Background: Preliminary evidence suggests that acupuncture applied proximally during a single bout of exercise can enhance exercise performance and/or expedite post-exercise recovery. The purpose of this investigation was to review trials, systematically and critically, that have investigated such hypotheses and delineate areas for future research.
Methods: A systematic review using computerized databases was performed.
Results: Four trials were found: Three involved within-subjects designs and one used a parallel group design. Few participants were enrolled (n = 10–20). Fourteen acupuncture sites were used across the four trials: DU 20, LI 15, LI 13, PC 6, ST 36, SP 6, PC 5, LU 7, LI 4, GB 37, GB 39, GB 34, and LI 11, and LR 3. PC 6, and ST 36 were the most commonly used sites. Three trials evaluated the effect of acupuncture on exercise performance. One of these trials noted that electroacupuncture stimulation of either PC 5 and PC 6 or LU 7 and LI4 significantly increased peak power output, blood pressure, and rate pressure product (RPP) versus control. However, two trials documented no effect of acupuncture on exercise performance using point combinations of either DU 20, LI 15, LI 13, PC 6, ST 36, and SP 6 or DU 20, ST 36, GB 34, LI 11, LR 3. One trial evaluated the effect of acupuncture on post-exercise recovery and found that heart rate, oxygen consumption, and blood lactate were significantly reduced secondary to acupuncture needling of PC 6 and ST 36 versus control and placebo conditions at 30 or 60 minutes post-exercise.
Conclusions: There is preliminary support for the use of acupuncture as a means to enhance exercise performance and post-exercise recovery, but many limitations exist within this body of literature. Adequately powered, RCTs with thorough and standardized reporting of research methods (e.g., acupuncture and exercise interventions) and results are required to determine more adequately the effect of acupuncture methods on exercise performance and post-exercise recovery. Future investigations should involve appropriate placebo methods and blinding of both participants and investigators.
Acupuncture originated in China *2500 years ago and remains an integral component of Traditional Chinese Medicine (TCM) today. Acupuncture involves inserting needles into specific points of the body and is believed to restore the balance of energy flow.1 Acupoints may be stimulated by manual insertion of needles and twirling them, or by a small electric current (i.e., electroacupuncture (EA). A recent review of empirical data conducted by the World Health Organization suggests that acupuncture may help treat more than twenty medical conditions, including, cardiovascular disease.2
Acute and chronic exposure to acupuncture treatment has been found to elicit cardiovascular adaptation. For example, ongoing acupuncture treatment has been shown to reduce the frequency of angina attacks significantly, reduce ST-segment depression, and raise the ischemic threshold in individuals with diagnosed angina pectoris; compared with a placebo pill.3 Single sessions of acupuncture treatment have been shown to significantly reduce systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) from pre- to post-insertion in patients with hypertension.4 Moreover, Park et al.5 recently demonstrated that a single session of acupuncture treatment could improve endothelial function significantly, measured via flow mediated dilation (FMD), in individuals with hypertension. Studies evaluating the effect of acupuncture on cardiovascular out- come measures have utilized a number of different acu- points. However, two acupoints in particular, Neiguan (PC 6), and Zusanli (ST 36), have been used consistently.4–7 PC 6 has been found to improve arterial distensibility from pre- to post-insertion,8 and ST 36 has been found an increase FMD,9 supporting the possibility that these could be important points for altering cardiovascular function.
