Bilateral Effects of 6 Weeks' Unilateral Acupuncture and Electroacupuncture on Ankle Dorsiflexors Muscle Strength: A Pilot Study

50

ORIGINAL ARTICLE

Bilateral Effects of 6 Weeks’ Unilateral Acupuncture and Electroacupuncture on Ankle Dorsiflexors Muscle Strength: A Pilot Study Shi Zhou, PhD, Li-Ping Huang, PhD, Jun Liu, MSc, Jun-Hai Yu, MSc, Qiang Tian, MSc, Long-Jun Cao, MSc ABSTRACT. Zhou S, Huang L-P, Liu J, Yu J-H, Tian Q, Cao L-J. Bilateral effects of 6 weeks’ unilateral acupuncture and electroacupuncture on ankle dorsiflexors muscle strength: a pilot study. Arch Phys Med Rehabil 2012;93:50-5. Objectives: To determine the effect of unilateral manual acupuncture at selected acupoints on ankle dorsiflexion strength of both limbs, and compare the effect with that of electroacupuncture at the same acupoints and sham points. Design: Randomized controlled trial. Setting: Rehabilitation laboratory of a university. Participants: Young men (N⫽43) were randomly allocated into 4 groups: control; manual acupuncture and electroacupuncture on 2 acupoints (ST-36 and ST-39); and electroacupuncture on 2 nonacupoints. These points were located on the tibialis anterior muscle. Interventions: The participants in the experimental groups received 15 to 30 minutes of acupuncture or electroacupuncture on the right leg in each session, 3 sessions per week for 6 weeks. Main Outcome Measures: The maximal strength in isometric ankle dorsiflexion of both legs was assessed before and after the experimental period. Results: Repeated-measures analysis of variance identified significant and similar strength gains (range, 35%– 64% in the right leg and 32%– 49% in the left leg; P⬍.01) in all acupuncture groups, but not in the control group (⫺2% to 2%, P⬎.05). Conclusions: Unilateral manual acupuncture and electroacupuncture at the acupoints can improve muscle strength in both limbs, and electroacupuncture at the nonacupoints as used in this study can also induce similar strength gains. Key Words: Acupuncture; Electric stimulation; Functional laterality; Muscle strength; Rehabilitation. © 2012 by the American Congress of Rehabilitation Medicine

T HAS BEEN REPEATEDLY reported that single-limb Imuscle resistance exercise can affect muscle strength in both the under training and the homologous muscle in the con-

myostimulation (EMS)7-12 or electroacupunture13 may also induce cross education, with the magnitude similar to that found in resistance training. It has been suggested that cross education can be used as a means of therapy or rehabilitation for certain neuromuscular disorders.2,14-16 Interestingly, the practice of unilateral therapy for conditions on the contralateral side has been used in traditional Chinese medicine (TCM) for centuries.17 One particular type of treatment, termed Juci, is to perform acupuncture on the unaffected side of the body for treatment of certain disorders on the contralateral side.18 There have been reports that acupuncture can increase muscle strength.13,19,20 For example, the muscle strength of the knee extensors was found to be increased after a single session of bilateral manual acupuncture in a randomized, placebo-controlled trial in recreational athletes.19 However, the effect of unilateral manual acupuncture on muscle strength of the contralateral side of the body has rarely been critically examined. With the development of technology, electroacupuncture became available several decades ago.21,22 Electroacupuncture involves applying acupuncture at selected acupoints with electrical pulses delivered to the needles. Both manual acupuncture and electroacupuncture techniques are receiving recognition in the West, but they are recommended primarily for pain modulation.23 There has been increased interest on the effect of acupuncture on muscle function and sports performance; however, the published work in this area is still very limited.19,20,24-26 For the purpose of developing optimal therapeutic, rehabilitation, and strength training programs, in relation to crosseducation effect, it would be interesting to investigate whether unilateral manual acupuncture can also induce a similar contralateral effect on muscle strength as that caused by electroacupuncture, and whether the effect occurs only when the needles are applied to specific acupoints. Therefore, the aim of this study was to determine the effect of 6 weeks of unilateral manual acupuncture at selected acupoints on muscle strength in ankle dorsiflexion of both limbs, and compare the effect with that of electroacupuncture at the same acupoints, and electroa-

tralateral limb, a phenomenon known as cross education.1-6 Furthermore, there have been reports that unilateral electro-

