Haemodynamic response to exercise in healthy young and elderly subjects

Whereas with advancing age, peak heart rate (HR) and cardiac index (CI) are clearly reduced, peak stroke index (SI) may decrease, remain constant or even increase. The aim of this study was to describe the patterns of HR, SI, CI, arteriovenous difference in oxygen concentration (C _a-vO₂), mean arterial pressure (MAP), systemic vascular resistance index (SVRI), stroke work index (SWI) and mean systolic ejection rate index (MSERI) in two age groups (A: 20–30 years, n = 20; B: 50–60 years n = 20. After determination of pulmonary function, an incremental bicycle exercise test was performed, with standard gas-exchange measurements and SI assessment using electrical impedance cardiography. The following age-related changes were found: similar submaximal HR response to exercise in both groups and a higher peak HR in A than in B[185 (SD 9) vs 167 (SD 14) beats · min⁻¹, P < 0.0005]; increase in SI with exercise up to 60–90 W and subsequent stabilization in both groups. As SI decreased towards the end of exercise in B, a higher peak SI was found in A [57.5 (SD 14.0) vs 43.6 (SD 7.7) ml · m⁻², P < 0.0005]; similar submaximal CI response to exercise, higher peak CI in A [10.6 (SD 2.5) vs 7.2 (SD 1.3) l · min⁻¹ · m⁻², P < 0.0005]; no differences in C _a-vO₂ during exercise; higher MAP at all levels of exercise in B; higher SVRI at all levels of exercise in B; lower SWI in B after recovery; higher MSERI at all levels of exercise in A. The decrease in SI with advancing age would seem to be related to a decrease in myocardial contractility, which can no longer be compensated for by an increase in preload (as during submaximal exercise). Increases in systemic blood pressure may also compromise ventricular function but would seem to be of minor importance. Accepted: 24 September 1996     

Prolonged exercise induces left ventricular dysfunction in healthy subjects

To determine the effects of a moderately prolonged exercise on left ventricular systolic performance, 23 healthy male subjects, aged 18 to 51 yr (mean 37 yr) were studied. The subjects exercised first on a treadmill (brief exercise) and completed, on a separate day, a 20-km run. M-mode, two-dimensional, and Doppler echocardiography, as well as calibrated carotid pulse tracings, were obtained at rest and immediately on completion of both brief and prolonged exercise. Left ventricular systolic function was assessed by end-systolic stress-shortening relationships. Heart rate increased similarly after brief and prolonged exercise (+30%). Mean arterial pressure decreased from 99 +/- 7 to 92 +/- 8 mmHg (P less than 0.001) after prolonged exercise, but it remained unchanged after brief exercise. Left ventricular end-diastolic volume was decreased after prolonged exercise (130 +/- 23 vs. 147 +/- 18 ml at rest, P less than 0.01). Both ejection fraction and rate-adjusted mean velocity of fiber shortening decreased after prolonged exercise [from 67 +/- 5 to 60 +/- 6% (P less than 0.001) and from 1.12 +/- 0.2 to 0.91 +/- 0.2 cm/s (P less than 0.001), respectively] despite a lower circumferential end-systolic wall stress (133 +/- 23 vs. 152 +/- 20 g/cm2). The relationship between ejection fraction (or mean velocity of fiber shortening adjusted for heart rate) and end-systolic wall stress was displaced downward on race finish (P less than 0.05). These changes were independent of the changes in left ventricular end-diastolic volume and hence those in preload. The data suggest that moderately prolonged exercise may result in depressed left ventricular performance in healthy normal subjects.     

