Prevalence of cerebral microhemorrhages in amateur boxers as detected by 3T MR imaging.

BACKGROUND AND PURPOSE: The evidence for traumatic brain injury in amateur boxers is controversial. Hypothetically, sudden acceleration of the head due to the impact of the blow during the boxing fight might result in diffuse axonal injury or contusion. We wanted to determine whether cerebral microhemorrhages occur more often in amateur boxers than in nonboxers. MATERIALS AND METHODS: In 42 male, classical amateur boxers and in 37 healthy, nonboxing male volunteers we performed cranial MR imaging at 3T. The study protocol included a transverse dual spin-echo MR imaging sequence, a 3D sagittal magnetization-prepared rapid acquisition of gradient echo sequence, a coronal T2*-weighted sequence, and an axial time-of-flight MR angiography sequence. MR imaging data were made anonymous before 2 neuroradiologists independently evaluated the images. In addition, the following risk factors were assessed: total numbers of fights and knockouts, weight division, and duration of boxing. We compared the group proportions of microhemorrhages with Fisher test of exact probability. RESULTS: There was a statistically higher prevalence of cerebral microhemorrhages in the group of boxers (3 of 42; 7.1%) than in nonboxing persons (0 of 37; 0%). This difference was not statistically significant, however (P = .2479; Fisher exact test). CONCLUSION: Although we detected more microhemorrhages in amateur boxers than in nonboxing persons, this difference did not prove to be significant.

Massive insulin secretion in response to anaerobic exercise in exercise-induced hyperinsulinism.

Exercise-induced hyperinsulinism (EIHI) is a recently described entity characterised by recurrent episodes of hypoglycaemia induced by physical exercise. The index patient for this disorder and a matched control were subjected to aerobic and anaerobic exercise tests on a cycle ergometer. Aerobic exercise was performed at an intensity of 60% of the respective 4 mmol/l lactate threshold (40 min). Anaerobic exercise with an intensity corresponding to 130% VO2max lead to exertion within 2-3 min and elicited comparable maximal lactate levels in both subjects (10-11 mmol/l). The patient experienced a massive increase in insulin from 34 to 649 mU/l after the anaerobic test, and a lower increase in insulin from 27 to 79 mU/l during the aerobic test. Insulin concentration remained unchanged during both tests in the control. Epinephrine increased in the EIHI patient, which was probably a counterregulatory response to hypoglycaemia. The activity of lactate dehydrogenase of the index patient in isolated leukocytes as well as the response to inhibition of oxamate was normal. The hypothesis of abnormal transport or metabolism of lactate/pyruvate in the beta-cells of patients with EIHI was further supported by the parallel increase of lactate and insulin in this study elicited in particular by anaerobic exercise.

Individual variation in the reduction of heart rate and performance at lactate thresholds in acute normobaric hypoxia.

Heart rate monitoring and lactate measurements are used to control exercise intensity during training at moderate altitude although there is some uncertainty about hypoxia-induced changes in these parameters at equivalent submaximal exercise intensities compared to normoxia. To study the influence of acute normobaric hypoxia (FiO2 0.15) on heart rate and performance at the individual anaerobic lactate threshold (IAT), at the 4 mmol x l(-1) threshold (AT) and at an intensity requiring 80 % of VO2max measured in the respective environment, 20 endurance-trained male athletes performed an incremental treadmill test in normoxia and normobaric hypoxia. During exercise in normobaric hypoxia, heart rate and velocity were significantly (p < 0.001) reduced with a wide individual variation at the IAT (range: - 1 to - 17 min(-1), - 0.3 to - 3.5 km x h(-1)), at the AT (- 2 to - 13 min(-1), - 0.2 to - 3.3 km x h(-1)) as well as at an intensity requiring 80 % of VO2max (0 to - 18 min(-1), - 1.1 to - 3.7 km x h(-1)). Relative VO2 at the lactate thresholds expressed as a percentage of VO2max was not significantly different compared to normoxia (86 +/- 6 % vs. 84 +/- 5 %, IAT; 90 +/- 5 % vs. 88 +/- 6 %, AT), but also showed a considerable individual variation. In conclusion, heart rate and performance have to be reduced individually to a varying extent during exercise in a hypoxic environment in order to achieve an equivalent intensity compared to exercise in normoxia.

