Differential response of central blood pressure to isometric and isotonic exercises

OCTA Signal Quality Augmentation Using the Isometric Handgrip Test to Maximize Vascular Flow (SQUEEZE): A Randomized Crossover Trial

Purpose

To determine if performing the isometric handgrip test (IHGT) can augment optical coherence tomography angiography (OCTA) vascular signal quality in eyes with macular abnormalities.

Methods

A randomized, single-blinded crossover trial was conducted including 36 participants with macular abnormalities, randomized to undergo OCTA with or without the IHGT, then crossed over to the alternate "intervention" after 1 minute. The primary outcome was OCTA signal quality after 1 minute of squeezing at 50% maximum grip strength. Secondary outcomes were other measures of vascular flow and systemic blood pressure (BP), also regressed against person- and eye-level covariables.

Results

Primary analysis of OCTA signal quality with versus without the IHGT was nonsignificant (P = 0.73). Nested analyses showed that the IHGT resulted in increased OCTA B-scan retinal vascular flow signal (2.95 [-1.64 to 7.55] Δ%, P < 0.05) and increased systolic BP, diastolic BP, pulse pressure, and mean arterial pressure (4.94 [0.41 to 9.47] to 12.38 [8.01 to 16.75] mm Hg, P < 0.05). OCTA signal quality and en face vessel density and perfusion changes were associated with sex, refraction, race/ethnicity, and right-hand IHGT use (P < 0.05). Greater increases in systolic and diastolic BP and mean arterial pressure were generally associated with right-hand IHGT use and greater maximum grip strength (P < 0.09).

Conclusions

The IHGT can temporarily increase OCTA B-scan retinal vascular flow signal in participants with macular abnormalities. IHGT-induced changes to systemic BP appear to be linked to absolute (rather than relative) grip strength, implying that the IHGT may be ineffective with low grip strength. Further research in larger populations is warranted.

Translational Relevance

This study provides early validation that the IHGT may augment OCTA output, which may lead to improved noninvasive detection of pathologic vascular changes.

Acute effects of high-intensity resistance training on central blood pressure parameters of elderly hypertensive women: a crossover clinical trial

OBJECTIVE

Assess the acute effects of a high-intensity resistance training session on central blood pressure (CBP) parameters of elderly hypertensive women.

METHODS

Forty physically active hypertensive women were included in resistance training and control protocols. Resistance training exercises were bench press, leg press and lat pull-down. The resistance training protocol consisted of three sets of 10 repetitions to volitional failure with 90 s of rest between sets. No exercise was performed in the control protocol. CBP parameters were measured in four moments: before (PRE), immediately after (T0), 30 min (T30) and 60 min (T60) following both protocols.

RESULTS

Resistance training significantly increased central SBP (cSBP) 107.4 ± 16.3 vs. 117.5 ± 16.7), augmentation index ((24.9 ± 12.7 vs. 33.1 ± 12.0), pulse wave velocity (PWV 9.7 ± 1.0 vs. 10.3 ± 1.1), peripheral pulse pressure (pPP 48.5 ± 11.7 vs. 58.9 ± 13.1), central pulse pressure (cPP 38.3 ± 11.6 vs. 46.5 ± 13.1) and amplified pulse pressure (ampPP 10.2 ± 4.2 vs. 12.4 ± 5.6) immediately after exercises. The comparison between groups showed higher values of cSBP (117.5 ± 16.7 vs. 106.3 ± 14.6), augmentation index (20.9 ± 11.0 vs. 33.1 ± 12.0), pPP (46.6 ± 11.0 vs. 58.9 ± 13.1) and cPP (36 ± 10.2 vs. 46.5 ± 13.1) at T0. After 30 min, all variables returned to the baseline values.

CONCLUSION

High-intensity resistance training session increased CBP parameters immediately after exercises, but those changes were not sustained after 30 min.

Assessment of baroreflex sensitivity during isometric handgrip exercise and oscillatory lower body negative pressure

Objectives

Baroreflex sensitivity (BRS) is an estimate of autonomic control of cardiovascular system via the baroreflex arc. It has been suggested that exercise pressure reflex and muscle metaboreflex override baroreflex during exercise to decrease baroreflex gain, which facilitates the simultaneous rise in blood pressure (BP) and heart rate during the exercise. This study investigated the effects of isometric handgrip exercise (IHE) on baroreflex gain and frequency dependence of baroreflex sensitivity while fluctuations in arterial BP were generated.

