驗過程中記錄腕關節力矩及伸腕肌群活化情形。
研究結果發現，伸腕肌群於斜向平面的表現確實與矢狀面活的表現有所不同，包括等長收縮時的肌肉活化、等速收縮時能產生的最大腕關節力矩及肌肉活化與收縮速度間的關係。而有關斜向平面的表現，等長收縮下腕關節角度顯著影響伸腕肌群力量與活化表現，動態收縮下腕關節角度與角速度有交互影響。整體而言，伸腕肌群能產生最大力量與施力最有效率之關節角度為手腕正中與些微伸直的姿勢。
本研究結果可用於探討上肢累積性傷害，實驗中使用之客製化測力儀能提供較接近功能性手腕活動的表現。研究結果也可提供網球教練之教學參考及臨床上肌力評估之應用，以及提供上肢人因工程領域的手部工具或工作環境設計之參考。未來有關腕關節的研究，建議使用改良之手腕測力儀，以探討更接近真實活動的表現。也期望有更多研究來建立腕關節角度與前臂肌肉表現的關係。

Cumulative trauma disorders of upper extremity, such as lateral epicondylitis, are common in sport activities and workplace. Inappropriate postures, repetitive movements and forceful exertions during tasks are risk factors. About 50% of novice tennis players are affected by lateral epicondylitis. This may be due to faulty mechanism of tennis backhand stroke in novices. Previous studies have investigated the effect of wrist angle on extension torque production. However, those information focused only on isometric and concentric contraction for wrist motions in sagittal plane. Furthermore, the available wrist dynamometers on the market provide wrist motions in sagittal or coronal plane, which are different from functional wrist activities in oblique plane. Besides that, there is also a lack of investigation about effect of wrist angle on wrist extensor activation.
In this study, performance of wrist extensors was compared between wrist motions in oblique and sagittal plane by using a custom made wrist dynamometer. The wrist motion simulated in oblique plane was tennis backhand stroke. The effect of wrist angle on torque production and muscle activation were examined during simulated tennis backhand stroke. Surface electromyography was used to record activation of wrist extensors during experimental tasks. Thirty healthy participants perform maximum isometric, concentric and eccentric wrist extension in oblique plane, and twelve of them also conducted the same tasks in sagittal plane. Wrist extension torque and activation of wrist extensors were both recorded during tasks.
The results showed that performance of wrist extensors was exactly different between wrist motions in oblique and sagittal plane, including muscle activation of wrist extensors during isometric contraction and peak torque magnitude and relationship between muscle activation and angular velocity during isokinetic contraction. About performance of wrist extensors in oblique plane, the wrist angle significantly affected extension torque and muscle activation during isometric contraction, whereas wrist angle interacted with angular velocity during dynamic contraction. Generally, the maximum wrist extension torque and neuromuscular efficiency occurred at wrist position of neutral and slight extension.
Results of this study can help to investigate cumulative trauma disorders of upper extremity. The custom made dynamometer used in current study provide wrist motions closer to functional wrist motions. This study can be further used in recommendations of tennis, muscle strength evaluation in the clinics and ergonomics of upper extremity. Future study about wrist joint is recommended to use modified dynamometer to investigate muscle performance which is closer to actual wrist motions. Further study is still necessary to confirm the relationship between wrist angle and forearm muscle performance.

Alizadehkhaiyat, O., A. C. Fisher, G. J. Kemp, K. Vishwanathan and S. P. Frostick (2007). "Upper limb muscle imbalance in tennis elbow: a functional and electromyographic assessment." J Orthop Res 25(12): 1651-1657.
Alizadehkhaiyat, O., J. Kemp, K. Vishwanathan and S. Frostick (2008). "P72 ELECTROMYOGRAPHIC ASSESSMENT OF FOREARM MUSCLES IN LATERAL EPICONDYLITIS." Journal of Bone & Joint Surgery, British Volume 90(SUPP II): 386-386.
Arampatzis, A., K. Karamanidis, S. Stafilidis, G. Morey-Klapsing, G. DeMonte and G.-P. Brüggemann (2006). "Effect of different ankle-and knee-joint positions on gastrocnemius medialis fascicle length and EMG activity during isometric plantar flexion." Journal of biomechanics 39(10): 1891-1902.
