Acupuncture, a representative non-pharmaceutical therapy of Oriental medicine, primarily involves inserting medical needles into acupoints and employing proper techniques to enhance therapeutic effects. Originating in East Asia with thousands of years of accumulated practical experience, acupuncture has gained growing interest across diverse fields since its introduction to Western countries [1-6]. Numerous studies have demonstrated its effectiveness [7-13], particularly for pain relief [14,15], with further evidence of efficacy supported by animal research in various fields [16-18].

Nevertheless, some questions still persist that prevent the Western medical community from fully embracing acupuncture as a mainstream therapy, with the foremost one revolving around the lack of a scientific understanding or explanation of this practice. Additionally, Langevin and Wayne [19] have highlighted issues in acupuncture research that mainly derive from the ambiguity surrounding the identity or concept of acupoints. In other words, the core of their arguments focuses on the question “What is the identity of acupoints?” We agree that these issues are important and urgent. Therefore, in an attempt to address them, we outlined our opinion on the basis of scientific research as well as the original concept of acupoints and suggested a hypothesis about what the identity of acupoints is.

Returning to and reviewing the original concept can help solve the problem of ambiguity. According to the original concept explained in Oriental medicine, acupoints are located on meridians, which are in turn known as channels or pathways that qi (energy) flows through [20-22]. These meridians are often compared to riverbeds, where water flows [23], or paths traversed by people. Importantly, these paths are not artificially constructed but naturally formed through frequent passage, similar to spaces devoid of grass. The key point, however, is that there is no apparent border or wall between the grassy and non-grassy areas. This invisible nature is a distinct characteristic of the original concept of meridians, contributing to the ambiguity surrounding the identity of acupoints. Moreover, original texts lack specific measurements for the absolute width or diameter of meridians or acupoints. This feature represents an important difference between the meridian system in Oriental medicine and the vascular system in Western medicine.

On the other hand, according to the original texts of Oriental medicine, acupoints (located on meridians) are spaces where qi (energy) congregates. Qi moves fast along meridians, entering and exiting acupoints [24]. In acupuncture treatment, it is common sense that the special sensation known as de qi plays a key role in provoking the desired effects [25,26], as described in original texts: “Acupuncture effects could be expected after de qi” and “withdraw the needle after de qi” [23,27]. The literal translation of de qi is “obtaining qi,” where “obtaining” implies “touching.” This suggests that acupuncture effects arise from the needle touching qi, rather than an anatomical structure such as a nerve or vessel [21,28]. While qi is deemed to correspond to the vital energy in Western medicine, there has been no detailed description of its structure or substance in Oriental medicine.

The term “acupoint” originally referred to a cavern in a mountain. Therefore, it can be interpreted that cavities similar to caverns are located on meridians in the human body. However, original texts have made no mention of the anatomical structure or substance of acupoints, as observed with meridians and qi. This may relate to the fact that most of the pathophysiological terms and descriptions in Oriental medicine are basically functional rather than structural. Hence it can be summarized from the original concept that these terms refer to entities that are not visible but do exist, a feature thought to be the underlying source of ambiguity in the identity of acupoints.

According to the original concept described in Oriental medicine, qi is a vital energy that moves fast along meridians and enters and exits acupoints [27,29]. Qi is not visible because it is a functional rather than a structural entity.

In Western medicine, a representative substance that is essential for maintaining life but cannot be seen is bioelectricity [30,31]. Bioelectricity moves extremely fast, and while its function can be measured with instruments, it remains inherently invisible. Every living entity requires electricity to stay alive, whether its activity manifests through neuronal or ionic mechanisms. Even within a cell, an ionic movement and the following electrical change is essential to remaining alive. Therefore, based on these two commonalities (i.e., measurability without visibility and indispensability to life as evidenced by disappearance in cadavers), we hypothesize that the concept of qi in Oriental medicine may correspond to bioelectricity and that the flow of qi is analogous to bioelectric currents. Consequently, acupoints would serve as spaces for bioelectricity (Fig. 1). Furthermore, the de qi sensation can be understood as a form of electric bridge building between the bioelectric currents of the acupuncturist and the patient.

Figure 1. Schematic of the acupoint. The space where the qi (bioelectricity) congregates and comes in and out. There is no obvious wall or boundary.

This hypothesis is supported by a line of evidence. Recent studies have demonstrated the superior efficacy of a newly modified acupuncture needle compared with conventional ones. The modification has involved creating numerous nanoporous indentations on the surface of the needle, leading to an approximate 20-fold increase in its surface area and consequently remarkable improvements in both electric conductance and neuronal activity in response to needle stimulation. This modified needle with increased electric conductance has resulted in considerably better acupuncture effects in animal models of colorectal cancer [17] and alcohol addiction [18], indicating that electric conductance is a crucial factor in the effectiveness of acupuncture.

