Differential arterial blood flow response of splanchnic and renal organs during low-intensity cycling exercise in women

Hepato-splanchnic fluxes during exercise in patients with cirrhosis-a pilot study

In cirrhotic patients, compromised hepatocyte function combined with disturbed hepatic blood flow could affect hepato-splanchnic substrate and metabolite fluxes and exacerbate fatigue during exercise. Eight cirrhotic patients performed incremental cycling trials (3 × 10 min; at light (28 [19-37] W; median with range), moderate (55 [41-69] W), and vigorous (76 [50-102] W) intensity). Heart rate increased from 68 (62-74) at rest to 95 (90-100), 114 (108-120), and 140 (134-146) beats/min (P < 0.05), respectively. The hepatic blood flow, as determined by constant infusion of indocyanine green with arterial and hepatic venous sampling, declined from 1.01 (0.75-1.27) to 0.69 (0.47-0.91) L/min (P < 0.05). Hepatic glucose output increased from 0.6 (0.5-0.7) to 1.5 (1.3-1.7) mmol/min, while arterial lactate increased from 0.8 (0.7-0.9) to 9.0 (8.1-9.9) mmol/L (P < 0.05) despite a rise in hepatic lactate uptake. Arterial ammonia increased in parallel to lactate from 47.3 (40.1-54.5) to 144.4 (120.5-168.3) μmol/L (P < 0.05), although hepatic ammonia uptake increased from 19.5 (12.4-26.6) to 69.5 (46.5-92.5) μmol/min (P < 0.05). Among the 14 amino acids measured, glutamate was released in the liver, while the uptake of free fatty acids decreased. During exercise at relatively low workloads, arterial lactate and ammonia levels were comparable to those seen in healthy subjects at higher workloads, while euglycemia was maintained due to sufficient hepatic glucose production. The accumulation of lactate and ammonia may contribute to exercise intolerance in patients with cirrhosis.

Aging in females has minimal effect on changes in celiac artery blood flow during dynamic light-intensity exercise

Blood flow to the active muscles and arterial blood pressure (ABP) increase during dynamic exercise, whereas blood flow to inactive organs (e.g., splanchnic organs and inactive limbs) declines. Aging leads to exaggerated ABP responses to exercise in females, but whether this is related to greater splanchnic vasoconstriction is unknown. This study sought to clarify the effect of aging in females on celiac artery blood flow during dynamic light-intensity exercise. Twelve healthy young females (YF: 20 ± 2 yr, mean ± SD) and 12 healthy older females (OF: 71 ± 4 yr) performed dynamic knee-extension and knee-flexion exercises at 30% of heart rate reserve for 4 min. The absolute changes from baseline (Δ) for mean arterial blood pressure (MAP), celiac artery mean blood flow (celMBF), and celiac vascular conductance (celVC) during exercise were calculated. ABP was measured using an automated sphygmomanometer, and celMBF was recorded by Doppler ultrasonography. The increase in MAP during exercise was greater in OF than in YF (YF: +14 ± 7 mmHg, OF: +24 ± 13 mmHg, P = 0.028). The celMBF decreased during exercise in both groups, but there was no significant difference in the response between YF and OF (YF: -93.0 ± 66.1 mL/min, OF: -89.6 ± 64.0 mL/min, P = 0.951). The celVC also decreased during exercise and remained lower than baseline during exercise. However, the response was not different between YF and OF (YF: -1.8 ± 1.0 mL/min/mmHg, OF: -1.5 ± 0.6 mL/min/mmHg, P = 0.517). These results demonstrate that aging in females has minimal influence on splanchnic artery hemodynamic responses during dynamic light-intensity exercise, suggesting that exaggerated ABP responses during exercise in OF are not due to greater splanchnic vasoconstriction.NEW & NOTEWORTHY During exercise, the splanchnic arteries vasoconstrict, contributing to blood flow redistribution and the blood pressure response. Blood pressure responses to exercise are exaggerated with aging in females; however, the physiological mechanism responsible has not been clarified. We show that celiac artery blood flow changes during light-intensity dynamic exercise do not differ with age in females. This indicates the exaggerated blood pressure to exercise with aging is likely not due to a difference in splanchnic vasoconstriction.

