Comparison of pituitary responses to physical exercise in athletes and sedentary subjects

Serum growth hormone (GH), prolactin (PRL), cortisol, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and thyroid-stimulating hormone (TSH) levels were evaluated before and after a bicycle ergometer exercise test in 8 male competitive volleyball players and in 8 sedentary healthy males of the same age. Increased serum GH and cortisol values after exercise in both groups were found, whereas an exercise-induced PRL release was observed in athletes only. Serum levels of LH, FSH and TSH were unaffected by the test in all subjects. A possible role of training in conditioning the hypothalamopituitary exercise-induced secretion is suggested.     

Cortisol and androgen concentrations in female and male elite endurance athletes in relation to physical activity.

To evaluate the effect of variations in physical activity on selected hormone concentrations in male versus female athletes, fasting serum concentrations of cortisol (C), total-testosterone, free-testosterone, non sex hormone binding globulin (SHBG) bound testosterone, dehydroepiandrosterone, 4-androstene-3,17-dione and SHBG were studied. The tests were performed in nine male and seven female elite endurance athletes during the off-season (test 1), early in the competition season (test 2) and at the end of the competition season (test 3). The C concentration increased significantly during the competition season in women but not in men. Further, the mean C concentrations at test 3 as well as the mean level during the whole observation period (tests 1, 2, 3) were significantly higher in women than in men. No significant changes were found in androgen concentrations or androgen:cortisol ratios within the two groups. The differences between the sexes in C response may indicate different adaptive mechanisms to similar physical stress.     

Two methods for determining trunk extensor endurance. A comparative study

In the last few years epidemiological surveys have shown correlation between low endurance capacity of the trunk extensors and low back trouble. In this report two methods for the determination of trunk extensor endurance are compared. In method I the fixated subject is lying prone with the cranial border of the iliac crest at the edge of a couch. The endurance time for maintaining the upper part of the body horizontal was measured (max. 240 s). In method II the standing subject performed a horizontal isometric pull on a strain gauge force transducer equivalent to 60% MVC of the trunk extensors. The time until complete exhaustion in the muscles (inability to maintain the preset force level) was determined. The methods were applied to two groups of normal, healthy subjects: 1) 23 female (22-61 years) and 53 male (27-60 years) postmen. 2) 10 male students (20-37 years). The results show that method II is preferable to method I, not least in the field of ergonomics. Method II is easily practicable and does not demand expensive or complicated equipment. Furthermore this method gives reliable results suitable for statistical preparation, and is not influenced by anthropometrical factors.     

Erythrocyte cations and Na+,K+-ATPase pump activity in athletes and sedentary subjects

The chronic effect of training on intraerythrocyte cationic concentrations and on red cell Na+,K+-ATPase pump activity was studied by comparing well-trained athletes with sedentary subjects at rest. Also the acute effect of a 50-min cross-country run on these erythrocyte measurements was studied in the athletes. At rest the intraerythrocyte potassium concentration was increased (P less than 0.01) in the athletes compared to that of the control subjects. The intraerythrocyte concentrations of sodium and magnesium and red cell Na+,K+-ATPase pump activity were, however, similar in the trained and the untrained subjects. As compared with the resting condition, the intraerythrocyte potassium concentration was decreased (P less than 0.05) after exercise in the athletes, and this was accompanied by a minor increase in the intraerythrocyte sodium concentration. Red cell Na+,K+-ATPase pump activity was slightly increased (P less than 0.05) after exercise.     

Intramyocellular lipid content in type 2 diabetes patients compared with overweight sedentary men and highly trained endurance athletes

Recent evidence suggests that intramyocellular lipid (IMCL) accretion is associated with obesity and the development of insulin resistance and/or type 2 diabetes. However, trained endurance athletes are markedly insulin sensitive, despite an elevated mixed muscle lipid content. In an effort to explain this metabolic paradox, we compared muscle fiber type-specific IMCL storage between populations known to have elevated IMCL deposits. Immunofluorescence microscopy was performed on muscle biopsies obtained from eight highly trained endurance athletes, eight type 2 diabetes patients, and eight overweight, sedentary men after an overnight fast. Mixed muscle lipid content was substantially greater in the endurance athletes (4.0 +/- 0.4% area lipid stained) compared with the diabetes patients and the overweight men (2.3 +/- 0.4 and 2.2 +/- 0.5%, respectively). More than 40% of the greater mixed muscle lipid content was attributed to a higher proportion type I muscle fibers (62 +/- 8 vs. 38 +/- 3 and 33 +/- 7%, respectively), which contained 2.8 +/- 0.3-fold more lipid than the type II fibers. The remaining difference was explained by a significantly greater IMCL content in the type I muscle fibers of the trained athletes. Differences in IMCL content between groups or fiber types were accounted for by differences in lipid droplet density, not lipid droplet size. IMCL distribution showed an exponential increase in lipid content from the central region toward the sarcolemma, which was similar between groups and fiber types. In conclusion, IMCL contents can be substantially greater in trained endurance athletes compared with overweight and/or type 2 diabetes patients. Because structural characteristics and intramyocellular distribution of lipid aggregates seem to be similar between groups, we conclude that elevated IMCL deposits are unlikely to be directly responsible for inducing insulin resistance.     

