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Biomedical subjects

A W Ziemba

Publications and source records attributed to A W Ziemba.

16 recordsLinked to original sources
PubMed2006

Effect of 6-week endurance training on hemodynamic and neurohormonal responses to lower body negative pressure (LBNP) in healthy young men.

Endurance training is considered as a factor impairing orthostatic tolerance although an improvement and lack of effect have been also reported. The mechanisms of the changes and their relation to initial tolerance of orthostasis are not clear. In the present study, effect of moderate running training on hemodynamic and neurohormonal changes during LBNP, a laboratory test simulating orthostasis, was investigated in subjects with high (HT) and low (LT) tolerance of LBNP. Twenty four male, healthy subjects were submitted to graded LBNP (-15, -30 and -50 mmHg) before and after training. During each test heart rate (HR), stroke volume (SV) and blood pressure, plasma catecholamines, ACTH, adrenomedullin, atrial natriuretic peptide, and renin activity were determined. Basing on initial test, 13 subjects who withstood LBNP at -50 mmHg for 10 min were allocated into HT group and 11 subjects who earlier showed presyncopal symptoms to LT group. Training improved LBNP tolerance in six LT subjects. This was associated with attenuated rate of HR increase and SV decline (before training, at -30 mmHg deltaHR was 21 +/- 4 beats/min and deltaSV - -36+/- 8 ml while after training the respective values were 8 +/- 4 beats/min and -11+/- 6 ml). No differences in hemodynamic response were found in HT subjects and those from LT group whose LBNP tolerance was unchanged. In neither group training affected neurohormonal changes except inhibition of plasma ACTH rise in subjects with improvement of LBNP tolerance. It is concluded that some subjects with low orthostatic tolerance may benefit from moderate training due to improvement of cardiac function regulation.

Adrenocorticotropic Hormone↗
PubMed2005

Exercise training and 3-day head down bed rest deconditioning: exercise thermoregulation.

UNLABELLED: Bed rest (BR) deconditioning causes excessive increase of exercise core body tempera-ture, while aerobic training improves exercise thermoregulation. The study was designed to determine whether 3 days of 6 degrees head-down bed rest (HDBR) affects body temperature and sweating dynamics during exercise and, if so, whether endurance training before HDBR modifies these responses. Twelve healthy men (20.7+/-0.9 yrs, VO2max: 46+/-4 ml x kg(-1) x min(-1) ) underwent HDBR twice: before and after 6 weeks of endurance training. Before and after HDBR, the subjects performed 45 min sitting cycle exercise at the same workload equal to 60% of VO2max determined before training. During exercise the VO2, HR, tympanic (Ttymp) and skin (Tsk) temperatures were recorded; sweating dynamics was assayed from a ventilated capsule on chest. Training increased VO2max by 12.1% (p<0.001). Resting Ttymp increased only after first HDBR (by 0.22 +/- 0.08 degrees C, p<0.05), while exercise equilibrium levels of Ttymp were increased (p<0.05) by 0.21 +/- 0.07 and 0.26 +/- 0.08 degrees C after first and second HDBR, respectively. Exercise mean Tsk tended to be lower after both HDBR periods. Total sweat loss and time-course of sweating responses were similar in all exercise tests. The sweating threshold related to Ttymp was elevated (p<0.05) only after first HDBR. IN CONCLUSION: six-week training regimen prevents HDBR-induced elevation of core temperature (Ttymp) at rest but not during ex-ercise. The post-HDBR increases of Ttymp without changes in sweating rate and the tendency for lower Tsk suggest an early (<3d) influence of BR on skin blood flow.

Adult↗
PubMed2003

Early effects of short-term aerobic training. Physiological responses to graded exercise.

AIM: The aim of this study was to find out how early the moderate training effects appear and to check the hypothesis that familiarization with exercise protocol may contribute to an early physiological responses to training in previously sedentary subjects. METHODS: Twelve male, sedentary volunteers (22.0+/-0.7 yrs) were submitted to 3 weeks of a bicycle ergometer training, consisting of 45 min of exercise (at 70% VO(2)max), 3-4 times a week. The subjects performed 4 incremental exercise tests until volitional exhaustion: 2 before training (C1 and C2), and then after 1 (T1) and 3 (T3) weeks of training. During exercise HR, VO(2), electrical activity (EMG) of rectus femoris, biceps femoris, soleus and trapezius muscles were recorded and blood samples were taken for blood lactate (LA) determination. RESULTS: Already after 1 week of training HR decreased (p<0.05) with a further decline after 3 weeks the training (p<0.01). Maximal work load after 3 weeks of training increased to 277+/-10.4 W vs 250+/-9.5 W (p<0.05), VO(2)max achieved higher values than in C1 and C2 tests (p<0.05) and LA and EMG thresholds were elevated (p<0.05). CONCLUSION: A decrease in the resting and submaximal heart rate is the earliest effect of increased physical activity. Familiarization to exercise protocol decreased EMG of biceps femoris and soleus muscles during exercise, but did not influence that of rectus femoris muscle the most engaged during cycling.