Methods

Thirteen healthy men performed IHE at 20% and 30% of their maximum voluntary contraction (MVC), while oscillatory lower body negative pressure (OLBNP) of 40 mmHg was applied in 0.1 and 0.25 Hz frequencies.

Results

Compared to the OLBNP at 0.25 Hz frequency alone, the baroreflex gain for diastolic BP (DBP) was significantly reduced with the addition of IHE at 20% and 30% of MVC in the high frequency band. At rest (without IHE and OLBNP) the baroreflex gain was significantly more in the high frequency band for DBP, but the baroreflex gain for DBP was not significantly different when IHE + OLBNP were applied at 20% and 30% of MVC in both frequencies.

Conclusions

The significant reduction of DBP baroreflex gain with the addition of graded IHE might indicate that exercise pressure reflex and muscle metaboreflex override baroreflex during exercise to decrease baroreflex gain at a high frequency band (0.25 Hz). The frequency-dependent phenomenon of BRS was altered when IHE and OLBNP were applied, meaning that the frequency dependence of BRS was nullified during IHE.

Cardiovascular responses to dynamic and static upper-body exercise in a cold environment in coronary artery disease patients

Purpose

Upper-body exercise performed in a cold environment may increase cardiovascular strain, which could be detrimental to patients with coronary artery disease (CAD). This study compared cardiovascular responses of CAD patients during graded upper-body dynamic and static exercise in cold and neutral environments.

Methods

20 patients with stable CAD performed 30 min of progressive dynamic (light, moderate, and heavy rating of perceived exertion) and static (10, 15, 20, 25 and 30% of maximal voluntary contraction) upper body exercise in cold (− 15 °C) and neutral (+ 22 °C) environments. Heart rate (HR), blood pressure (BP) and electrocardiographic (ECG) responses were recorded and rate pressure product (RPP) calculated.

Results

Dynamic-graded upper-body exercise in the cold increased HR by 2.3–4.8% (p = 0.002–0.040), MAP by 3.9–5.9% (p = 0.038–0.454) and RPP by 18.1–24.4% (p = 0.002–0.020) when compared to the neutral environment. Static graded upper-body exercise in the cold resulted in higher MAP (6.3–9.1%; p = 0.000–0.014), lower HR (4.1–7.2%; p = 0.009–0.033), but unaltered RPP compared to a neutral environment. Heavy dynamic exercise resulted in ST depression that was not related to temperature. Otherwise, ECG was largely unaltered during exercise in either thermal condition.

Conclusions

Dynamic- and static-graded upper-body exercise in the cold involves higher cardiovascular strain compared with a neutral environment among patients with stable CAD. However, no marked changes in electric cardiac function were observed. The results support the use of upper-body exercise in the cold in patients with stable CAD.

Trial registration

Clinical trial registration NCT02855905 August 2016.

Central Haemodynamics Are Associated With Pulmonary Function in Postmenopausal Women

PURPOSE

Increased arterial stiffness predicts cardiovascular disease, which is associated with deteriorated pulmonary function and worsened chronic obstructive pulmonary disease. The present study examined whether arterial function was associated with pulmonary function in postmenopausal women.

METHODS

This study evaluated 41 postmenopausal women (age range: 59-85 years). Arterial function was measured as central systolic blood pressure (cSBP), central pulse pressure (cPP), brachial systolic BP (bSBP), brachial diastolic BP (bDBP), brachial PP (bPP), brachial mean arterial pressure (bMAP) and the augmentation index (AIx). AIx was adjusted for a heart rate of 75 beats per minute (bpm) (AIx@75) and served as the index of arterial stiffness determined by the reflected wave at the central artery. Pulmonary function was measured as forced vital capacity (FVC), forced expiratory volume in 1 second (FEV₁) and the FEV₁/FVC ratio.

RESULTS

Univariate regression analysis demonstrated that cPP, bDBP and bPP were correlated with FVC and FEV₁ (p<0.05, respectively), while AI@75 was correlated with FVC, FEV₁ and FEV₁/FVC ratio (p<0.01, respectively). A stepwise multivariate regression analysis revealed that bDBP was independently associated with FVC (p=0.032), while AI@75 was independently associated with FVC, FEV₁ and FEV₁/FVC ratio (p=0.001, p=0.003 and p=0.017, respectively). The FVC, FEV₁ and FEV₁/FVC ratio were lower in participants with a high AIx versus with a low AIx (p=0.0001, p=0.001 and p=0.044, respectively).

