Cardiac and vasomotor components of the carotid baroreflex control of arterial blood pressure during isometric exercise in humans

Augmented sympathoexcitation slows postexercise heart rate recovery

Slow heart rate recovery following exercise may be influenced by persistent sympathoexcitation. This study examined 1) the effect of muscle metaboreflex activation (MMA) on heart rate recovery following dynamic exercise; and 2) whether the effect of MMA on heart rate recovery is reversible by reducing sympathoexcitation [baroreflex activation via phenylephrine (PE)] in canines. Twenty-two young adults completed control and MMA protocols during cycle ergometry at 110% ventilatory threshold with 5 min recovery. Heart rate recovery kinetics [tau (τ), amplitude, end-exercise, and end-recovery heart rate] and root mean square of successive differences (RMSSD) were measured. Five chronically instrumented canines completed control, MMA (50%-60% imposed reduction in hindlimb blood flow), and MMA with end-exercise PE infusion (MMA + PE) protocols during moderate exercise (6.4 km·h-1) and 3 min recovery. Heart rate recovery kinetics and MAP were measured. MAP increased during MMA versus control in canines (P < 0.001). Heart rate recovery τ was slower during MMA versus control in humans (17% slower; P = 0.011) and canines (150% slower; P = 0.002). Heart rate recovery τ was faster during MMA + PE versus MMA (40% faster; P = 0.034) and was similar to control in canines (P = 0.426). Amplitude, end-exercise, and end-recovery heart rate were similar between conditions in humans (all P ≥ 0.122) and in canines (all P ≥ 0.084). MMA decreased RMSSD in early recovery (P = 0.004). MMA-induced sympathoexcitation slows heart rate recovery and this effect is markedly attenuated with PE. Therefore, elevated sympathoexcitation via MMA impairs heart rate recovery and inhibition of this stimulus normalizes, in part, heart rate recovery.NEW & NOTEWORTHY Augmented sympathoexcitation, via muscle metaboreflex activation, functionally slows heart rate recovery in both young healthy adults and chronically instrumented canines. Furthermore, elevated sympathoexcitation corresponded with lower parasympathetic activity, as assessed by heart rate variability, during the first 3 min of recovery. Finally, sympathoinhibition, via phenylephrine infusion, normalizes heart rate recovery during muscle metaboreflex activation.

Effect of Resistance Training on Body Composition, Hemodynamic Parameters and Exercise Tolerance among Patients with Coronary Artery Disease: A Systematic Review

BACKGROUND

Effectiveness and safety of Resistance Training in treating various Cerebrovascular Disease diagnoses have drawn attention in recent years. Patients suffering with coronary artery disease should be offered individually tailored Resistance Training in their exercise regimen. Resistance Training was developed to help individuals with their functional status, mobility, physical performance, and muscle strength.

OBJECTIVE

The objective of this review was to collect, summarize and present information on the state of science focusing on usefulness, viability, safety and efficacy of Resistance Training in treating coronary artery disease and enhancing the aerobic capacity and improving overall health-related quality of life.

METHODS

The review is prepared in accordance with Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines. Searches were conducted in Cochrane Library, PubMed/MEDLINE, PEDro and Scopus database. PEDro scale was used for methodological quality assessment of included studies. Two independent reviewers determined the inclusion criteria of studies by classifying interventions based on core components, outcome measures, diagnostic population and rated the quality of evidence and strength of recommendations using GRADE criteria.

RESULTS

Total 13 studies with 1025 patients were included for the detailed analysis. Findings emphasize the importance of assessing effectiveness and safety of Resistance Training in individuals with coronary artery disease. Patient specific designed exercise programs as Resistance Training targets at enhancing patients' exercise tolerance, improves hemodynamic response and muscular strength with reduction in body fat composition.

CONCLUSION

Resistance Training is an effective exercise that should be incorporated to counteract the loss of muscle strength, muscle mass, and physiological vulnerability, as well as to combat the associated debilitating effects on physical functioning, mobility and overall independence and Quality of Life during rehabilitation of patients with coronary artery disease.

