Fascia is the “sensor” for the coupling response of manipulative therapies

CHENG Lulu (程露露), WANG Siyu (王思雨), WU Qinggang (吴庆港), CHEN Zhaohui (陈朝晖)

1 College of Acupuncture and Tuina, Anhui University of Chinese Medicine, Hefei 230012, China

2 Graduate School, Wuhan Sports University, Wuhan 430079, China

3 College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, China

Abstract Fascia, the initial response site for mechanical stimulation in manipulations, is also the target of the effect of manipulations.As the essence of manipulation is “force”, how mechanical stimuli are transduced into neuroelectric and biochemical signals in the fascia and how physical and chemical signals of the fascia initiate the mechanical stimulation effect are the common key questions in the study of the principle of manipulation.The physical changes in the fascial connective tissue caused by the manipulation, such as the deformation and displacement of the fascial tissue, can act on the nerve end receptors in the fascial layer and generate neural electrical signals; they can also activate the mechanoreceptors on the fascial cell membrane and convert mechanical signals into chemical signals via mechanosensitive ion channel transduction, triggering a physicochemical coupling response in the fascial microenvironment and producing mechanical stimulation through neuro-endocrine-immune system pathways.The“mechanical force of manipulation” in the fascia is transmitted through the meridian to facilitate the body’s perception and transmission of mechanical stimulation signals, indicating that the fascia is the “sensor” of coupled response to the physicochemical information of mechanical stimulation of manipulation.

Keywords: Tuina; Massage; Manual Therapies; Fascia; Stress, Mechanical; Mechanosensitive Ion Channel; Sense Organs

Manipulative therapy dates back thousands of years to ancient civilizations and is one of the most widely used therapeutic interventions worldwide[1].Osteopaths, chiropractors, physiotherapists, and massage therapists commonly use soft tissue relaxing techniques such as massage and fascial release[2].These techniques are guided by Chinese and Western anatomy and pathology and act on the body surface with a variety of techniques such as rubbing, kneading,and pressing to provide biophysical-mechanical stimulation to the tissue.These techniques stimulate the body’s intrinsic systems and self-regulation potential to improve the physiopathological state[3]and prevent and treat diseases.The fascia is considered to be the source of pain in many musculoskeletal diseases[4]and is the preliminary response site for manipulative treatments, as well as the source of the effect of manipulations.The fascia acts as a trigger for the regulation of manipulative therapy and as a basic functional unit for the body to connect, react, and regulate.It is a tensile integral structure that not only limits the tension around the bones and cartilage but also regulates muscle function[5].

Research has indicated that manipulative therapy has a mechanical stimulation effect, which is converted into a biological effectin vivothrough the mechanical effect on the subcutaneous fascia tissue and excites local nerve receptors[6].In addition, manipulative therapy also activates a variety of cellular functions and releases relevant chemicals to act on corresponding receptors at nerve endings, transmitting electrical and biochemical signals to the central nervous system[7]and exerting therapeutic effects.In this sense, the fascia is the sensor of the coupled response to the physical and chemical information of the massage manipulation, transforming mechanical signals into biochemical signals.However,the biological mechanism of how manipulation involves fascia in intracellular biochemical transmission mechanism and how the physicochemical signal of fascia initiates the effect of manipulation have not been fully understood, which has become an important scientific issue in the study of manipulation principle.Therefore, this review summarized the biophysical and biochemical changes of fascia induced by manipulation and the process of transforming physical signals of mechanical stimulation into neuroelectric and biochemical signals to preliminarily analyze the biological principles of localized sensory transmission of“mechanical stimulation by manipulation” in the fascia.

1 Manipulative Mechanical Stimulation Can Induce Physical Changes in Fascial Tissue and Mediate Mechanical Effects

Fascia is a soft tissue composed of connective tissue scattered throughout the body, mainly involving fibroblasts, macrophages, mast cells, and extracellular matrix (ECM).Furthermore, fascia is the connective tissue in the motor system and the tough outer membrane of the wrapped organ and is the network basis of the whole body tension transmission[8].Fascia can be divided into superficial and deep fascia.Under the skin is the superficial fascia, while deep fascia extends deep into the wall layers of muscles and viscera.Myofascia plays a key role in the transmission of muscle forces with complex tensile/compressive strain distribution.Histological studies have also revealed that fascia is rich in free nerve endings[9], acting as an important component of injury receptors and playing two major roles in reflecting disease and receiving manipulative mechanical stimuli to treat disease[10-12].