Individual variation in the erythropoietic response to altitude training in elite junior swimmers.

OBJECTIVES: Inter-individual variations in sea level performance after altitude training have been attributed, at least in part, to an inter-individual variability in hypoxia induced erythropoiesis. The aim of the present study was to examine whether the variability in the increase in total haemoglobin mass after training at moderate altitude could be predicted by the erythropoietin response after 4 h exposure to normobaric hypoxia at an ambient Po(2) corresponding to the training altitude. METHODS: Erythropoietin levels were measured in 16 elite junior swimmers before and after 4 h exposure to normobaric hypoxia (Fio(2) 0.15, approximately 2500 m) as well as repeatedly during 3 week altitude training (2100-2300 m). Before and after the altitude training, total haemoglobin mass (CO rebreathing) and performance in a stepwise increasing swimming test were determined. RESULTS: The erythropoietin increase (10-185%) after 4 h exposure to normobaric hypoxia showed considerable inter-individual variation and was significantly (p<0.001) correlated with the acute erythropoietin increase during altitude training but not with the change in total haemoglobin mass (significant increase of approximately 6% on average). The change in sea level performance after altitude training was not related to the change in total haemoglobin mass. CONCLUSIONS: The results of the present prospective study confirmed the wide inter-individual variability in erythropoietic response to altitude training in elite athletes. However, their erythropoietin response to acute altitude exposure might not identify those athletes who respond to altitude training with an increase in total haemoglobin mass.

Muscular adaptations to computer-guided strength training with eccentric overload.

AIMS: In order to investigate the muscular adaptations to a novel form of strength training, 18 male untrained subjects performed 4 weeks of low resistance-high repetition knee extension exercise. METHODS: Nine of them trained on a conventional weight resistance device (Leg curler, CON/ECC group), with loads equivalent to 30% of the concentric one-repetition maximum (1RM) for both the concentric and eccentric phase of movement. The other nine trained on a newly developed computer-driven device (CON/ECC-OVERLOAD group) with the concentric load equivalent to 30% of the concentric 1RM and the eccentric load equivalent to 30% of the eccentric 1RM. RESULTS: Training resulted in significantly (P < or = 0.05) increased peak torque and a tendency (P=0.092) to increased muscle cross-sectional area for the CON/ECC-OVERLOAD but not the CON/ECC group, while strength endurance capacity was significantly (P < or = 0.05) increased in the CON/ECC group only. RT-PCR revealed significantly increased myosin heavy chain (MHC) IIa and lactate dehydrogenase (LDH) A mRNAs, a tendency for increased MHC IIx mRNA (P = 0.056) and high correlations between the changes in MHC IIx and LDH A mRNAs (r=0.97, P=0.001) in the CON/ECC-OVERLOAD group. CONCLUSIONS: These results indicate a shift towards a more type II dominated gene expression pattern in the vasti laterales muscles of the CON/ECC-OVERLOAD group in response to training. We suggest that the increased eccentric load in the CON/ECC-OVERLOAD training leads to distinct adaptations towards a stronger, faster muscle.

Effects of low-resistance/high-repetition strength training in hypoxia on muscle structure and gene expression.

To test the hypothesis that severe hypoxia during low-resistance/high-repetition strength training promotes muscle hypertrophy, 19 untrained males were assigned randomly to 4 weeks of low-resistance/high-repetition knee extension exercise in either normoxia or in normobaric hypoxia ( FiO(2) 0.12) with recovery in normoxia. Before and after the training period, isokinetic strength tests were performed, muscle cross-sectional area (MCSA) measured (magnetic resonance imaging) and muscle biopsies taken. The significant increase in strength endurance capacity observed in both training groups was not matched by changes in MCSA, fibre type distribution or fibre cross-sectional area. RT-PCR revealed considerable inter-individual variations with no significant differences in the mRNA levels of hypoxia markers, glycolytic enzymes and myosin heavy chain isoforms. We found significant correlations, in the hypoxia group only, for those hypoxia marker and glycolytic enzyme mRNAs that have previously been linked to hypoxia-specific muscle adaptations. This is interpreted as a small, otherwise undetectable adaptation to the hypoxia training condition. In terms of strength parameters, there were, however, no indications that low-resistance/high-repetition training in severe hypoxia is superior to equivalent normoxic training.