Multi-site Pulse Transit Times, Beat-to-Beat Blood Pressure, and Isovolumic Contraction Time at Rest and Under Stressors

This study investigates the beat-to-beat relationships among Pulse Transit Times (PTTs) and Pulse Arrival Times (PATs) concomitantly measured from the heart to finger, ear and forehead vascular districts, and their correlations with continuous finger blood pressure. These aspects were explored in 22 young volunteers at rest and during cold pressure test (CPT, thermal stress), handgrip (HG, isometric exercise) and cyclo-ergometer pedalling (CYC, dynamic exercise). The starting point of the PTT measures was the opening of the aortic valve detected by the seismocardiogram. Results indicate that PTTs measured at the ear, forehead and finger districts are uncorrelated each other at rest, and during CPT and HG. The stressors produced district-dependent changes in the PTT variability. Only the dynamic exercise was able to induce significant changes with respect to rest in the PTTs mean values (-40%, -36% and -17%, respectively for PTTear, PTTfore, PTTfinger,), and synchronize their modulations. Similar trends were observed in the PATs. The isovolumic contraction time decreased during the stressors application with a minimum at CYC (-25%) reflecting an augmented heart contractility. The increase in blood pressure (BP) at CPT was greater than that at CYC (137 vs. 128 mmHg), but the correlations between beat-to-beat transit times and BP were maximal at CYC (PAT showed a higher correlation than PTT; correlations were greater for systolic than for diastolic BP). This suggests that pulse transit times do not always depend directly on the beat-to-beat BP values but, under specific conditions, on other factors and mechanisms that concomitantly also influence BP.

Hemodynamic Response to Isometric Handgrip Exercise in Adults with Intellectual Disability

INTRODUCTION

Individuals with intellectual disability (ID) have an increased risk of cardiovascular disease and reduced work capacity, which could partly be explained by alterations to autonomic and hemodynamic regulation. The measurement of heart rate and blood pressure during isometric handgrip (HG) exercise, a sympathoexcitatory stimulus, is a noninvasive method to investigate autonomic and hemodynamic alterations. The purpose of this study was to assess alterations to autonomic and associated hemodynamic regulation between individuals with ID and a matched control group during isometric HG exercise.

METHODS

Individuals with ID (n = 13; 31 ± 2 yr, 27.6 ± 7.7 kg·m-2) and without ID (n = 16; 29 ± 7 yr, 24.2 ± 2.8 kg·m-2) performed 2 min of isometric HG exercise at 30% of maximal voluntary contraction (MVC) in the seated position. Blood pressure was averaged for 2 min before, during, and after HG exercise (mean arterial pressure [MAP], systolic blood pressure, and diastolic blood pressure). Heart rate variability, blood pressure variability, and baroreflex sensitivity were calculated from the continuous blood pressure and heart rate recordings.

RESULTS

Isometric HG elicited a blunted response in systolic blood pressure, diastolic blood pressure, and MAP among individuals with ID compared with individuals without ID, even after controlling for strength (MAP: rest, HG, recovery; ID: 103 ± 7, 108 ± 9, 103 ± 7; without ID: 102 ± 7, 116 ± 10, 104 ± 10 mm Hg; interaction P < 0.05). Individuals with ID also had an attenuated baroreflex sensitivity response to HG exercise compared with individuals without ID (interaction P = 0.041), but these effects were no longer significant after controlling for maximal voluntary contraction. Indices of heart rate variability and blood pressure variability were not different between groups overall or in response to HG exercise (P > 0.05).

CONCLUSIONS

Individuals with ID have a blunted hemodynamic and autonomic response to isometric HG exercise compared with individuals without ID.

Autonomic regulation of systemic inflammation in humans: A multi-center, blinded observational cohort study

OBJECTIVE

Experimental animal models demonstrate that autonomic activity regulates systemic inflammation. By contrast, human studies are limited in number and exclusively use heart rate variability (HRV) as an index of cardiac autonomic regulation. HRV measures are primarily dependent on, and need to be corrected for, heart rate. Thus, independent autonomic measures are required to confirm HRV-based findings. Here, the authors sought to replicate the findings of preceding HRV-based studies by using HRV-independent, exercise-evoked sympathetic and parasympathetic measures of cardiac autonomic regulation to examine the relationship between autonomic function and systemic inflammation.

