THE JOURNAL OF ALTERNATIVE AND COMPLEMENTARY MEDICINE Volume 14, Number 8, 2008, pp. 1011–1016 © Mary Ann Liebert, Inc. DOI: 10.1089/acm.2008.0173
Effects of Acupuncture on Symptoms and Muscle Function in Delayed-Onset Muscle Soreness Markus Hübscher, Ph.D., Lutz Vogt, Ph.D., Marcus Bernhörster, M.D., Andreas Rosenhagen, M.D., and Winfried Banzer, M.D., Ph.D.
Abstract
Objective: This study was done to investigate the effects of a standardized acupuncture treatment on symptoms and muscle function in exercise-induced delayed-onset muscle soreness (DOMS). Methods: A prospective, randomized, controlled, observer and subject-blinded trial was undertaken. Twentytwo (22) healthy subjects (22–30 years; 10 males and 12 females) were randomly assigned to three treatment groups: real acupuncture (deep needling at classic acupuncture points and tender points; n 7), sham-acupuncture (superficial needling at nonacupuncture points; n 8), and control (no needling; n 7). DOMS of the nondominant elbow-flexors was experimentally induced through eccentric contractions until exhaustion. The outcome measures were pain perception (visual analogue scale; VAS; range: 0–10 cm), mechanical pain threshold (MPT; pressure algometer), and maximum isometric voluntary force (MIVF; force transducer). Treatment was applied immediately, 24 and 48 hours after DOMS induction. Measurements of MPT and MIVF were made prior to DOMS induction as well as before and after every treatment session. VAS data were acquired after DOMS induction as well as pre- and post-treatment. Final pain, MPT, and MIVF measurements were performed 72 hours after DOMS induction. Results: Following nonparametric testing, there were no significant differences between groups in outcome measures at baseline. After 72 hours, pain perception (VAS) was significantly lower in the acupuncture group compared to the sham acupuncture and control subjects. However, the mean MPT and MIVF scores were not significantly different between groups. Conclusions: Although acupuncture seemed to have no effects on mechanical pain threshold and muscle function, it proved to reduce perceived pain arising from exercise-induced muscle soreness.
Introduction
D
elayed-onset muscle soreness (DOMS) is classified as a type I muscle strain injury and is a phenomenon frequently observed in recreational or experienced athletes.1 It is mainly caused by exercises involving eccentric muscle work such as downhill running, jumping and strength training.2 DOMS is most prevalent at the beginning of the sporting season following a period of reduced activity, during the progression from low-intensity to high-intensity training due to periodization, or when unaccustomed or novel types of exercise are introduced.3 Several theories have been pro-
posed and integrated in an attempt to understand the mechanisms underlying DOMS. Accordingly, the high muscle tension developed during eccentric contractions may precipitate mechanical disruption of myofibrils and connective tissue, which triggers an inflammatory response.4 This is associated with tenderness, pain, and impairments in muscle function interfering with training capacity and athletic performance.5 The typical time course of DOMS is characterized by a prolonged strength loss immediately after exercise, accompanied by pain and discomfort that increase within the first 24 hours, peak between 48 and 72 hours, and disappear after 5–7 days postexercise.1,6 If a premature return to sports
Department of Sports Medicine, Goethe-University, Frankfurt/Main, Germany.
