Biomedical subjects

K Karelson

Publications and source records attributed to K Karelson.

9 recordsLinked to original sources

PubMed2006

Ghrelin response to acute aerobic exercise in boys at different stages of puberty.

The aim of this study was to investigate the changes in serum ghrelin and leptin concentrations during acute aerobic cycle ergometer test in 60 boys at different pubertal stages. Boys were divided according to their pubertal status as group I (Tanner stage 1, n=20), group II (Tanner stages 2 and 3, n=20) and group 3 (Tanner stages 4 and 5, n=20). Maximal oxygen consumption and individual ventilatory threshold of the subjects were measured directly using stepwise increasing loads on cycle ergometer. Second exercise test consisted of a 30 minute constant load exercise on the same ergometer at the level of approximately 95% of the individual ventilatory threshold. Venous blood samples were obtained before, immediately after and after 30 minutes of recovery for the measurement of serum ghrelin, leptin, testosterone and insulin. At baseline, prepubertal children had significantly higher values for serum ghrelin compared to the groups II and III. Acute exercise altered significantly only insulin concentration. In all the groups, the maximal oxygen consumption/kg correlated positively with basal levels of testosterone (r=0.60, p<0.001) and insulin (r=0.34), and negatively to ghrelin (r=-0.35) and leptin (r=-0.32) (p<0.05). We conclude that moderate acute aerobic exercise does not change serum ghrelin or leptin level in boys at different pubertal stages.

Adolescent↗

PubMed2003

Effects of sodium citrate ingestion before exercise on endurance performance in well trained college runners.

OBJECTIVE: To test the hypothesis that sodium citrate administered two hours before exercise improves performance in a 5 km running time trial. METHODS: A total of 17 male well trained college runners (mean (SD) O(2)MAX 61.3 (4.9) ml/kg/min) performed a 5 km treadmill run with and without sodium citrate ingestion in a random, double blind, crossover design. In the citrate trial, subjects consumed 1 litre of solution containing 0.5 g of sodium citrate/kg body mass two hours before the run. In the placebo trial, the same amount of flavoured mineral water was consumed. RESULTS: The time required to complete the run was faster in the citrate trial than the placebo trial (1153.2 (74.1) and 1183.8 (91.4) seconds respectively; p = 0.01). Lower packed cell volume and haemoglobin levels were found in venous blood samples taken before and after the run in the citrate compared with the placebo trial. Lactate concentration in the blood sample taken after the run was higher in the citrate than the placebo trial (11.9 (3.0) v 9.8 (2.8) mmol/l; p<0.001), and glucose concentration was lower (8.3 (1.9) v 8.8 (1.7) mmol/l; p = 0.02). CONCLUSION: The ingestion of 0.5 g of sodium citrate/kg body mass shortly before a 5 km running time trial improves performance in well trained college runners.

Adult↗

PubMed2001

Influence of prolonged continuous exercise on hormone responses to subsequent exercise in humans.

This study examined the possibility that fatigue may modify the hormone responses to exercise. A group of 12 endurance trained athletes ran for 2 h (blood lactate concentrations of approximately 2 mmol x l(-1)) in order to induce fatigue. The subjects exercised for 10 min at 70% maximal oxygen uptake before (1st test) and after (2nd test) the 2 h run to assess hormone responsiveness. A 1 min anaerobic power test was performed to assess muscle power. Cortisol, growth hormone, testosterone and insulin concentrations were determined before and after the 1st and 2nd tests. The 1st test resulted in increases in concentrations (P < 0.05) of cortisol and growth hormone, a decrease in insulin concentration (P<0.01) and no change in testosterone concentration. The 2 h run caused decreases of insulin, increases of growth hormone concentration and variable responses in the concentrations of cortisol and testosterone. The 2nd test decreased insulin concentration further (P < 0.05), but responses of the concentrations of testosterone, growth hormone and cortisol were variable. In 6 subjects (group A) cortisol displayed an increase [mean (SD)] from baseline concentrations [+ 304.0 (60.0) nmol x l(-1)], while in the other 6 subjects (group B) a decrease or no change was seen [+ 3.1 (5.3) nmol x l(-1), between groups, P<0.05]. Growth hormone concentration was substantially higher in group A [+ 14.7 (4.8) ng x ml(-1)] than group B [+ 6.0 (2.9) ng x ml(-1)] following the 2nd test. In group A anaerobic muscle power was higher, while in group B it was lower, after the 2 h run than before the 2 h run (P < 0.05). The findings suggest that fatigue from prolonged endurance activity may introduce a resetting in the pituitary-adrenocortical component of the endocrine system, expressed either by intensified or by suppressed endocrine functions.