METHODS

Sympathetic function was assessed by measuring heart rate changes during unloaded pedaling prior to onset of exercise, divided into quartiles; an anticipatory heart rate (AHRR) rise during this period is evoked by mental stress in many individuals. Parasympathetic function was assessed by heart rate recovery (HRR) 60s after finishing cardiopulmonary exercise testing, divided into quartiles. Parasympathetic dysfunction was defined by delayed heart rate recovery (HRR) ≤12.beats.min^-1, a threshold value associated with higher cardiovascular morbidity/mortality in the general population. Systemic inflammation was primarily assessed by neutrophil-lymphocyte ratio (NLR), where a ratio >4 is prognostic across several inflammatory diseases and correlates strongly with elevated plasma levels of pro-inflammatory cytokines. High-sensitivity C-reactive protein (hsCRP) was also measured.

RESULTS

In 1624 subjects (65±14y; 67.9% male), lower HRR (impaired vagal activity) was associated with progressively higher NLR (p=0.004 for trend across quartiles). Delayed HRR, recorded in 646/1624 (39.6%) subjects, was associated with neutrophil-lymphocyte ratio >4 (relative risk: 1.43 (95%CI: 1.18-1.74); P=0.0003). Similar results were found for hsCRP (p=0.045). By contrast, AHRR was not associated with NLR (relative risk: 1.24 (95%CI: 0.94-1.65); P=0.14).

CONCLUSIONS

Delayed HRR, a robust measure of parasympathetic dysfunction, is independently associated with leukocyte ratios indicative of systemic inflammation. These results further support a role for parasympathetic modulation of systemic inflammation in humans.

The effect of an acute bout of resistance exercise on carotid artery strain and strain rate

Arterial wall mechanics likely play an integral role in arterial responses to acute physiological stress. Therefore, this study aimed to determine the impact of low and moderate intensity double‐leg press exercise on common carotid artery (CCA) wall mechanics using 2D vascular strain imaging. Short‐axis CCA ultrasound images were collected in 15 healthy men (age: 21 ± 3 years; stature: 176.5 ± 6.2 cm; body mass; 80.6 ± 15.3 kg) before, during, and immediately after short‐duration isometric double‐leg press exercise at 30% and 60% of participants' one‐repetition maximum (1RM: 317 ± 72 kg). Images were analyzed for peak circumferential strain (PCS), peak systolic and diastolic strain rate (S‐SR and D‐SR), and arterial diameter. Heart rate (HR), systolic and diastolic blood pressure (SBP and DBP) were simultaneously assessed and arterial stiffness indices were calculated post hoc. A two‐way repeated measures ANOVA revealed that during isometric contraction, PCS and S‐SR decreased significantly (P < 0.01) before increasing significantly above resting levels post exercise (P < 0.05 and P < 0.01, respectively). Conversely, D‐SR was unaltered throughout the protocol (P = 0.25). No significant differences were observed between the 30% and 60% 1RM trials. Multiple regression analysis highlighted that HR, BP, and arterial diameter did not fully explain the total variance in PCS, S‐SR, and D‐SR. Acute double‐leg press exercise is therefore associated with similar transient changes in CCA wall mechanics at low and moderate intensities. CCA wall mechanics likely provide additional insight into localized intrinsic vascular wall properties beyond current measures of arterial stiffness.

Hemodynamic, Autonomic, Ventilatory, and Metabolic Alterations After Resistance Training in Patients With Coronary Artery Disease: A Randomized Controlled Trial

OBJECTIVE

The aim of this work was to evaluate the hemodynamic, autonomic, and metabolic responses during resistance and dynamic exercise before and after an 8-week resistance training program using a low-intensity (30% of 1 repetitium maximum), high-repetition (3 sets of 20 repetitions) model, added to an aerobic training program, in a coronary artery disease cohort.

DESIGN

Twenty male subjects with coronary artery disease (61.1 ± 4.7 years) were randomly assigned to a combined training group (resistance + aerobic) or aerobic training group (AG). Heart rate, stroke volume, cardiac output, minute ventilation, blood lactate, and parasympathetic modulation indices of heart rate (square root of the mean squared differences of successive RR intervals [RMSSD] and dispersion of points perpendicular to the line of identity that provides information about the instantaneous beat-to-beat variability [SD1]) were obtained before and after an 8-week RT program while performing exercise on a cycle ergometer and a 45-degree leg press.