Renin-angiotensin system: oral contraception and exercise in healthy female subjects

The effect of oral contraception and of exercise on the renin-angiotensin system was studied in 20 highly trained athletes, of whom 10 were ingesting oral contraceptives (users) and 10 were not (nonusers), and in 24 sedentary age-matched healthy female subjects, of whom 13 were users and 11 were nonusers. No training-related effects were observed with the exception of renin substrate, which was significantly higher in the athletes. The plasma concentrations of active renin and of trypsin-activatable prorenin were significantly lower in the subjects taking oral contraceptives. Renin substrate, however, was significantly higher in the oral contraceptives group. No difference in plasma renin activity (PRA) was observed between users and nonusers. The results demonstrate the well-known estrogen-induced stimulation of renin substrate synthesis by the liver and suggest a decreased secretion of renin by the kidney. Exhaustive exercise of short duration, performed by the trained athletes only, stimulated the renin-angiotensin system. An increase in PRA and in active renin concentration was observed. The prorenin concentration did not change significantly. The magnitude of the exercise-induced changes was considerably influenced by oral contraceptive medication. Nonusers showed a significantly greater increase in PRA and active renin and total renin concentration than users. Renin substrate decreased significantly during exercise in the nonusers only. These results demonstrate that oral contraceptives have a suppressive effect on renin secretion at rest, an effect that becomes more prominent during exercise, i.e., physiological stimulation.     

Clonidine and the hormonal responses to graded exercise in healthy subjects

The aim of this study was to assess the acute effects of clonidine, an alpha 2-adrenergic agonist, on hormonal responses to graded exercise in 8 healthy young men. After fasting overnight, each subject was tested on 2 mornings, 1 week apart. On one occasion he was given 200 micrograms clonidine orally and on the other identical placebo tablets, the order being randomized in a double-blind fashion over the 2 days. Thereafter each subject performed 2 successive treadmill runs, equivalent to 60 and 100%, respectively, of maximal aerobic power. Clonidine pretreatment blunted the maximal increase in plasma catecholamines by more than 60% of the control response (p less than 0.01), without significantly altering the rise of plasma cortisol or ACTH. Furthermore, clonidine significantly reduced the exercise-induced maximal rise in plasma glucose, without modifying the slight decline in mean plasma insulin or increase in pancreatic glucagon levels. The drug did not affect the maximal increments in plasma growth hormone or prolactin occurring after exercise. It was concluded that a single dose of clonidine suppressed peripheral sympathetic responses, without altering central (pituitary) alpha-adrenergic-mediated hormonal responses, to short-term exercise in healthy men.     

Plasma adrenomedullin response to maximal exercise in healthy subjects.

The aim of the study was to find out whether maximal exercise performed by healthy young men influences plasma adrenomedullin concentration (ADM) and is the peptide level related to the cardiovascular, metabolic and hormonal changes induced by exercise. Ten subjects (age 24+/-1.0 yr) participated in the study. They performed graded bicycle ergometer exercise until exhaustion. Heart rate (HR) and blood pressure (BP) were measured throughout the test. Before and at the end of exercise venous blood samples were taken for [ADM], noradrenaline [NA], adrenaline [A], growth hormone [hGH], cortisol and lactate [LA] determination. Plasma [ADM] decreased during exercise from 1.71+/-0.09 to 1.53+/-0.10 pmol x l(-1) (p<0.01). This was accompanied by increases in plasma catecholamines and [hGH], while plasma cortisol level did not change. Positive correlation was found between the exercise-induced decreases in plasma ADM and diastolic BP. Blood [LA], systolic and mean BP at the end of exercise correlated negatively with plasma [ADM]. No significant interrelationships were found between plasma ADM, catecholamines or the other hormones measured. The present data suggests, that maximal exercise inhibits ADM secretion in young healthy men. Metabolic acidosis and a decrease in peripheral resistance might be involved in this effect.     