List of Abbreviations From the Department of Health and Exercise Science, Tianjin University of Sport, Tianjin, China (Zhou, Huang, Liu, Yu, Tian, Cao); and the School of Health and Human Sciences, Southern Cross University, Lismore, NSW, Australia (Zhou). Supported by Tianjin Scientific Research Foundation (grant no. 05YFGDSF02100) and Internal Research Grant of Southern Cross University, Australia. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated. Correspondence to Li-Ping Huang, PhD, Dept of Health and Exercise Science, Tianjin University of Sport, 51 Weijin South Rd, Hexi District, Tianjin 300381, P. R. China, e-mail: [email protected]. Reprints are not available from the authors. 0003-9993/12/9301-00356$36.00/0 doi:10.1016/j.apmr.2011.08.010

Arch Phys Med Rehabil Vol 93, January 2012

CON EAcu EMS ESham fMRI H-reflex MAcu MVC RMANOVA TCM

control group electroacupuncture electromyostimulation electroacupuncture at sham point functional magnetic resonance imaging Hoffmann’s reflex manual acupuncture maximal voluntary contraction analysis of variance with repeated measures traditional Chinese medicine

51

ACUPUNCTURE AND MUSCLE STRENGTH, Zhou Table 1: Physical Characteristics of Participants Characteristic

CON (n⫽10)

MAcu Group (n⫽11)

EAcu Group (n⫽11)

ESham Group (n⫽11)

Total (N⫽43)

Age (y) Mass (kg) Height (cm)

21.6⫾1.4 68.8⫾5.3 175.1⫾7.1

19.5⫾0.9 64.3⫾6.6 171.8⫾4.1

21.6⫾3.4 69.4⫾11.5 172.8⫾5.4

19.6⫾1.3 62.5⫾10.3 169.4⫾3.9

20.6⫾2.2 66.2⫾9.1 172.2⫾5.5

NOTE. Values are mean ⫾ SD.

cupuncture at nonacupoints (sham points). The dorsiflexion muscle group was chosen because its normal function is essential to walking, and the dorsiflexors are often more significantly impaired than the plantar flexors in patients with hemiparesis.27-29 METHODS Participants Forty-three male university students with a mean age of 20.6 years (range, 18 –29y) volunteered for the study. The sample size was determined by a priori estimation based on the effect size of 0.8, power of .95, and ␣ level of .05, using the G*Power 3 program (version 3.0.3).30,a It was estimated that to detect between-factor differences using analysis of variance with repeated measures (RMANOVA), a minimum of 7 participants in each group would be required. Therefore, 10 participants in each group were thought to have sufficient statistical power to determine the effect of treatment in the present study. Participants had no musculoskeletal or neurologic disorders, had not been involved in regular strength training during the 6 months before the study, and had no previous experience with acupuncture or EMS. All participants were right foot dominant as identified using an established questionnaire.31 Participants were first given an individual registration number, then randomly allocated into 4 groups according to a random number table: control group (CON) (n⫽10), manual acupuncture on acupoints (MAcu) group (n⫽11), electroacupuncture on acupoints (EAcu) group (n⫽11), and electroacupuncture on sham points (ESham) group (n⫽11). The physical characteristics of the participants are presented in table 1. The experimental procedures obtained approval by the human research ethics committee of the university and were conducted in compliance with the Declaration of Helsinki. Consent was obtained from all participants before commencement of the study. Procedures Participants in the MAcu, EAcu, and ESham groups received acupuncture on the right leg, 3 sessions per week, for 6 weeks. All participants were given 1 minute of ankle exercise at a comfortable intensity before each session as warm-up, and similar exercise after each session as cool-down. The MAcu and EAcu groups received manual acupuncture or electroacupuncture at the acupoints of Zusanli (ST-36) and Xiajuxu (ST-39)32 (fig 1). The locations of these acupoints have been described in a previous report.13 For the ESham group, acupuncture needles were applied to a point at the top one third and a point at the lower one third length of muscle belly of the tibialis anterior, respectively, and 3cm laterally to the anterior crest of the tibia, avoiding any known TCM meridian channels and acupoints (see fig 1). For all participants in the 3 intervention groups, a stainless steel acupuncture needle (GB2024-94)b with a diameter of 0.3mm and length of 50mm was inserted vertically into the muscle at the selected point to a depth of 20 to 30mm. At the acupoints, a feeling of Deqi (ie, “needle sensation”—a soreness

