Validation of a field test to determine the maximal aerobic power in triathletes and endurance cyclists.

OBJECTIVE: To validate a field test to assess the maximal and submaximal exercise aerobic adaptation under specific conditions, for endurance modality cyclists and triathletes. METHODS: 30 male and 4 female endurance modality cyclists and triathletes, with heterogeneous performance levels, performed three incremental tests: one in the laboratory and two in the field. Assessment of the validity of the field protocol was carried out by the Student's t test, intraclass correlation coefficient (ICC) and coefficient of variation (CV) of the maximal variables (maximal aerobic speed (MAS), maximal aerobic power (MAP), maximal heart rate (HR(max)), maximal blood lactate concentration ([La(-)](max)) and maximal oxygen uptake (VO(2max))) and submaximal variables (heart rate, HR) measured in each one of the tests. The errors in measurement were calculated. The repeatability of the field tests was assessed by means of the test-retest of the two field tests, and the validity by means of the test-retest of the laboratory test with respect to the mean of the two field tests. RESULTS: No significant differences were found between the two field tests for any of the variables studied, but differences did exist for some variables between the laboratory tests with respect to the field tests (MAP, [La(-)](max), humidity (H), barometric pressure (Pb) and some characteristics of the protocols). The ICC of all the variables was high and the CV for the MAP was small. Furthermore, the measurement errors were small and therefore, assumable. CONCLUSIONS: The incremental protocol of the proposed field test turned out to be valid to assess the maximal and submaximal aerobic adaptation.

Comparison of nine theoretical models for estimating the mechanical power output in cycling.

OBJECTIVE: To assess which of the equations used to estimate mechanical power output for a wide aerobic range of exercise intensities gives the closest value to that measured with the SRM training system. METHODS: Thirty four triathletes and endurance cyclists of both sexes (mean (SD) age 24 (5) years, height 176.3 (6.6) cm, weight 69.4 (7.6) kg and Vo(2)max 61.5 (5.9) ml/kg/min) performed three incremental tests, one in the laboratory and two in the velodrome. The mean mechanical power output measured with the SRM training system in the velodrome tests corresponding to each stage of the tests was compared with the values theoretically estimated using the nine most referenced equations in literature (Whitt (Ergonomics 1971;14:419-24); Di Prampero et al (J Appl Physiol 1979;47:201-6); Whitt and Wilson (Bicycling science. Cambridge: MIT Press, 1982); Kyle (Racing with the sun. Philadelphia: Society of Automotive Engineers, 1991:43-50); Menard (First International Congress on Science and Cycling Skills, Malaga, 1992); Olds et al (J Appl Physiol 1995;78:1596-611; J Appl Physiol 1993;75:730-7); Broker (USOC Sport Science and Technology Report 1-24, 1994); Candau et al (Med Sci Sports Exerc 1999;31:1441-7)). This comparison was made using the mean squared error of prediction, the systematic error and the random error. RESULTS: The equations of Candau et al, Di Prampero et al, Olds et al (J Appl Physiol 1993;75:730-7) and Whitt gave a moderate mean squared error of prediction (12.7%, 21.6%, 13.2% and 16.5%, respectively) and a low random error (0.5%, 0.6%, 0.7% and 0.8%, respectively). CONCLUSIONS: The equations of Candau et al and Di Prampero et al give the best estimate of mechanical power output when compared with measurements obtained with the SRM training system.

Maximal lipidic power in high competitive level triathletes and cyclists.

OBJECTIVE: To describe the fat-oxidation rate in triathlon and different modalities of endurance cycling. METHODS: 34 endurance athletes (15 male triathletes, 4 female triathletes, 11 road cyclists and 4 male mountain bikers) underwent a progressive cycloergometer test until exhaustion. Relative work intensity (VO(2max)), minimal lactate concentration (La(-)(min)), lactic threshold, individual lactic threshold (ILT), maximal fat-oxidation rate (Fat(max), Fat(max) zone) and minimal fat-oxidation rate (Fat(min)) were determined in each of the groups and were compared by means of one-way analysis of variance. RESULTS: No significant differences were found for Fat(max), Fat(min) or for the Fat(max) zone expressed as fat oxidation rate (g/min). Intensities -20%, -10% and -5% Fat(max) were significantly lower for mountain bikers with respect to road cyclists and female triathletes, expressed as % VO(2max). Intensities 20%, 10% and 5% Fat(max) were significantly lower for mountain bikers with respect to male triathletes and female triathletes, and for male triathletes in comparison with female triathletes, expressed as % VO(2max). Lactic threshold and La(-)(min) did not show significant differences with respect to Fat(max). Lactic threshold was found at the same VO(2max) with respect to the higher part of the Fat(max) zone, and La(-)(min) at the same VO(2max) with respect to the lower part of the Fat(max) zone. CONCLUSIONS: The VO(2max) of Fat(max) and the Fat(max) zone may explain the different endurance adaptations of the athletes according to their sporting discipline. Lactic threshold and La(-)(min) were found at different relative work intensities with respect to those of Fat(max) even though they belonged to the Fat(max) zone.