[A brief account of the 130 year history of the First Czech Internal Medicine Clinic]. / Utrzky ze stotricetileté historie I. ceské (interní) kliniky.

The first Czech medical clinic in Prague was founded in 1871 during the period of Czech revival by prof. Bohumil Eiselt. Since that time the clinic was headed by eight professors, each of them being an impressive and outstanding personality contributed significantly to its future development. The clinic keeps its immense vitality and represents the place of an outstanding curative and research activity.

Blood volume and hemoglobin mass in elite athletes of different disciplines.

Although it is well known that athletes have considerably larger blood volumes than untrained individuals, there is no data available describing the blood volume variability among differently trained athletes. The first aim of the study was to determine whether athletes from different disciplines are characterized by different blood volumes and secondly to what extent the blood volume can possibly limit endurance performance within a particular discipline. We investigated 94 male elite athletes subdivided into the following 6 groups: downhill skiing (DHS), swimming (S), running (R), triathlon (TA), cycling junior (CJ) and cycling professional (CP). Two groups of untrained subjects (UT) and leisure sportsmen (LS) served as controls. Total hemoglobin (tHb) and blood volume (BV) were measured by the CO-rebreathing method. In comparison to UT (mean +/- SD: tHb 11.0 +/- 1.1 g/kg, BV 78.3 +/- 7.9 ml/kg) tHb and BV were about 35 - 40 % higher in the endurance groups R, TA, CJ, and CP (e. g. in CP: tHb 15.3 +/- 1.3 g/kg, BV 107.1 +/- 7.0 ml/kg). Within the endurance groups we found no significant differences. The anaerobic discipline DHS was characterized by very low BV (87.6 +/- 3.1 ml/kg). S had an intermediate position (BV 97.4 +/- 6.1 ml/kg), probably because of the immersion effects during training in the water. VO(2)max was significantly related to tHb and BV not only in the whole group but also in all endurance disciplines. The reasons for the different BVs are an increased adaptation to training stimuli and probably also individual predisposing genetic factors.

Effects of iron repletion on blood volume and performance capacity in young athletes.

PURPOSE: The purpose of this study was to find out whether iron repletion leads to an increase in red blood cell volume (RBV) and performance capacity in iron-deficient nonanemic athletes. METHODS: 40 young elite athletes (13-25 yr) with low serum ferritin (< 20 microg.L-1) and normal hemoglobin (males > 13.5 g.dL-1, females > 11.7 g.dL-1) were randomly assigned to 12-wk treatment with either twice a day ferrous iron (equivalent to 2 x 100 mg elemental iron) or with placebo using a double blind method. Before and after treatment, hematological measures and parameters of iron status were determined in venous blood. RBV, blood volume (BV), and plasma volume (PV) were measured by CO rebreathing. For determination of the aerobic and anaerobic capacity (maximal accumulated oxygen deficit, MAOD), the athletes performed an incremental as well as a highly intensive treadmill test. RESULTS: After 12 wk, ferritin levels were within the normal range in the iron-treated group (IG) with a significant (P < 0.001) mean increase by 20 microg.L-1 opposed to a slight nonsignificant decrease in the placebo group (PG). RBV did not change significantly in either group nor did any of the hematological measures. However, only in IG there were significant increases in VO2max and in O2 consumption in the MAOD test. MAOD and maximal capillary lactate concentration remained unchanged in both treatment groups. CONCLUSIONS: The results indicate that in young elite athletes with low serum ferritin and normal hemoglobin concentration iron supplementation leads to an increase in maximal aerobic performance capacity without an augmentation of RBV.

Effect of severe exercise on plasma catecholamines in differently trained athletes.