The physiologic mechanisms by which acupuncture induces cardiovascular benefits remain to be elucidated. Data suggest that acupuncture can induce release of endogenous opioids.10 b-Endorphins, in particular, have a high affinity to the l-receptor which appears to be a key mechanism for modulating blood pressure (BP).11–14 Down regulation of the sympathetic nervous system (SNS) has also been implicated. For example, acupuncture can trigger a somatoautonomic reflex,15 which can induce vasodilation.16 Clinical manifestations of these effects include relaxation, calmness, and reduced distress.17
Evidence suggesting that acupuncture may treat specific cardiovascular conditions effectively, and the relevance of the proposed mechanisms mediating this effect (e.g., vasodilation), has led to speculation that acupuncture may enhance exercise performance and post-exercise recovery. For example, preliminary evidence suggests that EA of Jianshi PC 5 and PC 6 just prior to a maximal exercise test can significantly increase peak workload.18 This novel application of acupuncture treatment as an ergogenic aid could be of particular interest to elite athletes and coaches who train to optimize cardiovascular adaptation and performance. However, such application may also be of importance to people exercising to obtain health-related benefits, including amelioration of chronic disease risk factors, such as patients with obesity and type 2 diabetes mellitus.
To date, a systematic review evaluating the effect of acute treatment on measures of exercise performance and post-exercise recovery has not been undertaken. Therefore, the purpose of this investigation was threefold:
- (1) To review, systematically and critically, trials that have investigated the effect of acute acupuncture on measures of exercise performance and post-exercise recovery
- (2) To summarize and contextualize the outcomes of these trials
- (3) To delineate areas for future investigation.
A literature review was conducted in July 2011 from the earliest available date to 2011, limited to the English language, using computerized databases: Medline,Ò Embase, PubMed, Google Scholar, and Scopus. The search combined key words related to acupuncture (i.e., acupuncture, electro-acupuncture (EA), needle, and acupoint) and exercise (i.e., exercise, aerobic training, sport, and physical activity). The articles retrieved were examined for further relevant references.
Study designs: Trials evaluating the effects of acute acupuncture on parameters of exercise performance and/or recovery were included, regardless of study design. Trials evaluating the effect of ongoing acupuncture treatment were excluded.
Participants: Trials involving adult participants (i.e., men and/or women age > 18) were included. Trials enrolling children and/or adolescents were excluded.
Acupuncture interventions: Trials prescribing acute acupuncture needling or EA were included. Trials investigating other modalities of TCM or trials combining acupuncture with other therapies were excluded.
Exercise interventions: Trials evaluating the performance of, and/or recovery from, an aerobic exercise session (e.g., running or cycling) were included. Trials involving resistance exercises or combined exercise modalities (e.g., aerobic and resistance exercise) were excluded.
Outcome measures: Variables altered by physical exertion were considered. These outcomes were both physiologic and psychological in nature, including HR and rating of perceived exertion (RPE), for example.
Data extraction: Two authors (P.U. and B.C.) reviewed the retrieved articles and independently extracted information on sample characteristics, study design, outcome variables, relevant results, and if the study fulfilled the inclusion criteria. Sample characteristics included sample size, proportion of female and male participants, and if the participants had previously used acupuncture. Study design variables included experimental design, characteristics of the acupuncture treatment that was delivered, and how expectancies were either assessed or manipulated. Differences between the reviewers were discussed, and a final assessment was negotiated for each study.
Statistical analysis: Given the heterogeneity of the interventions and the paucity of robust RCTs, the pooling of effect sizes across studies for meta-analysis was not considered appropriate for this review. Instead, a descriptive review of the studies meeting the inclusion criteria was provided. Results were considered statistically significant when p was £ 0.05.