RESULTS

Resistance training resulted in an increase in maximal and submaximal load tolerance (P < 0.01), a decreased hemodynamic response (P < 0.01), and a reduction in blood lactate in the combined training group compared to the aerobic training group during the 45-degree leg press. During exercise on a cycle ergometer, there was a decreased hemodynamic response and increased minute ventilation (P < 0.01). The 8-week RT program resulted in greater parasympathetic tone (RMSSD and SD1) and an increase in the SDNN index during exercise on a cycle ergometer and 45-degree leg press (P < 0.05).

CONCLUSIONS

An 8-week resistance training program associated with aerobic training may attenuate hemodynamic stress, and modify metabolic and autonomic responses during resistance exercise. The training program also appeared to elicit beneficial cardiovascular and autonomic effects during exercise.

Heart rate variability and blood pressure during dynamic and static exercise at similar heart rate levels

Aim was to elucidate autonomic responses to dynamic and static (isometric) exercise of the lower limbs eliciting the same moderate heart rate (HR) response. Method: 23 males performed two kinds of voluntary exercise in a supine position at similar heart rates: static exercise (SE) of the lower limbs (static leg press) and dynamic exercise (DE) of the lower limbs (cycling). Subjective effort, systolic (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP), rate pressure product (RPP) and the time between consecutive heart beats (RR-intervals) were measured. Time-domain (SDNN, RMSSD), frequency-domain (power in the low and high frequency band (LFP, HFP)) and geometric measures (SD1, SD2) as well as non-linear measures of regularity (approximate entropy (ApEn), sample entropy (SampEn) and correlation dimension D2) were calculated. Results: Although HR was similar during both exercise conditions (88±10 bpm), subjective effort, SBP, DBP, MAP and RPP were significantly enhanced during SE. HRV indicators representing overall variability (SDNN, SD 2) and vagal modulated variability (RMSSD, HFP, SD 1) were increased. LFP, thought to be modulated by both autonomic branches, tended to be higher during SE. ApEn and SampEn were decreased whereas D₂ was enhanced during SE. It can be concluded that autonomic control processes during SE and DE were qualitatively different despite similar heart rate levels. The differences were reflected by blood pressure and HRV indices. HRV-measures indicated a stronger vagal cardiac activity during SE, while blood pressure response indicated a stronger sympathetic efferent activity to the vessels. The elevated vagal cardiac activity during SE might be a response mechanism, compensating a possible co-activation of sympathetic cardiac efferents, as HR and LF/HF was similar and LFP tended to be higher. However, this conclusion must be drawn cautiously as there is no HRV-marker reflecting “pure” sympathetic cardiac activity.

Autonomic control of heart rate by metabolically sensitive skeletal muscle afferents in humans

Isolated activation of metabolically sensitive skeletal muscle afferents (muscle metaboreflex) using post-exercise ischaemia (PEI) following handgrip partially maintains exercise-induced increases in arterial blood pressure (BP) and muscle sympathetic nerve activity (SNA), while heart rate (HR) declines towards resting values. Although masking of metaboreflex-mediated increases in cardiac SNA by parasympathetic reactivation during PEI has been suggested, this has not been directly tested in humans. In nine male subjects (23 +/- 5 years) the muscle metaboreflex was activated by PEI following moderate (PEI-M) and high (PEI-H) intensity isometric handgrip performed at 25% and 40% maximum voluntary contraction, under control (no drug), parasympathetic blockade (glycopyrrolate) and beta-adrenergic blockade (metoprolol or propranalol) conditions, while beat-to-beat HR and BP were continuously measured. During control PEI-M, HR was slightly elevated from rest (+3 +/- 2 beats min(-1)); however, this HR elevation was abolished with beta-adrenergic blockade (P < 0.05 vs. control) but augmented with parasympathetic blockade (+8 +/- 2 beats min(-1), P < 0.05 vs. control and beta-adrenergic blockade). The HR elevation during control PEI-H (+9 +/- 3 beats min(-1)) was greater than with PEI-M (P < 0.05), and was also attenuated with beta-adrenergic blockade (+4 +/- 2 beats min(-1), P < 0.05 vs. control), but was unchanged with parasympathetic blockade (+9 +/- 2 beats min(-1), P > 0.05 vs. control). BP was similarly increased from rest during PEI-M and further elevated during PEI-H (P < 0.05) in all conditions. Collectively, these findings suggest that the muscle metaboreflex increases cardiac SNA during PEI in humans; however, it requires a robust muscle metaboreflex activation to offset the influence of cardiac parasympathetic reactivation on heart rate.