Chronic exercise and left ventricular structure and function in healthy human subjects

Twelve healthy well-trained participants in a supervised exercise program (mean age, 41.3 yr) were compared with 12 sedentary control subjects (mean age, 38.9 yr) with physical characteristics similar to the exercised group (EG) before training. Resting echocardiograms revealed significantly lower heart rates (HR) in the EG compared with control group (CG) but no evidence for cardiac structural differences between groups. Radionuclide angiograms performed at rest and during two levels of supine cycling (HR targets: 120 and 140 beats X min-1) resulted in increases in background-corrected end-diastolic counts [EDC(bc)] and confirmed use of the Frank-Starling mechanism in the majority of subjects. Mean values (+/- SD) for ejection fraction (EF) and normalized peak systolic ejection rate (PSER) (P greater than 0.05 between groups) were the following. (Formula: see text) The results suggested that fitness training does not induce significant cardiac enlargement as apparent from measurements at rest or important changes in contractile state during exercise. Increases in exercise stroke volume with such training may be the result of an increased end-diastolic volume.     

A study of some masticatory functions in 90-year old subjects

A group of 35 90-year old subjects, randomly selected from the gerontologic population study in Göteborg (H-70), were examined with respect to function and dysfunction of the masticatory system. The methods included a questionnaire, clinical examination and recording of bite force endurance and maximal bite force, measured in the central incisor region. Forty percent were edentulous, 29% were partially edentulous and wore a removable denture, while the others were dentate without removable prostheses. Signs and symptoms of temporomandibular disorders were mostly mild and infrequent, except TMJ crepitation which was recorded in 69% of the subjects. Maximal bite force was in general low (mean 94 N) but showed a great individual variation (range 10 to 410 N). Bite force endurance was also very variable (mean 72 s, range 10 to 205 s). None of the 35 subjects reported poor masticatory ability, but 2 said they could not chew all kinds of food. In spite of a reduced bite force this group of 90-year olds considered their masticatory ability as good and most of them had no severe signs and symptoms of temporomandibular disorders.     

Norepinephrine spillover at rest and during submaximal exercise in young and old subjects

Mazzeo, Robert S., Chakravarthi Rajkumar, Garry Jennings,and Murray Esler. Norepinephrine spillover at rest and during submaximal exercise in young and old subjects. J. Appl. Physiol. 82(6): 1869-1874, 1997.Aging isassociated with elevations in plasma norepinephrineconcentrations. The purpose of this investigation was toexamine total body and regional norepinephrine spillover as anindicator of sympathetic nerve activity. Eight young (26 ± 3 yr)and seven old (69 ± 5 yr) male subjects were studied at rest andduring 20 min of submaximal cycling exercise at 50% of peak workcapacity. Norepinephrine spillover was determined by continuousintravenous infusion of[³H]norepinephrine.Arterial norepinephrine concentrations were significantly greater atrest for old vs. young subjects (280 ± 36 vs. 196 ± 27 ng/ml,respectively). Whereas total norepinephrine spillover did not differbetween groups at rest, hepatomesenteric norepinephrine spillover was50% greater in old subjects compared with their young counterparts (51 ± 7 vs. 34 ± 5 ng/min, respectively). Additionally,norepinephrine clearance rates at rest were significantly lower for theold subjects (23%). During exercise, plasmanorepinephrine concentrations increased compared with rest, with oldsubjects again demonstrating greater values than the young group.Hepatomesenteric norepinephrine spillover was significantly greater(+36%) during exercise for old subjects compared with young; however,no difference was found for whole body spillover rates between agegroups. Norepinephrine clearance rates remained depressed(30%) in the old subjects during exercise. Clearance ofepinephrine mirrored that for norepinephrine both at rest and duringexercise across age groups. It was concluded that in old subjects, areduction in norepinephrine clearance and an increase in regionalnorepinephrine spillover can account for the higher plasmanorepinephrine concentrations observed at rest. This relationship isnot exacerbated by the stress imposed during an acute bout of exercise.

