Acupoint Sensitivity in Health and Disease: A Systematic Review.

Introduction: The concept of acupoints is a key defining feature of acupuncture, yet the scientific basis of acupoints remains unclear. In recent years, there has been an emerging body of animal studies demonstrating an association between cutaneous sensitivity and visceral pathophysiology, through which acupoints over the skin are sensitized in pathologic conditions. Several studies with humans have also been conducted to assess whether the sensitivity of acupoints is distinct in healthy versus clinical populations. However, no systematic review has been conducted to collate and synthesize the status and quality of human studies on this topic. Methods: A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA). Literature search was performed by combining variations of search terms related to acupoints and pain sensitivity in PubMed, EMBASE, and Alt HealthWatch (EBSCOHost). Screening of titles and abstracts and review of full-text articles for eligibility were performed by two independent investigators. Using a predefined template, information on subject characteristics, pathologic conditions, names of assessed acupoints, and relevant main findings were extracted from the included studies. The methodological quality of included studies was assessed using a modified Newcastle-Ottawa Scale (NOS) for case-control studies. A quality assessment checklist was also developed by the present authors to examine the quality of reporting of experimental variables that were considered important for evaluating acupoint sensitivity. Results: A total of 3453 studies were identified from the database search, of which 11 met the eligibility criteria to be included in this review. Six studies examined the mechanical sensitivity of body acupoints, and the remaining five studies examined the mechanical sensitivity of auricular points. Overall, findings suggest that the sensitivity of acupoints may be distinct in healthy versus clinical populations. However, there were various potential sources of bias and substantial heterogeneity across included studies in clinical conditions and acupoints. Conclusion: There is at present insufficient evidence to support or refute that acupoints in humans are sensitized in pathologic conditions. There were various methodological issues, including small sample size and poor reporting of experimental design and variables, which limit the ability to draw a definitive conclusion on this topic. It is also largely unclear whether it is the general body regions rather than specific acupoints that may be sensitized, as most studies did not include nonacupoint location(s) for comparison. Thus, further rigorous research is warranted.

Electrical potential of acupuncture points: use of a noncontact scanning Kelvin probe.

Objective. Acupuncture points are reportedly distinguishable by their electrical properties. However, confounders arising from skin-to-electrode contact used in traditional electrodermal methods have contributed to controversies over this claim. The Scanning Kelvin Probe is a state-of-the-art device that measures electrical potential without actually touching the skin and is thus capable of overcoming these confounding effects. In this study, we evaluated the electrical potential profiles of acupoints LI-4 and PC-6 and their adjacent controls. We hypothesize that acupuncture point sites are associated with increased variability in potential compared to adjacent control sites. Methods. Twelve healthy individuals were recruited for this study. Acupuncture points LI-4 and PC-6 and their adjacent controls were assessed. A 2 mm probe tip was placed over the predetermined skin site and adjusted to a tip-to-sample distance of 1.0 mm under tip oscillation settings of 62.4 Hz frequency. A 6 × 6 surface potential scan spanning a 1.0 cm × 1.0 cm area was obtained. Results. At both the PC-6 and LI-4 sites, no significant differences in mean potential were observed compared to their respective controls (Wilcoxon rank-sum test, P = 0.73 and 0.79, resp.). However, the LI-4 site was associated with significant increase in variability compared to its control as denoted by standard deviation and range (P = 0.002 and 0.0005, resp.). At the PC-6 site, no statistical differences in variability were observed. Conclusion. Acupuncture points may be associated with increased variability in electrical potential.

Skin Temperature of Acupoints in Health and Disease: A Systematic Review.