Effects of sex and menstrual cycle phase on celiac artery blood flow during dynamic moderate-intensity leg exercise in young individuals

The purpose of this study was to clarify the effect of sex and menstrual cycle phase on celiac artery blood flow during dynamic exercise in healthy young humans. Eleven healthy young females (21 ± 2 yr, means ± SD) and 10 males (23 ± 3 yr) performed dynamic knee-extension and -flexion exercises at 30% of heart rate reserve for 4 min. The percent changes from baseline (Δ) for mean arterial blood pressure (MAP), mean blood flow (celMBF) in the celiac artery, and celiac vascular conductance (celVC) during exercise were calculated. Arterial blood pressure was measured using an automated sphygmomanometer, and celiac artery blood flow was recorded by Doppler ultrasonography. Female subjects performed the exercise test in the early follicular phase (EF) and in the midluteal phase (ML) of their menstrual cycle. The increase in MAP during exercise was not significantly (P > 0.05) different between sexes or between menstrual cycle phases (ΔMAP, EF in females: +16.6 ± 6.4%, ML in females: +20.2 ± 11.7%, and males: +19.9 ± 12.2%). The celMBF decreased during exercise in each group, but the response was not significantly (P > 0.05) different between sexes or between menstrual cycle phases (ΔcelMBF, EF in females: -24.6 ± 15.5%, ML in females: -25.2 ± 18.7%, and males: -29.2 ± 4.0%). The celVC decreased during dynamic exercise in each group, with no significant (P > 0.05) difference in the responses between sexes or between menstrual cycle phases (ΔcelVC, EF in females: -38.3 ± 15.0%, ML in females: -41.5 ± 19.1%, and males: -43.4 ± 7.2%). These results suggest that sex and menstrual cycle phase have minimal influence on hemodynamic responses in the splanchnic artery during dynamic moderate-intensity exercise in young healthy individuals.NEW & NOTEWORTHY During dynamic exercise, splanchnic organ blood flow is reduced from resting values. Whether sex and menstrual cycle phase influence splanchnic blood flow responses during exercise remains unknown. We show that the decrease in celiac artery blood flow during dynamic leg exercise does not differ between young females and males or between menstrual cycle phases. In young individuals, sex and menstrual cycle have minimal influence on splanchnic artery hemodynamic responses during dynamic moderate-intensity leg exercise.

Blood pressure and celiac artery blood flow responses during increased inspiratory muscle work in healthy males

NEW FINDINGS

What is the central question of this study? Increased work of breathing and the accumulation of metabolites have neural and cardiovascular consequences through a respiratory muscle-induced metaboreflex. The influence of respiratory muscle-induced metaboreflex on splanchnic blood flow in humans remains unknown. What is the main finding and its importance? Celiac artery blood flow decreased gradually during inspiratory resistive breathing, accompanied by a progressive increase in arterial blood pressure. It is possible that respiratory muscle-induced metaboreflex contributes to splanchnic blood flow regulation.

ABSTRACT

The purpose of this study was to clarify the effect of increasing inspiratory muscle work on celiac artery blood flow. Eleven healthy young males completed the study. The subjects performed voluntary hyperventilation with or without inspiratory resistance (loading or non-loading trial) (tidal volume of 40% of vital capacity and breathing frequency of 20 breaths/min). The loading trial was conducted with inspiratory resistance (40% of maximal inspiratory pressure) and was terminated when the subjects could no longer maintain the target tidal volume or breathing frequency. The non-loading trial was conducted without inspiratory resistance and was the same length as the loading trial. Arterial blood pressure was recorded using finger photoplethysmography, and celiac artery blood flow was measured using Doppler ultrasound. Mean arterial blood pressure (MAP) increased gradually during the loading trial (89.0±10.8 to 103.9±17.3 mmHg, mean ± SD) but not in the non-loading trial (88.7±5.9 to 90.4±9.9 mmHg). Celiac artery blood flow and celiac vascular conductance decreased gradually during the loading trial (601.2±155.7 to 482.6±149.5 mL/min and 6.9±2.2 to 4.8±1.7 mL/min/mmHg, respectively), but were unchanged in the non-loading trial (630.7±157.1 to 635.6±195.7 mL/min and 7.1±1.8 to 7.2±2.9 mL/min/mmHg, respectively). These results show that increasing inspiratory muscle work affects splanchnic blood flow regulation, and we suggest that it is possibly mediated by the inspiratory muscle-induced metaboreflex. This article is protected by copyright. All rights reserved.