OBJECTIVE: In the present study we investigated whether plasma catecholamine (CA) responses to short-term severe exercise (SX) are affected by different training regimen and whether this test will increase plasma catecholamine sulfates. METHODS: Nine anaerobically (ANTA) and eight aerobically trained male athletes (ATA) performed a severe treadmill exercise test (SX) at similar oxygen demands, leading to exhaustion within 2-3 min. RESULTS: The anaerobic contribution to energy supply was higher in ANTA than in ATA as indicated by the higher maximal accumulated oxygen deficit (37.5+/-3.5 vs. 22.7+/-4.4 mL x kg(-1) x min(-1)) (means +/- SE) (P<0.009) and blood lactate concentration after exercise (19.4+/-2.4 vs. 15.0+/-1.9 mmol x L(-1)) (P<0.005). In both groups plasma norepinephrine (NE), norepinephrine sulfate (NE-S), epinephrine (EPI), and epinephrine sulfate (EPI-S) increased significantly (P<0.05) during exercise with higher increments (P<0.05) in ANTA than in ATA (NE: 87.5+/-9.7 vs. 60.8+/-7.1 nmol x L(-1), P<0.034; EPI: 16.6+/-3.3 vs. 6.9+/-1.2 nmol x L(-1), P<0.009). CONCLUSION: Data suggest that during this type of exercise the sympathoadrenergic system is more activated in ANTA than in ATA and seems related to the higher anaerobic contribution to energy supply in ANTA. The short duration of SX was sufficient to increase plasma NE-S and EPI-S concentration.

Effects of iron supplementation on total body hemoglobin during endurance training at moderate altitude.

The aim of the study was to test the hypothesis that iron supplementation in well-trained non-iron-depleted athletes leads to an enhanced increase of total body hemoglobin (TBH) during training at moderate altitude. Therefore, the members of the national German boxing team were randomly assigned to treatment with ferrous-glycine-sulfate (1335 mg equivalent to 200mg elementary iron daily) or with placebo during 18 days of endurance training at moderate altitude (1800 m). Before and after altitude training TBH was determined by CO-rebreathing, measures of exercise performance were determined with an incremental treadmill test. Before, during and after the stay at moderate altitude erythropoietin (Epo), reticulocytes (Retics) and parameters of iron metabolism were measured in venous blood. The results show that TBH did not change significantly in the placebo-group and even slightly, but significantly decreased in the iron-treated group. However, there was a significant increase of Epo and Retics in both groups during training at moderate altitude whereas parameters of iron metabolism remained unchanged. VO2max did not change either. To test whether a training-induced hemolysis, an increased urinary iron excretion or gastrointestinal blood loss could explain the unexpected drop of TBH we tested most of the boxers again during a similar training camp at low altitude (400-1000 m) to obtain measures of hemolysis, urinary iron excretion and occult hemoglobin loss with the stools. Although there were signs of an increased erythrocyte turnover no iron loss could be observed. We conclude that 18 days of endurance training at an altitude of 1800 m does not lead to an increase of TBH in non-iron-depleted athletes with and without iron supplementation.

Changes in bone turnover induced by aerobic and anaerobic exercise in young males.

Physical activity is considered an important factor in attaining bone mass. However, the mechanisms by which exercise affects bone metabolism are not completely understood. The present study was performed to investigate the effects of aerobic and anaerobic exercise on bone turnover. Twenty healthy young males (aged 20-29 years) were followed through an 8-week program of aerobic (n = 10) and anaerobic training (n = 10). Ten age-matched individuals served as controls. Serum bone-specific alkaline phosphatase (BAP), serum osteocalcin (OC), and urinary pyridinoline (Pyd) and deoxypyridinoline (Dpd) were determined as indices of bone metabolism. After 4 weeks of aerobic training, serum BAP and OC (p < 0.01), and urinary Pyd (p < 0.001) and Dpd (p < 0.01) were significantly reduced. After 8 weeks, BAP and OC levels had returned to baseline values, whereas the urinary cross-link excretion remained low. In the anaerobic training group, elevated levels of BAP (p < 0.05 vs. week 4), OC (p < 0.05 vs. week 4), and Pyd (p < 0. 01 vs. week 0) were observed after 8 weeks of exercise. Changes in urinary Pyd and Dpd (week 0 vs. week 8) were positively correlated with changes in the mean power level in the Wingate test, a parameter of the anaerobic performance capacity (r = 0.50 and r = 0. 55, p < 0.01, respectively). In the controls, no significant changes in biochemical markers were observed. We conclude that aerobic and anaerobic training excert different effects on bone metabolism. While aerobic training led to changes compatible with reduced bone resorption activity, anaerobic training seems to result in an overall accelerated bone turnover. Therefore, the impact of physical activity on bone turnover may depend on the kind of exercise performed.