According to the direction of the manipulative force,the manipulative force includes vertical force, horizontal longitudinal force, and horizontal transverse force.The force acting on the body is a gyroscopic or rotational force synthesized by each vector.Manipulations can generate pressure, tension, friction, shear, and other stimuli on the tissue[13-14], causing a series of biophysical changes in the fascial tissue and cells[15].The subcutaneous fascial connective tissue is the first bearer of the force of manipulation, so when palpation is meticulous and comprehensive, it is necessary to combine “point”, “line”, and “surface”.The “point” is the “tendon knot” point, which is the starting and ending points of muscle attachment and is the reaction point of the lesion and the pain trigger point.The “line”is to touch the entire muscle bundle from top to bottom,from outside to inside, from the starting point to the endpoint, and to feel whether there is any abnormality in the muscle tone.The “surface” is the anatomical level on which the disease of the musculoskeletal system can occur not only in the fascial layer but also in the muscle layer[16].During the examination, both hands are used for palpation for left and right comparisons and the layers of depth so that the “point” can lead to the “line and surface” to identify the lesion quickly[17].

In manipulative therapy, mechanical stimulation can trigger the physiological regulation of the body by acting on different types of cells, such as fibroblasts,skeletal muscle cells, adipocytes, chondrocytes, vascular endothelial cells, and mast cells.Force stimulus acting on the cell membrane induces intracellular signaling responses and causes changes in the ECM microenvironment.

When fascial fibroblasts are stimulated by pressure,the cell morphology changes from the original spindle to triangle, and the gap between the evenly distributed fibroblasts increases, the cells retract and shrink.ANLOAGUE A,et al[18]established anin vitromodel system for detecting mechanical stimulation to dermal fibroblasts.Simulating the periodic strain injury can induce the secretion of many pro-inflammatory cytokines.By simulating the mechanical strain with manual treatment of soft tissues, the secretion of proinflammatory cytokines induced by strain can be reduced.Among them, the fascia is stimulated by manual mechanics, which can transform physical force into intracellular biochemical reactions through“mechanical transduction”.The mechanical stimulation is transmitted at the cellular level, affecting the gene expression of fibroblasts and reducing the number of disordered collagen fibers, thereby altering the composition of the ECM and the order of collagen fibers[19-20].The fascial manipulation of STECCO A,et al[21]divided the body into 14 parts, each consisting of 6 myofascial units.Fascial manipulation aims to improve the areas of stiffness in the fascia to improve the body’s balance and optimize the activation patterns of the fascia.FIDUT-WROŃSKA J,et al[22]studied the effect of the fascial manipulation technique on the thermogram.The results showed an increase in the local fascial temperature after 5 min of frequency modulation, which reached the maximum after 24 h.The increase in local temperature can lead to a decrease in the hyaluronic acid viscosity, which allows nerve endings to slide freely.It is also able to deposit new collagen depending on the direction of the force lines, thus reshaping the dense fascia.All these changes can influence the regular day-to-day functions of force transmission or sliding required for the musculoskeletal system.In conclusion, fascia plays a key role in the transmission of muscle forces with complex tensile/compressive strain distribution, and physical changes in the fascia tissue induced by manipulative mechanical stimuli are important for the initiation of mechanical effects.

2 Mechanical Signal of Stimulating Fascia by Manipulative Therapy Can be Converted into Neuroelectric Signal

Fascia is a richly innervated tissue that contains proprioceptors and injury receptors.Fibroblasts are the main cells that make up the connective tissue of fascia[23].They are involved in the injury and repair processes of the body, synthesizing variety of cytokines and regulating the transcriptional levels of related genes.Fascia is very sensitive to local tension changes and is the main receptor and effector[24].

Manipulative therapy acts on the skin with compound mechanical stimulation, resulting in local skin and deep tissue deformation.Its mechanical force is alternately changed by rhythmicity, and the energy conversion and coding of the skin and subcutaneous fascia receptors excite tactile receptors, pressure receptors, and deep tissue traction receptors, forming different frequencies and numbers of action potentials.The action potentials are transmitted to different nerve centers through a number of complex factors, and undergo complex electrical, chemical, and tissue metabolic changes in the nervous system, finally playing a broader and more effective regulatory and therapeutic role through three intermediary pathways of the neuro-endocrine-immune system.As the intensity of the manipulation increases, when the stimulation reaches the level of injury to the organism,the nociceptive receptors are excited and the nerve fibers upload nociceptive signals.