and numbness sensation but not a sharp pain) was experienced by the participants. At the sham point, the needle was inserted to a similar depth as that for the acupoint; however, it was not necessary to experience Deqi but instead only a level of pain. The acupuncture was performed by a qualified acupuncturist who had a bachelor’s degree in TCM and practiced acupuncture in hospital for 10 years. The treatment time in each session was 15 minutes in the first week, 20 minutes in week 2, and 30 minutes in weeks 3 through 6. For the MAcu group, twirling and lift-thrusting techniques were applied for 15 seconds every 5 minutes. For the EAcu and ESham groups, an electroacupuncture apparatus (SDZ-II)b was used to deliver constant-current square-wave pulses at a frequency of 40Hz and a pulse width of 1ms, with a gradually increased intensity up to the maximal level the

Fig 1. Locations of ST-36, ST-39 acupoints and sham points. Cun is a unit for relative length used in TCM. Three cun is the breadth of participant’s index, middle, ring, and little fingers at the level of the proximal interphalangeal joint at the dorsum of the middle finger. Sham points are located at the top one third and lower one third length of the muscle belly of the tibialis anterior muscle, and 3cm lateral to the anterior crest of the tibia.

Arch Phys Med Rehabil Vol 93, January 2012

52

ACUPUNCTURE AND MUSCLE STRENGTH, Zhou

Fig 2. The maximum isometric ankle dorsiflexion strength (newtons) of the left (L, circles) and right (R, squares) leg before (Pre, unfilled) and after (Post, filled) 6 weeks of MAcu and EAcu on acupoints of ST-36 and ST-39, and ESham. *P<.05 compared with CON; † P<.000, Pre vs Post.

participants could tolerate. The cathode of the stimulator was connected to the proximal needle and the anode to the distal needle. The stimulation was applied continuously for the same period during each session as that for the MAcu group. Participants took a supine position and were instructed not to voluntarily contract the muscle during the acupuncture. For safety considerations, dorsiflexion force was not monitored when acupuncture needles were in the muscle. The electroacupuncture induced visible contractions, while manual acupuncture did not induce any visible muscle contraction. Participants in the CON continued with their normal daily activities without engaging in any specific physical training. For a more appropriate control of the potential effects from the experimental environment, all participants in the CON also visited the laboratory 3 times per week. They participated in the warm-up and cool-down activities but otherwise rested during the session. Before and after the 6 weeks of intervention, all participants were tested for their maximal voluntary contraction (MVC) strength in isometric dorsiflexion contractions on a custombuilt device. During the test, participants were supine with the nontested leg fully extended and relaxed. The leg for testing was strapped to the testing device by Velcro belts at the foot, leg, and the thigh, with the ankle joint at 15° plantar flexion and the knee joint angle at full extension. The force transducer (MCL-S)c was mounted on a metal bar with foam padding that was placed on the back of the foot at the level of the metatarsophalangeal joint. With the heel supported and rotation axis of the device and ankle joint aligned, the location of the metal bar was adjusted according to the foot size. This location was recorded for each individual for repeated testing. The signals collected from the force transducer were fed into a Medlab data acquisition system (Medlab-U8C)d at the analog-to-digital conversion rate of 500Hz. The participant was asked to perform at least 3 maximal dorsiflexions against the force transducer. Each contraction was maintained for 3 to 5 seconds followed by 1 minute of recovery. Strong verbal encouragement was given to the participants during the contraction, and 1 or 2 additional trials were allowed if participants thought they could do better.33 The research assistant who performed the strength test was not aware of which group the participants were from, and the data analysis was performed offline after completion of the experimental period by a research assistant who was also blinded to participants’ groups and the time (pre or post) of the Arch Phys Med Rehabil Vol 93, January 2012