Percentage of hypochromic erythrocytes and reticulocyte hemoglobin equivalent predictors of response to intravenous iron in hemodialysis patients.

INTRODUCTION: Reticulocyte hemoglobin content and percentage of hypochromic red cells are incorporated into the European best practice guidelines on anemia management in chronic kidney disease. Sysmex XN analyzer (Sysmex Corporation, Kobe, Japan) reports reticulocyte hemoglobin equivalent (Ret-He) and the hypochromic fraction of erythrocytes (%Hypo-He). Our aim was to assess the value of these parameters, in terms of the sensitivity and specificity for detecting functional iron deficiency, in hemodialysis (HD) patients. METHODS: Forty HD patients in the maintenance phase of erythropoietin therapy were included. Intravenous iron supplementation was interrupted at least 3 weeks before recruitment. Two samples were analyzed for each patient: the baseline after the iron-free period and the second sample after 4 weeks of IV iron administration. Hemogram and biochemical parameters of the iron status were measured. Patients were classified as responders or nonresponders to an iron load; responders had an increase in Hb of at least 10 g/L after iron administration, compared to the baseline. To identify the efficiency of the test for predicting the response to iron administration, receiver operating characteristic analysis (ROC) was performed. RESULTS: According to the established criteria, 21 patients were responders and 19 nonresponders. ROC analysis results: Ret-He area under curve (AUC) was 0.84 (95% CI 0.64-0.93), at cutoff 30.8 pg, sensitivity 78.7%, and specificity 87.2%. % Hypo-He AUC was 0.78 (95% CI 0.64-0.91), at cutoff 2.4%, sensitivity 72.2%, and specificity 88.1%. CONCLUSIONS: % Hypo-He and Ret-He are reliable parameters for the study of erythropoiesis status in HD patients.

Effects of trace elements on membrane fluidity.

According to the Fluid Mosaic Model, a biological membrane is a two-dimensional fluid of oriented proteins and lipids. The lipid bilayer is the basic structure of all cell and organelle membranes. Cell membranes are dynamic, fluid structures, and most of their molecules are able to move in the plane of the membrane. Fluidity is the quality of ease of movement and represents the reciprocal value of membrane viscosity. Fluid properties of biological membranes are essential for numerous cell functions. Even slight changes in membrane fluidity may cause aberrant function and pathological processes. Several evidences suggest that trace elements, e.g., iron, copper, zinc, selenium, chromium, cadmium, mercury and lead may influence membrane fluidity. The interaction of heavy metals with cellular membranes may contribute to explain, at least partially, the toxicity associated with these metals.

Differential diagnosis of microcytic anemia: the role of microcytic and hypochromic erythrocytes.

INTRODUCTION: Various indices derived from red blood cell (RBC) parameters have been described for distinguishing thalassemia and iron deficiency. We studied the microcytic to hypochromic RBC ratio as a discriminant index in microcytic anemia and compared it to traditional indices in a learning set and confirmed our findings in a validation set. METHODS: The learning set comprised samples from 371 patients with microcytic anemia mean cell volume (MCV < 80 fL), which were measured on a CELL-DYN Sapphire analyzer and various discriminant functions calculated. Optimal cutoff values were established using ROC analysis. These values were used in the validation set of 338 patients. RESULTS: In the learning set, a microcytic to hypochromic RBC ratio >6.4 was strongly indicative of thalassemia (area under the curve 0.948). Green-King and England-Fraser indices showed comparable area under the ROC curve. However, the microcytic to hypochromic ratio had the highest sensitivity (0.964). In the validation set, 91.1% of microcytic patients were correctly classified using the M/H ratio. CONCLUSIONS: Overall, the microcytic to hypochromic ratio as measured in CELL-DYN Sapphire performed equally well as the Green-King index in identifying thalassemia carriers, but with higher sensitivity, making it a quick and inexpensive screening tool.

