Hemodynamic and regional blood flow responses to nicotine at rest and during exercise

We hypothesized that nicotine compromises cardiovascular responses to dynamic exercise. Hemodynamic variables were measured in conscious miniswine before and at 2 min of nicotine infusion (20 micrograms.kg-1.min-1; i.a.; N = 6) during resting conditions. Mean arterial pressure elevations (MAP; 14%) and plasma nicotine concentrations (49 +/- 7 ng.ml-1) were similar to those elicited by cigarette smoking in humans. In addition, nicotine increased systemic vascular resistance (SVR; 56%), the heart rate x systolic blood pressure product (RPP; 11%), and regional vascular resistance in the left-ventricular, renal, and splanchnic circulations, while cardiac output decreased (CO; 23%) and skeletal muscle blood flow and vascular resistance were unaffected. Plasma norepinephrine and epinephrine increased by approximately 30% and 90%, respectively. On separate days, the same hemodynamic responses were measured before and at 20 min of treadmill running during vehicle or nicotine infusion for the last 2 min of exercise (N = 10). Nicotine increased MAP (6%), SVR (14%), and RPP (3%), and elevated vascular resistance in the proximal colon and pancreas. Moreover, compared to exercise + vehicle, norepinephrine and epinephrine increased by approximately 13% and 24%, respectively, during exercise + nicotine infusion. These findings suggest that the detrimental effects of nicotine observed at rest are minimized during exercise. Nicotine's effects may be reduced during exercise by competition from local vasodilators in the heart and active musculature, and/or by differing activation of sympathetic nerve activity.     

Hemodynamic assessment at rest and during dynamic physical exercise in young subjects with and without hypertensive parents

The antifols, inhibitors of the dihydrofolate reductase (DHFR), such as pyrimethamine and proguanil, have been used against Plasmodium falciparum in the areas where chloroquine resistance is widespread. This use has selected resistant strains in Southeast Asia and South America. The resistance is correlated with point mutations in precise positions of the DHFR gene. A reliable semi-nested PCR diagnosis test was established and used to determine the genotypic features of 29 isolates of P. falciparum originating from Africa. The results obtained by the PCR technique were compared with those of the in vitro drug sensitivity test. Some isolates were found to be polyclonal. Among the mutations tested, only mutations on codon 108 which generate an asparagine induce a decrease in sensitivity to pyrimethamine and cycloguanil, whereas mutation on codon 59 strengthens resistance to both antifols. No mutation on codon 16 or codon 164 was found.     

The intra- and interobserver variability of impedance cardiography in patients at rest and during exercise

In the present work we studied the levels of activities of dipeptidyl-peptidase I (or cathepsin C, DPP-I) and dipeptidyl-peptidase II (DPP-II) and examined their isoelectric focusing profiles in matched pairs of human squamous cell lung carcinoma (SQCLC) and the lung from surgically treated patients (n = 33). The mean specific activities of DPP-I and DPP-II were higher in SQCLC (Stages I and II) than in the lung, but only the activity of DPP-II in Stage I SQCLC was significantly higher compared to the lung. The activities of both enzymes were higher in the tumor than in the lung in 10 of 20 Stage I SQCLC patients, but only in 3 of 13 Stage II SQCLC patients. The specific activities of DPP-I and DPP-II in the lungs showed a good correlation while the correlation of both enzyme activities in SQCLCs was poor. We observed only a small and mutually comparable activation of DPP-I in extracts from SQCLCs and from the lungs by dithiothreitol. The isoelectric focusing profile of several DPP-II forms in SQCLCs and the lungs was similar and the single major DPP-II isoform revealed in the tumors and lungs showed a pIapp of 5.3-5.2. The isoelectric focusing profile of DPP-I showed multiple enzyme forms in SQCLCs (pIapp 6.3-4.5) as well as in the lungs (pIapp 6.4-4.8). In SQCLCs, as well as in the lungs, the activities of the DPP-I forms with pIapp values < or = 5.6 were shifted by neuraminidase treatment to the site of the major DPP-I isoform with pIapp of about 6.0 and the zymograms then showed an another DPP-I with pIapp of 5.7, which was less discernible in the lung. In some patients, the DPP-I forms with pIapp values < or = 5.6 from SQCLC retained a greater percentage of activity distribution than did the DPP-I pIapp-counterparts from the lung.     