Introduction: Despite substantial progress made in the field of acupuncture research, the existence and specificity of acupoints remain controversial. In recent years, the concept of acupoint sensitization has emerged as a theoretical framework for understanding acupoints as dynamic functional entities that are sensitized in pathological conditions. Based on this premise, some have claimed that specific acupoints are thermally distinct between healthy and clinical populations, but no systematic review has been conducted to synthesize and evaluate the quality of studies supporting such claims. In this review, we provide a summary and quality assessment of the existing literature addressing the question of whether changes in skin temperature at specific acupoints are indicative of pathological conditions. Methods: A systematic literature search was performed in PubMed, EMBASE, and AltHealthWatch (EBSCO Host), by combining variations of search terms relevant to acupoints and temperature. The search was limited to the English language, and publication dates ranged from database inception to December 2020. Two authors independently screened all resulting abstracts and subsequently read full-text articles for eligibility. Information on study design, sample, acupoints, parameters of skin temperature assessments, and main findings were extracted from included studies. Quality of the thermal sensing methodology was evaluated using a thermal assessment checklist, adapted from the Thermographic Imaging in Sports and Exercise Medicine (TISEM) consensus checklist, and a modified Newcastle-Ottawa Scale (NOS) for case-control studies. Results: The search strategy yielded a total of 1771 studies, of which 10 articles met the eligibility criteria. Eight studies compared skin temperature at acupoints in healthy versus clinical populations, and two studies assessed within-subject changes in temperature of acupoints in relation to changes in health status. There were seven clinical conditions examined in the included studies: chronic bronchial asthma, chronic hepatitis, hyperplasia of mammary glands, infertility, intracranial hypertension, obesity, and primary dysmenorrhea. There were numerous methodological quality issues related to skin temperature measurements. Eight studies with case-control designs reported significant differences between healthy and clinical populations in temperature at certain acupoints. Two studies with pre-post designs reported that changes in health-disease status could be associated with changes in temperature at specific acupoints. Conclusion: A review of the available literature suggests that certain acupoints may be thermally distinct between healthy and unhealthy states. However, given the methodological limitations and heterogeneity across included studies, no definitive conclusion could be drawn as to whether changes in skin temperature at specific acupoints are indicative of pathological conditions.

Spatial anisotropy analyses of subcutaneous tissue layer: potential insights into its biomechanical characteristics.

As the intermediate layer between the muscle and skin, the subcutaneous tissue frequently experiences shear and lateral stresses whenever the body is in motion. However, quantifying such stresses in vivo is difficult. The lack of such measures is partly responsible for our poor understanding of the biomechanical behaviors of subcutaneous tissue. In this study, we employ both ultrasound imaging and a novel spatial anisotropy measure - incorporating Moran's I spatial autocorrelation calculations - to investigate the structuromechanical features of subcutaneous tissues within the extremities of 16 healthy volunteers. This approach is based on the understanding that spatial anisotropy can be an effective surrogate for the summative, tensile forces experienced by biological tissue. We found that spatial anisotropy in the arm, thigh and calf was attributed to the echogenic bands spanning the width of the ultrasound images. In both univariable and multivariable analyses, the calf was significantly associated with greater anisotropy compared with the thigh and arm. Spatial anisotropy was inversely related to subcutaneous thickness, and was significantly increased with longitudinally oriented probe images compared with transversely orientated images. Maximum peaks in spatial anisotropy were frequently observed when the longitudinally oriented ultrasound probe was swept across the extremity, suggesting that longitudinal channels with greater tension exist in the subcutaneous layer. These results suggest that subcutaneous biomechanical tension is mediated by collagenous/echogenic bands, greater in the calf compared with the thigh and arm, increased in thinner individuals, and maximal along longitudinal trajectories parallel to the underlying muscle. Spatial anisotropy analysis of ultrasound images has yielded meaningful patterns and may be an effective means to understand the biomechanical strain patterns within the subcutaneous tissue of the extremities.

Attributable risk of all-cause mortality in hypertensive adults based on disease risk prediction model: A Chinese cohort study.

BACKGROUND: The aim of this study was to estimate the attributable risk for all-cause mortality in hypertensive adults living in Beijing, China. METHODS: We conducted a prospective cohort study on the basis of the disease risk prediction model, which included 3006 hypertensive patients aged 50 and over who participated in the annual health examination from thirty-eight community health centers were randomly selected from all 53 community health centers in Dongcheng district of Beijing in China. This cohort study was conducted from January 1, 2013 to June 31, 2018 in these community health centers. Data included age, gender, education level, BMI, smoking and drinking status, renal function, diabetes mellitus (DM), coronary heart disease, levels of blood pressure, use of medications, and blood lipid levels. RESULTS: the follow-up time was 4.90±0.51 years. There were significant survival differences by gender, renal function (eGFR>90 vs. 60-90 vs. <60mL/min per 1.73m2), smoking (smoking vs. No smoking), hypertension severity (SBP≥140 or DBP≥r vs. SBP/DBP<140/90mmHg), education level (<6 vs. 6-12 vs. >12 years), coronary heart disease (CHD) (CHD vs. NO CHD). In the multivariate Cox proportional hazard analysis, the prognostic factors of all-cause mortality in hypertensive patients were male [HR 1.662, 95% CI 1.110-2.489, p=0.014], educational level<6 years [HR 2.044, 95% CI 1.164-3.591, p 0.013], age ≥65 years [HR 3.092, 95% CI 1.717-5.571, p<0.001], smoking [HR 1.885, 95% CI 1.170-3.309, p=0.009], eGFR<60mL/min per 1.73m2 [HR 3.591, 95% CI 2.023-6.371, p<0.001]. CONCLUSIONS: we conclude that decreasing eGFR, increasing age, smoking, low education and gender (male) are significant and independent risk factor for mortality in hypertension for this urban cohort. Recommendations may include protecting renal function, providing patient education, and cessation of smoking. It highlights that early preventive measures are needed to detect kidney impairment and protect renal function. It also suggests that earlier smoking cessation may be important for hypertensive patients.