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1012 or physical activity is attempted, functional deficiency may theoretically increase the risk of more debilitating and severe injuries.1,6 Therefore, interventions that may prevent or counteract the symptoms of DOMS and facilitate muscle regeneration following intense exercise are of great interest in athletic health care delivery.3 Since recent research provides evidence for the efficacy of acupuncture on pain and dysfunction in various musculoskeletal and inflammatory disorders,7–9 it is conceivable that acupuncture could also be a potential treatment option in DOMS. However, there is no consistent evidence to support this hypothesis. Lin and Yang demonstrated significant reductions in muscle tenderness through acupuncture versus no acupuncture, whereas creatine kinase activity remained unchanged.10 These results could not be confirmed in a study by Barlas et al., who reported insignificant changes in tenderness and perceived muscle soreness when acupuncture was compared to shamacupuncture and no acupuncture.11 In addition, both studies did not include any measures of muscle function that might be, besides muscle soreness, tenderness, and inflammation, considered an important outcome when the objective is to appraise the efficacy of acupuncture in DOMS. Therefore, the purpose of the present study was to investigate the efficacy of acupuncture compared to sham-acupuncture and no acupuncture on symptoms and muscular performance in exercise-induced DOMS. Materials and Methods Subjects and study design The present randomized, controlled, observer and subjectblinded trial used a sample of convenience. Twenty-two (22) healthy, physically active sport students (22–30 years; 10 males and 12 females) voluntarily participated in this study. The exclusion criteria were cardiovascular, pulmonary, metabolic, neurological, psychiatric and musculoskeletal diseases, hemophilia, muscle soreness, pain, acupuncture treatment within the last 6 months, and the use of any medications. Subjects were instructed to refrain from any form of physical exercise for at least 1 week prior to as well as during the entire study period. Food intake was restricted to a light meal 3 hours before the measurement procedure. Beverages containing caffeine or alcohol were not allowed for at least 12 hours prior to the measurements. The experiment followed the Declaration of Helsinki recommendations for research involving human subjects. Procedures Subjects were requested to attend on 4 different occasions on consecutive days. On the first day they were randomly assigned to three treatment groups: real acupuncture (n 7), sham-acupuncture (n 8), and control (n 7). The randomization sequence was generated by a computer program (BiAS for Windows 7.0; Department of Mathematics, GoetheUniversity, Frankfort/Mein, Germany) and was retained by the principal investigator until the end of the trial to ensure allocation concealment. DOMS of the nondominant elbow-flexors was experimentally induced through eccentric contractions until exhaustion. The outcome measures were pain perception (visual analogue scale; VAS), mechanical pain threshold (MPT), and
HÜBSCHER ET AL. maximum isometric voluntary force (MIVF). Treatment was applied immediately, 24 and 48 hours after DOMS induction. Measurements of MPT and MIVF were made prior to DOMS induction as well as before and after every treatment session. VAS data were acquired after DOMS induction as well as preand post-treatment. Final pain, MPT, and MIVF measurements were performed 72 hours after DOMS induction. DOMS induction DOMS of the nondominant elbow flexors was experimentally induced on day 1 using a standardized exercise protocol. The nondominant arm was selected to design an experimental model that reflects the circumstances that usually provoke DOMS (i.e., when unaccustomed types of exercise are introduced). All subjects were seated at a preacher’s bench and performed isolated biceps curls with a dumbbell.11 At first, their individual one repetition maximum (1RM) (i.e., the maximum weight lifted with one concentric contraction), was determined for the elbow flexors by loading the dumbbell with free weights in 0.5-kg increments. Rest intervals of 2 minutes were utilized between trials. Subjects were encouraged verbally to elicit their maximal effort. The 1RM was then used to provoke DOMS through eccentric contractions until exhaustion. For this, the dumbbell was lifted by the experimenter until the subject’s elbow was fully flexed, and the subject then had to lower the weight eccentrically as slowly as possible until the elbow was fully extended. This procedure continued until the subject was no longer able to lower the dumbbell in a controlled manner. Altogether, each subject had to perform three sets separated by 30-second rest intervals. Interventions Acupuncture group. In consideration of the positive findings of Lin and Yang in terms of decreased muscle tenderness, the present study also used the following classical acupuncture points: gallbladder 34; lung 3, 5; large intestine 11; spleen 10; and ah shi (tender points), which were identified by palpation.10 Needling was carried out unilaterally using sterile disposable needles (Moxom® 0.3 30 mm; Moxom Medical GmbH, Graefenhainichen, Germany). De qi sensation was provoked by manual stimulation at the beginning of each session. Needles were subsequently retained in place for 15 minutes while subjects were lying in a supine position. The needle retention time was chosen with respect to previous investigations showing that a stimulation time of 15 minutes might be adequate for treating musculoskeletal disorders and acute pain.12–14 Acupuncture was carried out by the same skilled and experienced acupuncturist throughout the study. Sham-acupuncture group. Sham-acupuncture comprised superficial needling without stimulation at puncture sites that were at least 2 cun apart from the classical acupuncture points and tender points: sham-point 1: distal to gallbladder 34; sham-point 2: distal to lung 3; sham-point 3: proximomedial to lung 5; sham-point 4: proximomedial to large intestine 11; sham-point 5: medial to spleen 10. Subject position, acupuncturist, needle type, and retention time were identical to those in the acupuncture group.