Alanine and glutamine kinetics at rest and during exercise in humans

PURPOSE: The purpose of this study was to quantify both alanine and glutamine kinetics during exercise of moderate intensity to determine the sum total of alanine and glutamine flux. METHODS: Tracer methods were used to quantify alanine and glutamine rates of appearance (Ra) in plasma at rest and during 180 min of approximately 45% VO2max treadmill exercise in six normal volunteers (25 +/- 2 yr, 68 +/- 2.5 kg, VO2max 43 +/- 2.4 mL.min-1.kg-1; means +/- SE). Bolus injections (N = 3) or primed-constant infusions (N = 3) of 2H5-glutamine and 3-13C-alanine were given at rest on 1 d and 10-15 min after the onset of exercise on a separate day less than 2 wk later. Plasma enrichment decay curves and plateau enrichments were used to estimate alanine and glutamine kinetics. RESULTS: Whereas alanine Ra increased significantly from rest to exercise (5.72 +/- 0.31 vs 13.5 +/- 1.9 mumol.min-1.kg-1, respectively; P < 0.01), glutamine Ra was not significantly altered by exercise (6.11 +/- 0.44 and 6.40 +/- 0.69 mumol.min-1.kg-1 at rest and during exercise, respectively). The total of alanine and glutamine flux increased from 17.93 +/- 0.88 to 25.98 +/- 3.04 (P < 0.05). CONCLUSIONS: Since most muscle amino-N is released as alanine and glutamine, these findings provide strong evidence that amino-N delivery from muscle to the liver is increased during exercise. In addition, it appears that alanine, rather than glutamine, is the predominant N carrier involved in the transfer of N from muscle to the liver during moderate intensity exercise.     

Hypervolemia in men from fluid ingestion at rest and during exercise

BACKGROUND: Plasma osmolality (Osm) is important for controlling and maintaining plasma volume (PV) and body water. The effect of oral rehydration fluids for ameliorating dehydration is well-established; but optimal composition and Osm of fluids for hyperhydrating normally hydrated subjects is less clear. METHODS: Six treatments were used without and with oral fluids of varying ionic and constituent concentrations for hyperhydrating six previously euhydrated men (30 +/- SD 8 yr, 76.84 +/- 16.19 kg, 73 +/- 12 ml.kg-1 PV, 40 +/- 10 ml.min-1.kg-1 peak VO2) sitting at rest for 90 min (VO2 = 0.39 +/- SE 0.02 L.min-1) and during subsequent 70 min of submaximal exercise (VO2 = 2.08 +/- SE 0.33 L.min-1, 70 +/- 7% peak VO2). The hypothesis was that the fluid composition is more important than plasma Osm for increasing PV in euhydrated subjects at rest and maintaining it during exercise. Drink formulation compositions, given at 10 ml.kg-1 body wt, (mean = 768 ml), for the sitting period were: Performance 1 (P1; 55 mEq Na+, 365 mOsm.kg H2O-1), P2 (97 mEq Na+, 791 mOsm.kg-1), P2G (113 mEq Na+, 4% glycerol, 1382 mOsm.kg-1), AstroAde (AA; 164 mEq Na+, 253 mOsm.kg-1), and 01 and 02 (no drinking). The exercise drink (10 ml.kg-1, 768 ml) was P1 for all treatments except 02 (no drinking); thus, drink designations were: P1/P1, P2/P1, P2G/P1, AA/P1, 0/P1, and 0/0. RESULTS: PV at rest increased (p < 0.05) by 4.7% with P1 and by 7.9% with AA. Percent change in PV during exercise was +1% to +3% (NS) with AA/P1; -6% to 0% (NS) with P1/P1, P2/P1, P2G/P1, and 0/P1; and -8% to -5% (p < 0.05) with 0/0. AA, with the lowest Osm of 253 mOsm.kg-1, increased PV at rest (as did P1) and maintained it during exercise, whereas the other drinks with lower Na+ and higher Osm of 365-1382 mOsm.kg-1 did not. CONCLUSION: Drink composition appears to be more important than its Osm for increasing PV at rest and for maintaining it during exercise in previously euhydrated subjects.     