tests. The highest force value of the successful contractions from each participant was used in statistical analysis. Statistical Analysis A 3-way RMANOVA (intervention ⫻ leg, with the group as the between-subject factor) was performed to detect the main effect of intervention, leg, and group; and interactions between preintervention and postintervention, left and right legs, and the groups. If a significant effect or interaction was detected, Bonferroni adjustment was applied in post hoc analysis to compare the mean values, with an ␣ level of .05 set for statistical significance. These statistical analyses were performed using SPSS statistical package (Version 17).e RESULTS All participants successfully completed the study, except that the postintervention data of 2 participants in the MAcu group were invalid because of errors in recording. The results of RMANOVA indicated that there was a significant main effect of intervention (F⫽132.5, P⫽.000), and interaction of intervention by group (F⫽19.6, P⫽.000). Post hoc analyses indicated that the 6 weeks of intervention significantly improved dorsiflexion MVC in both legs in the MAcu, EAcu, and ESham groups (all P⬍.01), while the CON showed no change in MVC of both legs during the same period (fig 2). There were no significant differences in MVC between the 2 legs in either the preintervention or the postintervention test in all groups. There were no significant differences in MVC between the CON and other groups before the intervention. However, in the postintervention test, the right leg strength of the EAcu and ESham groups, and the left leg strength of all 3 acupuncture groups became significantly higher than that of the CON (P⬍.05) (see fig 2). DISCUSSION There have been reports that 1 session of bilateral acupuncture or electrical stimulation at selected acupoints may have an acute effect on muscle strength.20,34 A previous study13 in our laboratory has also demonstrated that 4 weeks of unilateral electroacupuncture can improve muscle strength bilaterally. The present study demonstrated, for the first time, that 6 weeks of unilateral manual acupuncture can also have bilateral effects on muscle strength, while the outcomes of electroacupuncture

ACUPUNCTURE AND MUSCLE STRENGTH, Zhou

intervention underscored our previous finding. The 18 sessions of electroacupuncture at the acupoints resulted in a 35% strength gain in the stimulated leg and 32% in the contralateral leg, and at the sham points resulted in a 64% and 55% strength gain, respectively, which appeared to be greater than the 21.3% and 15.2% strength gain found in our previous investigation13 on the effects of 4 weeks (12 sessions) of electroacupuncture. Whether the greater strength gain in the present study was due to the longer period of intervention would be an interesting question for future study. More interestingly, the MAcu group also demonstrated a significant strength gain, with 46% and 49% in the right and the left legs, respectively, while the CON showed no change in strength of both legs. These findings may have clinical implications. Although acupuncture has been practiced for centuries, only during the past several decades has its effectiveness for specific conditions been examined in randomized, controlled clinical trials.17,23,35 For example, a recent systematic review and meta-analysis17 of randomized clinical trials on the effect of acupuncture for poststroke rehabilitation indicated that contralateral treatment might have a superior effect compared with ipsilateral treatment for cerebral infarction. Acupuncture has also been used as an ergogenic aid for enhancing sports performance, with some evidence of improved muscle strength and power and hemodynamic parameters, although a larger number of randomized controlled trials are needed to confirm these effects.24 It has been reported that 50% of the acupoints are directly above major nerve trunks, and other acupoints are located within 0.5cm of the nerve trunks or are identical to the motor points.36 Sham points have been used as a “control” for the effect of acupuncture.35,37,38 In a recent literature review38 on the specificity of acupoints, it was reported that nearly 60% of the trials did not find a significant difference in the outcomes between acupuncture at acupoints and sham points. The present study also found no significant difference in the strength gains between the EAcu and ESham groups. However, the results should be interpreted with caution because the acupoints and sham points selected in this study might be in the same vicinity of the deep peroneal nerve (see fig 1), and electrical stimulation at these points could have stimulated the same nerve. Further studies may use other means of “control,” such as manual acupuncture on sham points, no needle insertion, or insertion at various depths, to provide alternative evidence.23 It is difficult to perform “placebo”-controlled trials for acupuncture because of the difficulty in finding an adjacent point that is far enough away from the acupoint without overlapping with another acupoint or a meridian channel,23 and because electroacupuncture and manual acupuncture at both acupoints or sham points cause a level of pain that may produce a placebo effect.37,38 A limitation of this pilot study was that additional control groups were not included to address these aspects. Nevertheless, the results of the present study appear to indicate that the 3 types of interventions as used in this study all can induce a significant bilateral effect on muscle strength. It is beyond the objectives of this study to discuss the possible mechanisms of acupuncture-induced cross education within the theoretic framework of TCM. We adopt the viewpoint that the bilateral effects of acupuncture and electrical stimulation are induced by plasticity of the nervous system,23,36 although the possibility of peripheral adaptations should not be excluded.4,5,12,39 It has been hypothesized that at the supraspinal levels, the contralateral strength gain in adaptation to resistance training could be due to either “crossed activation” (eg, activation of neural circuits on 1 side that chronically modifies the efficacy of motor pathways that project to the opposite untrained limb) or “bilateral access” (ie, the untrained

