Pilot Study: Physical Examination Evidence of Acupuncture Principal Meridian Coupling

Introduction

Traditional Chinese Medicine (TCM) theory describes 12 principal (primary) channels. ¹ The primary channels are of utmost importance in TCM physiology: “It is because of the twelve Primary channels that people live, that disease is formed, that people are treated, and disease arises.”^1,2 TCM physiology also describes 12 muscle channels, which are constituents of the channel system and largely coincide with the pathways of the 12 primary channels. ¹ The Shanghai College of Traditional Medicine text states: “the Muscle channels are not viewed as distinct anatomical entities, but rather represent an early description of the structure and function of the body's musculature within the framework of the traditional channel system…. because of the intimate relationship between the Primary and Muscle channels, an acupuncture point on the related Primary channel may be selected” (for treating musculoskeletal issues). ¹

In TCM, the “Six Levels (Stages)” is a theory that originated from Shang Han Lun (“On Cold Damage”) treatise by Zhang Zhongjing in 220 CE. ³ The 6 stages are Tai Yang or Greater Yang (BL-SI), Yang Ming or Bright Yang (ST-LI), Shao Yang or Lesser Yang (GB-TE), Tai Yin or Greater Yin (SP-LU), Shao Yin or Lesser Yin (KI-HT), and Jue Yin or Terminal Yin (LR-PC). The names of the 6 levels are the same as the names of the head and foot pairs of acupuncture primary channels. In the French energetic acupuncture style, these channel couplings are used in treatment, with Tai Yin+Yang Ming, Shao Yin+Tai Yang, and Jue Yin+Shao Yang stages further coupled energetically. ⁴ Owing to the intimate anatomic/physiologic relationships of the primary and muscle channels previously outlined, ¹ we postulated that the six stages relationships of the primary channels should also be evident in their associated muscle channels. Specifically, physical examination (muscle strength testing along coupled primary/muscle channels) should theoretically be able to provide objective evidence of the six stages channel relationships described by TCM theory.

Through decades of clinical experience, we have found physiologic (physical examination strength) evidence of acupuncture primary channel coupling that is consistent with six stages theory. These physical examination findings then can be used not only to help diagnose injury/illness (primary/muscle channel pathology), but also can be used to objectively follow response to acupuncture treatment. For example, we have found that on physical examination, shoulder elevation strength (anterior deltoid muscle, Large Intestine [LI] primary/muscle channel distribution) is altered by activation of the ipsilateral anterior tibialis (AT) muscle (ST primary/muscle channel distribution).

The purpose of this pilot study was to experimentally demonstrate whether AT muscle activation and inhibition can measurably affect ipsilateral shoulder elevation strength, in accordance with Yang Ming (LI-ST) energetic coupling described by six stages theory.

Materials and Methods

This pilot study was designed as a prospective before and after trial. The setting was an outpatient physical therapy department in an academic institution. Twenty young healthy adult volunteers (11 women and 9 men) ages 20–60 years having no shoulder pain were recruited to participate in this pilot study from our institution's employees, residents, and physical therapy students. Subjects were screened by the same examiner (E.B.) who has >25 years of clinical experience treating musculoskeletal disorders. Inclusion criteria included having full (180° elevation, 90° external rotation, and 70° internal rotation) and symmetric pain-free shoulder range of motion. Exclusion criteria included current pregnancy, known neuromuscular disease, known cardiovascular disease, shoulder pain within past 6 months, shoulder pathology (including instability), neck pain within past 6 months, and/or prior surgery of the shoulder or neck. The dominant arm was studied. All subjects signed an informed consent form approved by the human subjects committee of our institution. This was deemed a minimal risk study approved by Research Institutional Review Board Mayo Clinic.

Subjects’ shoulder elevation strength was tested by same examiner (E.B.) using handheld dynamometer (Lafayette Instrument's 01165 Manual Muscle Tester) applied just proximal to the radial styloid with scapula in neutral position and the arm held in 90° elevation in the sagittal plane with thumb pointed toward ceiling (Fig. 1). The examiner used his other arm to ensure each subject had steady trunk upright posture and properly balanced while standing and sitting during dynamometer application.

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FIG. 1.

Method of applying and measuring shoulder elevation force.