Adult↗

PubMed1999

Association of depressiveness with blunted growth hormone response to maximal physical exercise in young healthy men.

Blunted response of growth hormone secretion to several pharmacological challenges is present in depression, but much less is known about the relationship of depression and secretion of growth hormone elicited by physiological stimuli. Furthermore, it is not known whether blunted growth hormone response occurs in depressiveness as measured with psychometric scales. A total of 82 healthy male volunteers (age 18-26 years) exercised on a bicycle ergometer with incremental load to achieve their maximal performance. Before exercise, subjects filled in approbated versions of Beck Depression Inventory (BDI), Spielberger's State-Trait Anxiety Scale, Cohens Perceived Stress Scale, and Schwartzers Self-Efficacy Scale. Blood samples were collected before and after exercise, and growth hormone, cortisol, and testosterone were measured by chemiluminescence immunoassay. Median perceived stress score of the subjects was identical to our population-based database median value, but the subjects had higher self-efficacy and lower depressiveness as shown by median values. In the majority of subjects, physical exercise induced remarkable increases in blood levels of the hormones. Cortisol and testosterone levels were not associated with the scores of psychometric scales. However, growth hormone response was virtually absent in high scorers (above median population score, n = 24) in BDI total score and the negative attitude subcomponent. Hence, this study demonstrates that growth hormone response to physiological stimuli is reduced in psychometrically measured depressiveness.

Adolescent↗

PubMed1998

Exercise-induced hormone responses in girls at different stages of sexual maturation.

The dependence of exercise-induced hormone responses on sexual maturation was tested in a 3-year longitudinal experiment on 34 girls (aged 11-12 years at the beginning). Sexual maturation was evaluated by Tanners five-stage scale. Children cycled for 20-min at 60% maximal oxygen uptake once a year. Cortisol, insulin, growth hormone, beta-oestradiol, progesterone and testosterone concentrations in venous blood were determined by radioimmunoassay procedures. Basal concentrations of growth hormone increased and of cortisol decreased when breast stage III was reached. Reaching breast stage IV was associated with an increase in basal concentrations of beta-oestradiol, progesterone and testosterone. The exercise induced significant increases in concentrations of cortisol, growth hormone and beta-oestradiol and a decrease in insulin concentration. At breast stage III the increase in cortisol concentration was to a lower level [467 (SEM 42) vs 567 (SEM 46)nmol x l(-1)] and growth hormone concentration to a higher level [29.4 (SEM 0.5) vs 12.8 (SEM 0.4)ng x ml(-1)], while the fall in insulin concentration was less pronounced [postexercise level 10.6 (SEM 0.9) vs 7.8 (SEM 0.8)mU x l(-1)] than in stage II. The magnitude of the cortisol response was reduced in the last stage of breast development (+42.1% vs +55.5% at stage II, +66.2% at stage III, and +50.0% at stage IV). The magnitude of beta-oestradiol response was the lowest in breast stage IV (+15.8%) and the highest at stage V (+41.1%). The progesterone response became significant at stage IV and testosterone response at stage V. In conclusion, we found that reaching breast stage III was associated with altered responses of cortisol, insulin and growth hormone concentrations while the responses of the sex hormone concentrations became pronounced in the last stages of sexual maturation.

Adolescent↗

PubMed1998

Hormonal responses to exercise in girls during sexual maturation.