53

limb may access these modified neural circuits during training), which may subsequently lead to an increased capacity to drive the untrained muscles and thus result in increased strength.6,39 However, whether and how the contralateral strength gain induced by electrical stimulation or acupuncture can be manifested via these proposed cortical mechanisms are unknown. The principle of electrical stimulation training is to deliver electrical pulses to the target peripheral nerve to activate the muscle. Because the excitation threshold of the nerve fibers is significantly lower than that of the muscle fibers, transcutaneous stimulation, and perhaps electroacupuncture as well, will preferentially activate the nerve fibers.40 When the stimulation intensity is progressively increased, the nerve fibers that have a lower threshold (eg, the large Ia afferent fibers from muscle spindles) are activated before those with higher thresholds (eg, large Ia motor nerve fibers and small IV fibers from the pain and thermal receptors).41,42 It can be predicted that at the maximal stimulation intensity, all the sensory and motor nerve fibers in the nerve trunk will be activated. However, subject to participants’ tolerance to discomfort and pain, submaximal stimulation intensities are normally used in electrical stimulation training,41 and that was also the case for electroacupuncture as experienced in this study. Nevertheless, the sensory pathways are activated during the electrical stimulation and electroacupuncture, as the participants have perceived pain, indicating even the smallest nerve fibers are activated. The sensory afferents associated with electrical stimulation have been shown to cause cortical adaptations and improve MVC and muscle activation without significant muscle hypertrophy.41 There has been evidence from studies43,44 that used transcranial magnetic stimulation that peripheral electrical stimulation can result in rapid plastic change in the corticomotor pathway. A study45 that used functional magnetic resonance imaging (fMRI) technique showed that electrical stimulation applied to the tibialis anterior muscle of 1 side induced a widespread activation in the brain. The fMRI signals were stronger in voluntary ankle dorsiflexion than that in electrical stimulation-induced contractions in brain areas responsible for motor planning, execution, and visuomotor coordination, while the electrical stimulation-induced activity was stronger in bilateral secondary somatosensory areas and the insula, possibly because of increased sensory integration or nociceptive inputs. How these changes in brain activities are related to plasticity in motor function is still subject to elucidation. However, it can be speculated that the sensory afferents may play an important role in mediating the cross education associated with electrical stimulation training. The essential role of sensory afferents in mediating cross education is further supported by the effect of manual acupuncture as found in this study. The manual acupuncture did not appear to effectively activate the motor nerve because no visible muscle contraction was observed. Therefore, the crosseducation effect caused by acupuncture does not seem to be related to the contraction intensity, but must be related to the sensory inputs. The practice of traditional acupuncture is to manually manipulate the needle that results in Deqi, which is a mixture of aching, pressure, soreness, heaviness, fullness, warmth, cooling, numbness, tingling, and dull pain, but not sharp pain.46 These sensory inputs are conducted by type II, III, and IV fibers.46 Further research is needed to determine how these sensory inputs are related to cortical plasticity in motor performance. Spinal mechanisms may also be involved in cross education. It has been reported that unilateral voluntary dorsiflexion exercise increased dorsiflexion strength of both limbs, while the H-reflex at the threshold stimulation was increased in both the tibialis anterior Arch Phys Med Rehabil Vol 93, January 2012