Transfer function characteristics of the neural and peripheral arterial baroreflex arcs at rest and during postexercise muscle ischemia in humans

Previous studies have demonstrated an increase in the arterial baroreflex (ABR) control of muscle sympathetic nerve activity (MSNA) during isolated activation of the muscle metaboreflex with postexercise muscle ischemia (PEMI). However, the increased ABR-MSNA control does not appear to manifest in an enhancement in the ABR control of arterial blood pressure (BP), suggesting alterations in the transduction of MSNA into a peripheral vascular response and a subsequent ABR-mediated change in BP. Thus we examined the operating gains of the neural and peripheral arcs of the ABR and their interactive relationship at rest and during muscle metaboreflex activation. In nine healthy subjects, graded isolation of the muscle metaboreflex was achieved by PEMI following isometric handgrip performed at 15% and 30% maximal voluntary contraction (MVC). To obtain the sensitivities of the ABR neural and peripheral arcs, the transfer function gain from BP to MSNA and MSNA to femoral vascular conductance, respectively, was analyzed. No changes from rest were observed in the ABR neural or peripheral arcs during PEMI after 15% MVC handgrip. However, PEMI following 30% MVC handgrip increased the low frequency (LF) transfer function gain between BP and MSNA (ABR neural arc; +58 +/- 28%, P = 0.036), whereas the LF gain between MSNA and femoral vascular conductance (ABR peripheral arc) was decreased from rest (-36 +/- 8%, P = 0.017). These findings suggest that during high-intensity muscle metaboreflex activation an increased ABR gain of the neural arc appears to offset an attenuation of the peripheral arc gain to help maintain the overall ABR control of systemic BP.

Carotid baroreflex testing using the neck collar device

A neck chamber device for stimulation of carotid sinus baroreceptors by changing carotid transmural pressure was first described in 1957 by Ernsting and Parry and, with several modifications, has been extensively used in a number of physiological and clinical studies. This article outlines the evolution of neck chamber devices and describes some of the advantages and limitations of the technique. We also describe the responses in healthy subjects and the changes observed in patients with some disorders affecting the autonomic nervous system.

Stroke volume decreases during mild dynamic and static exercise in supine humans

AIM

The contributions of cardiac output (CO) and total peripheral resistance to changes in arterial blood pressure are debated and differ between dynamic and static exercise. We studied the role stroke volume (SV) has in mild supine exercise.

METHODS

We investigated 10 healthy, supine volunteers by continuous measurement of heart rate (HR), mean arterial blood pressure, SV (ultrasound Doppler) and femoral beat volume (ultrasound Doppler) during both dynamic mild leg exercise and static forearm exercise. This made it possible to study CO, femoral flow (FF) and both total and femoral peripheral resistance beat-by-beat.

RESULTS

During a countdown period immediately prior to exercise, HR and mean arterial pressure increased, while SV decreased. During mild supine exercise, SV decreased by 5-8%, and most of this was explained by increased mean arterial pressure. Dynamic leg exercise doubled femoral beat volume, while static hand grip decreased femoral beat volume by 18%. FF is tightly regulated according to metabolic demand during both dynamic leg exercise and static forearm exercise.

CONCLUSION

Our three major findings are, firstly, that SV decreases during both dynamic and static mild supine exercise due to an increase in mean arterial pressure. Secondly, femoral beat volume decreases during static hand grip, but FF is unchanged due to the increase in HR. Finally, anticipatory responses to exercise are apparent prior to both dynamic and static exercise. SV changes contribute to CO changes and should be included in studies of central haemodynamics during exercise.

Effect of muscle metaboreflex activation on carotid-cardiac baroreflex function in humans