Studies retrieved and design – The search resulted in four articles presenting findings of independent trials. Three trials involved a within-subjects, crossover design with randomization,18–20 and one used a parallel group design.21
ACUPUNCTURE AND EXERCISE
Overview of the participants: Sample size, gender, age, and fitness level
An overview of participants, interventions and outcomes is presented in Table 1. Eighty-four (N = 84) participants were enrolled in the four trials reviewed. Few participants were enrolled in each trial. One trial enrolled only 10 participants,20 while the other trials enrolled between 20 and 30 participants.18,19,21 Two trials were limited to male participants only,19,21 while the other two trials included both men and women.18,20 A total of 17 females and 67 males were enrolled across the trials reviewed. Age of the enrolled participants was expressed as mean – standard deviation in all trials,18–21 whereas two trials also presented an age range, in which the youngest and eldest participant enrolled were 18 and 54, respectively.18,19 Two studies enrolled athletes, including semi-competitive and competitive cyclists,19 and elite basketball players.21 Two trials did not specify level of fitness of physical activity of the cohort other than being apparently healthy.18,20
Overview of interventions
1–2 minutes,18,21 whereas one trial involved a staged exercise protocol in which the intensity was increased every 3 minutes.20 All three of these trials used volitional fatigue as the termination criteria.18,20,21 One study enrolling male cyclists involved a 20-km timed trial performed on a cycle ergometer.19
Outcome measures: Three trials evaluated the effect of acupuncture on exercise performance,18–20 while one trial evaluated the effect of acupuncture on post-exercise recovery.21 The outcome measures evaluated in these trials included: HR, RPE, volume of oxygen consumption (VO2), BP, RPP, workload, blood lactate, perception of pain, time to complete a 20-km timed trial, and time to return HR to pre-exercise (baseline) level (Table 1).
Effect of acupuncture on exercise performance. Li et al.18 recruited 24 healthy adults who completed four pre- exercise conditions: (1) EA at PC 5 and PC 6; (2) EA at LU 7 and LI 4; (3) EA at GB 37 and GB 39; and (4) a no-treatment control condition. The trial demonstrated that EA at PC 5 and PC6 and LU 7 and LI 4 significantly reduced exercise- induced increases in mean BP and SBP and RPP versus control. Moreover, treatment at PC 5 and PC 6 and at LU 7 and LI 4 significantly increased peak power output versus control. By contrast, DBP and HR were not significantly different between conditions. Notably, however, Li et al.18 limited their analyses to participants who were deemed to be responders (* 70% of their cohort).
Dhillon19 also investigated the effect of pre-exercise acu- puncture on exercise performance. Twenty (20) male cyclists completed a 20-km timed trial on a cycle ergometer under three conditions: (1) pre-exercise acupuncture at ST 36, GB 34, LI 11, LR 3, and DU 20; (2) pre-exercise placebo (i.e., needles inserted away from acupuncture sites); and (3) control. The investigators determined that RPE at the completion of the exercise protocol was significantly higher in the acupuncture condition versus the placebo and control conditions. How- ever, no other treatment effects were noted. In particular, no effect was noted among conditions on time to complete the 20-km timed trial or the rating of pain or blood lactate concentrations immediately post-exercise.
Karvelas et al.20 evaluated the effect of pre-exercise acupuncture at DU 20, LI 15, LI 13, PC 6, ST 36, SP 6 versus placebo (i.e., needles inserted away from acupuncture sites) and control conditions in a cohort of 10 healthy adults. Outcome measures, including HR, RPE, and VO2 were not significantly different between conditions at 3, 6, 9, and 12 minutes of the graded exercise test. HR and VO2 at peak exercise intensity were also not significantly different among conditions.20
Effect of acupuncture on post-exercise recovery
Lin et al.21 evaluated an effect of acupuncture on post-exercise recovery. Thirty (30) male athletes were randomly assigned to three conditions: (1) acupuncture; (2) placebo; and (3) control. The acupuncture needles were inserted at PC 6 and at ST 36 15 minutes pre-exercise and remained inserted during the graded exercise protocol to volitional fatigue. The acupuncture group had significantly reduced HR, VO2, and blood lactate versus the placebo and control groups at 30 minutes post-exercise. Blood lactate was also significantly lower in the acupuncture group versus the other two groups at 60 minutes post-exercise. No significant changes were no- ted among the groups at 5 minutes post-exercise. Notably, however, the bodily positioning of the participants during the post-exercise recovery period (e.g., seated, supine, etc.) was not reported.