Babault, N., M. Pousson, A. Michaut and J. Van Hoecke (2003). "Effect of quadriceps femoris muscle length on neural activation during isometric and concentric contractions." Journal of Applied Physiology 94(3): 983-990.
Blackwell, J. R. and K. J. Cole (1994). "Wrist kinematics differ in expert and novice tennis players performing the backhand stroke: implications for tennis elbow." Journal of biomechanics 27(5): 509-516.
Cram, J., G. Kasman and J. Holtz (1998). "Introduction to surface electromyography. 1998." Gaithersburg, Marland: Aspen publishers Inc.
Criswell, E. (2010). Cram's introduction to surface electromyography, Jones & Bartlett Publishers.
Cullinane, F. L., M. G. Boocock and F. C. Trevelyan (2014). "Is eccentric exercise an effective treatment for lateral epicondylitis? A systematic review." Clin Rehabil 28(1): 3-19.
De Smedt, T., A. de Jong, W. Van Leemput, D. Lieven and F. Van Glabbeek (2007). "Lateral epicondylitis in tennis: update on aetiology, biomechanics and treatment." Br J Sports Med 41(11): 816-819.
Deschenes, M. R., R. E. Brewer, J. A. Bush, R. W. McCoy, J. S. Volek and W. J. Kraemer (2000). "Neuromuscular disturbance outlasts other symptoms of exercise-induced muscle damage." Journal of the neurological sciences 174(2): 92-99.
Doheny, E. P., M. M. Lowery, D. P. FitzPatrick and M. J. O’Malley (2008). "Effect of elbow joint angle on force–EMG relationships in human elbow flexor and extensor muscles." Journal of Electromyography and Kinesiology 18(5): 760-770.
Elliott, B. (2006). "Biomechanics and tennis." Br J Sports Med 40(5): 392-396.
Fairbank, S. (2002). "The Role of the Extensor Digitorum Communis Muscle in Lateral Epicondylitis." The Journal of Hand Surgery: Journal of the British Society for Surgery of the Hand 27(5): 405-409.
Falla, D., G. Jull, S. Edwards, K. Koh and A. Rainoldi (2004). "Neuromuscular efficiency of the sternocleidomastoid and anterior scalene muscles in patients with chronic neck pain." Disability & Rehabilitation 26(12): 712-717.
Fleming, J. and A. McGregor (2005). "Forearm muscle profiles in tennis players." Isokinetics and exercise science 13(2): 147-151.
Forthomme, B., J.-L. Croisier, M. Foidart-Dessalle and J.-M. Crielaard (2002). "Isokinetic assessment of the forearm and wrist muscles." Isokinetics and exercise science 10(3): 121-128.
Friedman, P. J. (1998). "Isokinetic peak torque in women with unilateral cumulative trauma disorders and healthy control subjects." Archives of physical medicine and rehabilitation 79(7): 816-819.
Garg, R., A. P. Kraszewski, H. H. Stoecklein, G. Syrkin, H. J. Hillstrom, S. Backus, M. L. Lenhoff, A. L. Wolff, J. J. Crisco and S. W. Wolfe (2014). "Wrist kinematic coupling and performance during functional tasks: effects of constrained motion." J Hand Surg Am 39(4): 634-642 e631.
Gillard, D. M., S. Yakovenko, T. Cameron and A. Prochazka (2000). "Isometric muscle length–tension curves do not predict angle–torque curves of human wrist in continuous active movements." Journal of biomechanics 33(11): 1341-1348.
Glynn, J. A., B. B. Kentel, M. A. King and S. R. Mitchell (2007). "A comparison of wrist angular kinematics and forearm EMG data for an elite, intermediate and novice standard tennis player performing a one-handed backhand groundstroke."
Hoogvliet, P., M. S. Randsdorp, R. Dingemanse, B. W. Koes and B. M. Huisstede (2013). "Does effectiveness of exercise therapy and mobilisation techniques offer guidance for the treatment of lateral and medial epicondylitis? A systematic review." Br J Sports Med 47(17): 1112-1119.