Substrate oxidation at rest and during exercise: effects of menstrual cycle phase and diet composition

The estrogen hormones have been shown to be highly glycogenic as well as lipolytic in nature. It is unknown whether the metabolic actions of estrogens impact upon energy metabolism during exercise. The composition of prior diet, however, does affect exercise energy metabolism. This study examined the influence of menstrual cycle phase (mid-follicular [FP; low estrogen] vs. mid-luteal [LP; high estrogen]) and diet composition on the rate of substrate oxidation for carbohydrate (CHO) and lipid at rest and during various intensities of physical exercise. Nine subjects completed an experimental session under four different menstrual cycle-diet conditions: 1) FP following a 3-day high CHO diet [75% total caloric intake], 2) FP following a 3-day low CHO diet [35% total caloric intake], 3) LP following a 3-day high CHO diet, and 4) LP following a 3-day low CHO diet. In each of the experimental sessions substrate oxidation was determined at rest and during cycle ergometer exercise at intensities of 30, 50, and 70% VO2max, respectively. Statistically significant (p < 0.05) interaction effects on substrate oxidation due to the menstrual cycle phase and diet conditions were found at rest and during 30%-50% exercise. In general, CHO oxidation was lowest and lipid oxidation highest in the LP under a low CHO diet condition.     

Hemodynamic characteristics of young men at risk for hypertension at rest and during laboratory stressors.

Examined hemodynamic activity at rest and during arithmetic and cold pressor in 105 male medical students varying in risk for hypertension. Classification into low-, moderate-, and high-risk groups was based on resting systolic blood pressure (SBP) and parental history of essential hypertension (PH). Dependent variables were SBP, diastolic BP (DBP), heart rate, and rate-pressure product (RPP). Progressively greater hemodynamic activity was seen across risk groups at rest and during the tasks. Risk groups differed significantly in SBP, DBP, and RPP at baseline and in size of response to mental arithmetic but not cold pressor. These relationships were either absent or weaker when using either risk factor alone to form risk groups. Hemodynamic reactivity to mental stress appears to be predicted better by a combination of resting SBP and hypertension than by either risk factor alone. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermogenesis during rest and exercise in cold air

Nine non-cold-acclimated subjects (5 female, 4 male, mean age 22.5 years) were studied to determine whether nonshivering thermogenesis contributes to cold-induced metabolic heat production during rest (50 min standing) and exercise (40 min treadmill walking) in 5 degrees C. Propranolol was administered orally (females, 60 mg, 1.12 mg.kg-1; males, 80 mg, 0.96 mg.kg-1) to block nonshivering thermogenesis. Measurements were taken at both 25 degrees C, 13.1 Torr (water vapor pressure; 1 Torr = 133.3 Pa) and 5 degrees C, 3.6 Torr, with sessions randomly assigned to be drug-neutral (DN), drug-cold (DC), placebo-neutral (PN), and placebo-cold (PC). Body core temperature was not different between any of the experimental conditions. Mean body temperature (5 degrees C, 32.2 +/- 0.20 degrees C (+/- SEM); 25 degrees C, 35.3 +/- 0.20 degrees C) and mean skin temperature (5 degrees C, 22.4 +/- 0.70 degrees C; 25 degrees C, 31.4 +/- 0.60 degrees C) were lower (p < 0.05) in the 5 degrees C than 25 degrees C environment (rest, exercise, drug (D), placebo (P), combined); while shivering (EMG) was higher (16.5 +/- 3.9% above baseline) at 5 degrees C than 25 degrees C (15 +/- 2.1% below baseline) (p < 0.05). The greater VO2 in 5 degrees C compared with 25 degrees C for the same condition is the thermoregulatory VO2 (TVO2). TVO2 (mL.min-1) was lower (p < 0.05) on the D (mean = 189.5 +/- 17.7) than on the P (mean = 238.1 +/- 20.2) during rest and during exercise (D, 206.1 +/- 63.7; P, 338.4 +/- 46.7). The EMG was 21% above baseline in the DC, and 12% above baseline for PC (p > 0.05). These results suggest a nonshivering component to heat production during acute cold exposure, which can be blocked with propranolol.     