Dynamic brain-body coupling of breath-by-breath O2-CO2 exchange ratio with resting state cerebral hemodynamic fluctuations.

BACKGROUND: The origin of low frequency cerebral hemodynamic fluctuations (CHF) in the resting state remains unknown. Breath-by breath O2-CO2 exchange ratio (bER) has been reported to correlate with the cerebrovascular response to brief breath hold challenge at the frequency range of 0.008-0.03Hz in healthy adults. bER is defined as the ratio of the change in the partial pressure of oxygen (ΔPO2) to that of carbon dioxide (ΔPCO2) between end inspiration and end expiration. In this study, we aimed to investigate the contribution of respiratory gas exchange (RGE) metrics (bER, ΔPO2 and ΔPCO2) to low frequency CHF during spontaneous breathing. METHODS: Twenty-two healthy adults were included. We used transcranial Doppler sonography to evaluate CHF by measuring the changes in cerebral blood flow velocity (ΔCBFv) in bilateral middle cerebral arteries. The regional CHF were mapped with blood oxygenation level dependent (ΔBOLD) signal changes using functional magnetic resonance imaging. Temporal features and frequency characteristics of RGE metrics during spontaneous breathing were examined, and the simultaneous measurements of RGE metrics and CHF (ΔCBFv and ΔBOLD) were studied for their correlation. RESULTS: We found that the time courses of ΔPO2 and ΔPCO2 were interdependent but not redundant. The oscillations of RGE metrics were coherent with resting state CHF at the frequency range of 0.008-0.03Hz. Both bER and ΔPO2 were superior to ΔPCO2 in association with CHF while CHF could correlate more strongly with bER than with ΔPO2 in some brain regions. Brain regions with the strongest coupling between bER and ΔBOLD overlapped with many areas of default mode network including precuneus and posterior cingulate. CONCLUSION: Although the physiological mechanisms underlying the strong correlation between bER and CHF are unclear, our findings suggest the contribution of bER to low frequency resting state CHF, providing a novel insight of brain-body interaction via CHF and oscillations of RGE metrics.

Electrical properties of acupuncture points and meridians: a systematic review.

According to conventional wisdom within the acupuncture community, acupuncture points and meridians are special conduits for electrical signals. This view gained popularity after anecdotal reports and clinical studies asserted that these anatomical structures are characterized by lower electrical impedance compared to adjacent controls. To ascertain whether evidence exists to support or refute this claim, we conducted a systematic review of studies directly evaluating the electrical characteristics of acupuncture structures and appropriate controls. We searched seven electronic databases until August 2007, hand-searched references, and consulted technical experts. We limited the review to primary data human studies published in English. A quality scoring system was created and employed for this review. A total of 16 articles representing 18 studies met inclusion criteria: 9 examining acupuncture points and 9 examining meridians. Five out of 9 point studies showed positive association between acupuncture points and lower electrical resistance and impedance, while 7 out of 9 meridian studies showed positive association between acupuncture meridians and lower electrical impedance and higher capacitance. The studies were generally poor in quality and limited by small sample size and multiple confounders. Based on this review, the evidence does not conclusively support the claim that acupuncture points or meridians are electrically distinguishable. However, the preliminary findings are suggestive and offer future directions for research based on in-depth interpretation of the data.

Factors associated with herbal therapy use by adults in the United States.