Whether the activation of metabolically sensitive skeletal muscle afferents (i.e., muscle metaboreflex) influences cardiac baroreflex responsiveness remains incompletely understood. A potential explanation for contrasting findings of previous reports may be related to differences in the magnitude of muscle metaboreflex activation utilized. Therefore, the present study was designed to investigate the influence of graded intensities of muscle metaboreflex activation on cardiac baroreflex function. In eight healthy subjects (24 +/- 1 yr), the graded isolation of the muscle metaboreflex was achieved by post-exercise ischemia (PEI) following moderate- (PEI-M) and high- (PEI-H) intensity isometric handgrip performed at 35% and 45% maximum voluntary contraction, respectively. Beat-to-beat heart rate (HR) and blood pressure were measured continuously. Rapid pulse trains of neck pressure and neck suction (+40 to -80 Torr) were applied to derive carotid baroreflex stimulus-response curves. Mean blood pressure increased significantly from rest during PEI-M (+13 +/- 3 mmHg) and was further augmented during PEI-H (+26 +/- 4 mmHg), indicating graded metaboreflex activation. However, the operating point gain and maximal gain (-0.51 +/- 0.09, -0.48 +/- 0.13, and -0.49 +/- 0.12 beats.min(-1).mmHg(-1) for rest; PEI-M and PEI-H) of the carotid-cardiac baroreflex function curve were unchanged from rest during PEI-M and PEI-H (P > 0.05 vs. rest). Furthermore, the carotid-cardiac baroreflex function curve was progressively reset rightward from rest to PEI-M to PEI-H, with no upward resetting. These findings suggest that the muscle metaboreflex contributes to the resetting of the carotid baroreflex control of HR; however, it would appear not to influence carotid-cardiac baroreflex responsiveness in humans, even with high-intensity activation during PEI.

Exercise intensity influences cardiac baroreflex function at the onset of isometric exercise in humans

We sought to examine the influence of exercise intensity on carotid baroreflex (CBR) control of heart rate (HR) and mean arterial pressure (MAP) at the onset of exercise in humans. To accomplish this, eight subjects performed multiple 1-min bouts of isometric handgrip (HG) exercise at 15, 30, 45 and 60% maximal voluntary contraction (MVC), while breathing to a metronome set at eupneic frequency. Neck suction (NS) of -60 Torr was applied for 5 s at end expiration to stimulate the CBR at rest, at the onset of HG (<1 s), and after approximately 40 s of HG. Beat-to-beat measurements of HR and MAP were recorded throughout. Cardiac responses to NS at onset of 15% (-12 +/- 2 beats/min) and 30% (-10 +/- 2 beats/min) MVC HG were similar to rest (-10 +/- 1 beats/min). However, HR responses to NS were reduced at the onset of 45% and 60% MVC HG (-6 +/- 2 and -4 +/- 1 beats/min, respectively; P < 0.001). In contrast to HR, MAP responses to NS were not different from rest at exercise onset. Furthermore, both HR and MAP responses to NS applied at approximately 40s of HG were similar to rest. In summary, CBR control of HR was transiently blunted at the immediate onset of high-intensity HG, whereas MAP responses were preserved demonstrating differential baroreflex control of HR and blood pressure at exercise onset. Collectively, these results suggest that carotid-cardiac baroreflex control is dynamically modulated throughout isometric exercise in humans, whereas carotid baroreflex regulation of blood pressure is well-maintained.

Increases in central blood volume modulate carotid baroreflex resetting during dynamic exercise in humans

We sought to determine if resetting of the carotid-vasomotor baroreflex function curve during exercise is modulated by changes in central blood volume (CBV). CBV was increased during exercise by altering: (1) subject posture (supine versus upright) and (2) pedal frequency (80 versus 60 revolutions min(-1) (r.p.m.)); while oxygen uptake ( ) was kept constant. Eight male subjects performed three exercise trials: upright cycling at 60 r.p.m. (control); supine cycling at 60 r.p.m. (SupEX) and upright cycling at 80 r.p.m. to enhance the muscle pump (80EX). During each condition, carotid baroreflex (CBR) function was determined using the rapid neck pressure (NP) and neck suction (NS) protocol. Although mean arterial pressure (MAP) was significantly elevated from rest (88 +/- 2 mmHg) during all exercise conditions (P < 0.001), the increase in MAP was lower during SupEX (94 +/- 2 mmHg) and 80EX (95 +/- 2 mmHg) compared with control (105 +/- 2 mmHg, P < 0.05). Importantly, the blood pressure responses to NP and NS were maintained around these changed operating points of MAP. However, in comparison to control, the carotid-vasomotor baroreflex function curve was relocated downward and leftward when CBV was increased during SupEX and 80EX. These alterations in CBR resetting occurred without any differences in or heart rate between the exercise conditions. Thus, increasing CBV and loading the cardiopulmonary baroreflex reduces the magnitude of exercise-induced increases in MAP and CBR resetting. These findings suggest that changes in cardiopulmonary baroreceptor load influence carotid baroreflex resetting during dynamic exercise.