Adaptation, Physiological↗
PubMed2001

Influence of caffeine, cold and exercise on multiple choice reaction time.

RATIONALE: The effects of caffeine on psychomotor performance have been evaluated under resting conditions and in a thermoneutral environment. Our hypothesis was that these effects could be modified by factors enhancing the level of alertness, such as exercise and cold exposure. OBJECTIVE: The purpose of this study was to follow up changes in the multiple choice reaction time (RT) during exercise at room and low ambient temperatures after caffeine or placebo administered in a double blind manner. METHODS: Nine soccer players performed multistage, incremental exercise until volitional exhaustion on a bicycle ergometer at 22 degrees C or 4 degrees C, 1 h after ingestion of coffee with caffeine (CAF) or without it (PL). Immediately before exercise and at the end of each workload, RT and blood lactate (LA) were measured. Oxygen uptake (VO2) and heart rate (HR) were recorded continuously. Blood LA threshold and the workload associated with the shortest RT were determined. RESULTS: During exercise at 22 degrees C, RT was significantly shorter in CAF than in the PL test, while at 4 degrees C there were no differences in RT between CAF and PL trials. Cold exposure did not affect RT either at rest or during exercise. Neither caffeine nor cold exposure influenced the maximal VO2, the maximal HR and LA threshold. CONCLUSION: In the thermoneutral environment, caffeine ingestion improved psychomotor performance during exercise, whilst at low ambient temperature this effect was blunted. These findings suggest that the stimulating action of caffeine depends on the level and source of arousal.

Adolescent↗
PubMed2000

Cardiovascular, metabolic and plasma catecholamine responses to passive and active exercises.

Eight healthy male volunteers (aged 19.6+/-3.0 years) were submitted to the unloaded active (AE) and passive (PE) cycling exercise-tests performed on an adapted cycle ergometer at a pedalling rate of 50 rpm. Intensity of active exercise was about 10% of VO2 max. In the PE exercise test the ergometer was moved electrically. During both tests the systolic time intervals (STI), stroke volume (SV), heart rate (HR), blood pressure (BP), oxygen uptake (VO2), rating of perceived exertion (RPE), electrical muscle activity (EMG), plasma adrenaline (A), noradrenaline (NE) and blood lactate (LA) concentrations were measured. Exercise induced changes in VO2, RPE and EMG were significantly higher during AE than PE. Shortening of the pre-ejection period (PEP) and diminishing of the PEP to ejection time (ET) ratio were similar in both types of exercise, whereas HR increased only during AE. A significant increase in cardiac output (p<0.01) resulted from increased SV (p<0.01) during PE and from increased HR (p <0.01) during AE. MAP increased only during PE and it was higher than at rest and during AE (p<0.01). Absence of changes in SV and MAP during AE may be considered as a secondary effect of the decrease in TPR. Plasma catecholamines did not increase above resting values in either type of exercise. Blood LA concentration increased during both PE and AE but it reached higher values (p<0.01) after the latter test. The present data suggest that the inotropic state depends on the mechanoreflexes originated in skeletal muscles. However, contribution of changes in preload to shortening of PEP can not be excluded.

Adult↗
PubMed2000

Effects of three-day bed rest on metabolic, hormonal and circulatory responses to an oral glucose load in endurance or strength trained athletes and untrained subjects.

The study was designed to find out (1) whether the effect of 3-day bed rest on blood glucose (BG) and plasma insulin (IRI) responses to glucose ingestion depends on preceding physical activity and (2) whether plasma adrenaline (A), noradrenaline (NA) and cardiovascular changes following a glucose load are modified by bed rest. Eleven sedentary students (22.5+/-0.3 yrs), 8 long distance runners (18.6+/-0.3 yrs) and 10 strength trained athletes (21.2+/-2.1 yrs) were examined before and after bed rest. Plasma IRI, BG, NA, A, heart rate (HR), and blood pressure (BP) were measured during 2 hrs following glucose (75 g) ingestion. The responses of BG and IRI to glucose load were calculated as incremental areas under the curves (auc). Both in athletes and untrained subjects bed rest markedly increased IRIauc, while BGauc was elevated only in sedentary subjects (p<0.05). The greatest increases in IRIauc and IRI/BG ratios were found in the endurance athletes. The data from all subjects (n = 29) revealed that the initial plasma NA and glucose-induced increases in NA and A were lowered after bed rest (p < 0.01). These effects were most pronounced in the endurance athletes. Bed rest did not influence HR or BP in any group. It is concluded that (1) the athletes have more adequate compensation for the bed-rest-induced decrement in insulin sensitivity than sedentary men; (2) three-day bed rest diminishes basal sympathetic activity and attenuates sympathoadrenal response to oral glucose; (3) endurance athletes have greater sympathetic inhibition than strength athletes or sedentary men.