Warm-up included 3–5 repetitions of full shoulder range of motion followed by 3 submaximal voluntary contractions for 5 seconds at the 90° arm elevation test position. Force was then applied in an inferior direction (toward floor) just proximal to the radial styloid with the handheld dynamometer until the shoulder elevation position broke. The force (in kg) at which this occurred was recorded. Three shoulder elevation break strength measurements (repetitions) were obtained for each experimental condition, with a 30-second rest between repetitions^5–7 as well as 2 minutes between experimental conditions with the arm resting in the lap to prevent fatigue effects.^5–7

Experimental conditions: 1.

Baseline shoulder elevation strength (anterior deltoid: LI primary/muscle channel distribution) while standing

For each of the 3 repetitions at baseline and for each of the 3 experimental conditions (STAT, SEAT, and SEGS), shoulder elevation strength (break strength) in kilograms was recorded.

For data analysis, the average change of shoulder elevation strength from baseline (percentage of baseline strength) was calculated for each of the 3 experimental conditions for each subject, with mean and standard deviations calculated for the overall group as well as subanalysis of the male and female cohorts. Paired t-tests were performed to examine for changes in the percentage change of mean break strength measurements in the 3 experimental conditions. A statistical significance alpha level of 0.05 (P < 0.05) was used for all statistical analyses.

The primary outcome measures were the percentage changes in shoulder elevation isometric strength (“break strength”) for each experimental condition compared with baseline strength.

Results

The complete results for female and male subjects are presented in Table 1.

All 20 subjects completed the study with no adverse events noted from participation in the protocol. Subject 3 (male) had data that were clearly an outlier, as his shoulder elevation strength changes in the (STAT and SEAT) experimental conditions showed increases from baseline shoulder elevation strength, whereas for all other subjects these values decreased. This suggests that Subject 3's baseline shoulder strength was likely inaccurately low.

For the remaining 19 subjects, statistical analyses of their ages and shoulder elevation strengths subject at baseline and in the 3 experimental conditions (STAT-ipsilateral AT muscle activation while standing, SEAT-ipsilateral AT activation while seated with legs dangling, and SEGS-ipsilateral gastrocnemius activation (reciprocal AT inhibition) while seated with legs dangling are shown in Table 2. The percentage changes in shoulder elevation strength from baseline with each of the 3 experimental conditions are shown in Table 3 and graphically in Figure 2.

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FIG. 2.

Percentage decrease in shoulder elevation strength at each position by gender. SEAT, seated, anterior tibialis activated; SEGS, seated, gastrocsoleus activated; STAT, standing, anterior tibialis activated.

In the female cohort, activation of the AT muscle, whether in standing or seated position, reduced shoulder elevation strength by >12.5% from baseline on average (P < 0.001), whereas activation of the gastrocsoleus (GS) muscle (reciprocal inhibition of AT) produced a statistically significantly smaller 4% decrement in shoulder elevation strength (P < 0.05). In the male cohort, activation of the AT muscle, whether in standing or seated position, reduces shoulder elevation strength by >9.5% from baseline (P < 0.001), whereas activation of the GS muscle produced an ∼3% decrement in shoulder elevation strength, which approached but did not reach statistical significance (P = 0.15). Although there was significant variability in the baseline shoulder elevation strengths and the effects of AT and gastrocnemius activation on shoulder elevation strength was present as shown in Table 1, percentage changes of shoulder elevation strength from baseline were similar among subjects for the different experimental conditions.

The minimal clinical detectable change at 90% confidence level was determined for the overall cohort to be a MDC90% = 2.07 kg (8.18% of baseline). The decrease in shoulder elevation strength with ipsilateral AT activation (whether standing or seated conditions) in the male and female cohorts exceeded the MDC90% level, which indicates this strength change is clinically significant as well.

Discussion

Although it is well accepted among acupuncturists that Six Levels (Stages) energetic primary channel coupling is effective in clinical practice, this study is the first that we are aware of that has experimentally demonstrated physical examination evidence of this channel coupling. The data demonstrate primary/muscle channel (LI-ST, Yang Ming) coupling, evidenced by a > 12.5% (women) and >9.5% (men) reduction of shoulder elevation strength (anterior deltoid muscle, LI primary/muscle channel distribution) that is both statistically (P < 0.001) and clinically significant, due to activation of the ipsilateral AT muscle (ST primary/muscle channel distribution muscle). This shoulder elevation strength decrement in male and female subjects was 3 times greater in magnitude reduction than with reciprocal inhibition of the AT muscle by ipsilateral gastrocnemius activation, which was statistically significant in women (P < 0.05) and was trending to significance in the men (P = 0.15). These results also serve to confirm TCM theory's conceptualization that primary and muscle channels are intimately physiologically linked and not to be considered anatomically/physiologically distinct. ¹ In our current practice, we effectively use these primary/muscle channel coupling effects on strength both in evaluation of acupuncture channel pathologies and to assess response to acupuncture intervention.