CONCLUSION

These results suggest that increased AIx is associated with lower pulmonary function in postmenopausal women.

Effect of online low-intensity exercise training on fitness and cardiovascular parameters

Online exercise is undoubtedly useful and important; however, chronic adaptations to online exercise, particularly strength gain, muscle hypertrophy, and cardiovascular parameters, remain unclear. We investigated the effect of online exercise training using Zoom on fitness parameters compared with the same exercises supervised directly. In the present study, 34 subjects (age: 42.9±14.4 years) were included. Twenty-three subjects performed eight weeks of body mass-based exercise training online using Zoom, and eleven subjects performed the same exercise supervised directly as the control group. The subjects performed low-load resistance exercises twice a week for 8 weeks for a total of 16 sessions. The sessions included 9 exercises: leg raises, squats, rear raises, shoulder presses, rowing, dips, lunges, Romanian dead lifts, and push-ups. Chair-stand, push-up, and sit-and-reach tests were performed on all subjects. Overall, the home exercise program effectively increased strength and muscle mass and decreased blood pressure and arterial stiffness, but there were no differences between the groups. Changes in chair-stand and sit-and-reach test results were higher in the control group than in the online group. Our results show that there is a similar training response to body mass-based training in both groups, even with virtual experiences using Zoom.

A Systematic Review of Handgrip Strength Measurement in Clinical and Epidemiological Studies of Kidney Disease: Toward a Standardized Approach

In chronic kidney disease (CKD), handgrip strength (HGS) is recommended as a surrogate measure of protein-energy status and functional status. However, it is not routinely used because of inconsistencies such as the optimal timing of the HGS measurement and unclear guidance regarding technique. We aimed to determine the extent of variation in the protocols and methods of HGS assessment. We aimed to identify clinical and epidemiological studies conducted on CKD that reported on the use of HGS as an outcome. A systematic literature search identified n = 129 studies with a total participant population of n = 35,192. We identified large variations in all aspects of the methodology including body and arm position, repetitions, rest time, timing, familiarization, and how scores were calculated. The heterogeneous methodologies used reinforce the need to standardize HGS measurement. After reviewing previously employed methodology in the literature, we propose a comprehensive HGS assessment protocol for use in CKD.

Central aortic hemodynamics following acute lower and upper-body exercise in a cold environment among patients with coronary artery disease

Exercise is beneficial to cardiovascular health, evidenced by reduced post-exercise central aortic blood pressure (BP) and wave reflection. We assessed if post-exercise central hemodynamics are modified due to an altered thermal state related to exercise in the cold in patients with coronary artery disease (CAD). CAD patients (n = 11) performed moderate-intensity lower-body exercise (walking at 65–70% of HR_max) and rested in neutral (+ 22 °C) and cold (− 15 °C) conditions. In another protocol, CAD patients (n = 15) performed static (five 1.5 min work cycles, 10–30% of maximal voluntary contraction) and dynamic (three 5 min workloads, 56–80% of HR_max) upper-body exercise at the same temperatures. Both datasets consisted of four 30-min exposures administered in random order. Central aortic BP and augmentation index (AI) were noninvasively assessed via pulse wave analyses prior to and 25 min after these interventions. Lower-body dynamic exercise decreased post-exercise central systolic BP (6–10 mmHg, p < 0.001) and AI (1–6%, p < 0.001) both after cold and neutral and conditions. Dynamic upper-body exercise lowered central systolic BP (2–4 mmHg, p < 0.001) after exposure to both temperatures. In contrast, static upper-body exercise increased central systolic BP after exposure to cold (7 ± 6 mmHg, p < 0.001). Acute dynamic lower and upper-body exercise mainly lowers post-exercise central BP in CAD patients irrespective of the environmental temperature. In contrast, central systolic BP was elevated after static exercise in cold. CAD patients likely benefit from year-round dynamic exercise, but hemodynamic responses following static exercise in a cold environment should be examined further.

Clinical trials.gov: NCT02855905 04/08/2016.