Administration, Oral↗
PubMed1999

Ginseng treatment improves psychomotor performance at rest and during graded exercise in young athletes.

This study was designed to determine the effect of ginseng treatment on multiple choice reaction time (RT) during exercise. Fifteen soccer players (age 19.07 +/- 0.62 yrs) were placed in a double-blind manner into one of two groups: ginseng (n = 7), receiving 350 mg of ginseng daily for 6 weeks, or placebo (n = 8), receiving a placebo daily for 6 weeks. Before and after the treatment all the subjects performed an incremental bicycle ergometer exercise with intensity increasing 50 W every 3 min until volitional exhaustion. RT was measured before exercise, and then in the last 2 min of each exercise load. Maximal oxygen uptake (VO2max) and lactate threshold (LAT) were also determined from the exercise test. Ginseng treatment was found to shorten RT at rest and during exercise, shifting the exercise load associated with the shortest RT toward higher exercise loads. Neither ginseng nor placebo influenced VO2 max and LAT. In conclusion, ginseng extract does improve psychomotor performance during exercise without affecting exercise capacity.

Adult↗
PubMed1998

Psychomotor performance during prolonged exercise above and below the blood lactate threshold.

Previous investigations from this laboratory have demonstrated that during graded exercise with exercise intensities increasing every 3 min until exhaustion the multiple choice reaction time (RT) decreased until the intensity exceeded the lactate threshold (LT) by approximately 25%, and then rapidly increased. The aim of this study was to follow up changes in RT during prolonged exercise at constant intensities above and below LT and to relate these changes to changes in venous blood lactate [La-]b, and plasma catecholamine [CA]pl concentration responses to the exercise. For this purpose eight young soccer players exercised for 20-min on a cycle ergometer at 10% above LT, and nine exercised for 60 min at an intensity 30% below LT. During both tests RT, heart rate (HR), as well as [La-]b, and [CA]pl were measured. Above LT, RT decreased from the 5th min until the end of exercise, whilst HR, [La-]b, and [CA]pl increased progressively. Significant inverse correlations were ascertained between RT and plasma adrenaline (r = -0.651) and noradrenaline concentrations (r = -0.678). During exercise below LT, RT decreased up to approximately 40 min, then it reached a nadir, and stabilized at this level. This was accompanied by only small changes in [La-]b and [CA]pl. The present findings would indicate that young athletes are able to maintain for a relatively long time, or even increase, their psychomotor performance during endurance exercise both below and above the LT.

Adult↗
PubMed1994

Effect of mild psychological stress on physiological responses to exercise in men.

UNLABELLED: To find out whether a negative shift in subject's mood alters cardio-respiratory and endocrine responses to exercise, 20 young men performed a graded bicycle ergometer test (50, 100, 150 W): 1) when they experienced a mixed emotional and cognitive stress before exercise (1st session), 2) when they were familiarized with the laboratory and rested quietly before exercise (2nd session). The subjects' mood was assessed by the Profile of Mood State (POMS) questionnaire. In the 1st session the subjects started exercise with significantly higher scores of tension, anger, depression, confusion and global mood in comparison with the 2-nd session. They also had slightly elevated systolic blood pressure, blood lactate, plasma cortisol and noradrenaline concentrations. During exercise performed in the 1st session only plasma free and total noradrenaline and cortisol levels were higher than those in the 2nd session. IN CONCLUSION: a mild psychological stress, causing the mood worsening before standard exercise test, does not evoke pronounced alterations in cardio-respiratory responses to exercise in healthy men, but it does affect the magnitude of exercise-induced changes in both plasma free and total noradrenaline concentrations.

Adult↗
PubMed1991

Age as independent determinant of glucose tolerance.

It has been proposed that the decline in glucose tolerance with age is not a primary aging effect but is secondary to a combination of other age-associated characteristics, i.e., disease, medication, obesity, central and upper-body fat deposition, and inactivity. To test this hypothesis, we first eliminated from analysis the Baltimore Longitudinal Study of Aging participants with identifiable diseases or medications known to influence glucose tolerance. Seven hundred forty-three men and women, aged 17-92 yr, remained for analysis. As indices of fatness, body mass index and percent body fat were determined. As indices of body fat distribution, waist-hip ratio and subscapular triceps skin-fold ratio were calculated. As indices of fitness, physical activity level, determined by detailed questionnaire, and maximum 02 consumption were calculated. We tested whether the effect of age on glucose tolerance remains when data were adjusted for fatness, fitness, and fat distribution; 2-h glucose values were 6.61, 6.78, and 7.83 mM for young (17-39 yr), middle-aged (40-59 yr), and old (60-92 yr) men and 6.22, 6.22, and 7.28 mM for the three groups of women, respectively. The differences between the young and middle-aged groups were not significant, but the old groups had significantly higher values than young or middle-aged groups. Fatness, fitness, and fat distribution can account for the decline in glucose tolerance from the young adult to the middle-aged years. However, age remains a significant determinant of the further decline in glucose tolerance of healthy old subjects.