Lack of effect of oral Mg-supplementation on Mg in serum, blood cells, and calf muscle.

UNLABELLED: Magnesium (Mg) is important for regulating ion transport and cellular metabolism in all body tissues. In skeletal muscle Mg is involved in the neuromuscular activity, excitation, and muscle contraction. Mg deficiency can cause muscle weakness and muscle cramps. Less than 1% of total body Mg is found in serum, yet the serum Mg concentration is used to assess the body's Mg status. PURPOSE: The purpose of this study was to determine whether an oral Mg supplementation (500 mg Mg-oxide.d-1 for 3 wk) affects exercise performance, clinical symptoms, and the Mg concentration in various body compartments in athletes with low-normal serum Mg levels (N = 10 in each group). METHODS: In a double-blind, placebo-controlled study, correlation analysis between the Mg concentration in serum, blood cells, and skeletal muscle was performed to establish a measure for muscle cell Mg. RESULTS: The data indicate that a 3-wk Mg supplementation did not affect exercise performance, neuromuscular activity, or muscle related symptoms. Also, the supplementation did not increase the Mg concentration in serum or any cellular compartment studied. However, in the placebo group the renal Mg clearance decreased, whereas it increased in the subjects receiving Mg supplementation. Correlation analysis revealed that serum Mg only correlated with red cell Mg and that only leukocyte Mg correlated with the nuclear magnetic resonance (NMR)-measured muscle cell Mg concentration. CONCLUSIONS: These results indicate that Mg supplementation in athletes with low-normal serum Mg did not improve performance and failed to increase the body's Mg stores. Serum Mg appears to be a poor indicator for Mg in skeletal muscle or most other cellular compartments, but the concentration of Mg in mononuclear leukocytes might be used as an indicator of skeletal muscle Mg when NMR is not available.

Coagulation and thrombomodulin in response to exercise of different type and duration.

PURPOSE: The present study was conducted to evaluate the role of the duration of exercise and the impact of the exercise type for exercise-induced activation of coagulation. METHODS: Eleven male triathletes were subjected to stepwise maximal (17 min) and 1-h maximal exercise in swimming, cycling, and running. Changes of hemostatic variable sand of plasma thrombomodulin, a marker of endothelial cell activation, were monitored. RESULTS: Irrespective of the type of exercise, alterations in markers of thrombin (prothrombin fragment 1 + 2, thrombin-antithrombin III complexes) and fibrin formation (fibrinopeptide A) were more pronounced after 1-h exercise than after stepwise maximal exercise. Hemostatic parameters rose to the highest levels after running resulting in substantial fibrin formation as indicated by fibrinopeptide A increasing from 1.33 ng.mL-1 to 2.25 ng.mL (P < 0.05) after 1-h exercise testing. Significant changes of plasma thrombomodulin were detected exclusively after running with increases from 38.2 ng.mL-1 to 44.2 ng.mL-1 (1 h, P < 0.01). CONCLUSIONS: The data demonstrated that prolonged exercise is necessary for exercise-induced activation of coagulation resulting in thrombin and fibrin formation and suggested that endothelial cell activation possibly due to mechanical factors associated with running might play a role.

[Diagnosis of performance capacity and guided training for physical endurance]. / Leistungsdiagnostik und Trainingssteuerung im Ausdauerbereich.

The evaluation of the aerobic capacity is of great importance for athletes as well as for patients with cardiac and pulmonary diseases. For objective measurements of cardiorespiratory and metabolic responses heart rate, lactate concentration in capillary blood and ventilatory gas exchange are determined during incremental exercise tests either on different ergometers in a laboratory or under training conditions in the field. Besides the maximal O2-uptake (VO2max) several ventilatory and lactate thresholds have been proposed as reliable values for assessing the aerobic capacity and giving training recommendations. For interpretation of the results the training and nutrional behaviour in the previous days have to be considered as especially the lactat thresholds are influenced by the glycogen content of the muscles. Furthermore, training recommendations cannot always be easily transferred from test to training conditions as these can be very different from each other.

