Blood viscosity in broilers: influence on pulmonary hypertension syndrome

Elevation in apparent blood viscosity may enhance the pulmonary hypertension that leads to pulmonary hypertension syndrome (PHS) and ascites in fast-growing broilers. We investigated the importance of packed cell volume (PCV) and shear rate in modifying apparent viscosity of the blood from broilers assigned to normal, preascites, and ascites groups. Apparent viscosity of broiler blood increased at all shear rates as PCV increased; the increase in apparent viscosity became greater as the shear rate decreased at PCV above 0.30. At the PCV of normal broilers (0.30 or below), apparent viscosity was nearly shear rate independent, at least down to 11.25 per second, the lowest shear rate studied. Apparent viscosity, at any given PCV and shear rate, was significantly lower in the blood of birds with ascites than in normal birds; however, the relative viscosity was not different between those groups, indicating that lower plasma viscosity in the birds with PHS was responsible for the finding. The results show that the principal factor responsible for increased apparent viscosity of blood in birds with PHS is the increase in PCV. The increased resistance to flow of blood as the result of higher blood viscosity may contribute to the pulmonary hypertension.     

Influence of Procedure Parameters on Rheological Property of Semi-Solid AZ91D Magnesium Alloy

Semi-solid AZ91D magnesium alloy was investigated in isothermal steady-state condition. The influence of stirring technological parameters such as stirring temperature and shear rate to apparent viscosity of semi-solid alloy slurry was discussed. Apparent viscosity increases with stirring temperature decreases at the same shear rate. At the same stirring temperature, apparent viscosity decreases rapidly at first with shear rate increases, and then apparent viscosity decreases slowly with shear rate increases, when shear rate reaches a certain value, apparent viscosity appears tiny increase. According to the experimental data, the relation between solid volume fraction and apparent viscosity of semi-solid AZ9l D alloy at shear rate 238 s- 1 is fitted by regression method, it supplies useful data to the numerical simulation of semi-solid AZ91D alloy die casting process.     

Alar fold resection in horses: 24 cases (1979-1992)

Between 1979 and 1992, the alar folds were resected bilaterally in 22 horses and unilaterally in 2 horses. Abnormal respiratory tract noise and exercise intolerance were the primary complaints prior to surgery. Significantly (P = 0.01) more Standardbreds underwent resection of the alar folds, compared with the number of Standardbreds in the hospital population during the same period. The alar folds palpated abnormally thick in 13 horses and normal in 11 horses. Temporary dilatation of the nares with mattress sutures or clips lessened the respiratory tract noise and improved exercise tolerance in all 8 horses in which the diagnostic test was performed. Manual elevation of the alar folds reduced respiratory noise in the 11 horses evaluated. Long-term follow-up evaluation by telephone was available for 14 horses. All surgical incisions had healed cosmetically. Respiratory tract noise was decreased, and exercise tolerance improved in 10 of 14 (71%) horses. Complete charted racing information was obtained for 16 horses. Fourteen horses started their first race a mean of 118 days (range, 13 to 321 days) after surgery. The mean number of starts after surgery was 51, with 14 of 16 (88%) horses starting more than 6 times after surgery. Of the 16 horses, 8 horses raced at least 3 times before and after surgery; 4 had improved racing performance, 2 had similar performance, and 2 had decreased performance. Five Standardbreds never raced, and 1 Standardbred raced once before surgery.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of training on some metabolic changes associated with submaximal endurance exercise in the horse

The effects of prolonged cantering before and after a 10 week training programme were studied in 6 horses. Determinations were carried on on venous blood for packed cell volume, glucose, glycerol, free fatty acids, beta-hydroxybutyrate, 11-hydroxycorticosteroids, pH and pCO2. Exercise caused a slight increase in glucose, lactate and pH, a moderate rise in PCV, glycerol and free fatty acids, and a marked rise in 11-hydroxycorticosteroids. A decrease in venous pCO2 occurred and a slight but not significant decrease in beta-hydroxybutyrate. Training was found to cause no significant difference in the changes seen. However, there was a tendency for exercise to result in higher 11-hydroxycorticosteroid levels after training.     