Effects of cooling or warming of the distal upper limb on skin vascular conductance and brachial artery shear profiles during cycling exercise

The relative influence of skin vascular conductance in glabrous (G; palm) and non-glabrous (NG; dorsal and forearm) regions to upstream brachial artery-shear stress (BA-SS) profile are unknown. This study aimed to elucidate the effects of G and/or NG skin vascular conductance (VC), which were modulated by warming or cooling manipulation, on BA-shear rate (SR, an estimate of SS) during cycling exercise. Seven healthy subjects performed 60-min exercise. Between 20 and 50 min of the exercise, the NG+G or G skin region were warmed to 42°C or cooled to 15°C using a water bath. Throughout the protocol, diameter and blood velocity in BA and skin VCs in forearm and palm were measured. All measurements showed that a steady-state response was reached after 20 min of exercise. Subsequently, during cooling manipulation, forearm VC was significantly decreased, and the concomitant BA-SR profile was revealed (primarily characterized by decreased antegrade SR and increased retrograde SR) in the NG+G. Such changes were not observed in G alone. During warming manipulation, forearm VC and mean BA-SR significantly increased only in the NG+G. In conclusion, vascular response in NG skin possibly plays a major role in the modulation of BA-SS profile during cycling exercise.

Role of Regular Physical Exercise in Tumor Vasculature: Favorable Modulator of Tumor Milieu

The tumor vessel network has been investigated as a precursor of an inhospitable tumor microenvironment, including its repercussions in tumor perfusion, oxygenation, interstitial fluid pressure, pH, and immune response. Dysfunctional tumor vasculature leads to the extravasation of blood to the interstitial space, hindering proper perfusion and causing interstitial hypertension. Consequently, the inadequate delivery of oxygen and clearance of by-products of metabolism promote the development of intratumoral hypoxia and acidification, hampering the action of immune cells and resulting in more aggressive tumors. Thus, pharmacological strategies targeting tumor vasculature were developed, but the overall outcome was not satisfactory due to its transient nature and the higher risk of hypoxia and metastasis. Therefore, physical exercise emerged as a potential favorable modulator of tumor vasculature, improving intratumoral vascularization and perfusion. Indeed, it seems that regular exercise practice is associated with lasting tumor vascular maturity, reduced vascular resistance, and increased vascular conductance. Higher vascular conductance reduces intratumoral hypoxia and increases the accessibility of circulating immune cells to the tumor milieu, inhibiting tumor development and improving cancer treatment. The present paper describes the implications of abnormal vasculature on the tumor microenvironment and the underlying mechanisms promoted by regular physical exercise for the re-establishment of more physiological tumor vasculature.

Facial Blood Flow Responses to Dynamic Exercise

We reported previously that a static handgrip exercise evoked regional differences in the facial blood flow. The present study examined whether regional differences in facial blood flow are also evoked during dynamic exercise. Facial blood flow was measured by laser speckle flowgraphy during 15 min of cycling exercise at heart rates of 120 bpm, 140 bpm and 160 bpm in 12 subjects. The facial vascular conductance index was calculated from the blood flow and mean arterial pressure. The regional blood flow and conductance index values were determined in the forehead, eyelid, nose, cheek, ear and lip. One-way ANOVA and Tukey's post-hoc test were used to examine effects of exercise intensity and target regions. The blood flow and conductance index in skin areas increased significantly with the exercise intensity. The blood flow and conductance index in the lip increased significantly at 120 bpm and 140 bpm compared to the control, while the values in the lip at 160 bpm did not change from the control values. These results suggest that the blood flow in facial skin areas, not in the lip, responds similarly to dynamic exercise, in contrast to the responses to static exercise.

Effects of Unilateral Arm Warming or Cooling on the Modulation of Brachial Artery Shear Stress and Endothelial Function during Leg Exercise in Humans

Aim: We examined the effect of modulating the shear stress (SS) profile using forearm warming and cooling on subsequent endothelial function in the brachial artery (BA) during exercise.