     

Ultrafine and fine particulate matter inhalation decreases exercise performance in healthy subjects

The purpose of this study was to investigate effects of PM1 (particulate matter with aerodynamic diameter 0.02-2 microm) inhalation on exercise performance in healthy subjects. Inhalation of internal combustion-derived PM is associated with adverse effects to the pulmonary and muscle microcirculation. No data are available concerning air pollution and exercise performance. Fifteen healthy college-aged males performed 4 maximal effort 6-min cycle ergometer trials while breathing low or high PM1 to achieve maximal work accumulation (kJ). Low PM1 inhalation trials 1 and 2 were separated by 3 days; then after a 7 day washout, trials 3 and 4 (separated by 3 days) were done while breathing high PM1 generated from a gasoline engine; CO was kept below 10 ppm. Lung function was done after trial 1 to verify nonasthmatic status. Lung function was normal before and after low PM1 exercise. PM1 number counts were not different between high PM1 trials (336,730 +/- 149,206 and 396,200 +/- 82,564 for trial 3 and 4, respectively) and were different from low PM1 trial number counts (2,260 +/- 500) (P < 0.0001). Mean heart rate was not different between trials (189 +/- 6.0, 188 +/- 7.6, 188 +/- 7.6, 187 +/- 7.4, for low and high PM1 trials; respectively). Work accumulated was not different between low PM1 trials (96.1 +/- 9.38 versus 96.6 +/- 10.83 kJ) and the first high PM1 trial (trial 3, 96.8 +/- 10.65 kJ). Work accumulated in the second high PM1 trial 4, 91.3 +/- 10.04 kJ) was less than in low PM1 trials 1 and 2, and high PM1 trial 3 (P = 0.004, P = 0.003, P = 0.0008; respectively). Acute inhalation of high (PM1) typical of many urban environments could impair exercise performance.     

Effect of acute exercise on some haematological parameters and neutrophil functions in active and inactive subjects

In this work we studied the possible effects of acute exercise on some haematological parameters and on some functions of neutrophils in seven active and six inactive subjects. Physical exercise (10 min on a cycle ergometer at a heart rate of 150 beats · min^–1) induced a significant increase in total leucocyte, lymphocyte and neutrophil concentrations in active subjects; serum iron and ferritin concentrations were lower in active compared to inactive subjects. Cellular adhesion, bactericidal activity and superoxide anion production did not change after exercise, while we also observed some differences between active and inactive subjects before exercise. In particular, the neutrophils from active subjects showed a significantly higher percentage of adhesion, higher bactericidal activity and lower superoxide anion production. In conclusion, the training induced changes in some neutrophil functions, while acute exercise influenced, overall, leucocyte concentrations.     

The effect of exercise intensity on hematuria in healthy male runners

The purpose of this study were: (1) to establish the prevalence of exercise-induced hematuria in a group of otherwise healthy male runners (n = 70), and (2) to investigate the role of exercise intensity in those runners who exhibited exercise-related hematuria (n = 10) by evaluating the effect of running and cycling at high and low intensities. The identified and recruited subjects participated in four different exercise protocols: (1) a 60-min treadmill run (RUN) at 90% of anaerobic threshold (Th_ae), (2) a 60-min leg cycle ergometer ride (BIKE) at 90% of Th_ae, (3) a 3×400-m sprint (SPRINT), each followed by 4 min of rest or light walking, and (4) 3×60-Wingate leg cycle ergometry tests, each followed by 4 min of rest or light cycling. The study employed a 3×4 (time by protocol) within-subjects design and dependent variables were measured before exercise, 4 min after, and 1 h after exercise, and included measurements of hematuria, proteinuria, urinary pH, serum haptoglobin concentration, serum creatine phosphokinase activity, plasma lactate concentration, and hemoglobin. The 400-m sprint at maximal effort significantly increased both hematuria and proteinuria (P < 0.01). Post-exercise hematuria for the SPRINT protocol was significantly different than that for the BIKE (P < 0.01) and RUN (P < 0.01) protocols. Due to the significant increase in hematuria and proteinuria following the SPRINT protocol, it was concluded that exercise-related changes in renal function were associated with weight-bearing exercise intensity rather than non-weight-bearing exercise duration. Accepted: 30 April 1998     

Interrelationships between left ventricular volume and output during exercise in healthy subjects.