Hemorheologic considerations in the pathogenesis of vascular occlusive events in polycythemia vera

Polycythemia vera (PV) commonly presents with vascular occlusion. Untreated patients have a poor prognosis due to the occurrence of thromboses. Treatment outcomes in PV and thrombotic events in other forms of polycythemia and in primary thrombocythemia lead to the conclusion that both raised packed cell volume (PCV) values and quantitative/qualitative platelet changes play a role in the pathogenesis of these vascular occlusive events. In vitro blood viscosity values are predominantly affected by the PCV, particularly at low shear rates and are thus high in untreated PV. Generally, under physiologic conditions blood flow is not governed by blood viscosity due to a number of factors, such as prevailing high shear rates, red cell axial migration, and adaptive vessel diameter changes. Peripheral blood flow is low in untreated PV. Whereas some untreated patients maintain adequate oxygen transport to the tissues, this may not apply in those with cardiac or local vessel disease. There is evidence that low flow rates predispose to occlusive events. Under pathologic low blood flow or static conditions, the rheologic blood changes of untreated PV, demonstrated in vitro, play a role in producing a more deleterious outcome of an occlusive event. Under blood flow conditions, red cell axial migration occurs. This leaves a plasmatic zone at the vessel wall into which platelets are dispersed and where shearing forces are maximal. These forces lead to platelet activation. Increased PCV values reduce the width of the plasmatic zone and lead to an increased possibility of platelet activation, platelet-platelet contact and platelet-vessel wall interaction, particularly when the platelet count is raised as well. These effects increase the likelihood of the initiation of thrombus formation in PV.     

Shear stress abnormalities contribute to endothelial dysfunction in hypertension but not in type II diabetes

BACKGROUND: The relative contribution of the various hemodynamic and metabolic mechanisms leading to endothelial dysfunction may be different in specific vascular diseases. Since shear stress is one of the main mechanical stimuli of endothelial cells, the aim of this study was to investigate its contribution to endothelial dysfunction in two distinct vascular diseases, hypertension and type II diabetes. SUBJECTS AND METHODS: We measured the radial artery diameter at baseline, after ischemic vasodilation and after nitroglycerin vasodilation in 16 untreated patients with high blood pressure, in 15 type II normotensive diabetic patients and in 17 healthy controls. Wall shear stress was evaluated by simultaneous measurements of whole blood viscosity and blood flow velocity. RESULTS: In diabetic patients, whole blood viscosity was significantly higher whereas wall shear stress was similar compared to controls. In hypertensive patients, whole blood viscosity was higher and wall shear stress was lower than in controls. Endothelium-dependent vasodilation was impaired in both hypertensive and diabetic patients (P < 0.01) after adjustment for age, sex, body mass index and postnitroglycerin vasodilation. When adjustments were made for maximal systolic shear stress, endothelium-dependent vasodilation remained lower in the diabetic patients (P < 0.01), but not in those with high blood pressure compared to controls. CONCLUSIONS: In hypertension, endothelium-dependent vasodilation is mainly due to a chronic decrease in shear stress (the most important physiological stimulus of the endothelial cells) with no major intrinsic endothelial cell dysfunction. In contrast, in diabetics, the lower endothelium-dependent vasodilation was not the result of an altered shear stress.     

Pharmacokinetics and pharmacodynamics of acepromazine in horses

A specific, sensitive, reverse-phase high-performance liquid chromatographic assay for acepromazine, with analytic sensitivity as low as 5 ng/ml of plasma, and electrochemical detection with an oxidation potential of 0.7 V, was used to study the pharmacokinetics of acepromazine given at a dosage of 0.15 mg/kg of body weight in horses. The relation between effect and pharmacokinetics of the drug was examined. The effects studied included those on blood pressure, pulse, PCV, measures of respiration function, and sedation. Intravenously administered doses led to a biphasic concentration decay pattern with an alpha-phase distribution half-life of < 3 minutes. The beta-phase half-life was in the range of 50 to 150 minutes. The CNS effects peaked at 20 minutes after administration, and the hemodynamic effects peaked at 100 minutes. In all horses, the most sensitive variable was the PCV, which decreased by up to 20% (P < 0.0001). Systolic, diastolic, and mean blood pressures decreased (P < 0.0001); heart rate was unchanged (P > 0.05). Neither blood gas tensions nor blood pH changed noticeably (P > 0.05). In all horses studied, acepromazine had a significant (P < 0.0001) sedative effect, as observed by posture and alertness. None of the observed pharmacodynamic effects correlated well with plasma acepromazine concentration. These effects persisted beyond the time of detectable acepromazine concentration, indicating that they might be caused by active metabolites, or that their timing could result from complex pharmacokinetic compartment influences.     