Dynamic and isometric handgrip exercise increases wave reflection in healthy young adults

Early return and increased magnitude of wave reflection augments pulsatile load, wastes left ventricular effort, and is associated with cardiovascular events. Acute handgrip (HG) exercise increases surrogate measures of wave reflection such as augmentation index. However, augmentation index does not allow distinguishing between timing versus magnitude of wave reflection and is affected by factors other than wave reflection per se. Wave separation analysis decomposes central pressure into relative contributions of forward (Pf) and backward (Pb) pressure wave amplitudes to calculate reflection magnitude (RM = Pb/Pf) and determine the timing of apparent wave reflection return. We tested the hypothesis that acute dynamic and isometric HG exercise increases RM and decreases reflected wave transit time (RWTT). Applanation tonometry was used to record radial artery pressure waveforms in 30 adults (25 ± 4 yr) at baseline and during dynamic and isometric HG exercise. Wave separation analysis was performed offline using a physiological flow wave to derive Pf, Pb, RM, and RWTT. We found that RM increased during dynamic and isometric HG exercise compared with baseline (P = 0.04 and P < 0.01, respectively; baseline 40 ± 5, dynamic 43 ± 6, isometric 43 ± 7%). Meanwhile, RWTT decreased during dynamic and isometric HG exercise compared with baseline (P = 0.03 and P < 0.001, respectively; baseline 164 ± 23, dynamic 155 ± 23, isometric 148 ± 20 ms). Moreover, the changes in RM and RWTT were not different between dynamic and isometric HG exercise. The present data suggest that wave reflection timing (RWTT) and magnitude (RM) are important factors that contribute to increased central blood pressure during HG exercise.NEW & NOTEWORTHY This study demonstrated that wave reflection magnitude is increased while reflected wave transit time is decreased during handgrip exercise in healthy young adults. The larger backward pressure waves and earlier return of these pressure waves were not different between dynamic and isometric handgrip exercise. These acute changes in wave reflection during handgrip exercise transiently augment pulsatile load.

Isometric handgrip training reduces blood pressure and wave reflections in East Asian, non-medicated, middle-aged and older adults: a randomized control trial

PURPOSE

The aim of this study was to investigate the effects of isometric handgrip (IHG) training on central and peripheral blood pressure (BP) and wave reflections in East Asian non-medicated middle-aged and older adults.

METHODS

Twenty-two men and women (mean age 65 ± 11 years) who were not actively involved in regular resistance or endurance training were randomly assigned to a group that did IHG and a control (CON) group. The IHG training was comprised of four unilateral 2-min isometric contractions at 30% of maximal voluntary contraction using a programmed handgrip dynamometer with 1-min rest periods for 5 days per week for 8 weeks.

RESULTS

Baseline central systolic BP (cSBP), brachial systolic BP (bSBP), brachial diastolic BP (bDBP), and the augmentation index (AIx) (via an automated applanation tonometric system) did not differ significantly between the groups. Compared to baseline, cSBP, bSBP, bDBP, and AIx decreased significantly after the 8-week study period in the IHG group (P < 0.05). No significant changes in central and peripheral BP and AIx were observed in the CON group.

CONCLUSIONS

These results suggest that IHG training could reduce central and peripheral BP and wave reflections in East Asian non-medicated middle-aged and older adults.

Effects of blackcurrant extract on arterial functions in older adults: A randomized, double-blind, placebo-controlled, crossover trial

PURPOSE

Blackcurrant extract mainly contains anthocyanins. Several reports suggest that anthocyanins have beneficial effect for cardiovascular functions. The aim of this study was to examine the effect of 7-day intake of New Zealand blackcurrant (NZBC) extract on arterial functions, e.g. arterial stiffness, and serum lipids.

METHODS

A randomized, double-blind, placebo-controlled, crossover design study with a washout period of 28 days was conducted. Fourteen older adults participated in this study (age 73.3 ± 1.7 years). Participants took either a 7-day course of placebo or two capsules of NZBC extract (each 300 mg capsule contains 35% blackcurrant extract). Participants took one of the two trials first and then took the other after a washout period. Carotid-femoral pulse-wave velocity, an index of central arterial stiffness, and central blood pressure were measured at baseline and again at the end of the 7-day study period.