[Pseudo-anemia caused by sports]. / Pseudoanämie durch Sport.

Regular physical training leads to an increase of plasma volume by 10-20 percent. Therefore, hemoglobin concentration slightly below normal values in the presence of low-normal serum ferritin levels in athletes are usually due to a dilutional "pseudoanemia". Several cross sectional studies indicate that true iron deficiency anemia is not more frequent in athletes than in the general population. Since regular physical activity, especially extensive, running increases iron loss, mild iron deficiency (abnormal serum ferritin and normal hemoglobin concentration) and sometimes true iron deficiency anemia can occur especially when nutritional iron intake is insufficient and iron demand is increased because of growth (children, adolescents) or additional iron loss (menstruation). Several controlled studies indicate that iron supplementation (recommended dose 2 x 100 mg elementary iron/day) improves performance only when hemoglobin concentration increases, i.e. when iron deficiency anemia is present. On the contrary, iron supplementation has no measurable effects on performance when hemoglobin concentration cannot be increased, i.e. in mild iron deficiency.

Effect of repeated bouts of short-term exercise on plasma free and sulphoconjugated catecholamines in humans.

We tested the hypothesis that measurement of plasma catecholamine sulphate concentration after exercise reflects the overall activation of the sympathoadrenergic system during the whole period of repeated bouts of short-term exercise. A group of 11 male athletes performed two exercise tests at similar average power outputs consisting of three sets each. The tests either started with one set of three very intense sprints (95% of maximal running speed) followed by two sets of three less intense sprints (85% of maximal running speed; HLX) or vice versa (LHX). Similar mean areas under the curve of free noradrenaline (NA) during HLX and LHX [622 (SEM 13) v.s. 611 (SEM 14) nmol x l(-1) min) as well as similar mean heart rates [143 (SEM 9) v.s. 143 (SEM 8) beats x min(-1)] indicated comparable sympathetic activation during both exercise tests. Even so, plasma concentration of free NA was still significantly higher at the end of LHX than of HLX [35.7 (SEM 3.5) v.s. 22.5 (SEM 2.1) nmol x l(-1), respectively], i.e. when exercise ended with the more intense set of sprints. Plasma noradrenaline sulphate (NA-S) increased with exercise intensity showing higher mean increments after the first set of HLX compared to LHX [1.83 (SEM 0.42) v.s. 1.18 (SEM 0.29) nmol x l(-1); P<0.05]. However, after the end of HLX and LHX, increments in plasma NA-S were similar [4.52 (SEM 0.76) v.s. 4.06 (SEM 0.79) nmol x l(-1)], suggesting that NA-S response changed in parallel with the overall activation of the sympathetic nervous system during repeated bouts of short-term exercise. The results supported the hypothesis that measurement of plasma NA-S immediately after repeated bouts of short-term exercise reflects overall activation of the sympathetic nervous system during prolonged periods of this type of exercise.

[The importance of iron in humans]. / Význam zeleza v lidském organismu.

The authors submitted a very brief review of some biological properties of iron in particular protein-bound iron and on the immense amount of iron which surrounds us (it is the fourth most frequent element). In the human organism there is no physiological system for iron elimination. Therefore its absorption is regulated and restricted. Some substances promote its absorption, other inhibit it. An important factor in the regulation of iron absorption are the iron reserves of the organism, the amount of dietary iron and the enhanced erythropoiesis (incl. the ineffective one), while reduced erythropoiesis does not affect iron absorption. Ascorbic acid forms chelates with iron and thus remains soluble and can be absorbed despite the alkaline pH in the duodenum. Unbound trivalent iron remains insoluble. An important asset to rational iron therapy are Lauberger's discovery of ferritin (1936), assessment of the iron plasma level (Heilmeyer and Plötner, 1937), Laurell's discovery of transferrin (1947), and Addison's RIA method for assessment of the serum ferritin level (1974). Sideropenia remains the most widespread deficiency in human pathology, sideropenic anaemia the most readily diagnosed anaemia which is, however, most wrongly treated.