Methods: Twelve healthy young subjects immersed their right forearm in water (15°C or 42°C) during a leg cycling exercise at 120–130 bpm for 60 min. The same exercise without water immersion served as a control. The BA diameter and blood velocity were simultaneously recorded using Doppler ultrasonography to evaluate the antegrade, retrograde, and mean shear rates (SRs, an estimate of SS) before, during, and after exercise. The endothelial function in the right BA was evaluated using flow-mediated dilation (FMD) (%) using two-dimensional high-resolution ultrasonography before (baseline) and 15 and 60 min after exercise.

Results: During exercise, compared with the control trial, higher antegrade and mean SRs and lower retrograde SRs were observed in the warm trial; conversely, lower antegrade and mean SRs and higher retrograde SRs were observed in the cool trial. At 15 min postexercise, no significant change was observed in the FMD from baseline in the warm (Δ%FMD: +1.6%, tendency to increase; p = 0.08) and control trials (Δ %FMD: +1.1%). However, in the cool trial, the postexercise FMD at 60 min decreased from baseline (Δ%FMD: −2.7%) and was lower than that of the warm (Δ%FMD: +1.5%) and control (Δ%FMD: +1.2%) trials. Accumulated changes in each SR during and after exercise were significantly correlated with postexercise FMD changes.

Conclusion: Modulation of shear profiles in the BA during exercise appears to be associated with subsequent endothelial function.

Effect of sinusoidal leg cycling exercise period on brachial artery blood flow dynamics in humans

Purpose

To quantify the dynamics of blood flow in brachial artery (BF-BA) in response to sinusoidal work rate (WR) leg cycling exercises of 2-, 4-, and 6-min periods and to examine their relationship with the forearm skin blood flow (SBF).

Methods

Seven healthy young male subjects performed upright leg ergometer exercise with a constant WR (mean sinusoidal WR) for 30 min followed by sinusoidal WR exercise of three different periods (number of repetitions): 2 min (7), 4 min (4), and 6 min (3). The WR fluctuated from 20 W to a peak WR corresponding to 60% peak oxygen uptake (VO₂). We continuously measured pulmonary gas exchange, heart rate (HR), blood velocity and cross-sectional area of BA, and forearm SBF and sweating rate (SR).

Results

All variables were followed by the sinusoidal WR. The phases of the variables for gas exchange and central circulation, such as VO₂ and HR with WR forcing were similar (e.g., phase shift (θ) in HR [°]: 2 min, 60 ± 7; 4 min, 45 ± 10; 6 min, 37 ± 8; mean ± SD) to previous study results, that is, a longer period showed a shorter θ and larger amplitude of responses. Contrarily, the BF-BA response showed anti-phase (approximately 180°) regardless of the period, whereas the θ of forearm SBF and SR were similar to gas exchange and central circulation.

Conclusions

Inactive limb BF-BA during sinusoidal leg cycling exercise was out of phase relative to the regulation of O₂-delivery to active muscles and thermoregulation. The response of BF-BA seems to not always reflect the response of forearm SBF in the downstream area.

Effect of exercise intensity on renal blood flow in patients with chronic kidney disease stage 2

BACKGROUND

Acute exercise reduces renal blood flow (RBF). However, the effect of exercise intensity on RBF in patients with chronic kidney disease (CKD) stage 2 is not known. We investigated the association between RBF and exercise intensity in patients with CKD stage 2 using pulsed Doppler ultrasonography.

METHODS

Eight men with CKD stage 2 (cystatin C-based estimate of glomerular filtration rate: 60-89 ml/min/1.73 m²) participated in this study. Using a bicycle ergometer, participants undertook a maximal graded exercise test (MGET) (experiment 1) and a multi-stage exercise test (experiment 2) to determine their lactate threshold (LT). Participants undertook a multi-stage exercise test for 4-min each. Workloads of 60%, 80%, 100%, 120%, and 140% of LT were used in experiment 3. RBF was measured by pulsed Doppler ultrasonography at rest, immediately after exercise, and 1 h after exercise in experiment 1, and at rest and immediately after each exercise bout in experiment 3.

RESULTS

Renal blood flow after the MGET was 52% lower than at rest, and did not recover as well as after the exercise test. Cross-sectional area (CSA) was significantly lower after graded exercise. RBF tended to be lower at 100% of LT and was significantly lower at 120% of LT. CSA was significantly lower at 100% of LT.

CONCLUSIONS

Renal blood flow does not change during exercise until the LT is reached. These findings may assist in making appropriate exercise recommendations to patients with CKD stage 2.