OBJECTIVE: To examine the patterns of herbal therapy use among adults in the United States and to describe factors associated with herb use. DESIGN: We examined the use of natural herbs from the 2002 National Health Interview Survey (NHIS). We analyzed factors associated with herb use and reasons for herb use with logistic regression. RESULTS: Factors associated with herb use include the following: age (45-64 years old), being uninsured, being female, having a higher education, living in the West, using prescription medications or over-the-counter (OTC) medications, and self-identified as "non-Hispanic other." Factors associated with no herb use include being non-Hispanic black and living in the South or Midwest. Seventy-two percent of those who used herbs used prescription medications, and 84% of those who used herbs also used an OTC medication in the prior 12 months. Among adults who used herbs, the most commonly mentioned were echinacea (41%), ginseng (25%), gingko (22%), and garlic (20%). The most frequent conditions for herb use were head or chest cold (30%), musculoskeletal conditions (16%), and stomach or intestinal illness (11%). Among those who used herbs in the prior year, factors associated with using herbs because conventional medical treatments were too expensive included being uninsured, having poor health, and being 25-44 years old. CONCLUSIONS: Nearly 1 in 5 people in the US population report using an herb for treatment of health conditions and/or health promotion. More than half did not disclose this information to a conventional medical professional.

Electrical characterization of acupuncture points: technical issues and challenges.

Acupuncture points are frequently described as having distinct electrical properties. These properties include increased conductance, reduced impedance and resistance, increased capacitance, and elevated electrical potential compared to adjacent nonacupuncture points. Commercial electrodiagnostic devices have used this assertion as a means to localize and analyze acupuncture points for diagnostic purposes. Yet, the electrical characterization of acupuncture points is associated with important technical issues that are often overlooked. Electrode polarizability, stratum corneum impedance, presence of sweat glands, choice of contact medium, electrode geometry, and other factors contribute to the final electrodermal reading and may cause doubts about the validity of available electrodiagnostic devices. The goal of this review is to help researchers and clinicians understand these factors affecting electrodermal readings, to make apparent the difficulties and challenges confronting electrodermal readings, and to increase understanding about how these possible associations can be interpreted and understood from the perspective of biology.

Two styles of acupuncture for treating painful diabetic neuropathy--a pilot randomised control trial.

In a pilot study, we evaluated the clinical and mechanistic effects of two styles of acupuncture, Traditional Chinese Medicine (TCM) and Japanese acupuncture, for the treatment of painful diabetic neuropathy. Out of seven patients enrolled, three received Traditional Chinese acupuncture while four received Japanese style acupuncture. Treatments were delivered once a week for 10 weeks. Acupuncturists were permitted to select the needle interventions. Substantial differences in diagnostic techniques, choice of acupuncture points, and needle manipulation were observed between TCM and Japanese acupuncturists. Clinically, patients allocated to Japanese acupuncture reported decreased neuropathy-associated pain according to the daily pain severity score, while the group allocated to the TCM acupuncture reported minimal effects. Both acupuncture styles, however, lowered pain according to the McGill Short Form Pain Score. The TCM style improved nerve sensation according to quantitative sensory testing while the Japanese style had a more equivocal effect. No evident changes were observed in glucose control or heart rate variability in either group.

Can Tai Chi training impact fractal stride time dynamics, an index of gait health, in older adults? Cross-sectional and randomized trial studies.

PURPOSE: To determine if Tai Chi (TC) has an impact on long-range correlations and fractal-like scaling in gait stride time dynamics, previously shown to be associated with aging, neurodegenerative disease, and fall risk. METHODS: Using Detrended Fluctuation Analysis (DFA), this study evaluated the impact of TC mind-body exercise training on stride time dynamics assessed during 10 minute bouts of overground walking. A hybrid study design investigated long-term effects of TC via a cross-sectional comparison of 27 TC experts (24.5 ± 11.8 yrs experience) and 60 age- and gender matched TC-naïve older adults (50-70 yrs). Shorter-term effects of TC were assessed by randomly allocating TC-naïve participants to either 6 months of TC training or to a waitlist control. The alpha (α) long-range scaling coefficient derived from DFA and gait speed were evaluated as outcomes. RESULTS: Cross-sectional comparisons using confounder adjusted linear models suggest that TC experts exhibited significantly greater long-range scaling of gait stride time dynamics compared with TC-naïve adults. Longitudinal random-slopes with shared baseline models accounting for multiple confounders suggest that the effects of shorter-term TC training on gait dynamics were not statistically significant, but trended in the same direction as longer-term effects although effect sizes were very small. In contrast, gait speed was unaffected in both cross-sectional and longitudinal comparisons. CONCLUSION: These preliminary findings suggest that fractal-like measures of gait health may be sufficiently precise to capture the positive effects of exercise in the form of Tai Chi, thus warranting further investigation. These results motivate larger and longer-duration trials, in both healthy and health-challenged populations, to further evaluate the potential of Tai Chi to restore age-related declines in gait dynamics. TRIAL REGISTRATION: The randomized trial component of this study was registered at ClinicalTrials.gov (NCT01340365).