Fascial manipulation stimulates both the central nervous system and the autonomic nervous system through manual compression.Whereas the central nervous system alters systemic muscle tone, the autonomic response includes changes in vasodilation,tissue viscosity, and systemic muscle tone, as well as a decrease in smooth muscle cell tone in the fascia[25-26].It will allow free nerve endings to glide more freely and allow new deposition of collagen and elastin fibers,thereby reducing pain[27].Manipulative stimulation also activates the parasympathetic nervous system, which acts throughout the body.Parasympathetic stimulation alters the levels of serotonin, cortisol, endorphins, and oxytocin, thereby reducing pain sensation[28].HOLEY L A,et al[29]explored the clinical decision-making of manipulation for patient assessment and guiding treatment based on a theoretical model that manipulation stimulates the cutaneous-visceral reflex by manipulating the intradermal and subcutaneous fascial layers to produce a reflex effect on the autonomic nervous system.Different treatment modalities and therapeutic techniques produce different amounts of stimulation and morphological changes in the fascia, causing different changes in the neuro-endocrine-immune system as well.The neural signaling pathway is the intermediate link between the fascia and micro-substances, such as cytokines, and the difference in neural signaling is related to the concentration of cytokines.Manipulative mechanical stimulation works in close relationship with fascia,nerves, and cytokines, mostly acting directly on fascial connective tissues, changing the local microenvironment, converting external stimuli into biological signals, and amplifying this signal to activate the body’s neuro-endocrine-immune network regulatory system.

Therefore, fascial afferent nerve excitation is one of the most important links in the initiation and conduction of manipulative mechanical stimuli.

3 Mechanical Signal of Stimulating Fascia by Manipulative Therapy Can be Converted into Biochemical Signal

As a membrane structure that runs throughout the body and maintains baseline tension, fascia has an important kinetic role in conducting mechanical stretch forces[30].In-vitrostudies of fascia have shown that fascia contains cells that allow it to contract autonomously, such as fibroblasts, which cause myofibroblasts to contract after expressing alphasmooth muscle proteins[31].We believe that the innervation and mechanical conduction mechanisms of fascia allow the organism to be more receptive and responsive to external stimuli[32].

The effect of manipulation therapy is affected by a variety of operating variables, especially frequency,duration, and force[33].The mechanical stimulation formed by the combined action of these variables can be felt by various tissue cells in the body.Through direct or indirect effects, the organism produces a series of biophysical and biochemical changes to exert therapeutic effects.The therapeutic effects of manipulative therapy can produce different effects by interacting with different types of cells to stimulate the physiological regulation function of the body and play a role in disease prevention and treatment.The response of tissue cells to mechanical stimulation may be one of the cellular biomechanical principles of massage.

3.1 Manipulative mechanical stimulates fascia to recruit immune cells

Fascia connective tissue (such as loose connective tissue) is composed of cells and ECM.Cells are mainly undifferentiated potential cells, among which the largest number is the fibroblast.The unique role of fibroblasts is to transform perfectly from the “tissuebone” world of macroscopic tensegrity structure to the cytoskeleton world of a microscopic tensegrity structure.ECM is mainly composed of collagen, elastin, and proteoglycans, and the type of collagen and its arrangement play an extremely important role in the physiological activities of meridian information and energy exchange.The endogenous cannabinoid receptors CB1 and CB2 receptors in fascial fibroblasts contribute to the regulation of fascial fibrosis and inflammation[34].The presence of these receptors helps to provide a description of the distribution of cannabinoid receptors and to better explain the role of fascia as a pain generator and the efficacy of some fascial treatments.The endogenous cannabinoid system in the deep fascia may also be stimulated during manual therapy and exercise.