Horii, E., K. N. An and R. L. Linscheid (1993). "Excursion of prime wrist tendons." The Journal of hand surgery 18(1): 83-90.
Ingelman, J. P. (1991). Biomechanical comparison of backhand techniques used by novice and advanced tennis players: implications for lateral epicondylitis, Theses (School of Kinesiology)/Simon Fraser University.
Jung, M. C. and M. S. Hallbeck (2002). "The effect of wrist position, angular velocity, and exertion direction on simultaneous maximal grip force and wrist torque under the isokinetic conditions." Int J Ind Ergon 29: 133-143.
Kannus, P. (1997). "Etiology and pathophysiology of chronic tendon disorders in sports." Scandinavian journal of medicine & science in sports 7(2): 78-85.
Kathleen Killough, M. and L. L. Crumpton (1996). "An investigation of cumulative trauma disorders in the construction industry." International Journal of Industrial Ergonomics 18(5): 399-405.
Kennedy, P. and A. Cresswell (2001). "The effect of muscle length on motor-unit recruitment during isometric plantar flexion in humans." Experimental brain research 137(1): 58-64.
Keyserling, W. M. (2000). "Workplace Risk Factors and Occupational Musculoskeletal Disorders, Part 2: A Review of Biomechanical and Psychophysical Research on Risk Factors Associated with Upper Extremity Disorders." AIHAJ - American Industrial Hygiene Association 61(2): 231-243.
Krishnan, C., E. J. Allen and G. N. Williams (2011). "Effect of knee position on quadriceps muscle force steadiness and activation strategies." Muscle & nerve 43(4): 563-573.
Kroemer, K. (1989). "Cumulative trauma disorders: their recognition and ergonomics measures to avoid them." Applied ergonomics 20(4): 274-280.
Loren, G., S. Shoemaker, T. Burkholder, M. Jacobson, J. Friden and R. Lieber (1996). "Human wrist motors: biomechanical design and application to tendon transfers." Journal of biomechanics 29(3): 331-342.
M., R., M. M.A., M. B. and C. J. (2007). "Activation of forearm muscles for wrist extension in patients affected by lateral epicondylitis " Conf Proc IEEE Eng Med Biol Soc: 4858-4861.
Marley, R. J. and M. R. Thomson (2000). "Isokinetic strength characteristics in wrist flexion and extension." International Journal of Industrial Ergonomics 25(6): 633-643.
Mohamed, O., J. Perry and H. Hislop (2002). "Relationship between wire EMG activity, muscle length, and torque of the hamstrings." Clinical Biomechanics 17(8): 569-579.
Moore, K. L., A. F. Dalley and A. M. Agur (2013). Clinically oriented anatomy, Lippincott Williams & Wilkins.
Morse, J. L., M. C. Jung, G. R. Bashford and M. S. Hallbeck (2006). "Maximal dynamic grip force and wrist torque: the effects of gender, exertion direction, angular velocity, and wrist angle." Appl Ergon 37(6): 737-742.
Navsaria, R., D. M. Ryder, J. S. Lewis and C. M. Alexander (2013). "The Elbow-EpiTrainer: a method of delivering graded resistance to the ECRB. Effectiveness of a prototype device in a healthy population." Br J Sports Med 0: 1-6.
Nicolas, A., A. Gauthier, N. Bessot, S. Moussay and D. Davenne (2005). "Time-of-day effects on myoelectric and mechanical properties of muscle during maximal and prolonged isokinetic exercise." Chronobiology international 22(6): 997-1011.
Nourbakhsh, M. R. and C. G. Kukulka (2004). "Relationship between muscle length and moment arm on EMG activity of human triceps surae muscle." Journal of Electromyography and Kinesiology 14(2): 263-273.
O'Neil, B. A., M. E. Forsythe and W. D. Stanish (2001). "Chronic occupational repetitive strain injury." Canadian Family Physician 47(2): 311-316.
Onishi, H., R. Yagi, M. Oyama, K. Akasaka, K. Ihashi and Y. Handa (2002). "EMG-angle relationship of the hamstring muscles during maximum knee flexion." Journal of Electromyography and Kinesiology 12(5): 399-406.