54

ACUPUNCTURE AND MUSCLE STRENGTH, Zhou

and soleus muscles of the trained limb, indicating that more lowthreshold motoneurons were recruited. Furthermore, the H-reflex at maximum (H@max) of the antagonist (soleus) in both limbs decreased after 5 weeks of training.29 Equivocal evidence has been reported for the effect of acupuncture on the H-reflex. Electroacupuncture at Hegu (LI-4) acupoint (in the hand) has been shown to increase H-reflex amplitude, while manual acupuncture did not have a significant effect.47 Study Limitations A limitation of this pilot study was not including additional control groups for manual acupuncture on sham points or at various depths to address the potential placebo effects. The findings of the present study were from a healthy, young population with participants who had not participated in specific resistance training for the previous 6 months. It is known that muscle strength can improve quickly at the beginning of a training program because of neural adaptations, particularly in previously untrained individuals.48 Whether the strength gain induced by the acupuncture relies on the same neural mechanism is unknown. Furthermore, it is speculated that the contralateral effect of unilateral acupuncture on neuromuscular function might have clinical implications—for instance, in rehabilitation for single-limb injuries or hemiparesis, or as an ergogenic aid for enhancement of motor performance. Further studies are needed to confirm the therapeutic effect in patients or ergogenic effect in resistance-trained individuals such as athletes. CONCLUSIONS The present study demonstrated that dorsiflexion muscle strength was significantly improved in response to 6 weeks of unilateral manual acupuncture in healthy young men. The results also showed that the bilateral strength gain induced by electroacupuncture was not different when the stimulation was applied to ST-36 and ST-39 compared with that to the 2 nonacupoints on the leg. Acknowledgments: We thank Qing-Wen Li, PhD, for her guidance on acupuncture, and Ming Ao, BSc, and Wen-Long Wang, BEd, Tianjin University of Sport, for data collection and analysis. References 1. Lee M, Carroll TJ. Cross education: possible mechanisms for the contralateral effects of unilateral resistance training. Sports Med 2007;37:1-14. 2. Hortobagyi T. Cross education and the human central nervous system. IEEE Eng Med Biol Mag 2005;24:22-8. 3. Munn J, Herbert RD, Gandevia SC. Contralateral effects of unilateral resistance training: a meta-analysis. J Appl Physiol 2004; 96:1861-6. 4. Zhou S. Chronic neural adaptations to unilateral exercise: mechanisms of cross education. Exerc Sport Sci Rev 2000;28:177-84. 5. Farthing JP. Cross-education of strength depends on limb dominance: implications for theory and application. Exerc Sport Sci Rev 2009;37:179-87. 6. Lee M, Hinder MR, Gandevia SC, Carroll TJ. The ipsilateral motor cortex contributes to cross-limb transfer of performance gains after ballistic motor practice. J Physiol 2010;588(Pt 1):201-12. 7. Cabric M, Appell H-J. Effect of electrical stimulation of high and low frequency on maximum isometric force and some morphological characteristics in man. Int J Sports Med 1987;8:256-60. 8. Hortobagyi T, Scott K, Lambert J, Hamilton G, Tracy J. Crosseducation of muscle strength is greater with stimulated than voluntary contractions. Motor Control 1999;3:205-19. 9. Singer K. The influence of unilateral electrical muscle stimulation on motor unit activity patterns in atrophic human quadriceps. Aust J Physiother 1986;32:31-7. Arch Phys Med Rehabil Vol 93, January 2012