Brachial artery blood flow dynamics during sinusoidal leg cycling exercise in humans

To explore the control of the peripheral circulation of a nonworking upper limb during leg cycling exercise, blood flow (BF) dynamics in the brachial artery (BA) were determined using a sinusoidal work rate (WR) exercise. Ten healthy subjects performed upright leg cycling exercise at a constant WR for 30 min, followed by 16 min of sinusoidal WR consisting of 4‐min periods of WR fluctuating between a minimum output of 20 W and a maximum output corresponding to ventilatory threshold (VT). Throughout the protocol, pulmonary gas exchange, heart rate (HR), mean arterial blood pressure (MAP), blood velocity (BV), and cross‐sectional area of the BA, forearm skin BF (SBF), and sweating rate (SR) were measured. Each variable was fitted to a sinusoidal model with phase shift (θ) and amplitude (A). Nearly all variables closely fit a sinusoidal model. Variables relating to oxygen transport, such as VO₂ and HR, followed the sinusoidal WR pattern with certain delays (θ: VO₂; 51.4 ± 4.0°, HR; 41.8 ± 5.4°, mean ± SD). Conversely, BF response in the BA was approximately in antiphase (175.1 ± 28.9°) with a relatively large A, whereas the phase of forearm SBF was dissimilar (65.8 ± 35.9°). Thus, the change of BF through a conduit artery to the nonworking upper limb appears to be the reverse when WR fluctuates during sinusoidal leg exercise, and it appears unlikely that this could be ascribed exclusively to altering the downstream circulation to forearm skin.

Baroreflex and neurovascular responses to skeletal muscle mechanoreflex activation in humans: an exercise in integrative physiology

Cardiovascular adjustments to exercise resulting in increased blood pressure (BP) and heart rate (HR) occur in response to activation of several neural mechanisms: the exercise pressor reflex, central command, and the arterial baroreflex. Neural inputs from these feedback and feedforward mechanisms integrate in the cardiovascular control centers in the brain stem and modulate sympathetic and parasympathetic neural outflow, resulting in the increased BP and HR observed during exercise. Another specific consequence of the central neural integration of these inputs during exercise is increased sympathetic neural outflow directed to the kidneys, causing renal vasoconstriction, a key reflex mechanism involved in blood flow redistribution during increased skeletal muscle work. Studies in humans have shown that muscle mechanoreflex activation inhibits cardiac vagal outflow, decreasing the sensitivity of baroreflex control of HR. Metabolite sensitization of muscle mechanoreceptors can lead to reduced sensitivity of baroreflex control of HR, with thromboxane being one of the metabolites involved, via greater inhibition of cardiac vagal outflow without affecting baroreflex control of BP or baroreflex resetting. Muscle mechanoreflex activation appears to play a predominant role in causing renal vasoconstriction, both in isolation and in the presence of local metabolites. Limited investigations in older adults and patients with cardiovascular-related disease have provided some insight into how the influence of muscle mechanoreflex activation on baroreflex function and renal vasoconstriction is altered in these populations. However, future research is warranted to better elucidate the specific effect of muscle mechanoreflex activation on baroreflex and neurovascular responses with aging and cardiovascular-related disease.

Muscle mechanoreflex activation via passive calf stretch causes renal vasoconstriction in healthy humans

Reflex renal vasoconstriction occurs during exercise, and renal vasoconstriction in response to upper-limb muscle mechanoreflex activation has been documented. However, the renal vasoconstrictor response to muscle mechanoreflex activation originating from lower limbs, with and without local metabolite accumulation, has not been assessed. Eleven healthy young subjects (26 ± 1 yr; 5 men) underwent two trials involving 3-min passive calf muscle stretch (mechanoreflex) during 7.5-min lower-limb circulatory occlusion (CO). In one trial, 1.5-min 70% maximal voluntary contraction isometric calf exercise preceded CO to accumulate metabolites during CO and stretch (mechanoreflex and metaboreflex; 70% trial). A control trial involved no exercise before CO (mechanoreflex alone; 0% trial). Beat-to-beat renal blood flow velocity (RBFV; Doppler ultrasound), mean arterial blood pressure (MAP; photoplethysmographic finger cuff), and heart rate (electrocardiogram) were recorded. Renal vascular resistance (RVR), an index of renal vasoconstriction, was calculated as MAP/RBFV. All baseline cardiovascular variables were similar between trials. Stretch increased RVR and decreased RBFV in both trials (change from CO with stretch: RVR - 0% trial = Δ 10 ± 2%, 70% trial = Δ 7 ± 3%; RBFV - 0% trial = Δ -3.8 ± 1.1 cm/s, 70% trial = Δ -2.7 ± 1.5 cm/s; P < 0.05 for RVR and RBFV). These stretch-induced changes were of similar magnitudes in both trials, e.g., with and without local metabolite accumulation, as well as when thromboxane production was inhibited. These findings suggest that muscle mechanoreflex activation via passive calf stretch causes renal vasoconstriction, with and without muscle metaboreflex activation, in healthy humans.