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Control group. Subjects in this group did not receive any treatment and were asked to maintain a supine position for 15 minutes. Outcome measures Mechanical pain threshold. MPT was employed as a measure of tenderness and was assessed along the median line of the biceps brachii using a handheld mechanical pressure algometer (manufactured by pdt, Rome, Italy). According to previous investigations,11,15 MPT measurements were performed on seven equidistant points along a line joining the insertion of the biceps brachii on the radius and the acromion. These points were marked with semipermanent ink to ensure that measurement sites were consistent throughout the study (Fig. 1). Pressure was applied to each of these points with increasing force at a rate of approximately 1 kg/cm2/s through the head of the algometer (1-cm diameter) until the subject reported a painful sensation. At this time, the force value was recorded (kg/cm2). An upper limit of MPT was set at 5 kg/cm2 to avoid bruising. Each point was measured three times, with 10-second intervals between trials, and the mean of the second and third trials was used for further analysis.16 From these seven values, an average score was calculated to provide an estimate of whole-muscle tenderness. The higher the score (i.e., the pressure threshold) the lower the tenderness. Sufficient repeated-measures reliability of this procedure has been demonstrated by Nussbaum and Downes.16 Pain perception. Subjectively perceived muscle soreness was assessed on a VAS ranging from 0 to 10 cm, with 0 being “no soreness” and 10 being “extreme soreness.” Subjects were asked to rate their current level of muscle soreness during assisted elbow flexion and extension of the nondominant arm. Sufficient reliability of the VAS in assessing pain has been confirmed by Jensen et al. and Bijur et al.17,18 Isometric strength. MIVF of the nondominant elbow flexors was measured using a commercially available strain-
FIG. 2. Absolute changes in mechanical pain threshold (MPT) (mean values) over time. Data were collected before delayed-onset muscle soreness induction (0 hour, before), pre- and post-treatment on days 1–3, respectively (0–48 hours, pre and post), and finally on day 4 (72 hours). gauge force transducer (ASYS,® SPOREG, Offenbach/Main, Germany). Subjects were seated at a preachers’ bench with the elbow flexed at 90° and performed maximum isometric contractions against an inelastic strap that was placed around the wrist, and connected to the force transducer (100Hz sampling rate). Three (3) trials were performed with contractions lasting 5 seconds separated by 2-minute rest intervals. Subjects were encouraged verbally to elicit their maximal effort, and force was displayed on a visual display in real time providing an immediate feedback. Peak strength values were recorded in Newtons, and the highest of the three trials was considered to be representative of MIVF and was used for statistical analysis. Sufficient test–retest reliability of the device has been shown by Pfeifer et al.19 Statistical analysis The Kruskal-Wallis test with post-hoc Dunn’s multiple comparison test were applied to evaluate differences between groups. The threshold value for statistical significance was predetermined at p 0.05. All statistical computations were performed with BiAS for Windows 7.0. Results Results of MPT, VAS, and MIVF in terms of absolute changes from baseline are given in Figures 2–4. There were no statistically significant differences between groups in any of the outcome measures at baseline. Mechanical pain threshold
FIG. 1. Mechanical pain threshold measurements were performed on seven equidistant points along a line joining the insertion of the biceps brachii on the radius and the acromion.
All subjects experienced an increase in tenderness over time, followed by full recovery on the last day of the experiment. Although the group average increase was more marked in the control group when compared to real or sham acupuncture, no significant group differences could be observed at any of the time points (Fig. 2).
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FIG. 3. Absolute changes in visual analogue scale (VAS) scores (mean values) over time. Data were collected pre- and post-treatment on days 1–3, respectively (0–48 hours, pre and post), and finally on day 4 (72 hours). *Significant group differences, p 0.05.
Pain perception All groups showed an increase in muscle soreness during assisted elbow flexion and extension of the nondominant arm until 48 hours after DOMS induction. Similar to the MPT values, the increase in perceived pain was more pronounced in the control group. Seventy-two (72) hours after DOMS induction, only the acupuncture group nearly attained full recovery, and reported significant less pain than the other groups. Indeed, the sham acupuncture and control groups demonstrated their highest and second highest pain levels, respectively, during the whole observational period (Figure 3).