MCPARTLAND J M,et al[35]showed that after osteopathic treatment, the serum level of anandamide increased by 168% compared to the pre-treatment level.Fascial manipulation stimulates fascial fibroblasts,thereby modulating the release of the endogenous cannabinoid system and anti-inflammatory cytokines[34].CHEN B,et al[36]investigated the effect of compressive stress on the synthesis of nitric oxide (NO) and interleukin (IL)-1β by rat fascial tissue cells from the perspective of cell biomechanics by simulating the form of pressure stimulation during massage therapyin vitro.The results showed that the amount of NO and IL-1β synthesized by fibroblasts increased after the application of 50 kPa pressure stimulation and that NO had the effect of relaxing blood vessels and inhibiting platelet aggregation to reduce thrombosis, while IL-1β also promoted the regeneration and functional recovery of injured nerves.When the fibroblasts were stimulated with the pressure of 100 kPa and 200 kPa in a simulated massage mode, the cell volume shrunk back into a round shape, and the cell gap increased,while the synthesis of intracellular enzymes that can regulate the degradation of ECM changed.The results showed that the matrix degradation ability of fibroblasts increased, which may be the reason why the massage technique stimulation exerted the effect of“soothing tendons and dispersing knots”.

3.2 Manipulative mechanics stimulates fascia to activate the signal pathway

Integrins, as transmembrane proteins, play a key role in the ECM-integrin-cytoskeleton signaling pathway.It mainly mediates intercellular and ECM adhesion, as well as the bidirectional transmission of mechanistic signals between inside and outside cells[37].The mechanical signals are transmitted to the cytoskeleton through the integrin-microfilament pathway, and the cytoskeletal aggregation and distribution of the associated cells are altered, resulting in the rearrangement of microfilaments.At the same time, the activity of some surface receptors and the permeability of ion channels associated with them are increased so that the functions of functional enzymes and proteins in various signaling pathways associated with them are changed,and the second messengers are produced.Finally, the signal is transmitted to the nucleus, causing changes in cell proliferation, differentiation, protein secretion and synthesis, and other metabolic activities[38].Moreover,the reorganization of the cytoskeleton facilitates the transmission of extracellular signals into cells and diffusion along the microfilament skeleton, leading to gene transcription, cell cycle changes, and cell morphology changes[39].This may be a signal transduction mechanism in which the mechanomechanical signals are transmitted intracellularly and transformed into biochemical signals.Fibroblasts can perceive frictional stimuli through integrin B1, so the alteration of integrin B1 expression in the fibroblast cytoskeletal system during frictional stimulation may reveal the physical signal and transduction mechanism of frictional stimulation in massage from a mechanical perspective[40].

Fibroblasts in the body can both passively and actively respond to biochemical and mechanical stimuli inside and outside the cells.On the basis of mechanical stimulation, fibroblasts can transmit mechanical signals[41].Under the coordination of the cell signal transduction system, physical signals (heat, pressure,shear force, tensile force, etc.), chemical signals [IL, NO,prostaglandin E2(PGE2), and Ca2+], and biological signals act on corresponding signaling pathways on the cytoskeleton.With the help of the cytoskeleton,mechanical signals are transmitted to various parts of the cell, such as the ECM and nucleus, to activate,synthesize, and secrete corresponding effector molecules, which affect cell metabolism, gene expression, cell proliferation, differentiation, and apoptosis[42].Fibroblasts maintain a stable equilibrium state under the coupling of mechanics-chemistrybiology.Manual stimulation promotes the expression of α1, α3, and β1 subunits, which are the force receptor integrins of fascial fibroblasts, and fascial fibroblasts can perceive stress stimuli through the β1 subunit.

3.3 Manipulative mechanics stimulates fascia to release chemical substances

The response of fascial cells to mechanical stimulation is essentially carried out in a signal transmission manner.Fascia cells transmit mechanical signals from outside the body through both immediate cell-to-cell effects (such as intracellular skeleton system)and transduction of mechanical signals into certain electrochemical signals in the organism, producing corresponding changes in biological behaviors by modulating cellular responses (such as cell deformation,activation of force-sensitive ion channels, expression of mechanosensitive proteins, etc.).Under the action of mechanical forces, the cells can adjust their life activities through local and global effects caused by mechano-biological coupling at the cellular level(proliferation, differentiation, apoptosis, perception and response to mechanical forces, etc.), mechano-chemical coupling at the molecular level (proteins, DNA, and other biomolecules), or multi-scale mechano-chemicalbiological coupling.It involves various changes in the mechanical behavior of cells under the action of mechanical loads and a series of changes in cell proliferation and apoptosis, metabolism, etc.It is concluded that the realization of the effect of manipulation “activating tendons and collaterals” is closely related to the synthesis and release of PGE2,matrix metalloproteinase-1, tissue inhibitor of metalloproteinase 1, and insulin-like growth factor-1[43].The synthesis and release of NO, PGE2, endothelin-1,and prostacyclin 2 and the change in intracellular Ca2+concentration are related to the effect of “activating blood circulation and removing blood stasis”[44-46].The effect of “relaxing the muscle and eliminating stagnation” is closely related to the regulation of cell proliferation and apoptosis in relevant tissue[33], while cell proliferation and apoptosis are closely related to the myogenic regulatory factor myogenic differentiation/myogenic factors 5 (MyoD/Myf5)[47].The realization of the effect of “eliminating pathogens to support the healthy” is closely related to the regulation of cytokines with immunomodulatory effects, such as IL-6[48].Under mechanical forces, the cell cycle, proliferation,apoptosis, secretion, and protein expression of fascial cells are altered at the cellular and molecular level, and such alterations are related to the timing, nature, and intensity of mechanical stimulation.