Sparse representation-based ECG signal enhancement and QRS detection.

Electrocardiogram (ECG) signal enhancement and QRS complex detection is a critical preprocessing step for further heart disease analysis and diagnosis. In this paper, we propose a sparse representation-based ECG signal enhancement and QRS complex detection algorithm. Unlike traditional Fourier or wavelet transform-based methods, which use fixed bases, the proposed algorithm models the ECG signal as the superposition of a few inner structures plus additive random noise, where these structures (referred to here as atoms) can be learned from the input signal or a training set. Using these atoms and their properties, we can accurately approximate the original ECG signal and remove the noise and other artifacts such as baseline wandering. Additionally, some of the atoms with larger kurtosis values can be modified and used as an indication function to detect and locate the QRS complexes in the enhanced ECG signals. To demonstrate the robustness and efficacy of the proposed algorithm, we compare it with several state-of-the-art ECG enhancement and QRS detection algorithms using both simulated and real-life ECG recordings.

Advancing acupuncture research.

Since the early 1970s, acupuncture has been the subject of multiple animal experiments and randomized clinical trials. Our understanding of acupuncture from both the clinical and mechanistic perspectives has, as a result, grown tremendously. Yet the final word on acupuncture as a therapy remains mixed, largely due to the contradictory nature of the evidence. With some exception, what clinical conditions would benefit and how acupuncture physiologically operates remains unclear. The impediment to progress is found in three disjunctions in acupuncture research: (1) the biomedical need to standardize treatments creates uncertainty about whether we are studying acupuncture appropriately; (2) the variability in acupuncture styles creates ambiguity about whether we are studying the right style; and (3) the discrepancy between animal and human studies creates questions about whether we truly understand the underlying mechanism responsible for acupuncture's therapeutic effect. We propose that these disjunctions are best addressed with the use of "manualized" protocols in clinical trials that are linked with mechanistic studies. Through this approach, we can create a healthy dialogue between the medical and acupuncture communities and recognize the unique physiologic properties that may be found in each acupuncture style. To illustrate how this proposal may fundamentally change acupuncture research, we present diabetic neuropathy as a particularly interesting model because of its complex heterogeneous pathophysiology.

Electrical impedance along connective tissue planes associated with acupuncture meridians.

BACKGROUND: Acupuncture points and meridians are commonly believed to possess unique electrical properties. The experimental support for this claim is limited given the technical and methodological shortcomings of prior studies. Recent studies indicate a correspondence between acupuncture meridians and connective tissue planes. We hypothesized that segments of acupuncture meridians that are associated with loose connective tissue planes (between muscles or between muscle and bone) visible by ultrasound have greater electrical conductance (less electrical impedance) than non-meridian, parallel control segments. METHODS: We used a four-electrode method to measure the electrical impedance along segments of the Pericardium and Spleen meridians and corresponding parallel control segments in 23 human subjects. Meridian segments were determined by palpation and proportional measurements. Connective tissue planes underlying those segments were imaged with an ultrasound scanner. Along each meridian segment, four gold-plated needles were inserted along a straight line and used as electrodes. A parallel series of four control needles were placed 0.8 cm medial to the meridian needles. For each set of four needles, a 3.3 kHz alternating (AC) constant amplitude current was introduced at three different amplitudes (20, 40, and 80 microAmps) to the outer two needles, while the voltage was measured between the inner two needles. Tissue impedance between the two inner needles was calculated based on Ohm's law (ratio of voltage to current intensity). RESULTS: At the Pericardium location, mean tissue impedance was significantly lower at meridian segments (70.4 +/- 5.7 Omega) compared with control segments (75.0 +/- 5.9 Omega) (p = 0.0003). At the Spleen location, mean impedance for meridian (67.8 +/- 6.8 Omega) and control segments (68.5 +/- 7.5 Omega) were not significantly different (p = 0.70). CONCLUSION: Tissue impedance was on average lower along the Pericardium meridian, but not along the Spleen meridian, compared with their respective controls. Ultrasound imaging of meridian and control segments suggested that contact of the needle with connective tissue may explain the decrease in electrical impedance noted at the Pericardium meridian. Further studies are needed to determine whether tissue impedance is lower in (1) connective tissue in general compared with muscle and (2) meridian-associated vs. non meridian-associated connective tissue.