HÜBSCHER ET AL. the biceps brachii. According to the findings, the induction procedure used in the present study was effective in producing the typical symptoms of DOMS (i.e., pain, tenderness, and strength loss), with their respective time courses.1,5,6 The results indicate that, even though DOMS could not be prevented, needling at classical acupuncture points and tender points was more efficacious than sham acupuncture or no acupuncture in reducing perceived muscle soreness. Seventy-two (72) hours after DOMS induction, participants who received acupuncture had significant lower VAS values than did participants who received sham acupuncture or no acupuncture. Indeed, the sham acupuncture and control groups reached peak values, whereas in the acupuncture group the VAS scores approached baseline. These results may be of notable interest in athletic health care delivery since scientific evidence suggests that pain may cause alterations to neuromuscular joint control and joint kinematics.1 These compensatory mechanisms may provoke, besides impaired muscular performance, reduced training capacity and may increase the risk of further injury.1 However, the question whether acupuncture induced pain reductions in DOMS could have beneficial effects on training capacity, long-term competition performance and incidence of sports injuries should be addressed in further studies. The improvements in subjects’ perceived muscle soreness could only in part be supported by the MPT measures, since the increase in tenderness was less pronounced in both acupuncture groups than in control subjects. However, no significant group differences were observed. This discrepancy might be explained by different mechanisms underlying the induced pain during assisted elbow movements (VAS measurement) and pressure stimuli (MPT measurement), respectively. Furthermore, it has been suggested that the more objective measurements of MPT do not always reflect the subjective perception of pain in myogenic or neuropathic pain conditions.20
Isometric strength DOMS induction led to remarkable decreases in muscular performance in all groups as indicated by MIVF scores. Immediately after DOMS induction, strength values decreased in all groups to nearly the same extent. Then, after the first treatment, both acupuncture groups appeared to maintain their strength capacity at a relatively constant level throughout the rest of the experimental period, whereas in the control group further decreases were found until 24 hours. However, on day 3, these differences diminished, and even after 72 hours, only partial recovery has taken place, irrespective of treatment modality. None of the described group differences reached statistical significance (Fig. 4). Discussion The present study aimed to investigate the efficacy of acupuncture compared with sham-acupuncture and no acupuncture on symptoms and muscle function in exerciseinduced DOMS. For this purpose, muscle soreness of the nondominant elbow-flexors was experimentally induced through a standardized exercise regimen employing eccentric contractions until exhaustion. Assessment of treatment effects was based upon MPT, VAS pain scale, and MIVF of
FIG. 4. Absolute changes in maximum isometric voluntary force (MIVF) (mean values) over time. Data were collected before delayed-onset muscle soreness (DOMS) induction (0 hours, before), pre- and post-treatment on days 1–3, respectively (0–48 hours, pre and post), and finally on day 4 (72 hours).
ACUPUNCTURE FOR DELAYED-ONSET MUSCLE SORENESS The results of the present study are partly in line with previous investigations by Lin and Yang,10 who evaluated effects of acupuncture compared to no acupuncture on MPT. Seventy-two (72) hours after DOMS induction, they found significantly reduced MPT values when acupuncture treatment was applied immediately, 24 and 48 hours postexercise. Although acupuncture seemed to have no significant effects on MPT under the conditions of the present study, it also proved to be efficacious on symptoms of muscle soreness (perceived pain) 72 hours after exercise, when adequate acupuncture points were chosen, and consecutive treatment was administered. Otherwise, no effects of acupuncture at classical points or tender points on MPT, perceived pain, and range of movement were observed by Barlas et al.11 These contradictory findings might be related to the fact that different acupuncture points were selected and classical points were not combined with tender points. Thus, the issue of most appropriate acupuncture points and acupuncture point combinations should systematically be addressed in future studies. Even though perceived muscle soreness was significantly reduced on the last day of our experiment (VAS), only nonsignificant effects on strength performance measured via MIVF could be detected. No more than a trend was identified in both acupuncture groups immediately after and 24 hours postinduction, showing a less marked decrease in MIVF versus no needling. Nevertheless, this benefit decreased over time, and even after 72 hours, only partial recovery was observed in all groups. Although the physiologic mechanisms inducing the beneficial effects of acupuncture on perceived pain of DOMS need further clarification, it may be explained in consideration of basic evidence on local and central neurobiological mechanisms of acupuncture analgesia. In this context, acupuncture has been shown to improve microcirculation,21 to decrease inflammatory processes,22 to release endogenous endorphins,23 to modulate sympathetic nerve activity,24 to alter cerebral activation,25 to inhibit spinal and supraspinal nociceptive transmission,26,27 as well as to activate signal transduction pathways through a mechanical coupling between the needle and connective tissue.28 Conclusions Although acupuncture seemed to have no significant effects on mechanical pain threshold and muscle function, it proved to reduce perceived pain arising from exerciseinduced muscle soreness. This may be of practical value for athletic health care delivery as the recovery of performance capacity as well as the risk of sports injury may be influenced by the magnitude and duration of muscle soreness after exercise. Therefore, future studies should examine the effectiveness of acupuncture in routine athletic care. References 1. Cheung K, Hume P, Maxwell L. Delayed onset muscle soreness: Treatment strategies and performance factors. Sports Med 2003;33:145–164. 2. Bakhtiary AH, Safavi-Farokhi Z, Aminian-Far A. Influence of vibration on delayed onset of muscle soreness following eccentric exercise. Br J Sports Med 2007;41:145–148.