In conclusion, all levels of fascial cells, signaling pathways, and chemical substances confirm that the biochemical changes in the fascia induced by the massage technique are also an important part of the initiation of healing.

4 Physical Changes in Manipulative Mechanics Stimulation May Awaken the “Silent Receptors” of Fascia to Realize Physical Signals of Manipulative Mechanics via Meridian Sensing

The movement form and “manipulation force”constitute the two elements of manipulation, of which“manipulation force” consists of two parts: force and frequency.To a certain extent, force determines the amount of stimulation and directly affects the clinical efficacy of mechanical stimulation[49].The amount of stimulation covers the range of intensity between the threshold stimulus and the injury stimulus[50].Only a certain amount of stimulation can activate the body’s perceptual system and play its therapeutic role.Too little stimulation is not enough to trigger the body’s response and exert an effect, while too intense stimulation will cause damage.The electrical signal reaches the central nervous system in the form of nerve impulses through afferent fibers, where complex electrical and chemical changes occur in the nervous system and three major systems, neuroendocrine and immune, to play their regulatory and therapeutic roles[51].The amount of stimulation produced during manipulation is one of the key factors that trigger the biological effect of mechanical stimulation[18].The 2021 Nobel Prize in Physiology or Medicine was awarded to breakthrough transient receptor potential channel receptor (TRP) cation channels and piezoelectric channels, which are involved in toughness, temperature,and tactile receptor mechanics.It is important to reveal the biological basis[52]for the initiation of the mechanistic effect of the maneuver and to elucidate the nature of the mechanical stimulus itself.Among them,mechanosensitive ion channels (MSC) play a key role in converting mechanical stimulus signals into bioelectrical signals, which can be transmitted through nerve fibers and recognized by the brain.MSC are a class of multimeric pore proteins.When the cell membrane tension changes during mechanical stimulation, poreopening ions (calcium, potassium, sodium, etc.)undergo transmembrane transport, and mechanical force signals can be rapidly converted into electrochemical signals[53].Therefore, MSC are often used to initiate cellular mechanical signal transduction pathways and play an important role in a variety of physiological processes, such as tactile sensation,pressure perception, and osmotic pressure[54].As a mechanical stimulation, the organism may perceive the mechanical force of manipulation through the MSC existing in the fascia.Through the corresponding ion changes and intracellular signal transmission, the physical signal of manipulation is transformed into biochemical signals, and the mechanical transduction process of manipulation mechanics is realized.

Fascia is a somatosensory allotropic zone of target organ pathological responses and can express a variety of receptors sensitive to proprioceptors, mechanical stimuli, and tissue damage[55].It includes MSC such as the TRP family and Piezo.The TRP family is a class of channel proteins widely distributed in the peripheral and central nervous system and can be divided into 7 subclasses: TRPC, TRPV, TRPM, TRPA, TRPN, TRPP, and TRPML[56].As non-selective cation channels in cell membranes, most of the TRPs have good selective permeability for Ca2+and can directly convert mechanical signals into transfusible electrochemical signals, as well as mechanical signal transduction via Ca2+second messenger pathway[57].It has been found that massage is characterized by force and direct stimulation to soft tissues innervated by peripheral nerve fibers and that MSC in peripheral nerve fibers are the key pathway to convert mechanical force stimulation into bioelectrical signals to the center.Recent experiments have demonstrated that Piezo MSC are also present in peripheral myelinated nerve fibers,and this may be the mechanism by which massage exerts its therapeutic effect[58].Mechanical activation of fascial TRPV1 by manual force transmits mechanical information through two parallel pathways.First,manual activation of TRPV1 on nerve fibers opens the channel to a large Ca2+inward flow, and nerve cells generate action potentials, or Ca2+inward flow causes cells to release ATP, which activates nerve electrical impulses by acting on the cells’ purinergic receptors(P2Y or P2X) in an autocrine form.Second, in nonneuronal cells, mechanical stimulation activates the TRPV1 channel on myofibers or fibroblasts to open Ca2+inward flow, and the cells release ATP to the ECM,which transmits the acupuncture signals to nerve cells through calcium wave propagation.Nerve cells transmit the information of manipulative mechanical stimulation to the center and thus exert mechanical stimulation.