Use of complementary and alternative medical therapies among racial and ethnic minority adults: results from the 2002 National Health Interview Survey.

PURPOSE: Complementary and alternative medicine (CAM) use among ethnic minority populations is poorly understood. We sought to examine CAM use in Hispanics, non-Hispanic blacks and non-Hispanic whites. METHODS: We analyzed data from the Alternative Health Supplement to the 2002 National Health Interview Survey (NHIS), including information on 19 different CAM therapies used in the past 12 months. RESULTS: An estimated 34% of Hispanic, non-Hispanic black and non-Hispanic white adults in the United States used at least one CAM therapy (excluding prayer) during the prior 12 months (2002). CAM use was highest for non-Hispanic whites (36%), followed by Hispanics (27%) and non-Hispanic blacks (26%). Non-Hispanic whites were more likely to use herbal medicine, relaxation techniques and chiropractic more frequently than Hispanics and non-Hispanic blacks. After controlling for other sociodemographic factors, Hispanic and non-Hispanic black races/ethnicities were associated with less CAM use, with adjusted odds ratios (95% confidence intervals) of 0.78 (0.70, 0.87) and 0.71 (0.65, 0.78), respectively. Hispanics cited using CAM because conventional medical treatments were too expensive more frequently than non-Hispanic blacks or whites. Hispanics had the highest provider nondisclosure rates (68.5%), followed by non-Hispanic blacks (65.1%) and non-Hispanic whites (58.1%). CONCLUSIONS: Excluding prayer, Hispanics and non-Hispanic blacks used CAM less frequently than non-Hispanic whites and were less likely to disclose their use to their healthcare provider. Further research is needed to improve our understanding of the disparities in CAM use.

Complexity-Based Measures Inform Effects of Tai Chi Training on Standing Postural Control: Cross-Sectional and Randomized Trial Studies.

BACKGROUND: Diminished control of standing balance, traditionally indicated by greater postural sway magnitude and speed, is associated with falls in older adults. Tai Chi (TC) is a multisystem intervention that reduces fall risk, yet its impact on sway measures vary considerably. We hypothesized that TC improves the integrated function of multiple control systems influencing balance, quantifiable by the multi-scale "complexity" of postural sway fluctuations. OBJECTIVES: To evaluate both traditional and complexity-based measures of sway to characterize the short- and potential long-term effects of TC training on postural control and the relationships between sway measures and physical function in healthy older adults. METHODS: A cross-sectional comparison of standing postural sway in healthy TC-naïve and TC-expert (24.5±12 yrs experience) adults. TC-naïve participants then completed a 6-month, two-arm, wait-list randomized clinical trial of TC training. Postural sway was assessed before and after the training during standing on a force-plate with eyes-open (EO) and eyes-closed (EC). Anterior-posterior (AP) and medio-lateral (ML) sway speed, magnitude, and complexity (quantified by multiscale entropy) were calculated. Single-legged standing time and Timed-Up-and-Go tests characterized physical function. RESULTS: At baseline, compared to TC-naïve adults (n = 60, age 64.5±7.5 yrs), TC-experts (n = 27, age 62.8±7.5 yrs) exhibited greater complexity of sway in the AP EC (P = 0.023), ML EO (P<0.001), and ML EC (P<0.001) conditions. Traditional measures of sway speed and magnitude were not significantly lower among TC-experts. Intention-to-treat analyses indicated no significant effects of short-term TC training; however, increases in AP EC and ML EC complexity amongst those randomized to TC were positively correlated with practice hours (P = 0.044, P = 0.018). Long- and short-term TC training were positively associated with physical function. CONCLUSION: Multiscale entropy offers a complementary approach to traditional COP measures for characterizing sway during quiet standing, and may be more sensitive to the effects of TC in healthy adults. TRIAL REGISTRATION: ClinicalTrials.gov NCT01340365.

A systems biology approach to studying Tai Chi, physiological complexity and healthy aging: design and rationale of a pragmatic randomized controlled trial.