Patsika, G., E. Kellis and I. G. Amiridis (2011). "Neuromuscular efficiency during sit to stand movement in women with knee osteoarthritis." J Electromyogr Kinesiol 21(5): 689-694.
Peterson, M., S. Butler, M. Eriksson and K. Svardsudd (2011). "A randomized controlled trial of exercise versus wait-list in chronic tennis elbow (lateral epicondylosis)." Ups J Med Sci 116(4): 269-279.
Qi, L., J. M. Wakeling and M. Ferguson-Pell (2011). "Spectral properties of electromyographic and mechanomyographic signals during dynamic concentric and eccentric contractions of the human< i> biceps brachii</i> muscle." Journal of Electromyography and Kinesiology 21(6): 1056-1063.
Riek, S., A. E. Chapman and T. Milner (1999). "A simulation of muscle force and internal kinematics of extensor carpi radialis brevis during backhand tennis stroke: implications for injury." Clinical Biomechanics 14(7): 477-483.
Roetert, P. and J. L. Groppel (2001). World-class tennis technique, Human Kinetics.
Roman-Liu, D. and P. Bartuzi (2013). "The influence of wrist posture on the time and frequency EMG signal measures of forearm muscles." Gait & posture 37(3): 340-344.
Roy, A., T. Keller and C. Colloca (2003). "Posture-dependent trunk extensor EMG activity during maximum isometrics exertions in normal male and female subjects." Journal of Electromyography and Kinesiology 13(5): 469-476.
Saito, A. and H. Akima (2013). "Knee joint angle affects EMG–force relationship in the vastus intermedius muscle." Journal of Electromyography and Kinesiology 23(6): 1406-1412.
Salvia, P., L. Woestyn, J. H. David, V. Feipel, S. Van, S. Jan, P. Klein and M. Rooze (2000). "Analysis of helical axes, pivot and envelope in active wrist circumduction." Clinical biomechanics 15(2): 103-111.
Seo, N. J., T. J. Armstrong, J. A. Ashton-Miller and D. B. Chaffin (2008). "Wrist strength is dependent on simultaneous power grip intensity." Ergonomics 51(10): 1594-1605.
Seo, N. J., T. J. Armstrong, D. B. Chaffin and J. A. Ashton-Miller (2008). "Inward torque and high-friction handles can reduce required muscle efforts for torque generation." Human Factors: The Journal of the Human Factors and Ergonomics Society 50(1): 37-48.
Solomonow, M. and M. Krogsgaard (2001). "Sensorimotor control of knee stability. A review." Scandinavian journal of medicine & science in sports 11(2): 64-80.
Tan, J. C., M. Parnianpour, M. Nordin, H. Hofer and B. Willems (1993). "Isometric maximal and submaximal trunk extension at different flexed positions in standing: triaxial torque output and EMG." Spine 18(16): 2480-2490.
Tesch, P., G. Dudley, M. Duvoisin, B. Hather and R. Harris (1990). "Force and EMG signal patterns during repeated bouts of concentric or eccentric muscle actions." Acta Physiologica Scandinavica 138(3): 263-271.
Tyler, T. F., G. C. Thomas, S. J. Nicholas and M. P. McHugh (2010). "Addition of isolated wrist extensor eccentric exercise to standard treatment for chronic lateral epicondylosis: a prospective randomized trial." J Shoulder Elbow Surg 19(6): 917-922.
Viswas, R., R. Ramachandran and P. Korde Anantkumar (2012). "Comparison of effectiveness of supervised exercise program and Cyriax physiotherapy in patients with tennis elbow (lateral epicondylitis): a randomized clinical trial." The Scientific World Journal 2012.
Walmsley, R. P., N. Pearson and P. Stymiest (1986). "Eccentric wrist extensor contractions and the force velocity relationship in muscle." Journal of Orthopaedic & Sports Physical Therapy 8(6): 288-293.
Widmaier, E. P., H. Raff and K. T. Strang (2011). Vander's human physiology: the mechanisms of body function, McGraw-Hill Higher Education.
Wilhelm, G. and M. Hallbeck (1997). The effects of gender, wrist angle, exertion direction, angular velocity, and simultaneous grasp force on isokinetic wrist torque. Triennial Congress of the International Ergonomics Association.