Cardiopulmonary function at rest and during exercise after resection for bronchial carcinoma

BACKGROUND: Measurements of postoperative spirometric values after pneumonectomy and lobectomy vary considerably, and few researchers have studied the changes in exercise capacity during maximal work after lung resection. The purpose of this study was to describe the postoperative alterations in cardiopulmonary function. METHODS: Ninety-seven consecutive patients with lung malignancy were prospectively examined with maximal exercise test, spirometry, and arterial gas tensions. Fifty-seven patients were reinvestigated 6 months postoperatively. RESULTS: In patients having lobectomy, forced expiratory volume in 1 second decreased 8%, and exercise capacity, expressed by maximal oxygen uptake and maximal work rate, significantly decreased 13%. In patients having pneumonectomy forced expiratory volume in 1 second significantly decreased 23%, but the loss in lung volume was partly compensated as measured by exercise capacity, which decreased only 16%. Generally patients with the smallest preoperative forced vital capacity had the smallest postoperative deterioration expressed in percentages. We found a weak correlation between alterations in maximal oxygen uptake and lung function after resection. CONCLUSIONS: Lobectomy is associated with only minor deterioration of lung function and exercise capacity. Pneumonectomy causes a decrease in pulmonary volumes to about 75% of the preoperative values, partly compensated in better oxygen uptake, which postoperatively was about 85% of the preoperative values. Alteration in forced expiratory volume in 1 second is a poor predictor of change in exercise capacity after pulmonary resection.     

Plasma volume expansion with oral fluids in hypohydrated men at rest and during exercise

A case of malignant fibrous histiocytoma (MFH) in a 29-year-old man was reported. CT scans revealed an iso density mass which was homogeneously enhanced by contrast medium. MRI demonstrated that the right frontal tumor showed slight low signal intensity in T1-weighted image, and iso signal intensity in T2-weighted image. Gadolinium-enhanced T1-weighted image showed a homogeneously enhanced multinodular tumor. Right carotid angiogram revealed a tumor stain fed by the precentral artery. On operation, en-bloc resection was performed successfully. Postoperatively, local irradiation of 60Gy was performed. Microscopically, fibroblast-like cells arranged in storiform pattern were observed, and bizarre multinucleated giant cells were also observed. Ki-67 labelling index was 54%. We considered the tumor was a MFH and arose from an intracerebral mesenchymal tissue. We reviewed some literature and briefly discussed clinicopathological features and therapy of intracranial MFH.     

Direct vs indirect blood pressure at rest and during isometric exercise in normal subjects

Systolic and diastolic blood pressures were measured by intraarterial means and by auscultation. Comparisons were made with simultaneously determined intraarterial catheter and auscultation measurements. Five healthy males were measured at rest and during handgrip and deadlift isometric exercises, utilizing small and large muscle mass. The data suggest that indirect systolic blood pressure is highly correlated with the direct method at rest, during handgrip and deadlift (0.8, 0.9 and 0.91 respectively) isometric exercises. Indirect diastolic blood pressure correlates well with intraarterial at rest (0.7) and during the isometric handgrip bout which utilized small muscle mass (0.8). As for the deadlift manoeuvre, the correlation coefficients between the indirect and direct methods were low. These results suggest that when utilizing large muscle mass during isometric deadlift exercise, the indirect method is not valid for assessment of diastolic blood pressure.     

Controlled trial of penfluridol and thiothixene in the maintenance treatment of chronic schizophrenic syndromes

In a controlled trial of penfluridol and thiothixene as maintenance drugs in patients with chronic schizophrenic syndromes, some improvement over previous neuroleptics was seen with both drugs. This improvement was mainly evident in variables concerned with participation in social activities as assessed with the S-scale and by ward behaviour. The drug dosages necessary were very low and gave few and easily manageable side-effects. There was no significant difference between penfluridol and thiothixene. Penfluridol has the clear practical advantage of being the only long-acting drug for oral administration so far available.     