The dependence of hormonal responses to exercise on sexual maturation was tested in three-year longitudinal experiment on 34 girls (11-12 years old at the beginning of the study). Sexual maturation of the girls was evaluated using Tanner scale. Girls were divided into three groups: maturation stages 1-2, 2-4 and 4-5. Children performed a 20-min cycle exercise at 60% of maximal oxygen uptake (VO max) once a year. Cortisol, insulin, somatotropin, beta-estradiol, progesterone and testosterone were determined in venous blood by RIA procedures. High basal levels of beta-estradiol and somatotropin appeared in stages 2-4 (387 +/- 92 pmol.l-1) and 12.9 +/- 2.85 ng.ml-1, respectively) and 4-5 (358 +/- 54 pmol.l-1) and 14.3 +/- 1.53 ng.ml-1, respectively). The basal progesterone level increased with maturation, testosterone appeared in the blood in stages 2-4 and 4-5. The exercise resulted in increased levels of cortisol and somatotropin, and a drop in insulin in all girls. The cortisol response was most pronounced in stage 1-2. Postexercise insulin concentration was the highest in stage 4-5. beta-estradiol level increased by 23% in stages 1-2 and 4-5, while the response was insignificant in stages 2-4. Exercise-induced progesterone increase was significant in stage 4-5. In conclusion, sexual maturation associates with several quantitative changes in exercise-induced hormonal responses.

Child↗

PubMed1992

Stability and variability in hormonal responses to prolonged exercise.

To study the dynamics of alterations in blood hormones and their individual variability during prolonged exercise, changes in plasma levels of corticotropin, cortisol, aldosterone, testosterone, progesterone, somatotropin, insulin and C-peptide were recorded in 32 endurance athletes and 50 untrained persons during a 2-hour exercise on a cycle ergometer at 60% VO2max. Common changes were activation of the pituitary corticotropin function, mostly at the end of exercise, rises in aldosterone and somatotropin concentrations and decreases in insulin and C-peptide levels during exercise. The activation of pituitary-adrenocortical system and the decrease of insulin but not C-peptide levels were more pronounced in athletes than in untrained persons. A large inter-individual variability existed in changes of cortisol, testosterone and progesterone in both groups. Five variants were found in the dynamics of cortisol concentration. Whereas the alterations of corticotropin were characterized mainly by a biphasic increase, the dynamics of corticotropin and cortisol coincided only in one variant out of five. Most characteristic for the postexercise recovery period were decreased activity of the pituitary-adrenocortical system and delayed normalization of aldosterone level.

Adolescent↗

PubMed1990

The effect of a single-circuit weight-training session on the blood biochemistry of untrained university students.

The metabolic and hormonal responses to an intensive single-circuit weight-training session were studied in 15 untrained male students. The training programme consisted of ten exercises, employing all the large groups of muscles. Students performed three circuits using a work-to-rest ratio of 30 s:30 s at 70% of one-repetition maximum. The whole programme lasted 30 min. Blood samples were obtained from the anticubital vein 30 min before exercise, immediately after exercise finished and after 1-h, 6-h, and 24-h periods of recovery. The training session produced significant increases in the plasma adrenocorticotropic hormone, cortisol, aldosterone, testosterone, progesterone and somatotropin concentrations. The plasma level of insulin and C-peptide remained unchanged. The strength exercises caused elevated ratios of cortisol:testosterone and cortisol:insulin, indicating a prevalence of stimulation of catabolic processes as well as of mobilization of energy reserves but during the recovery period the reverse of this was observed. Immediately after exercise the mean lactate concentration was 7.19 mmol.l-1, SD 0.56, the glucose concentration increased significantly during exercise and decreased rapidly during recovery. The high density lipoprotein-cholesterol increased in 1-h period of recovery compared with the initial level. The concentration of total cholesterol, low density lipoprotein-cholesterol and triglyceride, did not change. Packed cell volume did not change during exercise or recovery.

Adrenocorticotropic Hormone↗

PubMed1989

Biochemical changes in blood during the long and short triathlon competition.

The purpose of the study was to compare the effects of long (3.8 km swimming, 180 km biking, 42.2 km running, n = 7) and short (1.5 km swimming, 42 km biking, 14 km running, n = 14) triathlons on blood hormones, metabolites and substrates. Both variants of triathlon caused a significant rise in cortisol, somatotropin and aldosterone levels, the insulin and C-peptide levels decreased. The progesterone level increased considerably only after long triathlon. The testosterone level did not change essentially. The level of plasma glucose, total cholesterol, HDL, LDL did not change substantially during the both competitions. FFA concentration increased significantly and triglycerides concentration decreased only during the prolonged variant.

Adult↗