Venous dysfunction and the change of blood viscosity during head-up tilt

The precise stimulus that induces vasovagal syncope is still unclear. We have previously demonstrated that the peripheral distribution of blood volume (venous pooling) is a strong predictor of tilt induced vasovagal reaction. We hypothesized that an increase in venous pooling during tilt accentuates the measured increase in blood viscosity. This hypothesis is based on the previously demonstrated increase in venous pressure and subsequent increase in transcapillary fluid transudation during tilt. The increased blood viscosity, in turn, increases vascular shear rate, which may alter the vasoconstrictive and other cardiovascular responses to decreased preload. We measured blood viscosity (supine and tilt) in 56 patients with a history of orthostatic intolerance (37 with venous pooling [VP] and 19 without venous pooling [non-VP]). VP and non-VP were separated into subgroups based on blood pressure and heart rate response to tilt. There was a positive correlation between blood viscosity and plasma aldosterone in the supine. In the group as a whole, neither supine blood viscosity nor its increase during tilt differed between VP and non-VP. However, the tilt induced increase of blood viscosity was significant only in patients with tilt provoked tachycardia plus normal blood pressure response in VP group. We suggest that the increase of blood viscosity in this group led to the normal blood pressure response. The positive correlation between supine blood viscosity and supine plasma aldosterone indicates that the normal blood pressure response in this group possibly was via stimulation of the renin-angiotensin-aldosterone system.     

Postmortem lesions in the intercarpal ligaments of the equine midcarpal joint

OBJECTIVE: To determine the frequency of damage to the medial palmar intercarpal ligament (MPICL), and the range of sizes of the dorsomedial intercarpal ligament (DMICL) of the midcarpal joint in horses with no history of carpal joint disease. MATERIALS AND METHODS: Cadaver limbs were collected from 72 horses with no history of carpal joint disease. One hundred and forty-two midcarpal joints were dissected and the MPICL and DMICL were examined. Measurements were made with a digital micrometer. RESULTS: MPICL tearing was present in 88 of 96 joints from horses 2 years and older. Tears were predominantly of the dorsolateral bundle and complete rupture of the dorsolateral and dorsomedial bundles was not observed. Tearing was not present in foals less than 4 months of age and the severity of tearing increased significantly with age (P < 0.0001). Severity of tearing was significantly greater in racing Standardbreds than racing Thoroughbreds (P < 0.01), but there was no significant difference between racing and non-racing horses. The lateromedial thickness of the DMICL ranged from 0.4 mm to 2.6 mm in horses 2 years and older. Lateromedial thickness increased significantly with age, and was significantly greater in racing Standardbreds than racing Thoroughbreds (P < 0.01). There was no significant difference between racing and nonracing horses. CONCLUSIONS: Damage confined to the dorsolateral bundle of the MPICL is a common finding in horses over 1 year of age and is probably of little clinical significance. Complete rupture of both dorsolateral and dorsomedial bundles is uncommon in horses with no history of midcarpal joint disease. Variation in size of the DMICL is observed in horses of all ages, but is most marked in 2-year-old horses.     

L-NAME does not affect exercise-induced pulmonary hypertension in thoroughbred horses

The present study was carried out to examine the effects of nitric oxide synthase inhibition with Nomega-nitro-L-arginine methyl ester (L-NAME) on the right atrial as well as on the pulmonary arterial, capillary, and venous blood pressures of horses during rest and exercise performed at maximal heart rate (HRmax). Experiments were carried out on seven healthy, sound, exercise-trained Thoroughbred horses. Using catheter-tip manometers, with signals referenced at the point of the shoulder, we determined phasic and mean right atrial and pulmonary vascular pressures in two sets of experiments [control (no medications) and L-NAME (20 mg/kg iv given 10 min before exercise studies)]. The studies were carried out in random order 7 days apart. Measurements were made at rest and during treadmill exercise performed on a 5% uphill grade at 6, 8, and 14.2 m/s. Exercise on a 5% uphill grade at 14.2 m/s elicited HRmax and could not be sustained for >90 s. In quietly standing horses, L-NAME administration caused a significant rise in right atrial, as well as pulmonary arterial, capillary, and venous pressures. This indicates that nitric oxide synthase inhibition modifies the basal pulmonary vasomotor tone. In both treatments, exercise caused progressive significant increments in right atrial and pulmonary vascular pressures, but the values recorded in the L-NAME study were not different from those in the control study. The extent of exercise-induced tachycardia was significantly decreased in the L-NAME study at 6 and 8 m/s but not at 14.2 m/s. Thus, L-NAME administration may not modify the equine pulmonary vascular tone during exercise at HRmax. However, as indicated by a significant reduction in heart rate, L-NAME seems to modify the sympathoneurohumoral response to submaximal exercise.     