These LI-ST primary/muscle channel coupling findings most likely have a neurologic basis, due to the immediate shoulder elevation strength changes produced with AT activation and inhibition. These strength changes would not be consistent with a fascial signaling mechanism underlying acupuncture's clinical effects, as AT activation in the standing or seated positions (legs dangling) produced similar decrements in shoulder elevation strength, despite the anterior thigh/leg fascia being under significantly different resting and dynamic tensions in those 2 positions. Ascending fascial signaling from the calf in these 2 different body positions would have been expected to be significantly different, which then should have produced differing shoulder elevation strengths.

The classical acupoint ST-38, which is anatomically located in the AT muscle region (ST primary/muscle channel distribution), is described by acupuncture references^1,8 to treat shoulder pain and stiffness, and the Deadman reference text ⁸ suggests this may be “partially explained by the close link between the Stomach and Large Intestine channels,” compatible with our postulation and Six Stages theory. ³ Metanalyses of experimental studies that used ST-38 to treat shoulder adhesive capsulitis have confirmed its efficacy, ⁹ and at least one study suggested that contralateral ST-38 treatment provides even greater clinical benefit than ipsilateral ST-38 in chronic shoulder pain. ¹⁰ That finding is consistent with the LI primary channel's crossing of the body's midline, in terms of LI-ST channel energetic coupling.

The magnitude of this LI-ST primary/muscle channel coupling effect of AT activation on ipsilateral shoulder elevation strength effect is clinically significant not only by achieving the minimally clinically significant difference of 8% from baseline shoulder elevation strength but also represents a strength change that has significance in real-world applications such as elite athletics. The 2016 Olympics results for 76 kg weight class for snatch and clean+jerk weightlifting showed a 3%–9% difference in maximum weights lifted between gold and bronze medal athletes, and a 1%–9% difference in strength between athletes who medaled in that Olympic weightlifting competition versus those who did not medal. Primary/muscle channel issues in the AT then can produce enough alteration in shoulder elevation strength to prevent medaling or produce a bronze medal instead of a gold medal in these lifting athletes.

Our pilot study had small patient numbers (19 total), but the magnitude of effect on shoulder elevation strength by ipsilateral AT activation was large enough to produce statistically significant differences at a level of P < 0.001 from baseline strength values. Although GS activation (reciprocal inhibition effect on AT muscle) produced some decrement of ipsilateral shoulder elevation strength, this effect was only one-third the magnitude of that due to AT activation. This difference was statistically significantly smaller than with AT activation in females (P < 0.05) and trended toward significance in males—statistical power estimates were that 6 more males (total of 25 males) would need to be recruited to achieve P = 0.05 significance level.

Conclusions

Ours is the first study that we are aware of that has been able to produce objective evidence on quantitative strength testing of Six Stages channel (LI-ST, Yang Ming) physiologic channel coupling, which was both statistically and clinically significant. The intimate physiologic and anatomic relationships of the primary and muscle channels described in TCM theory ¹ allowed this pilot study to be designed, and this study's results also serve to confirm the fundamental correspondences of the primary and muscle channels. Activation of AT muscle (ST primary/muscle channel distribution), whether in the standing or seated position, produced statistically significant reductions of ipsilateral shoulder elevation strength (anterior deltoid: LI primary/muscle channel distribution) strength compared with baseline strength testing, whereas reciprocal inhibition of AT through GS activation produced much (66%) smaller shoulder elevation strength decrements in both men and women subjects. Thus, the AT activation effect on ipsilateral shoulder elevation strength is a real physiologic effect, is clinically significant, and is not attributable to distraction or other confounding factors. There are other examples providing evidence to confirm these Six Stages primary/muscle channel couplings, as well as other examples showing these effects directly along primary/muscle channels, which will be the subjects of future reports. Physical examination strength evaluation using these principles can be used both to diagnose channel pathology as well as evaluate response to acupuncture treatments.

This study's findings are also consistent with prior literature that documents beneficial clinical effect of ST-38 acupoint on shoulder pain/function that cannot be explained by standard Western musculoskeletal or neurologic understanding, but is consistent with TCM theory including the Six Stages.