Two-level spinal stenosis in minipigs. Hemodynamic effects of exercise

STUDY DESIGN: Twenty-two G?ttingen minipigs were trained to run on a treadmill. Two-level lumbar spinal stenosis was created in 12 pigs, 10 were unoperated control subjects. Blood flow of the spinal cord and nerve roots was determined with microspheres at rest, during exercise, and after exercise. OBJECTIVES: To study the effect of lumbar spinal stenosis and exercise on blood flow of spinal neural tissue. SUMMARY OF BACKGROUND DATA: Neurogenic claudication, the key symptom of lumbar spinal stenosis, may be caused by vascular impairment or mechanical distress of neural tissue during exercise. Experimental compression of the cauda equina causes reversible nerve root edema, stasis, blood flow decrease, and compromised neural function. The vascular pathophysiology of spinal stenosis during exercise has not been studied previously. METHODS: Pigs were trained daily for 3 months. Two-level 25% lumbar spinal stenosis was introduced by placement of stenosing bands around the dural sac. Neurologic function was monitored before surgery by evoked potentials and after surgery by the Tarlov score. Regional blood flow in lumbosacral neural tissue was measured 3 days after chronic catheterization using microspheres at rest, during exercise at 3 km/h for 15 minutes, and at rest 30 minutes after exercise. RESULTS: Blood flow of grey and white matter increased during exercise in both groups, with no differences between groups. slight hyperemia prevailed after exercise in white matter of the stenotic area but not in grey matter. Nerve root blood flow was largely unchanged in control subjects during exercise but was reduced in spinal stenosis at rest, further depressed during exercise, and normalized after exercise. Dural blood flow was elevated throughout. CONCLUSION: The study suggests that exercise-induced impairment of spinal nerve root blood flow plays a role in the pathophysiology of neurogenic claudication.     

Hemodynamic effects of warm bathing in a Hubbard tank and exercise loading in patients after myocardial infarction

Hemodynamic parameters were measured during bathing and exercise testing in 43 patients with myocardial infarction (mean age: 60.2 years) to investigate the predictive parameters to determine when patients could safely resume bathing. Patients took a fresh water bath at 42 degrees C in the supine position for 5 min in a Hubbard tank. Group A showed an elevation of pulmonary capillary wedge pressure (PCWP) during bathing of 10 mmHg or more (23 patients, mean age: 61.7 years) and group B showed an elevation of less than 10 mmHg (20 patients, mean age: 60.5 years). Continuous multistep exercise tests were performed with a bicycle ergometer in the supine position, and hemodynamic parameters were measured at up to 50 W for 3 min on the day before the warm bathing test. There were no significant differences in the changes of arterial pressure and heart rate between the two groups. The PCWP at 3 min with a load of 50 W was significantly higher in group A (26.9 +/- 9.0 mmHg) than in group B (16.7 +/- 9.1 mmHg, p < 0.01). The stroke index (SI) during exercise testing was significantly lower in group A than in group B. The difference in the stroke index from baseline values (delta SI) at 3 min with a load of 50 W was significantly lower in group A (3.5 +/- 5.5 ml/m2/beat) than in group B (10.6 +/- 7.0 ml/m2/beat, p < 0.01). Similarly, delta CI and delta oxygen pulse during testing were significantly lower in group A than in group B. The physical work capacity and ejection fraction of the left ventricle of group A were significantly lower than those of group B, whereas the left ventricular end-diastolic pressure was higher in group A than in group B. CI, delta CI, SI, delta SI, METs, oxygen pulse, and delta oxygen pulse were examined by regression analysis and multivariate analysis to predict a significant elevation of delta PCWP during bathing. delta SI (p = 0.0032), delta CI (p = 0.0094), delta SI + METs (p = 0.0051), delta CI + METs (p = 0.0061), delta CI + delta SI (p = 0.0084), and delta CI + delta SI + METs (p = 0.0093) showed the highest correlations with delta PCWP. These findings suggest that changes in delta CI, delta SI, and METs are good predictive parameters for determining when patients may safely resume bathing. We suggest that patients with myocardial infarction, reduced cardiac function and a physical work capacity of approximately 4.0 METs, delta SI: 5 ml/m2/beat and delta CI: 2.4 l/min/m2 resume bathing only after careful consideration.     