RESULTS

Compared to baseline, carotid-femoral pulse-wave velocity (P = .03) and central blood pressure (P = .02) decreased significantly after the 7-day study period with NZBC intake. In addition, carotid-femoral pulse-wave velocity (P = .04) and central blood pressure (P = .001) in the NZBC intake trial decreased significantly more than in the placebo intake trial. No effects were observed on serum lipids.

CONCLUSION

These results suggest that short-term NZBC intake reduces central arterial stiffness and central blood pressure in older adults. Therefore, anthocyanin-rich blackcurrants might be beneficial for maintaining or improving cardiovascular health as an alternative to pharmaceutical medications.

ABBREVIATIONS

Aix: augmentation index; BP: blood pressure; cfPWV: carotid-femoral pulse-wave velocity;  CVD: cardiovascular diseases; DBP: diastolic blood pressure;  faPWV: femoral-ankle pulse-wave velocity; FG: fasting glucose; HDL: high-density lipoprotein cholesterol; LDL: low-density lipoprotein cholesterol; MBP: mean blood pressure; NZBC: New Zealand blackcurrant; PP: pulse pressure; SBP: systolic blood pressure; TG: triglycerides.

Evaluation of the reduction in central and peripheral arterial blood pressure following an oral glucose load

The clinical significance of measuring central arterial blood pressure has been recently discussed. Although the postprandial reduction in blood pressure is well known, postprandial changes in central blood pressure have not been intensively studied. The present study investigated differences in the reduction of central and peripheral arterial blood pressure after administration of an oral glucose load.An oral glucose tolerance test (75 g) was performed in 360 participants in our physical checkup program. Brachial and central systolic blood pressures were assessed before and after the glucose load. Central arterial blood pressure was measured noninvasively using an automated device.The mean age was 53.6 ± 8.2 years. Both brachial (127.9 ± 17.7 to 125.0 ± 16.3 mm Hg) and central arterial blood pressures were significantly decreased after an oral glucose load (118.9 ± 17.9 to 112.8 ± 16.8 mm Hg). The reduction in blood pressure was greater in central (7.3 ± 11.5 mm Hg) than in brachial blood pressure measurements (3.4 ± 11.3 mm Hg, P < .001). Extreme blood pressure reduction (>20 mm Hg) was recorded more frequently in central (n = 43, 12.3%) than brachial blood pressure measurements (n = 20, 5.6%).An oral glucose load decreases both central and brachial systolic blood pressure, with more pronounced effects on central blood pressure. Postprandial reductions in blood perfusion of the important organs such as the brain may be underestimated when postprandial BP reduction is assessed using brachial BP measurements.

Oxidative Stress is Closely Associated with Increased Arterial Stiffness, Especially in Aged Male Smokers without Previous Cardiovascular Events: A Cross-Sectional Study

Aim: Cigarette smoking is one of the major risk factors for cardiovascular diseases and induces deleterious vascular damage. Oxidative stress is involved in vascular inflammation, the process of atherosclerosis. The purpose of the present study was to investigate whether the effects of oxidative stress on the arterial wall differ between smokers and non-smokers.

Methods: Male smokers and non-smokers without physical deconditioning who visited Enshu hospital for an annual physical check-up were enrolled in the study. To assess oxidative stress, serum levels of derivative reactive oxygen metabolites (d-ROM) were measured. The radial augmentation index (RAI) was measured using an automated device and was used as an index for arterial stiffness.

Results: Univariate and multivariate linear regression analysis showed that RAI was independently associated with d-ROM levels only in smokers. Moreover, RAI was significantly higher in smokers than in non-smokers. Logistic regression analysis with the endpoint of a higher RAI than the mean revealed that older age (> 65 years), hypertension, and smoking were independently associated with higher RAI. Similarly, logistic regression analysis with the endpoint of higher d-ROM levels than the mean showed that older age and smoking were independently associated with higher d-ROM levels.

Conclusions: Increased RAI is significantly associated with smoking and, in smokers, with increased d-ROM levels. These results suggest that the effects of oxidative stress on arterial properties differ between smokers and non-smokers and that oxidative stress is closely associated with arterial stiffness, especially in smokers.