INTRODUCTION: Aging is typically associated with progressive multi-system impairment that leads to decreased physical and cognitive function and reduced adaptability to stress. Due to its capacity to characterize complex dynamics within and between physiological systems, the emerging field of complex systems biology and its array of quantitative tools show great promise for improving our understanding of aging, monitoring senescence, and providing biomarkers for evaluating novel interventions, including promising mind-body exercises, that treat age-related disease and promote healthy aging. MATERIAL AND METHODS: An ongoing, two-arm randomized clinical trial is evaluating the potential of Tai Chi mind-body exercise to attenuate age-related loss of complexity. A total of 60 Tai Chi-naïve healthy older adults (aged 50-79) are being randomized to either six months of Tai Chi training (n=30), or to a waitlist control receiving unaltered usual medical care (n=30). Our primary outcomes are complexity-based measures of heart rate, standing postural sway and gait stride interval dynamics assessed at 3 and 6months. Multiscale entropy and detrended fluctuation analysis are used as entropy- and fractal-based measures of complexity, respectively. Secondary outcomes include measures of physical and psychological function and tests of physiological adaptability also assessed at 3 and 6months. DISCUSSION: Results of this study may lead to novel biomarkers that help us monitor and understand the physiological processes of aging and explore the potential benefits of Tai Chi and related mind-body exercises for healthy aging.

Pulsatile hemodynamics of hypertension: systematic review of aortic input impedance.

OBJECTIVE: Input impedance is the frequency-dependent afterload to pulsatile blood flow. Studies of input impedance have been performed as early as the 1960s and have been applied to hypertension (HTN). However, to date, these studies have not been systematically evaluated. This systematic review aims to summarize the literature, interpret existing data from the perspective of impedance theory, and to discuss their potential for generating physiological insights into HTN. METHODS: We identified 11 studies wherein computed impedance moduli from both HTN and control (CNT) groups were reported. In addition, we performed bivariate analyses of raw data from three of these studies. RESULTS: Major findings include HTN groups had consistently elevated impedance moduli at 0 Hz (Z(0)) and at heart rate frequency (Z(1)), an increased frequency wherein impedance phase first crosses 0 (f(0)), but no consistent pattern in characteristic impedance (Z(c)), when compared to CNT groups; SBP and DBP are highly correlated with Z(0) and Z(1), moderately correlated with f(0), less correlated with Z(c); the measurement and calculation methods for Z(c) are varied and inconsistent; and a not insignificant proportion of hypertensive individuals have 'normal' Z(0), Z(1) and Z(c) values. These findings are limited by the heterogeneous study populations and small sample sizes. CONCLUSION: These findings suggest that Z(0), Z(1) and f(0) are significantly associated with HTN, whereas the role of Z(c) is less clear. Additional studies are needed to evaluate these input impedance variables in order to generate substantial implications in clinic settings.

Applying the Kelvin probe to biological tissues: theoretical and computational analyses.

The Kelvin probe measures surface electrical potential without making physical contact with the specimen. It relies on capacitive coupling between an oscillating metal tip that is normal to a specimen's surface. Kelvin probes have been increasingly used to study surface and electrical properties of metals and semiconductors and are capable of detecting material surface potentials with submillivolt resolution at a micrometer spatial scale. Its capability for measuring electrical potential without being confounded by electrode-specimen contact makes extending its use towards biological materials particularly appealing. However, the theoretical basis for applying the Kelvin probe to dielectric or partially conductive materials such as biological tissue has not been evaluated and remains unclear. This study develops the theoretical basis underlying Kelvin probe measurements in five theoretical materials: highly conductive, conductive dielectric with rapid charge relaxation, conductive dielectric with slow charge relaxation, perfect dielectric, and tissue with a bulk serial resistance. These theoretically derived equations are then computationally analyzed using parameters from both theoretical specimens and actual biomaterials-including wet skin, dry skin, cerebrospinal fluid, and tendon. Based on these analyses, a Kelvin probe performs in two distinct ways depending on the charge relaxation rates of the sample: The specimen is treated either as a perfect dielectric or as highly conductive material. Because of their rapid relaxation rate and increased permittivity biomaterials behave similarly to highly conductive materials, such as metal, when evaluated by the Kelvin probe. These results indicate that the Kelvin probe can be readily applied to studying the surface potential of biological tissue.