Effects of thermal stress during rest and exercise in the paediatric population

Thermoregulation during exposure to hot or cold environments differs between children and adults. Many physical and physiological changes occur during growth and maturation that can affect thermoregulation during rest as well as during exercise. Thus, physical as well as physiological differences between children and adults may explain the different response to thermal stress. The main physical difference between children and adults affecting thermoregulation is the much higher surface-area-to-mass ratio of children. In a warm environment this allows them to rely more on dry heat loss and less on evaporative cooling. However, in extreme conditions, hot or cold, the greater surface-area-to-mass ratio results in a higher rate of heat absorption or heat loss, respectively. The lower body fat in girls compared with women provides lower insulation and presents a disadvantage in a cold environment. The smaller blood volume in children compared with adults, even relative to body size, may limit the potential for heat transfer during heat exposure and may compromise exercise performance in the heat. The main physiological difference between children and adults is in the sweating mechanism, affecting their thermoregulation in the heat, but not in the cold. The lower sweating rate characteristic of children is due to a lower sweating rate per gland and not to a lower number of sweat glands. In fact, children are characterised by a higher density of heat-activated sweat glands. The lower sweating rate per gland may be explained by the smaller sweat gland size, a lower sensitivity of the sweating mechanism to thermal stimuli and, possibly, a lower sweat gland metabolic capacity. Other physiological differences between children and adults that may affect thermoregulation include metabolic, circulatory and hormonal disparities. The higher metabolic cost of locomotion in children provides an added strain on the thermoregulatory system during exercise in the heat. On the other hand, during acute exposure to cold it may prove advantageous by increasing heat production. Circulatory differences, such as a lower cardiac output at any given exercise intensity and the lower haemoglobin concentration in boys compared with men, are likely to increase the cardiovascular strain during exercise in the heat, although their effects in a cold environment are unknown. Finally, testosterone and prolactin are 2 hormones that differ in baseline levels between children and adults and may affect sweat gland function and sweat composition. These possible effects need to be further investigated. The effectiveness of thermoregulation is reflected by the stability of core temperature. In a thermoneutral environment, children are characterised by a similar rectal temperature and a higher skin temperature when compared with adults. The latter may reflect the higher reliance on dry heat loss compared with evaporative cooling in children. In a hot environment, children's body temperatures are higher compared with adults while walking and running but not necessarily while cycling. This may be related to the higher metabolic cost, and therefore higher heat production, in children while walking or running but not while cycling. In a cold environment, children are characterised by lower skin temperatures, reflecting greater vasoconstriction. Their metabolic heat is increased in the cold to a greater extent than that of adults, although this appears to be sufficient to maintain their body temperature during exercise but not during prolonged rest. Neither children nor adults sufficiently replace fluid loss during exercise in the heat. Nevertheless, recent studies suggest that in children, when the available beverage is flavoured and enriched with NaCl and carbohydrates, dehydration can be prevented. (ABSTRACT TRUNCATED)     

Effect of lung volume reduction surgery on gas exchange and pulmonary hemodynamics at rest and during exercise

The present study was an investigation of the regulation of anion secretion across cultured mouse endometrial epithelium by prostaglandin E2 (PGE2) using the short-circuit current (ISC) technique. The cultured endometrial monolayers responded to both apical and basolateral application of PGE2 with a sustained rise in ISC in a concentration-dependent manner. However, the potencies of apical and basolateral addition of PGE2 were different, with apparent EC50 of 200 and 4 nM, respectively. Replacement of Cl- or HCO3- in the bathing solution significantly reduced the ISC responses to both apical and basolateral addition of PGE2; however, the apical response exhibited greater dependence on HCO3- . Pretreatment with diphenylamine 2,2'-dicarboxylic acid, a Cl- channel blocker, significantly reduced both PGE2-induced ISC responses, while pretreatment with amiloride, a Na+ channel blocker, did not exert any effect. Forskolin, an adenylate cyclase activator, and 3-isobutyl-dihydro-testosterone-1-methyl-xanthine, a cAMP phosphodiesterase inhibitor, mimicked the ISC response to PGE2 while MDL12330A, an adenylate cyclase inhibitor, completely abolished the PGE2-induced ISC. The results of the present study indicate that the anion secretion across the mouse endometrial epithelium may be regulated by PGE2 involving a cAMP-dependent mechanism predominantly. The differential responses to apical and basolateral challenge with PGE2 also suggest that PGE2 of different origins may play different roles in uterine function.     