Indomethacin but not metoprolol reduces exercise-induced albumin excretion rate in type 1 diabetic patients with microalbuminuria

The effects of a single oral dose of indomethacin (1 mg kg-1) metoprolol (1.5 mg kg-1) and placebo on exercise-induced albumin excretion rate (AER) were compared in a randomized, crossover design in 14 normotensive, young Type 1 diabetes patients, nine of them with microalbuminuria (AER > 15 micrograms min-1) and five without microalbuminuria at rest. The albumin excretion rate, blood pressure, heart rate, blood glucose, and plasma concentrations of indomethacin and metoprolol were determined before and after 30 min submaximal physical exercise. In microalbuminuric patients the rise in albumin excretion rate after exercise on indomethacin (7 micrograms min-1) was lower than after placebo (29 micrograms min-1, p < 0.001) whereas the rise in albumin excretion rate with metoprolol during exercise (18 micrograms min-1) did not differ from placebo (p = 0.48), in spite of the expected less marked increase in blood pressure. In normoalbuminuric patients no significant increase in albumin excretion rate was noted by exercise in any of the treatment periods. A tendency to a linear correlation (r = -0.54, p = 0.07) was seen between the plasma concentration of indomethacin and the inhibition of exercise-induced increase in albumin excretion rate. No correlations were observed between exercise-induced changes in albumin excretion rate and systolic blood pressure, heart rate or blood glucose. In conclusion, acute indomethacin treatment, presumably through inhibition of renal prostaglandin synthesis, reduces the exercise-induced rise in albumin excretion rate in Type 1 diabetic patients with microalbuminuria.(ABSTRACT TRUNCATED AT 250 WORDS)     

Psychosocial rehabilitation for the mentally disabled: what have we learned?

To investigate the possibility of hemodilution with oxygen carrying fluid, we measured the viscosity effects of LEH which was suspended in different weight percentage of plasma expanders for different shear rates. All of LEH/Plasma expander suspensions show shear thinning flow behavior, and the viscosity of those suspensions increase with increased the weight percentage of each expander in suspensions for a fixed shear rate. Compared the viscosity data to those of human blood at 40% of hematocrit, LEH/albumin suspensions contained with 4% to 8% of albumin are the most suitable, whereas LEH/dextran (Dex) suspensions contained with 6% Dex70c is the least favorable suspension media for LEH. In point of viscosity effects, hemodilution with LEH/albumin or LEH/0.9% oxypolygelatin (Gel) may be valuable for further testing their efficacy in animal model.     

Restoration of water and electrolyte balance in horses after repeated exercise in hot and humid conditions

Nine adult riding horses performed on a treadmill a competition exercise test (CET) and 24 h later a standardised exercise test (SET) at mean temperature 28 degrees C and relative humidity 58%. Each horse performed the tests 5 times at 2 week intervals. The horses were given isotonic glucose-electrolyte solution via a nasogastric tube 30 min after the CET, except after the last trial when water was given. Blood lactate, plasma concentration of aldosterone, arginine vasopressin, protein, sodium, potassium, chloride, magnesium and calcium were measured. Heart rate at blood lactate concentration 4 mmol/l (PLa4) in the SET, plasma volume (PV) and red cell volume (CV) were determined. Mean weight loss after CET was 3.1% and did not change significantly during the study. Bodyweight loss (BWL2) before SET (-1.8% after the first trial) decreased linearly with time (P < 0.05) and was -0.8% after the fourth trial. After the fifth trial, when only water was given, the weight loss was -2.5%. PLa4 correlated significantly (P < 0.001) with BWL2 when BWL2 was greater than -1.2%. The horses acclimated to exercise in hot and humid conditions as indicated by better recovery of bodyweight, increased PV, lower peak lactate concentrations and heart rate and attenuated decrease in the concentrations of sodium and chloride. It is concluded that changes in bodyweight provide a good indication of recovery of horses after exercise in hot and humid conditions; and administration of an isotonic glucose-electrolyte rehydration solution after exercise helps to overcome dehydration better than water alone.     