Iron, transferrin, and haptoglobin levels after a single bout of exercise in men.

Twelve, healthy male university student volunteers, between the ages of 20 and 23, were studied. All subjects were considered normal after cardiopulmonary and electrocardiographic examination. The maximal aerobic capacity (Vo2 max) of each subject was determined. The exercise programmes were performed on a mechanically braked Monark cycle ergometer. The subjects were required to perform the three tests, one per week. Each subject had a catheter inserted in an antecubital vein and blood samples were drawn at rest and at the end of exercise. Before and immediately after each exercise session total proteins (TP), hematocrit (Hct), hemoglobin (Hb), and other hematological parameters were measured. Serum iron (Fe), transferrin (TRF), and haptoglobin (HPT) were also determined. Immediately after the end of the exercise (TPT, RST, and IET), TP, Hb, Hct, and RBC increased significantly. TRF and HPT concentrations remained unchanged and iron decreased significantly after maximum sustained test (RST).

Effect of swimming to exhaustion, at low temperatures, on serum Zn, Cu, Mg and Ca in rats.

In order to study the response of plasma trace minerals during exercise in cold water at varying temperatures, three groups of ten male Wistar rats each were forced to swim until exhaustion in water at different constant temperatures (10, 20 and 32 degrees C), while another 3 groups were kept at rest in water at the same temperatures and another group at rest out of the water, at room temperature (21 degrees C). Rectal temperature (RT) was measured before and after the exercise. Samples of arterial blood were obtained under anaesthesia (pentobarbital) from the abdominal aorta after the exercise, and serum concentrations of Cu, Zn, Mg and Ca were determined by flame atomic absorption spectrophotometry (FAAS). The swimming time (ST) decreased in cold water, the values obtained at 10 and 20 degrees C being 3.3% and 8.5%, respectively, of those observed at 32 degrees C. The RT of the animals swimming at 32 degrees C was 32.5 +/- 1.8 degrees C (mean +/- SD) and fell to 25.0 +/- 2.0 and to 19.1 +/- 1.5 degrees C in those swimming, respectively, at 20 and 10 degrees C. The concentrations of Mg, Cu and Ca were significantly higher (+50%, +36% and +7%, respectively) in animals subjected to exercise with respect to the control groups in water, although there were no differences among the three groups. On the contrary, Zn rose progressively with the increase of WT (+32% at 10 degrees C, +60% at 20 degrees C and +76% at 32 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)

Iron stores in professional athletes throughout the sports season.

Sports anemia provoked by iron deficiency develops slowly and although the existence or reality of this condition is under discussion, the ferritin levels tend to reduce with sports practice. This paper analyzes the variations of iron metabolism, including the organism stores of this metal throughout a sports season in a group of professional sportsmen (soccer players) belonging to a team of the Spanish First Division. For the determination of the iron stores, a computer program has been developed that takes into account the ferritin concentrations, hemoglobin, and saturation of transferrin. The results show that at the end of the season, when the ferric supplementation, which had been performed at the other moments of analysis, was no longer administered the iron stores reduced significantly, as well as the serum ferritin concentration, without such decreases being considered as a prelatent (grade I) anemia.

Iron nutritional status in female karatekas, handball and basketball players, and runners.

The iron nutritional status was studied in 84 sportswomen (19 karatekas, 20 handball players, 20 basketball players, and 25 middle and long distance runners) and in 82 nonathletic females of similar characteristics (control group). After a 7-day nutritional survey by means of the food weighing method, it was found that iron intake was significantly higher in the handball players (p < 0.05), basketball players (p < 0.01), and runners (p < 0.01) with regard to the control group; the basketball players were the only ones to cover the recommended minimum intake (15 mg/day). The heme iron intake was significantly greater in the handball and basketball players (p < 0.01), who, together with the runners, reached the value of 1.5 mg/day, which is considered to be optimal. In relation to the control group, the karatekas and handball and basketball players had lower levels of serum ferritin, although their iron intake was greater, whereas the runners had higher values that were very similar to those of the control group, due to the iron supplementation they had received. Despite finding a marked prevalence of inadequate iron intake, both in the sportswomen and in the control group, the manifest cases of anemia are relatively scarce. The organic iron stores do not seem to depend exclusively on the iron intake but also on intimate mechanisms of intestinal absorption and diverse causes of iron loss.