10. Tachino K, Susaki T, Yamazaki T. Effect of electro-motor stimulation on the power production of a maximally stretched muscle. Scand J Rehabil Med 1989;21:147-50. 11. Zhou S, Oakman A, Davie A. Effects of unilateral voluntary and electromyostimulation training on muscular strength on the contralateral limb. Hong Kong J Sports Med Sports Sci 2002;14:1-11. 12. Bezerra P, Zhou S, Crowley Z, Brooks L, Hooper A. Effects of unilateral EMS superimposed on voluntary training on strength and cross-sectional area. Muscle Nerve 2009;40:430-7. 13. Huang LP, Zhou S, Lu Z, et al. Bilateral effect of unilateral electroacupuncture on muscle strength. J Altern Complement Med 2007;13:539-46. 14. Kannus P, Alosa D, Cook L, et al. Effect of one-legged exercise on the strength, power and endurance of the contralateral leg. A randomized, controlled study using isometric and concentric isokinetic training. Eur J Appl Physiol 1992;64:117-26. 15. Devine KL, LeVeau BF, Yack HJ. Electromyographic activity recorded from an unexercised muscle during maximal isometric exercise of the contralateral agonists and antagonists. Phys Ther 1981;6:898-903. 16. Farthing JP, Krentz JR, Magnus CRA. Strength training the free limb attenuates strength loss during unilateral immobilization. J Appl Physiol 2009;106:830-6. 17. Kim M-K, Choi T-Y, Lee MS, Lee H, Han C-H. Contralateral acupuncture versus ipsilateral acupuncture in the rehabilitation of post-stroke hemiplegic patients: a systematic review. BMC Complement Altern Med 2010;10:41. 18. Lin YP, Pan L. Current research on Juci. J Yun Nan Chinese Med 2004;25:41-3. 19. Hübscher M, Vogt L, Ziebart T, Banzer W. Immediate effects of acupuncture on strength performance: a randomized, controlled crossover trial. Eur J Appl Physiol 2010;110:353-8. 20. Yang HY, Liu TY, Kuai L, Gao M. [Electrical acupoint stimulation increases athlete’s rapid strength] [Chinese]. Zhongguo Zhen Jiu 2006;26:313-5. 21. Shen J. Research on the neurophysiological mechanisms of acupuncture: review of selected studies and methodological issues. J Altern Complement Med 2001;7(Suppl 1):S121-7. 22. Ulett GA, Han S, Han JS. Electroacupuncture: mechanisms and clinical application. Biol Psychiatry 1998;44:129-38. 23. Han J-S. Acupuncture analgesia: areas of consensus and controversy. Pain 2011;152:S41-8. 24. Ahmedov S. Ergogenic effect of acupuncture in sport and exercise: a brief review. J Strength Cond Res 2010;24:1421-7. 25. Toma K, Conatser RR, Gilders RM, Hagerman FC. The effects of acupuncture needle stimulation on skeletal muscle activity and performance. J Strength Cond Res 1998;12:253-7. 26. Yan T, Hui-Chan CWY. Transcutaneous electrical stimulation on acupuncture points improves muscle function in subjects after acute stroke: a randomized controlled trial. J Rehabil Med 2009;41:312-6. 27. MacIntosh BJ, Mraz R, Baker N, Tam F, Staines WR, Graham SJ. Optimizing the experimental design for ankle dorsiflexion fMRI. Neuroimage 2004;22:1619-27. 28. Winter DA, Bishop PJ. Lower extremity injury. Biomechanical factors associated with chronic injury to the lower extremity. Sports Med 1992;14:149-56. 29. Dragert K, Zehr EP. Bilateral neuromuscular plasticity from unilateral training of the ankle dorsiflexors. Exp Brain Res 2011;208: 217-27. 30. Faul F, Erdfelder E, Lang A-G, Buchner A. G*Power 3: a flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods 2007;39:175-91. 31. Li XT. Handedness in Chinese. Acta Psychologica Sinica 1983; 15:27-35. 32. Beijing College of Traditional Chinese Medicine, Shanghai College of Traditional Chinese Medicine, Nanjing College of Tradi-

ACUPUNCTURE AND MUSCLE STRENGTH, Zhou

33. 34.