Capacity for red blood cell aggregation is higher in athletic mammalian species than in sedentary species

The purpose of this study was to show that two rheological parameters, red blood cell (RBC) sedimentation rate and apparent blood viscosity at low shear rate, characterizing the degree of RBC aggregation, correlate significantly with the maximal mass-specific rate of oxygen consumption or aerobic capacity (VO2max). Comparisons were made within two groups of similarly sized athletic and sedentary species: group 1, pronghorn antelope, dog, goat, and sheep; and group 2, horse and cow. The pronghorn antelope (Antilocapra americana) is one of the most athletic mammals, and we have obtained data on the rheological properties of blood from this species for the first time. The values of apparent viscosity at hematocrit = 40% and shear rate = 0.277 s-1 measured in a rotational viscometer were 59.5, 42.6, and 9.1 cP for antelope, dog, and sheep blood, respectively, and 55.3 and 11.5 cP for horse and cow blood, respectively. The viscosity values for antelope, dog, and sheep blood can be correlated with aerobic capacity: ln viscosity = 4.48-106.3 VO2(-1)max (r2 = 0.998; P < 0.05). The values of RBC sedimentation rate at hematocrit = 40% were 12.8, 7.0, and 0 mm/h for antelope, dog, and sheep blood, respectively, and 45.3 and 0.1 mm/h for horse and cow blood, respectively. Therefore, the data showed that the athletic species exhibit a consistently higher degree of RBC aggregation than do the corresponding nonathletic species.     

Communication between the left ventricle and the right atrium in infectious endocarditis. Diagnosis using Doppler-echocardiography

OBJECTIVE: To examine regional distribution of blood flow in the brain of horses at rest and during exercise. ANIMALS: 9 clinically normal horses. PROCEDURE: Regional brain blood flow was measured using radionuclide-labeled 15-microns-diameter microspheres injected into the left ventricle, while reference blood samples were obtained from the aorta. RESULTS: At rest, cerebral cortex and caudate nuclei received significantly higher blood flow, compared with cerebral white matter. A similar perfusion heterogeneity existed in the cerebellum. In the brain stem, a gradual tapering of blood flow from thalamus-hypothalamus towards medulla was observed in standing horses. Progressive significant increases in heart rate and in aortic and right atrial pressures occurred during exercise at 8 and 13 m/s, and horses developed significant arterial hypoxemia and hypercapnia. Cerebral and cerebellar gray- to white-matter perfusion heterogeneity was maintained during exercise, indicating differential metabolic O2 needs. Despite arterial hypoxemia, hypercapnia, and hypertension, exercise did not result in significant changes in blood flow to the cerebral cortex and caudate nuclei whereas, in cerebral white matter, a significant decrease in blood flow was observed. In all cerebral tissues, vascular resistance increased during exercise, indicating autoregulation of cerebral blood flow. In the cerebellar cortex, blood flow increased significantly with strenuous exercise as vasodilation occurred. Vascular resistance in cerebellar white matter increased during exercise at 13 m/s. Blood flow in the medulla, pons, midbrain, and thalamus-hypothalamus was not significantly altered during exercise from that at rest. CONCLUSION: Despite arterial hypoxemia, hypercapnia, and hypertension, autoregulation of cerebral and cerebellar blood flow is maintained in horses during exercise.     

Pulmonary function changes after nebulised and intravenous frusemide in ventilated premature infants

AIMS: To compare the effects of a single dose of frusemide administered either intravenously or by nebulisation on pulmonary mechanics in premature infants with evolving chronic lung disease. METHODS: The effect of frusemide on pulmonary mechanics was studied at a median postnatal age of 23 (range 14-52) days in 19 premature infants at 24 to 30 weeks gestational age, who had been dependent on mechanical ventilation since birth. Frusemide (1 mg/kg/body weight) was administered, in random order, intravenously and by nebulisation, on two separate occasions 24 hours apart. Pulmonary function studies were performed before and at 30, 60, and 120 minutes after administration of frusemide. Urine was collected for six hours immediately before and for six hours after administration of frusemide. RESULTS: Nebulised frusemide increased the tidal volume 31 (SE 11.5)% and compliance 34 (SE 12)% after two hours, whereas no change in either was noted for up to two hours after intravenous frusemide administration. Neither intravenous nor nebulised frusemide had any effect on airway resistance. Six hour urine output increased from a mean (SE) of 3.3 (0.4) ml/kg/hour to 5.9 (0.8) ml/kg/hour following intravenous frusemide administration while nebulised frusemide had no effect on urine output. Urinary sodium, potassium, and chloride losses were also significantly higher after intravenous frusemide, whereas nebulised frusemide did not increase urinary electrolyte losses. CONCLUSION: Single dose nebulised frusemide improves pulmonary function in premature infants with evolving chronic lung disease without adverse effects on fluid and electrolyte balance.     