A comparative study of albumin variants found in Brazil

10 rare albumin variants found in Brazil have been compared with 6 others, discovered elsewhere, through horizontal starch gel electrophoresis in four buffer systems. Belém V can be clearly distinguished from Naskapi but shows the same mobility as Máku (= Belém III) in two different pHs. Coari II, Manaus I and Porto Alegre II can be separated from all others in three buffer systems. Belém II (= Mexico) and Belém I also show unique patterns, but Coari I, Porto Alegre I and Belém IV could not be distinguished from Santa Ana. The possibly synonymous Belém III-Belém V-Máku should have originated from an Amerindian gene pool, but Coari I-Porto Alegre I-Belém IV-Santa Ana may have a Caucasoid origin.     

Live high-train low for 24 days increases hemoglobin mass and red cell volume in elite endurance athletes.

The effect of live high-train low on hemoglobin mass (Hbmass) and red cell volume (RCV) in elite endurance athletes is still controversial. We expected that Hb(mass) and RCV would increase, when using a presumably adequate hypoxic dose. An altitude group (AG) of 10 Swiss national team orienteers (5 men and 5 women) lived at 2,500 m (18 h per day) and trained at 1,800 and 1,000 m above sea level for 24 days. Before and after altitude, Hbmass, RCV (carbon monoxide rebreathing method), blood, iron, and performance parameters were determined. Seven Swiss national team cross-country skiers (3 men and 4 women) served as "sea level" (500-1,600 m) control group (CG) for the changes in Hbmass and RCV. The AG increased Hbmass (805+/-209 vs. 848+/-225 g; P<0.01) and RCV (2,353+/-611 vs. 2,470+/-653 ml; P<0.01), whereas there was no change for the CG (Hbmass: 849+/-197 vs. 858+/-205 g; RCV: 2,373+/-536 vs. 2,387+/-551 ml). Serum erythropoietin (P<0.001), reticulocytes (P<0.001), transferrin (P<0.001), soluble transferrin receptor (P<0.05), and hematocrit (P<0.01) increased, whereas ferritin (P<0.05) decreased in the AG. These changes were associated with an increased maximal oxygen uptake (3,515+/-837 vs. 3,660+/-770 ml/min; P<0.05) and improved 5,000-m running times (1,098+/-104 vs. 1,080+/-98 s; P<0.01) from pre- to postaltitude. Living at 2,500 m and training at lower altitudes for 24 days increases Hbmass and RCV. These changes may contribute to enhance performance of elite endurance athletes.     

Upper body muscle strength and endurance in relation to peak exercise capacity during cycling in healthy sedentary male subjects

The aim of this study was to investigate the relation between upper body muscle strength and endurance, and exercise capacity during an incremental cycle exercise test in sedentary healthy male subjects before and after 6 months of combined supervised group training. Exercise capacity was measured as maximal oxygen consumption (VO?peak) and maximum work rate (WR(peak)). Muscle strength and endurance of the upper body were assessed by bench press and isometric measurement of trunk extensor and flexor maximum voluntary contraction (MVC) and trunk extensor and flexor endurance. Thirty-one subjects were studied before and after the training period. Bench press and trunk extensor MVC correlated to exercise capacity at baseline and after training. Training improved VO?peak and WR(peak). The correlation between trunk extensor MVC and exercise capacity improved after training. Upper body strength may affect exercise capacity by increasing the rider's ability to generate force on the handlebar that can be transmitted to the pedals. Resistance training of the arms, chest, and trunk may help improve cycling performance.     

Tissue cholinesterases. A comparative study of their kinetic properties

The substrate saturation and temperature-dependent kinetic properties of soluble and membrane-bound forms of acetylcholinestarase (AChE) from brain and butyrylcholinesterase (BChE) from heart and liver were examined. In simultaneous studies these parameters were also measured for AChE in erythrocyte membranes and for BChE in the serum from rat and humans. For both soluble and membrane-bound forms of the enzyme from the three tissues, two components were discernible. In the brain, Km of component I (high affinity) and component II (low affinity) was somewhat higher in membrane-bound form than that of the soluble form components, while the Vmax values were significantly higher by about five fold. In the heart, Km of component II was lower in membrane-bound form than in the soluble form, while Vmax for both the components was about four to six fold higher in the membrane-bound form. In the liver, Vmax was marginally higher for the two components of the membrane-bound enzyme; the Km only of component I was higher by a factor of 2. In the rat erythrocyte membranes three components of AChE were present showing increasing values of Km and Vmax. In contrast, in the human erythrocyte membranes only two components could be detected; the one corresponding to component II of rat erythrocyte membranes was absent. In the rat serum two components of BChE were present while the human serum was found to possess three components. Component I of the human serum was missing in the rat serum. Temperature kinetics studies revealed that the Arrhenius plots were biphasic for most of the systems except for human serum. Membrane binding of the enzyme resulted in decreased energy of activation with shift in phase transition temperature (Tt) to near physiological temperature.     