To better characterize the relationship between left ventricular volume response and improved ventricular ejection and output during supine exercise in normal subjects, 36 healthy asymptomatic volunteers (age 39 +/- 17 yr) were studied with radionuclide ventriculography during recumbent bicycle ergometry. Relative changes in left ventricular end-diastolic and end-systolic volume were measured at rest and during exercise by a modification of the radionuclide counts-based method that accounted for variability in stress blood pool counts. A biphasic response was noted in left ventricular end-diastolic volume with an initial increase in early exercise (8.5 +/- 11% at 200 kpm/min and 11 +/- 12% at 300 kpm/min) followed by a progressive and significant decline at peak exercise (-3.3 +/- 18% at 547 +/- 140 kpm/min; P < 0.05). There was substantial variation in end-diastolic volume response at peak exercise in the group as a whole, which could be more closely related to changes in end-systolic volume (r = 0.84, P < 0.0001) than in heart rate (r = -0.57, P < 0.01) or age (r = 0.36, P < 0.05) of the study subjects. Despite the decline in ventricular filling, systolic function appeared to improve dramatically at peak exercise (change in left ventricular ejection fraction 15.5 +/- 6.4, P < 0.0001). Although not directly related to increasing systolic ejection, end-diastolic volume was directly related to the percent change in stroke volume at peak exercise among the study subjects (r = 0.88, P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of electrical stimulation of leg muscles on physiological responses during arm-cranking exercise in healthy men

The purpose of this study was to investigate the hypothesis that changes in physiological responses during arm-cranking exercise using electrical stimulation of the leg muscles (ACE-ES) compared to arm-cranking exercise alone (ACE) in able-bodied subjects (ABS) are based on an increase in active muscle mass rather than the enhancing effect of the leg muscle pump. In ABS the sympathetic nervous system induced vasoconstriction and activity of the leg muscle pump are intact, therefore, a normal redistribution of blood takes place during exercise. Consequently, ES should have no additional effect on the redistribution of blood in these ABS during exercise and, thus, changes in physiological responses will be based on an increase in active muscle mass. A group of 11 ABS performed three maximal arm-cranking tests. In the first test peak power output (PO _peak) was determined. The other tests were both submaximal and maximal ACE, once with ACE-ES and once with ACE. The PO _peak was not significantly different between ACE-ES and ACE. Oxygen uptake (O₂) increased significantly during ACE-ES compared to ACE. Cardiac output (), stroke volume (SV), heart rate and ventilation were not significantly different during ACE-ES compared to ACE. Respiratory exchange ratios were significantly lower during ACE-ES compared to ACE at 60% PO _peak and at maximal exercise. In conclusion, ACE-ES caused significant increases in O₂ with a lack of elevation in and SV during submaximal and maximal exercise in ABS. The results of this study suggest that changes in physiological responses during ACE-ES are based on an increase in the active muscle mass rather than stimulation of the leg muscle pump. Accepted: 6 August 1996     

Protective effect of Acorus calamus on kidney and liver functions in healthy mice

Acorus calamus (AC), is an herbal medicine commonly used as traditional practice in pharmacological applications. Present study initiated was evident to proof the hepatoprotective and nephroprotective activity with supporting histopathological status of kidneys and liver. Investigation done with the 5% (w/v) of AC dissolved in tap water (50 g/l) given for 15 days compared with control tap water to 5-7 week old C57Bl/6 mice both sexes. Renal function, liver function, biochemical and complete blood count was evaluated. AC significantly reduced food intake, body weight, also plasma concentration of electrolytes such as Na⁺, K⁺, Ca²⁺, were reduced as the excretion of electrolytes were increased in urine, significantly increased Fluid Intake, with Urinary urea, Urinary creatinine, Glomerular Filtration Rate, creatinine clearance, High-density lipoproteins, Mean Corpuscular Volume. The biochemical findings showed the hepatoprotective and histopathological changes showed the nephroprotective nature of AC by normal structure with no necrosis.