The mechanism of manual therapies on the human body and the “sensing” process of coupled response to physicochemical information from manual forensic stimulation of fascia are shown in Figure 1 and Figure 2.

Figure 2 Mechanism of action of manual therapy on the human body

5 Discussion

Manipulative therapy acts on the skin with compound stimulation, resulting in the deformation of local skin and deep tissue, which is the perception of subcutaneous touch-pressure and temperature receptors, and then converts the stimulation of mechanical force into electrical signals.The electrical signal reaches the central nervous system through afferent fibers in the form of nerve impulses, and complex electrical, chemical, and tissue metabolic changes occur in the nervous system.Fascial cells, the initial site receiving manipulative stimulation, provide the site for the transduction of physicochemical information and coupling response to the manipulation and play an important role in the initiation of mechanical effects.

While the physical transformation of fascial tissue is induced by manipulative stimulation, the activation of MSC in fascial nerve cells and nerve endings works,causing local nerve action potentials, which directly initiate neuromodulation, converting physical signals of manipulative stimulation into electrical signals, and transmitting mechanical stimulation information.It may also activate MSC on non-neural cells of the fascia,causing the cells to release chemicals that act on corresponding receptors in the peripheral nerve cells or nerve endings.This initiates neuroimmune modulation of the fascial cells and converts the physical signal of the mechanical stimulation into a biochemical signal,resulting in subsequent biological effects.Therefore,fascia can be used as a “sensor” for coupled response to physical and chemical information of manipulative mechanical stimulation, which can convert physical and electrochemical information of manipulative stimulation and initiate mechanical effects.There are relatively few studies on the conductivity of manipulative effects and the physical and chemical transduction of fascia.Most of the studies are fragmented, lacking a coupled biophysical-chemical study of the fascial microenvironment and the systematic generalization and distillation of the laws,and the complete interconnection between the studies has not been established.

However, based on the innervation and mechanical transmission mechanism of fascia and the relationship between the mechanical effects of manipulation and different levels of tissue in the body, we believe that fascia is probably an important pathway and carrier of the mechanical stimulation effects of manipulation, and this is the direction we will explore in the future.

In addition, the results of massage manipulation studies are influenced by various aspects, such as the type of manipulation, the standardization of manipulation, and the degree of stimulation.Among the basic studies on massage manipulation, there are more pain relief mechanisms by manipulation[59].Among the studies on the mechanism of manipulation initiation, the focus has been on cellular molecular, local circulation, spinal cord level, and other mechanisms.From a holistic view of Chinese medicine, the above theories have some limitations.If objective and accurate test data are provided by MSC and the molecular mechanism of the body’s perception of mechanical stimulation by manipulation is elucidated from fascial-neural conduction, it is believed that some of the theories on the mechanism of massage can be improved.

Conflict of Interest

The authors declare that there is no potential conflict of interest in this article.

Acknowledgments

This work was supported by the Major Project of Natural Science Research in Anhui Province (安徽省高校自然科学研究项目重大项目, No.KJ2021ZD0062); TCM Health Science and TCM Rehabilitation Open Subject of Anhui University of Chinese Medicine (安徽中医药大学中医养生学及中医康复学学科开放课题, No.2022ZJXK07); Key Project of Natural Science Research in Anhui Province (安徽省高校自然科学研究重点项目,No.2023AH050725).

Authors’ Contributions

The study was designed by CHENG Lulu, WANG Siyu,WU Qinggang, and CHEN Zhaohui.CHENG Lulu wrote the first draft.WANG Siyu and WANG Qinggang corrected the manuscript.CHEN Zhaohui supervised the conduct of the study.All authors read and approved the final manuscript.

Received:15 December 2022/Accepted: 18 May 2023