Displacement of rifampicin bound to serum proteins by addition of levamisole.

We have studied, by ultrafiltration, the interactions between rifampicin (15 and 30 microM) and levamisole (7 microM) since both drugs may be associated for the treatment of brucellosis. We can observe a statistically significant increase in the free plasmatic fraction of rifampicin at the studied concentration of levamisole, which indicated that levamisole reduced rifampicin bound to proteins (290 and 250%, respectively).

Hematological indices as markers of ischemic heart disease in young smokers.

This paper evaluates the hematological indices in young smokers compared to non-smokers of similar age, diet, physical exercise, profession and alcohol consumption.

Calcitonin and metabolic alkalosis.

Calcitonin is used in the treatment of osteoporosis and several adverse effects, such as rash, antibody presence, hypocalcemia, etc have been reported with the therapeutic use of large quantities of this hormone. The results found in this paper show that 7 h after administration of large doses of calcitonin to osteoporotic patients on hormone treatment, the acid-base status shifts to metabolic alkalosis. This represents another adverse effect of the use of pharmacological doses of calcitonin.

Longitudinal study of serum copper and zinc levels and their distribution in blood proteins after acute myocardial infarction.

The levels and distribution of serum Cu and Zn were studied in patients diagnosed with acute myocardial infarction from the day of admission to the Cardiovascular Intensive Care Unit until the 10th day following the attack. The results obtained show that Cu increases significantly (p < 0.01) after the 5th day after the acute myocardial infarction, while Zn decreases significantly (p < 0.01) with respect to the control group from the first day on, with the lowest values being found on the 3rd day after the attack. Further, total serum Cu showed an excellent correlation with the albumin-bound and globulin-bound Cu (ceruloplasmin), as well as with the concentrations of both serum protein fractions. In contrast, total serum Zn only presents this correlation with Zn bound to albumin, but not with Zn bound to globulin nor with the albumin concentration. These findings suggest the existence of some type of relationship between the two fractions of the element bound to protein. This relationship is probably different for both metals.

Short- and long-term effects of calcitonin and calcium administration on blood calcium, magnesium and inorganic phosphorus in post menopausal osteoporosis.

This paper studies the effects of the administration of calcitonin (CT) and Ca on post menopausal osteoporosis, immediately (short-term) and after three months (long-term) of treatment, on total and ionic calcium (Ca), magnesium (Mg), inorganic phosphorus (Pi), calcitonin (CT) and parathyroid hormone (PTH) in plasma. The short-term results show a decrease in total and ionic Ca and Pi four hours after the beginning of the treatment; at seven hours, only Pi varies. A decrease in the total and ionic Ca was observed after three months of CT treatment (long-term effects). No hormonal (PTH and CT) variations were found either in the short or the long-term. However, the PTH/CT ratio decreased significantly during the experiment and this may be an important factor in explaining the long-term Ca variations.

The effect of exercise and zinc supplement on the hematological parameters in rats.

This study evaluates the consequences of a session of intensive short-duration exercise and Zn supplementation on different hematological variables. Forty male Wistar rats were divided into four groups (n = 10): the first nonsupplemented, maintained at rest (R); the second nonsupplemented, undergoing exercise (E); the third supplemented with Zn, kept at rest (ZnR); and the fourth supplemented with Zn, undergoing exercise (ZnE). Zinc supplements (200 ppm) were given in drinking water. The exercise consisted of a single session of swimming until exhaustion. At rest, RBC, Hb, and Hto fell (p < 0.05), whereas red cell indices, MCV, and MCH rose (p < 0.05) in +ZnR compared with R; MCHC remained unchanged (ZnR vs R). After exercise, RBC, Hb, and Hto increased significantly in E and in ZnE compared with R and ZnR, respectively. In addition, RBC and Hb were lower (p < 0.01) in ZnE compared with E; however, MCV and MCH were higher (p < 0.05) in the group ZnE vs E. With respect to white blood cells--leukocytes (WBC), lymphocytes (LYMPH), and neutrophils (NEUT)--no significant differences were observed between groups at rest (ZnR vs R). WBC and LYMPH increased significantly in E with respect to the rest situation (E vs R), but this did not happen in supplemented animals (ZnE vs ZnR). Level of pH decreased after exercise both in E and in ZnE, but the fall was lower in the latter. We believe that a single session of swimming until exhaustion leads to an increase in RBC, Hb, and Hto without causing changes in MCV, MCH, and MCHC.(ABSTRACT TRUNCATED AT 250 WORDS)

Zinc uptake by human erythrocytes with and without serum albumins in the medium.