Non-exercise daily energy expenditure and physical activity pattern in male endurance athletes.

The present study was performed to determine whether differences in non-exercise daily energy expenditure (Md,ne) exist between trained and untrained individuals. The data from seven cross-country skiers were compared with those from eight sedentary men. Daily energy expenditure (Md) was determined using the heart rate-oxygen consumption relationship; resting metabolic rate (Mr) was measured using indirect calorimetry. A physical activity questionnaire and ratios of Md or Md,ne to Mr were used as indices of physical activity. Md and Mr were significantly higher in the trained subjects whereas Md,ne was identical in the two groups. The ratio of Md,ne to Mr and the data from the physical activity questionnaire showed that there was no significant difference in daily energy expenditure and physical activity pattern during the non-exercise time. These results suggest that the exercise-induced increase in daily energy requirements is not compensated by a more sedentary life during the other daily activities in these trained men.     

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

Endurance trained long distance runners and untrained individuals underwent three days of bed rest and oral glucose loading. Before and after bed rest, individuals were given glucose tolerance tests, and their heart rates, blood pressure, blood glucose levels, insulin levels, and catecholamine interactions were measured. Results indicated that glucose tolerance is more affected by bed rest-induced deconditioning in untrained individuals than in trained individuals.     

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.     

Effects of Swiss-ball core strength training on strength, endurance, flexibility, and balance in sedentary women

The purpose of this study was to investigate the effects of Swiss-ball core strength training on trunk extensor (abdominal)/flexor (lower back) and lower limb extensor (quadriceps)/flexor (hamstring) muscular strength, abdominal, lower back and leg endurance, flexibility and dynamic balance in sedentary women (n = 21; age = 34 ± 8.09; height = 1.63 ± 6.91 cm; weight = 64 ± 8.69 kg) trained for 45 minutes, 3 d·wk-1 for 12 weeks. Results of multivariate analysis revealed significant difference (p ≤ 0.05) between pre and postmeasures of 60 and 90° s trunk flexion/extension, 60 and 240° s-1 lower limb flexion/extension (Biodex Isokinetic Dynamometer), abdominal endurance (curl-up test), lower back muscular endurance (modified Sorensen test), lower limb endurance (repetitive squat test), lower back flexibility (sit and reach test), and dynamic balance (functional reach test). The results support the fact that Swiss-ball core strength training exercises can be used to provide improvement in the aforementioned measures in sedentary women. In conclusion, this study provides practical implications for sedentary individuals, physiotherapists, strength and conditioning specialists who can benefit from core strength training with Swiss balls.     

Plasma volume regulation during heat stress: albumin synthesis vs capillary permeability. A comparison between desert and non-desert species

1. Plasma albumin synthesis was measured in rats and sand rats (Psammomys obesus) during heat acclimation (34 degrees C) and following thermal dehydration (37 degrees C) using 3H 1-leucine as a tracer. 2. In rats, heat acclimation resulted in 48% reduction in albumin synthesis. In sand rats synthesis increased by 160%. Both species achieved a new stabilization of the albumin synthetic system on the 5th day of acclimation. 3. Following thermal dehydration albumin synthesis increased in rats and decreased in sand rats. Acclimation did not alter this response. 4. In our dehydrating system plasma volume was maintained via maintenance of adequate albumin mass. In rats, albumin synthesis apparently contributes to this process. In sand rat, vascular permeability rather than albumin synthesis plays this role.     

Plasma ferritin concentrations: their clinical significance and relevance to patient care.

In healthy persons the plasma ferritin concentration is a sensitive index of the size of body iron stores. It has been successfully applied to large-scale surveys of the iron status of populations. It has also proved useful in the assessment of clinical disorders of iron metabolism. A low plasma ferritin level has a high predictive value for the diagnosis of uncomplicated iron deficiency anemia. It is of less value, however, in anemia associated with infection, chronic inflammatory disorders, liver disease and malignant hematologic diseases, for which a low level indicates iron deficiency and a high level excludes it, but intermediate levels are not diagnostic. Measuring the plasma ferritin concentration is also useful for the detection of excess body iron, particularly in idiopathic hemochromatosis, but again it lacks specificity in the presence of active hepatocellular disease. If iron overload is suspected in these circumstances determination of the iron content of a percutaneous liver biopsy specimen is required. In families with idiopathic hemochromatosis the combined determination of the plasma ferritin concentration and the transferrin saturation is a sufficient screen to identify affected relatives; however, estimation of the hepatic iron concentration is required to establish the diagnosis.