Study quality assessment: Study quality assessment was based on the McMaster Critical Review Form for Quantitative Studies22 with minor adjustments made to accommodate the acute study designs. A summary of the quality assessment is presented in Table 2. The authors of all four studies clearly stated the purposes of their research and reviewed the appropriate background literature, and samples were reasonably well-described, ac- cording to age, gender, and health status; however, the authors of the majority of trials did not describe their samples with respect to general body measures (e.g., height, weight, and body mass index), which can confound the exercise response.18,19 Moreover, only one trial included participants who were acupuncture naıve,19 whereas the authors of the other trials did not describe the acupuncture experience of their cohorts. Sample-size estimates were computed a priori in only one trial.18 Outcome measures were generally reliable and valid across all trials. All three within-subjects studies controlled for time of day of repeated assessments.18–20 Exercise protocols and acupuncture interventions were de- scribed in sufficient detail to ensure replication with the exception of one trial that did not provide any details on acupuncture-needle manipulation.21 All studies were unable to avoid contamination of results thoroughly through significant blinding of participants to the intervention, and the authors did not disclose if co-interventions, such as medication, massages, acupuncture, or other health/mental strategies were avoided during testing sessions. No studies reported on any potential adverse events caused by the acupuncture treatment. Only one study mentioned that outcome assessors were blinded to the intervention.20 The findings of all trials were reported in terms of statistical
significance. In general, appropriate statistical analyses were used, and the clinical importance of the findings were dis- cussed in accordance with the outcomes. One trial limited statistical analyses to participants who responded favorably to the intervention (* 70% of the sample) rather than analysing the total cohort, which could be interpreted as a source of bias, although justification was provided a priori within the study methods. Participant attrition encountered prior to, or during, the testing sessions was not reported in any trial (Table 1).
To the current authors’ knowledge, this is the first systematic review to investigate the effect of acute acupuncture on exercise performance and post-exercise recovery. The literature search identified four unique trials, the findings of which provide only some support for the use of acupuncture as a means of enhancing exercise performance, with only one trial finding a positive effect18 and two finding no effect.19,20 In terms of exercise recovery, however, there is preliminary support, as the only trial to date reported a positive find- ing.21 Both trials reporting a positive finding18,21 applied acupuncture at Neiguan (PC 6), whereas only one trial showing a null effect involved applying needles at PC 6.20 However, this latter trial20 involved only 10 participants and may have been underpowered. There was also heterogeneity with respect to the design of the acupuncture interventions, with especially regarding duration of the needling.
Enhancement of exercise performance and post-exercise recovery may be of benefit to a broad spectrum of individuals, ranging from cohorts of patients with chronic diseases to elite, high-performance athletes. Increased exercise tolerance (i.e., the ability to tolerate higher workloads) within a given exercise session could enhance ongoing, training-induced adaptation, including improvement of health and performance-related fitness variables and amelioration of chronic disease–risk factors. Moreover, expeditious post- exercise recovery could be particularly important for athletes who engage in heavy volumes of training, including many sessions per day, whereas people who perform exercise for health-related reasons and for rehabilitation may be able to experience better recovery and fewer exercise-related com- plications.
The evidence reviewed is preliminary and should be interpreted with caution. Many methodological limitations exist within this body of literature, and many research questions remain to be investigated. Limitations of the trials reviewed were evident with respect to sample sizes, study designs, participant blinding and placebo methods, clinical heterogeneity of the acupuncture interventions, and report- ing of pertinent participant characteristics of co-interventions and adverse events. Addressing the shortcomings of these trials in future trials will enable collection of more-accurate and unbiased data.