Blood viscosity and triglyceridemia. Findings using a co-axial cylindrical viscosimeter at low "shear rates"

Examination of blood viscosity at low shear rates using a co-axial cylinder viscometer showed a significant difference between the means of values observed in hypertrigliceridemic patients compared with that of control subjects. This result differs from what has been reported by most workers although generally greater shear rates have been used. Calculation of the "r" coefficient and plotting of the regression line for each shear rate showed that there is no linear correlation between blood viscosity and triglyceridaemia, whose variations occur quite independently. It is suggested that the absence of a correlation between the two parameters examined may depend on various factors, of which the most important are those pertaining to the rheological properties of red blood cells and to the structure and chemical and physical characteristics of the triglyceride molecule and of the lipoproteins and chylomicrons which transport them.     

Inhibition of transforming growth factor beta 1 induction by dietary vitamin E in unilateral ureteral obstruction in rats

OBJECTIVE: To assess the effect of incomplete, midsagittal fractures of the proximal phalanx (P1) on racing performance in Standardbreds. DESIGN: Retrospective cohort study. ANIMALS: 49 Standardbred horses admitted to the George D. Widener Hospital for Large Animals between July 1986 and December 1992 with a definitive radiographic diagnosis of an incomplete, midsagittal fracture of P1 and a known method of treatment. PROCEDURE: Performance index and racing time were compared before and after diagnosis and treatment of fracture, using ANOVA that controlled for the effects of horse, gender, age, track length, and track condition. RESULTS: Expected racing time increased by 0.7 seconds and performance index decreased by 0.7 points, although controlling for factors known to affect racing performance had a substantial impact on these results. CLINICAL IMPLICATIONS: Standardbreds with incomplete, midsagittal fractures of P1 have a favorable prognosis for return to racing; recovered horses will likely have slower racing times and decreased performance indices.     

Measurements of heart scores and heart weights in horses of two different morphic body types

Heart scores (the arithmetic mean of the QRS durations of the three bipolar limb leads for 10 cycles) and heart weights were determined from five draft type horses and five racing type horses, and evaluated for relationships between heart score and heart size within and between the two different types of horses. Horses were killed using a captive bolt gun, and actual heart weights were recorded using an electronic digital scale. The linear regression equation for heart weight versus heart score had a significant (P < 0.05) negative slope for racing types. The regression coefficients for heart weight versus heart score for draft types were not significantly (P > 0.05) different than zero. There was no significant (P > 0.05) difference found between draft and racing types. Significant (P < 0.01) differences were found between the heart ratios (heart weight as a percentage of live body weight) of racing and draft types. Heart scores were not found to be significantly (P > 0.05) different between racing and draft type horses.     

Eccentric exercise augments the cardiovascular response to static exercise

High-force eccentric exercise induces neuromuscular dysfunction and may augment the cardiovascular response to exercise. This investigation sought to determine whether changes in strength and sense of force following high-force eccentric exercise alter heart rate and blood pressure responses during isometric contractions. Subjects (4F,6M) performed 50 maximum resistance eccentric actions with one arm (ECC arm). Contractions at 10% of the ECC arm maximum were held for 7 min on two pre-exercise days. The force output perceived to be the same as 10% of the pre-exercise maximum was determined using a force matching task. This force, 35.6, 27.2, and 21.1% lower on days 1, 3, and 5 post-exercise, was held during isometric contractions on these days, respectively. Despite a lowering of absolute contraction force, heart rate (P < 0.05) and blood pressure (P < 0.001) responses during contractions using the ECC arm were consistently elevated relative to the control arm. However, subjects perceived that they were exerting forces similar to those achieved before eccentric exercise-induced neuromuscular dysfunction. These findings suggest that perceived effort following strength loss induced by mechanically stressful exercise dictates the cardiovascular responses during isometric contractions.