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3. Barnett A. Using recovery modalities between training sessions in elite athletes: Does it help? Sports Med 2006;36: 781–796. 4. Connolly DA, Sayers SP, McHugh MP. Treatment and prevention of delayed onset muscle soreness. J Strength Cond Res 2003;17:197–208. 5. Clarkson PM, Hubal MJ. Exercise-induced muscle damage in humans. Am J Phys Med Rehabil 2002;81(11 suppl): S52–S69. 6. Smith LL. Acute inflammation: The underlying mechanism in delayed onset muscle soreness? Med Sci Sports Exerc 1991;23:542–551. 7. Brinkhaus B, Witt CM, Jena S, et al. Acupuncture in patients with chronic low back pain: A randomized controlled trial. Arch Intern Med 2006;166:450–457. 8. Irnich D, Karg H, Behrens N, et al. Controlled trial on point specificity of acupuncture in the treatment of lateral epicondylitis (tennis elbow). Phys Med Rehab Kuror 2003;13: 215–219. 9. Tam LS, Leung PC, Li TK, et al. Acupuncture in the treatment of rheumatoid arthritis: A double-blind controlled pilot study. BMC Complement Altern Med 2007;7:35. 10. Lin JG, Yang SH. Effects of acupuncture on exercise-induced muscle soreness and serum creatine kinase activity. Am J Chin Med 1999;27:299–305. 11. Barlas P, Robinson J, Allen J, Baxter GD. Lack of effect of acupuncture upon signs and symptoms of delayed onset muscle soreness. Clin Physiol 2000;20:449–456. 12. David J, Modi S, Aluko AA, et al. Chronic neck pain: A comparison of acupuncture treatment and physiotherapy. Br J Rheumatol 1998;37:1118–1122. 13. Guerra de Hoyos JA, Andrés Martín Mdel C, Bassas y Baena de Leon E, et al. Randomised trial of long term effect of acupuncture for shoulder pain. Pain 2004;112:289–298. 14. Leung AY, Kim SJ, Schulteis G, Yaksh T. The effect of acupuncture duration on analgesia and peripheral sensory thresholds. BMC Complement Altern Med 2008;8:18. 15. Craig JA, Bradley J, Walsh DM, et al. Delayed onset muscle soreness: Lack of effect of therapeutic ultrasound in humans. Arch Phys Med Rehabil 1999;80:318–323. 16. Nussbaum EL, Downes L. Reliability of clinical pressurepain algometric measurements obtained on consecutive days. Phys Ther 1998;78:160–169. 17. Jensen MP, Karoly P, Braver S. The measurement of clinical pain intensity: A comparison of six methods. Pain 1986; 27:117–126. 18. Bijur PE, Silver W, Gallagher EJ. Reliability of the visual analog scale for measurement of acute pain. Acad Emerg Med 2001;8:1153–1157. 19. Pfeifer K, Vogt L, Banzer W. Measurement positions and their reproducibility in the assessment of maximum isometic voluntary force of different muscle groups [in German]. Gesundheitssport Sportther 2002;18:4–9. 20. Drobek W, De Laat A, Schoenaers J. Tactile threshold and pressure pain threshold during treatment of orofacial pain: An explorative study. Clin Oral Investig 2001;5:185–193. 21. Kuo TC, Lin CW, Ho FM. The soreness and numbness effect of acupuncture on skin blood flow. Am J Chin Med 2004;32:117–129. 22. Moon PD, Jeong HJ, Kim SJ, et al. Use of electroacupuncture at ST36 to inhibit anaphylactic and inflammatory reaction in mice. Neuroimmunomodulation 2007;14:24–31. 23. Hwang BG, Min BI, Kim JH, et al. Effects of electroacupuncture on the mechanical allodynia in the rat model of neuropathic pain. Neurosci Lett 2002;320:49–52.
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Address reprint requests to: Markus Hübscher, Ph.D. Department of Sports Medicine Goethe-University Frankfurt/Main Ginnheimer Landstrae 39 60487 Frankfurt/Main Germany E-mail:
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