Three of the four trials reviewed involved a within- subjects, crossover design with randomization.18–20 Researchers who plan future studies should be made aware that this type of design increases the likelihood of participants being able to differentiate among interventions, particularly the acupuncture condition and control (no intervention) condition. Although the intention is for participants to be blinded to what they they were receiving (i.e., sham or verum acupuncture), none of the researchers in the reviewed studies actually tested maintenance of blinding. Dissociating results from a placebo effect is an important factor to consider in studies involving acupuncture, given that a placebo effect may account for at least some of the treatment responses to acupuncture.10,23,24 Therefore, researchers involved in future studies should be encouraged to use an RCT design to overcome this important limitation within this field of research.
Only one of the studies reviewed provided justification of the sample size.18 It is important to conduct statistical analyses to reduce the possibility of committing errors when determining results. Conducting a power analysis in future studies would determine what sample size would be needed to determine the presence of an effect; studies can be underpowered or overpowered in this sense. The sample size in some of the studies could have been too small to produce significant results, which may have been the case in the study by Karvelas et al.,20 in which only 10 participants were enrolled. By contrast, a sample size that is too large might produce too much of an effect and increase the possibility of a Type 2 error.
Three of the studies reviewed involved a placebo condition that was achieved via placing needles 2–3 cm away from acupoints, for example.19–21 A placebo involves giving a participant a treatment that does not contain the specific treatment being tested.24,25 In these cases, the placebo involved needling non-acupoints. The literature suggests that any penetration of the skin, even at non-acupoints, can induce physiologic responses,27–30 and, on this basis some researchers have argued that placebo acupuncture is not a valid control condition for acupuncture.31–33 It is, however, difficult to delineate treatment effects from placebo effects24 and, as a result, there is some controversy regarding the best control condition for RCTs investigating acupuncture. Researchers involved in future studies should consider carefully which control condition is most appropriate to their particular study designs. Ideally, a study should include both a placebo control and a no-treatment control, so that responses to a verum acupuncture intervention and placebo acupuncture can be compared with each other and with no treatment.
Pertinent participants’ characteristics, including previous acupuncture experience, were not well-described in the re- viewed studies.18,20,21 The involvement of participants who have previously experienced acupuncture could have in- creased the risk of failed blinding in the within-subject crossover trials. The inclusion of acupuncture-naive participants may be a suitable strategy for mitigating such risk, as attempted by Dhillon et al.19 However, more-rigorous study designs (i.e., parallel-group RCTs) are also required.
All trials failed to report on, and control for, confounding interventions. Medications and non-pharmacologic factors (e.g., other therapies, supplements, diet, sleep patterns, etc.) can potentially alter responses to acupuncture and exercise, and should therefore be monitored. All trials also failed to report on adverse events that may have been caused by acupuncture and/or exercise. Although adverse events are not commonly experienced secondary to acupuncture treatment,34,35 appropriate documentation within future trials is essential for establishing safety, which could potentially facilitate translation of research into clinical application.
Adequately powered RCTs with thorough and standardized reporting of research methods (e.g., acupuncture and exercise interventions) and outcomes are required to deter- mine, more adequately, the effect of acupuncture methods on exercise performance and recovery. Future investigations should involve appropriate placebo methods and blinding of both participants and outcome assessors. Participant entry and exclusionary criteria should be clearly defined a priori, and the use of co-interventions (i.e., medications, other therapies, etc.) should be documented adequately. Participants with no prior experience with acupuncture should preferably be enrolled, as this will mitigate the risk of participants detecting the placebo condition(s).
This review found only preliminary evidence that acupuncture methods may enhance exercise performance and post-exercise recovery. However, many limitations were also identified in the trials conducted to date, and further investigations involving more-rigorous study designs and methods of reporting are required. The potential translation of this research into practice in an attempt to enhance health and performance should remain the overall objective.
Paola Urroz, BApplSci,1 Ben Colagiuri, PhD,2 Caroline A. Smith, PhD,3 and Birinder Singh Cheema, PhD1
THE JOURNAL OF ALTERNATIVE AND COMPLEMENTARY MEDICINE Volume 19, Number 1, 2013, pp. 9–16
a Mary Ann Liebert, Inc.