Systematic review: the impact of exercise on mesenteric blood flow and its implication for preoperative rehabilitation

BACKGROUND

Exercise in the preoperative period, or prehabilitation, continues to evolve as an important tool in optimising patients awaiting major intra-abdominal surgery. It has been shown to reduce rates of post-operative morbidity and length of hospital stay. The mechanism by which this is achieved remains poorly understood. Adaptations in mesenteric flow in response to exercise may play a role in improving post-operative recovery by reducing rates of ileus and anastomotic leak.

AIMS

To systematically review the existing literature to clarify the impact of exercise on mesenteric arterial blood flow using Doppler ultrasound.

METHODS

PubMed, EMBASE and the Cochrane library were systematically searched to identify clinical trials using Doppler ultrasound to investigate the effect of exercise on flow through the superior mesenteric artery (SMA). Data were extracted including participant characteristics, frequency, intensity, timing and type of exercise and the effect on SMA flow. The quality of each study was assessed using the Downs and Black checklist.

RESULTS

Sixteen studies, comprising 305 participants in total, were included. Methodological quality was generally poor. Healthy volunteers were used in twelve studies. SMA flow was found to be reduced in response to exercise in twelve studies, increased in one and unchanged in two studies. Clinical heterogeneity precluded a meta-analysis.

CONCLUSION

The weight of evidence suggests that superior mesenteric arterial flow is reduced immediately following exercise. Differences in frequency, intensity, timing and type of exercise make a consensus difficult. Further studies are warranted to provide a definitive understanding of the impact of exercise on mesenteric flow.

Cardiovascular control during whole body exercise

It has been considered whether during whole body exercise the increase in cardiac output is large enough to support skeletal muscle blood flow. This review addresses four lines of evidence for a flow limitation to skeletal muscles during whole body exercise. First, even though during exercise the blood flow achieved by the arms is lower than that achieved by the legs (∼160 vs. ∼385 ml·min(-1)·100 g(-1)), the muscle mass that can be perfused with such flow is limited by the capacity to increase cardiac output (42 l/min, highest recorded value). Secondly, activation of the exercise pressor reflex during fatiguing work with one muscle group limits flow to other muscle groups. Another line of evidence comes from evaluation of regional blood flow during exercise where there is a discrepancy between flow to a muscle group when it is working exclusively and when it works together with other muscles. Finally, regulation of peripheral resistance by sympathetic vasoconstriction in active muscles by the arterial baroreflex is critical for blood pressure regulation during exercise. Together, these findings indicate that during whole body exercise muscle blood flow is subordinate to the control of blood pressure.

Temporal assessment of pancreatic blood flow and perfusion following secretin stimulation using noninvasive MRI

PURPOSE

To dynamically quantify pancreatic perfusion and flow within the arteries supplying the pancreas in response to secretin stimulation.

MATERIALS AND METHODS

Twelve healthy male subjects were scanned at 1.5T with arterial spin labeling to measure tissue perfusion and phase contrast magnetic resonance imaging (MRI) to measure vessel flow. Superior mesenteric (SMA), gastroduodenal (GDA), common hepatic (HA), and splenic (SA) arterial flow and pancreatic perfusion were serially measured for 50 minutes following 1 IU/kg intravenous secretin. The significance of differences between timepoints was tested using a repeated measures one-way analysis of variance (ANOVA).