35.

36.

37.

38.

39.

40.

41.

tional Chinese Medicine, The Acupuncture Institute of the Academy of Traditional Chinese Medicine. Essentials of Chinese acupuncture. 1st ed. Beijing: Foreign Languages Pr; 1980. Gandevia SC. Spinal and supraspinal factors in human muscle fatigue. Physiol Rev 2001;81:1725-89. Ozerkan KN, Bayraktar B, Sahinkaya T, Goksu OC, Yucesir I, Yildiz S. Comparison of the effectiveness of the traditional acupuncture point, ST. 36 and Omura’s ST.36 Point (True ST. 36) needling on the isokinetic knee extension & flexion strength of young soccer players. Acupunct Electrother Res 2007;32:71-9. Zhang H, Bian Z, Lin Z. Are acupoints specific for diseases? A systematic review of the randomized controlled trials with sham acupuncture controls. Chin Med 2010;5:1. Balogun JA, Biasci S, Han L. The effects of acupuncture, electroneedling and transcutaneous electrical stimulation therapies on peripheral haemodynamic functioning. Disabil Rehabil 1998;20:41-8. Lundeberg T, Lund I, Sing A, Näslund J. Is placebo acupuncture what it is intended to be? Evid Based Complement Altern Med 2011;2011:1-5. Moffet HH. Sham acupuncture may be as efficacious as true acupuncture: a systematic review of clinical trials. J Altern Complement Med 2009;15:213-6. Carroll TJ, Herbert RD, Munn J, Lee M, Gandevia SC. Contralateral effects of unilateral strength training: evidence and possible mechanisms. J Appl Physiol 2006;101:1514-22. Paillard T. Combined application of neuromuscular electrical stimulation and voluntary muscular contractions. Sports Med 2008;38:161-77. Maffiuletti NA. Physiological and methodological considerations for the use of neuromuscular electrical stimulation. Eur J Appl Physiol 2010;110:223-34.

55

42. Chen YS, Zhou S. Soleus H-reflex and its relation to static postural control. Gait Posture 2011;33:169-78. 43. Gondin J, Guette M, Ballay Y, Martin A. Electromyostimulation training effects on neural drive and muscle architecture. Med Sci Sports Exerc 2005;37:1291-9. 44. Chipchase LS, Schabrun SM, Hodges PW. Peripheral electrical stimulation to induce cortical plasticity: a systematic review of stimulus parameters. Clin Neurophysiol 2011;122:456-63. 45. Francis S, Lin X, Aboushoushah S, et al. fMRI analysis of active, passive and electrically stimulated ankle dorsiflexion. Neuroimage 2009;44:469-79. 46. Hui KKS, Nixon EE, Vangel MG, et al. Characterization of the ”deqi” response in acupuncture. BMC Complement Altern Med 2007;7:33. 47. Chang Q-Y, Lin J-G, Hsieh C-L. Effect of electroacupuncture and transcutaneous electrical nerve stimulation at Hegu (LI.4) acupuncture point on the cutaneous reflex. Acupunct Electrother Res 2002;27:191-202. 48. Sale DG. Neural adaptation to resistance training. Med Sci Sports Exerc 1988;20(5 Suppl):S135-45. Suppliers a. G*Power. Free software. Available for downloading at: http:// www.psycho.uni-duesseldorf.de/aap/projects/gpower/. b. Suzhou Medical Appliance Factory, Ltd, 12-14 W Qiling Ln, Suzhou, Jiangsu Province 215005, P.R. China. c. Beijing Zhengkai Instruments Co, Ltd, 10 Xinkangyuan, Xisanqi E Rd, Haidian District, Beijing 100096, P.R. China. d. Nanjing MedEase Science and Technology Co, Ltd, 119 Jinghuai St, Jiangning Economic and Technology Development Zone, Nanjing, Jiangzu Province, P.R. China. e. SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.

Arch Phys Med Rehabil Vol 93, January 2012