Different mechanisms of Zn uptake are present in mammalian cells. The variations in the Zn uptake by human erythrocytes in the absence and presence of albumins, bovine and human, as well as the differences of Zn uptake with and without 4-4'-diidothiocyanatostilbene-2,2'-disulfonic acid have been analyzed in this study. The results show a significantly greater rate of Zn uptake in the absence rather than in the presence of albumins in the extracellular medium and being significantly greater with bovine than with human serum albumin when the experiments were performed in media with equimolar concentrations of Zn. However, when comparing Zn uptake in a medium without albumin with similar free-Zn concentration to Zn ultrafiltrable (20%) of other one with albumin, a significantly greater Zn uptake on the latter was observed. The DIDS inhibition on Zn uptake is higher if the albumin is also present in the medium. These results suggest that in Zn uptake by erythrocytes the albumin directly or indirectly would be involved, facilitating the well-known processes of passive transport and anionic exchanger.

Effects of albumin and adenosine phosphates on iron transfer from ferric lactate.

Ferric lactate is known to modify Ca2+ uptake by the cells. To enlighten the role of protein and ATP in this phenomenon, iron transfer from ferric lactate to albumin and adenosine polyphosphates was determined by electrophoresis. The order of iron affinity was ATP > ADP > AMP for the polyphosphates, and albumin does not compete for iron binding with the polyphosphates. The iron transfer to ATP was also observed in vivo by adsorption chromatography of the adenosine polyphosphates fraction from blood plasma of mice injected with ferric lactate plus ATP. In vitro iron and calcium uptake by Ehrlich ascites tumor cells showed that albumin and ATP decreased iron uptake, whereas calcium incorporation is diminished by albumin but augmented by ATP. This difference might be explained by albumin binding of ferric lactate that is inhibited from reaching cell structures, whereas ATP, known to be an inhibitor of iron polymerization, facilitates it.

Effects of calcium, magnesium, tobramycin and theophylline on phenobarbitone binding to serum proteins.

Binding of phenobarbitone to human serum proteins was determined in vitro using ultrafiltration. At therapeutic concentrations of 10-600 microM, 63.51 +/- 2.5% of the phenobarbitone was bound to total serum proteins. The binding kinetics were non-saturable and the plasma apparent affinity coefficient (NKa) was 0.791 +/- 0.09 for normal serum and 0.664 +/- 0.06 for chromatographed serum. Tobramycin and theophylline at therapeutic concentrations of 10 and 15 micrograms/ml, respectively, reduced NKa compared with the values found in normal serum. Calcium and especially magnesium at physiological concentrations of 2.5 and 5 mM, respectively, increased NKa compared with values obtained in chromatographed serum, whereas at supraphysiological concentrations of magnesium of 15 mM NKa was reduced. It is concluded that free phenobarbitone concentrations in serum can be modified by calcium, magnesium, tobramycin and theophylline, and this fact must be considered when studying enzyme induction and other properties of phenobarbitone.

Changes in serum lipid and lipoprotein measures after maximal exercise in men.

Normolipidaemic, healthy male volunteers (age range 20-23 years) were studied after a session of three maximal exercises and serum lipid and lipoprotein concentrations were measured. The exercise programmes, one of which was performed each week, consisted of a triangular progressive test (TPT), a rectangular sustained test (RST) and an interval endurance test (IET). There was a significant (P less than 0.05) increase of 14% in serum total cholesterol concentrations after TPT, 9.6% after RST and 14% after IET. Serum triglyceride concentrations increased by 17% after TPT, 5.7% after RST and 8.2% after IET, but increases were not significant. High-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C), and apolipoprotein (A-I, A-II) concentrations rose significantly (P less than 0.05) after TPT. There were also insignificant increases in AI, AII and LDL-C after RST and IET, whereas HDL-C rose significantly (P less than 0.05) after IET. It is concluded that the three maximal exercises had similar metabolic effects which were independent of the exercise duration.