RESULTS

Baseline blood flow (mean ± SEM or median [IQR]) for SMA, HA, SA, and GDA was 7.6 ± 1.3, 4.0 ± 0.5, 8.2 ± 0.8, and 0.9 (0.8-1.4) ml/s, respectively. Baseline pancreatic perfusion was 200 ± 25 ml/100g/min. Blood flow increased in the SMA (234%, P < 0.0001) and GDA (155%, P = 0.015) immediately after secretin injection. Reduced HA blood flow was observed after 10 minutes (P = 0.066) with no change in SA flow (P = 0.533). Increased pancreatic perfusion was maintained for 40 minutes after injection with a maximal increase at 5 minutes (16.8%, P = 0.025).

CONCLUSION

Intravenous secretin resulted in significant temporal changes in pancreatic perfusion and arterial blood flow.

Acute responses of regional vascular conductance to oral ingestion of fructose in healthy young humans

Background

Recently, it was reported in healthy young subjects that fructose containing drinks increased blood pressure acutely, without any apparent change in total vascular conductance (TVC). However, because it is well known that the splanchnic vasculature is dilated by oral fructose ingestion, it is assumed to be the concomitant vasoconstriction in other peripheral region(s) that is responsible for this finding. Thus, the purpose of this study was to determine the acute response of regional VC to oral fructose ingestion in young healthy humans.

Results

In 12 healthy young subjects, mean arterial blood pressure (MAP), heart rate, cardiac output, and blood flow (BF) in the superior mesenteric (SMA), brachial (BA), and popliteal (PA) arteries, in addition to forearm skin BF, were measured continuously for 2 h after ingestion of 400 ml fructose solution (containing 50 g fructose). Regional VC was calculated as BF/MAP. MAP increased for 120 min after fructose ingestion without any change in TVC. While VC in the SMA was elevated after ingestion, VC in BA and PA and forearm skin decreased.

Conclusions

While TVC was apparently unchanged during the 2 h after fructose ingestion, there were coincident changes in regional VCs in the peripheral circulation, but no net change in TVC.

Peripheral circulation

Blood flow (BF) increases with increasing exercise intensity in skeletal, respiratory, and cardiac muscle. In humans during maximal exercise intensities, 85% to 90% of total cardiac output is distributed to skeletal and cardiac muscle. During exercise BF increases modestly and heterogeneously to brain and decreases in gastrointestinal, reproductive, and renal tissues and shows little to no change in skin. If the duration of exercise is sufficient to increase body/core temperature, skin BF is also increased in humans. Because blood pressure changes little during exercise, changes in distribution of BF with incremental exercise result from changes in vascular conductance. These changes in distribution of BF throughout the body contribute to decreases in mixed venous oxygen content, serve to supply adequate oxygen to the active skeletal muscles, and support metabolism of other tissues while maintaining homeostasis. This review discusses the response of the peripheral circulation of humans to acute and chronic dynamic exercise and mechanisms responsible for these responses. This is accomplished in the context of leading the reader on a tour through the peripheral circulation during dynamic exercise. During this tour, we consider what is known about how each vascular bed controls BF during exercise and how these control mechanisms are modified by chronic physical activity/exercise training. The tour ends by comparing responses of the systemic circulation to those of the pulmonary circulation relative to the effects of exercise on the regional distribution of BF and mechanisms responsible for control of resistance/conductance in the systemic and pulmonary circulations.

Peripheral and central vascular conductance influence on post-exercise hypotension

Background

Post-exercise hypotension (PEH) following prolonged dynamic exercise arises from increased total vascular conductance (TVC) via skeletal muscle vasodilation. However, arterial vasodilation of skeletal musculatures does not entirely account for the rise in TVC. The aim of the present study was to determine the contribution of vascular conductance (VC) of the legs, arms, kidneys and viscera to TVC during PEH.

Methods

Eight subjects performed a single period of cycling at 60% of heart rate (HR) reserve for 60 minutes. Blood flow in the right renal, superior mesenteric, right brachial and right femoral arteries was measured by Doppler ultrasonography in a supine position before exercise and during recovery. HR and mean arterial pressure (MAP) were measured continuously. MAP decreased significantly from approximately 25 minutes after exercise cessation compared with pre-exercise baseline. TVC significantly increased (approximately 23%; P <0.05) after exercise compared with baseline, which resulted from increased VC in the leg (approximately 33%) and arm (approximately 20%), but not in the abdomen.

Conclusion

PEH was not induced by decreased cardiac output, but by increased TVC, two-thirds of the rise in which can be attributed to increased VC in active and inactive limbs.