Adipose Tissue↗
PubMedDate not supplied

A decreased hyperglycemic response to adrenaline after prolonged, exhausting exercise in dogs.

The aim of the investigations carried out on dogs was to elucidate possible causes of the decreased hyperglycemic response to adrenaline after exhausting exercise. The k-values of i.v. glucose tolerance tests were calculated and the dose-response relationship to infused adrenaline was analyzed under control, resting conditions, and after exhausting exercise. K-values (KG-exc.) were significantly higher (p less than 0.01) after exercise than in control experiments, whereas hyperglycemic responses to the applied doses of adrenaline: 0.25, 0.5, 1.0, 2.0 and 3.0 mug-kg-1min-1 were considerably lower. In both situations a linear relationship was found between the hyperglycemic response and the dose of adrenaline, although the slope of the regression line, expressing this relationship, was significantly lower after exercise than that under control conditions. It is suggested that the decreased hyperglycemic response to adrenaline after prolonged, exhausting exercise may be attributed to both the increased rate of glucose elimination from blood, and a decreased responsiveness of the liver to adrenaline.

Animals↗
PubMedDate not supplied

Influence of hypercapnia on certain aspects of heat exchanges at room temperature in the rabbit.

Heat production as well as heat loss from the surface of the ear and airways during and after hypercapnia induced by one hour inhalation of 10% mixture was studied in conscious rabbits. The arterial CO2 tension increased by about 45 mm Hg and pH fell by about 0.3. These changes were associated with decreasing of heat production while heat loss from the ears and airways increased significantly. Consequently the rectal temperature fell meanly by about 0.9 degrees C. The data show that fall of body temperature in the rabbits exposed on 10% CO2 at room temperature is due both to heat production changes and heat loss changes.

Acid-Base Equilibrium↗
PubMedDate not supplied

Effect of hypercapnia on thermoregulation at high ambient temperature.

The reported investigations were carried out on rabbits exposed for three hours to ambient temperature of 25 degrees C or 35 degrees breathing athmospheric air (controls) or gas mixtures containing 4% or 7% of CO2. During the exposure to 35 degrees C in rabbits breathing the gas mixture with 7% of CO2 the rise of rectal temperature was significantly greater, heat elimination from the auricular surface was increased, whereas the oxygen uptake was increased insignificantly. In tracheostomized rabbits breathing the gas mixture with 7% of CO2 at 32 degrees C the respiratory rate decreased but the respiration volume increased as compared with the animals breathing atmospheric air. It seems that the hyperthermic effect of hypercapnia demonstrated in this work can be attributed to the impairment of heat elimination through the upper airways due to an inhibition of thermal panting.

Animals↗
PubMedDate not supplied

Hyperglycaemic effect of glucagon after prolonged exhausting exercise in dogs.

The purpose of this work was to compare the hyperglycaemic effect of glucagon at rest and after prolonged exhausting exercise in dogs. The following doses of glucagon were administered in 10-minute i.v. infusions: 0.1, 0.5, 1.0 micgrogram-kg-1 min-1. Significant differences were demonstrated in the blood glucose level after glucagon administration in doses of 0.1 and 0-5 microgram-kg-1 min-1 at rest as well as after exercise, and glucagon-induced hyperglycaemia was always lower after exercise than at rest. Increasing of glucagon dose from 0.5 to 1.0 microgram-kg-1 min-1 was not followed by a similar increase of the hyperglycaemic response. In additional experiments glucagon was administered together with adrenaline using two combinations of doses: 0.1 micron g-kg-1min-1 of glucagon and 0.25 microgram-kg-1 min-1 of adrenaline or 1.0 microgram-kg-1 min-1 of glucogen and 1.0 microgram-kg-1 min-1 of adrenaline. The hyperglycaemic effects of glucagon and adrenaline were additive at rest and after exercise when low doses of both hormones were used. After prolonged exercise this additive effect was not found when the "saturating" doses of glucagon and adrenaline were used (1.0 microgram-kg-1 min-1). The results obtained suggest that the hyperglycaemic response to glucagon is decreased in dogs after prolonged excise. It seems that this can be partly explained by the changed reactivity of hepatic tissue to this horme after prolonged exercise.

Animals↗