Additionally, a novel medical tape (Chimsband) has successfully treated serious chronic neuropsychiatric diseases [32,33]. The unique feature of this tape is its use of special substances, silver and optical fiber, which have high electric conductance. Researchers treated patients with obstinate insomnia and depression by only attaching this tape to acupoints and trigger points (muscle stiffness points) where acupuncture needles are typically inserted. This approach reduced the bioelectric current gap between the abnormal attachment sites and the normal surrounding areas. Interestingly, the treatment effects appeared immediately after tape attachment, as evidenced by the amelioration of tachycardia, a common sign of chronic neuropsychiatric diseases. The immediate onset of effects was attributed to the ability of the tape to regulate patients’ bioelectric currents by using highly conductive substances (silver and optical fiber), allowing for rapid bioelectric current movement. Unless the qi that congregates at acupoints is regarded as bioelectricity, this immediate appearance of the taping effect is difficult to explain.

On the other hand, Eight Constitution Acupuncture (ECA), which was established and is widely practiced in Korea, involves needle stimulation of acupoints only on the surface of the skin, without the needle remaining under the skin, but still producing considerable effects [34,35]. Therefore, given the original concept that acupuncture produces effects by touching qi, it can be deduced that qi exists not only inside but also on the skin. This aligns with the fact that electric shocks can occur even on unwounded skin because bioelectricity exists both under and on the skin. If qi were not bioelectricity and if the de qi sensation were produced mainly by connective tissue [36] rather than electric stimulation, it would be difficult to explain why noninvasive acupoint treatments such as Chimsband and ECA could produce acupuncture-like effects.

It is well known that acupoints have higher electric conductance and lower electric resistance/impedance than their surroundings [37]. Acupoints have also been reported to exhibit more pronounced electrical properties compared with adjacent areas [38]. These pieces of evidence support our hypothesis that qi, which congregates at and flows in and out of acupoints, is bioelectricity. Additionally, electroacupuncture, a modern type of acupuncture where electric stimulation is applied to needles inserted at acupoints, indicates that electric stimulation at acupoints modulates acupuncture effects and that qi, the target of the needles, might indeed be bioelectricity.

Thus, acupuncture can likely be viewed as the process of using needles to bridge the bioelectric currents of the acupuncturist and the patient. Interestingly, Lee et al. reported that the suppressive effect of acupuncture on exercise-induced tachycardia was blocked when the acupuncturist wore double latex gloves [39]. These gloves were used to prevent contact between the bioelectric currents of the acupuncturist and the subject. The researchers suggested that the transfer of bioelectric currents between the acupuncturist and the subject was necessary to produce the acupuncture effect. In another study [40], acupuncture performed on subjects with gastric disease produced different results, depending on whether the acupuncturist’s hands were insulated or not, suggesting that the acupuncture effect may be attributed to the acupuncturist’s bioelectric charge rather than mechanical stimulation. Furthermore, grounding the acupuncturist produced better effects than did grounding the patient [41,42], underscoring the importance of electric conductance in acupuncture effects. These studies imply that electrical characteristics play an important role in acupuncture effects.

In addition, it has been reported that acupoints are closely related to neuronal distribution or activity [43]. A higher density of nerve distribution has been observed in acupoints than in their surrounding areas. Moreover, local nerve anesthesia around an acupoint has been shown to block acupuncture effects [44]. These findings imply that acupoints probably exert their function through neuronal actions.

Most importantly, a recent study has demonstrated the pivotal role of neuronal responses (actions), rather than connective tissue, in mediating acupuncture effects [45]. As is well known, neuronal activity underlies bioelectric currents. Considering the original concept that acupoints are spaces where qi congregates and that acupuncture works by touching qi, we can deduce that acupoints may be spaces for bioelectricity.

In their commentary, Langevin and Wayne argued that there were no anatomical, histological, or biochemical measurements in acupuncture research. However, this may be understandable if our hypothesis proves to be true, because measuring the space for bioelectricity anatomically, histologically, or biochemically is challenging [21,46]. They also contended that defining acupoints energetically rather than anatomically would be controversial. Nonetheless, such a definition is inevitable if acupoints are deemed to be spaces for bioelectricity.

Based on an integrative interpretation of the original concept and a body of modern scientific research, it can be hypothesized that acupoints might be spaces for bioelectricity. This characteristic could explain, at least in part, the scarcity of anatomical, histological, or biochemical measurements of acupoints.

Authors thank Nathan Knispel in New Haven, CT, USA who is a writer and Arnyce Pock, Uniformed Services University of the Health Sciences, Bethesda, MD, USA for their valuable language edition and advice for the improvement of this manuscript.

This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2018R1A5A2025272, 2020R1A 2C1103154), and the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (HF22C0081).

The authors declare no conflict of interest.