Review article: the pathophysiology and management of gastrointestinal symptoms during physical exercise, and the role of splanchnic blood flow

BACKGROUND

The prevalence of exercise-induced gastrointestinal (GI) symptoms has been reported up to 70%. The pathophysiology largely remains unknown.

AIM

To review the physiological and pathophysiological changes of the GI-tract during physical exercise and the management of the most common gastrointestinal symptoms.

METHODS

Search of the literature published in the English and Dutch languages using the Pubmed database to review the literature that focused on the relation between splanchnic blood flow (SBF), development of ischaemia, postischaemic endotoxinemia and motility.

RESULTS

During physical exercise, the increased activity of the sympathetic nervous system (SNS) redistributes blood flow from the splanchnic organs to the working muscles. With prolonged duration and/or intensity, the SBF may be decreased by 80% or more. Most studies point in the direction of increased SNS-activity as central driving force for reduction in SBF. A severely reduced SBF may frequently cause GI ischaemia. GI-ischaemia combined with reduced vagal activity probably triggers changes in GI-motility and GI absorption derangements. GI-symptoms during physical exercise may be prevented by lowering the exercise intensity, preventing dehydration and avoiding the ingestion of hypertonic fluids.

CONCLUSIONS

Literature on the pathophysiology of exercise-induced GI-symptoms is scarce. Increased sympathetic nervous system activity and decreased splanchnic blood flow during physical exercise seems to be the key factor in the pathogenesis of exercise-induced GI-symptoms, and this should be the target for symptom reduction.

Are splanchnic hemodynamics related to the development of gastrointestinal symptoms in Ironman triathletes? A prospective cohort study

OBJECTIVE

To determine if prerace to postrace changes in superior mesenteric artery (SMA) and coeliac artery hemodynamics were related to the development of gastrointestinal (GI) symptoms during a triathlon.

DESIGN

Prospective cohort study.

SETTING

Field study at an international Ironman Triathlon.

PARTICIPANTS

Fifty-nine Ironman triathletes of whom 59% (n = 35) reported GI symptoms (GI group) during the race and 41% (n = 24) remained asymptomatic (CON group).

ASSESSMENT OF RISK FACTORS

Prerace questionnaire (personal details, racing and training history, personal general medical history, and medication) and splanchnic hemodynamics.

MAIN OUTCOME MEASURES

Prerace and postrace measurements of splanchnic hemodynamics [artery diameter, systolic velocity, diastolic velocity, and resistive index (RI) of the SMA and coeliac artery] using duplex Doppler ultrasound.

RESULTS

There was a significant decrease in the diameter of the SMA after the race (P = 0.003) and a significant decrease in the RI of the SMA and coeliac artery (P < 0.001) in both the GI and CON groups, but there were no significant differences between the groups. The only significant risk factor for the development of GI symptoms was younger age (P = 0.041). Other risk factors, including high-intensity exercise, poorly trained athlete, and medication use, were not associated with the development of GI symptoms.

CONCLUSIONS

The hypothesis that altered blood flow is related to the development of GI symptoms in endurance athletes is not supported by the results of this study. Other mechanisms for GI symptoms associated with endurance exercise should be investigated.

Chewing and taste increase blood velocity in the celiac but not the superior mesenteric arteries

To investigate the role of chewing and taste in the meal-induced rapid increase in splanchnic blood flow, we compared the blood flow responses in the celiac artery (CA) and superior mesenteric artery (SMA) to chewing solid food with a chocolate taste (FOOD) and paraffin wax without taste (WAX). After 5 min of baseline measurement, 15 healthy subjects repeated chewing and expectorating the FOOD or WAX every 20 s for 4 min followed by 10 min of recovery measurement. We measured the mean blood velocity (MBV) in the CA and SMA. The baseline MBVs in the CA and SMA did not differ between the FOOD and WAX trials. The MBV in the CA was lower than baseline at the 1st min of chewing in both trials. It was higher than baseline at the 3rd min of FOOD chewing, whereas it did not increase during and after WAX chewing. The MBV in the CA was higher in the FOOD trial than in the WAX trial at the 3rd min of chewing and thereafter. In contrast, the MBV in the SMA did not change throughout the protocols. These results suggest that the taste of food plays a role in meal-induced hyperemia in the CA but not the SMA.