A systematic review on the effect of acute aerobic exercise on arterial stiffness reveals a differential response in the upper and lower arterial segments

The objective of this systematic review was to provide insight into the controversy that still abounds as to the impact of acute aerobic exercise on immediate changes in arterial stiffness. Electronic databases were searched to identify articles assessing the effects of acute aerobic exercise on parameters of arterial stiffness. Eligible studies included arterial stiffness measurements before and after acute aerobic exercise in healthy human subjects. Forty-three studies were included. The effect of acute aerobic exercise on arterial stiffness was found to be dependent on the anatomical segment assessed, and on the timing of the measurement post-exercise. Arterial stiffness of the central and upper body peripheral arterial segments was found to be increased relative to resting values immediately post-exercise (0-5 min), whereas, thereafter (>5 min), decreased to a level at or below resting values. In the lower limbs, proximal to the primary working muscles, arterial stiffness decreased immediately post-exercise (0-5 min), which persisted into the recovery period post-exercise (>5 min). This systematic review reveals a differential response to acute exercise in the lower and upper/central arterial segments in healthy adult subjects. We further showed that the effect of acute aerobic exercise on arterial stiffness is dependent on the timing of the measurements post-exercise. Therefore, when assessing the overall impact of exercise on arterial stiffness, it is important to consider the arterial segment being analyzed and measurement time point, as failure to contextualize the measurement can lead to conflicting results and misleading clinical inferences.

Cardiovascular Responses to an Isometric Handgrip Exercise in Females with Prehypertension

BACKGROUND

Hypertensive individuals are known to exhibit greater increases in blood pressure during an isometric handgrip exercise (IHE) than their normotensive counterparts.

AIM

This study tests the hypothesis that, compared to normotensive individuals, prehypertensive individuals exhibit an exaggerated response to IHE.

MATERIALS AND METHODS

In this study, the effects of IHE were compared in matched prehypertensive vs. normotensive healthy African-American females. Six healthy young adult African-American female university students were screened in a physician's office for blood pressure in the range of prehypertension, systolic blood pressure (SBP) 120-139 mmHg and diastolic blood pressure (DBP) 80-89 mmHg. Six young adult African-American women were also recruited to serve as a healthy normotensive control group with SBP ≤119 mmHg and DBP ≤79 mmHg. Cardiovascular fitness was determined by peak oxygen uptake (VO2 peak) measured during a progressive exercise test.

RESULTS

During the handgrip exercise, the prehypertensive group exhibited greater increases in SBP (from 139 ± 6 to 205 ± 11 mmHg, +48%) than the controls (from 132 ± 3 to 145 ± 3 mmHg, +10%); intergroup difference P < 0.001. The prehypertensive group also exhibited greater increases in DBP (from 77 ± 2 to 112 ± 5 mmHg, +46%) compared to the controls (from 72 ± 3 to 78 ± 4 mmHg, +8%); intergroup difference P < 0.001. The increase in systemic vascular resistance was also greater in the prehypertensive group (from 1713 ± 91 to 2807 ± 370 dyne.s.cm(-5), +64%) than in the controls (from 1668 ± 80 to 1812 ± 169 dyne.s.cm(-5), +9%); intergroup difference P < 0.05.

CONCLUSION

These results suggest that blood pressure measurements performed during IHE may be a useful screening tool in evaluating prehypertensive individuals for antihypertensive treatments.

Hybrid System for Ex Vivo Hemorheological and Hemodynamic Analysis: A Feasibility Study

Precise measurement of biophysical properties is important to understand the relation between these properties and the outbreak of cardiovascular diseases (CVDs). However, a systematic measurement for these biophysical parameters under in vivo conditions is nearly impossible because of complex vessel shape and limited practicality. In vitro measurements can provide more biophysical information, but in vitro exposure changes hemorheological properties. In this study, a hybrid system composed of an ultrasound system and microfluidic device is proposed for monitoring hemorheological and hemodynamic properties under more reasonable experimental conditions. Biophysical properties including RBC aggregation, viscosity, velocity, and pressure of blood flows are simultaneously measured under various conditions to demonstrate the feasibility and performance of this measurement system. The proposed technique is applied to a rat extracorporeal loop which connects the aorta and jugular vein directly. As a result, the proposed system is found to measure biophysical parameters reasonably without blood collection from the rat and provided more detailed information. This hybrid system, combining ultrasound imaging and microfluidic techniques to ex vivo animal models, would be useful for monitoring the variations of biophysical properties induced by chemical agents. It can be used to understand the relation between biophysical parameters and CVDs.