Haemodynamics in children during rest and exercise: methods and normal values

Measuring haemodynamic performance in children is either invasive, and thus unacceptable, or noninvasive when the measured variable is often remote from the true variable. Measuring only maximum performance variables relies too heavily on motivation, especially in disease groups. We describe a method for the measurement of haemodynamic performance using respiratory mass spectrometry during rest, exercise and recovery therefrom. One hundred and six healthy children (55 male, 51 female) aged 8-16.9 yrs underwent an identical exercise protocol. Following studies at rest, they initially bicycled at 25 W x m(-2), increasing every 3 min by 15 W x m(-2) until exhaustion, after which measurements were made during recovery. Effective pulmonary blood flow, stroke volume, oxygen consumption, arteriovenous oxygen difference and functional residual capacity (FRC) together with estimates of pulmonary capillary blood volume and transit time were assessed at every exercise stage using inert gas rebreathing techniques. Haemodynamic performance is highly dependent on surface area, age, gender and pubertal stage. Many parameters, for example transfer factor, demonstrate pubertal stage-dependent differences at identical workloads even after correction for size. Females have a lower capillary blood volume at rest compared to age and size-matched males, but it is equalized during exercise. FRC unexpectedly rose with exercise, and peak exercise was associated with a falling stroke volume in 91% (95% CI 84-96%) of children, a possible demonstration of Starling's law of the heart. Oxygen pulse (oxygen consumption/cardiac frequency) is a very poor marker for pulmonary blood flow. Normal values are provided for all haemodynamic parameters for rest and every exercise stage for all subgroups of children. This should allow accurate comparison of normal and disease groups in future.     

Resistance exercise prevents plantar flexor deconditioning during bed rest

Because resistance exercise (REX) and unloading induce opposing neuromuscular adaptations, we tested the efficacy of REX against the effects of 14 d of bed rest unloading (BRU) on the plantar flexor muscle group. Sixteen men were randomly assigned to no exercise (NOE, N = 8) or REX (N = 8). REX performed 5 sets x 6-10 repetitions to failure of constant resistance concentric/eccentric plantar flexion every other day during BRU. One-repetition maximum (1RM) strength was tested on the training device. The angle-specific torque-velocity relationship across 5 velocities (0, 0.52, 1.05, 1.75, and 2.97 rad.s-1) and the full range-of-motion power-velocity relationship were assessed on a dynamometer. Torque-position analyses identified strength changes at shortened, neutral, and stretched muscle lengths. Concentric and eccentric contractile work were measured across ten repetitions at 1.05 rad.s-1. Maximal neural activation was measured by surface electromyography (EMG). 1RM decreased 9% in NOE and improved 11% in REX (P < 0.05). Concentric (0.52 and 1.05 rad.s-1), eccentric (0.52 and 2.97 rad.s-1), and isometric angle-specific torques decreased (P < 0.05) in NOE, averaging 18%, 17%, and 13%, respectively. Power dropped (P < 0.05) in NOE at three eccentric (21%) and two concentric (14%) velocities. REX protected angle-specific torque and average power at all velocities. Concentric and eccentric strength decreased at stretched (16%) and neutral (17%) muscle lengths (P < 0.05) in NOE while REX maintained or improved strength at all joint positions. Concentric (15%) and eccentric (11%) contractile work fell in NOE (P < 0.05) but not in REX. Maximal plantar flexor EMG did not change in either group. In summary, constant resistance concentric/eccentric REX completely prevented plantar flexor performance deconditioning induced by BRU. The reported benefits of REX should prove useful in prescribing exercise for astronauts in microgravity and for patients susceptible to functional decline during bed- or chair-bound hospital stays.     

Effect of a new calcium antagonist on hemodynamics at rest and exercise loading in patients with essential hypertension

MPC-1304 ((+-)-methyl 2-oxopropyl 1,4-dihydro 2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridinedicarboxylate, CAS 86780-90-7), a new calcium antagonist, was orally administered to 10 outpatients with mild essential hypertension. It was observed that MPC-1304 inhibited elevations of blood pressure both at rest and under exercise loading without any adverse hemodynamic effects. The findings obtained indicated that MPC-1304 would be clinically useful in the treatment of hypertensive patients undergoing therapy while continuing normal everyday activities including physical exertion.