Minerals: exercise performance and supplementation in athletes

Effects of Supplementing Zinc Magnesium Aspartate on Sleep Quality and Submaximal Weightlifting Performance, following Two Consecutive Nights of Partial Sleep Deprivation

Purpose: We examined whether supplementation of zinc magnesium aspartate (ZMA), while partially sleep deprived, was beneficial to sleep quality and subsequent morning (07:00 h) submaximal weightlifting. Methods: Using a double-blinded, randomized counterbalanced design, sixteen trained males were recruited and completed six sessions: (i) one repetition max (1 RM) for bench press and back squat; (ii) two familiarisation sessions; (iii) three conditions with 4 h sleep and either: ZMA, placebo (PLA), or NoPill control (NoPill). Submaximal exercise session consisted of three repetitions at 40, 60 and 80% of 1 RM for bench press and back squat. Average power (AP), average velocity (AV), peak velocity (PV), displacement (D) and time-to-peak velocity (tPV) were recorded using MuscleLab linear encoders. Data were analysed using a general linear model with repeated measures and linear correlation. Results: No significant main effect for condition was found for performance values or subjective ratings of fatigue. Main effect for "load" on the bar was found, where AP and tPV values increased with load (p < 0.05). No significant relationship between dose of zinc or magnesium ingested and change in performance for 80% 1 RM power-outputs was found. Conclusion: Supplementation of ZMA for two nights of partial sleep deprivation had no effect on sleep or subsequent morning performance.

Erythrocyte concentrations of chromium, copper, manganese, molybdenum, selenium and zinc in subjects with different physical training levels

Background

The aim of the present study was to determine changes occurring in the erythrocyte concentrations of chromium (Cr), copper (Cu), manganese (Mn), molybdenum (Mo), selenium (Se) and zinc (Zn) in male subjects with different training levels living in the same region (Spain).

Methods

Thirty sedentary subjects (24.34 ± 3.02 years) formed the control group (CG); 24 moderately trained (4–7 h/week) subjects (23.53 ± 1.85 years) formed the group with a moderate degree of training (MTG) and 22 professional cyclists (23.29 ± 2.73 years), who performed more than 20 h/week of training, formed the high-level training group (HTG). Erythrocyte samples were collected from all subjects in fasting conditions, washed and frozen at − 80 °C until analysis. Erythrocyte analysis of trace elements was performed by inductively coupled plasma mass spectrometry (ICP-MS).

Results

The results showed that there was a statistically significant lower erythrocyte concentration of Cu, Mn, Mo and Zn in the MTG and HTG than CG. Se was only significantly lower in HTG than CG. The correlation analysis indicates that this change was correlated with training in the case of Cu, Mn, Se and Zn. All results are expressed in μg/g Hb.

Conclusions

We can conclude that physical training produces a decrease in erythrocyte concentrations of Cu, Mn, Se and Zn, which can cause a decrement in athletes’ performance given the importance of these elements. For this reason, erythrocyte monitoring during the season would seem to be advisable to avoid negative effects on performance.

Responses of trace elements to aerobic maximal exercise in elite sportsmen

Trace elements are chemical elements needed in minute quantities for the proper growth, development, and physiology of the organism. In biochemistry, a trace element is also referred to as a micronutrient. Trace elements, such as nickel, cadmium, aluminum, silver, chromium, molybdenum, germanium, tin, titanium, tungsten, scandium, are found naturally in the environment and human exposure derives from a variety of sources, including air, drinking water and food. The Purpose of this study was investigated the effect of aerobic maximal intensity endurance exercise on serum trace elements as well-trained individuals of 28 wrestlers (age (year) 19.64±1.13, weight (Kg) 70.07 ± 15.69, height (cm) 176.97 ± 6.69) during and after a 2000 meter Ergometer test protocol was used to perform aerobic (75 %) maximal endurance exercise. Trace element serum levels were analyzed from blood samples taken before, immediately after and one hour after the exercise. While an increase was detected in Chromium (Cr), Nickel (Ni), Molybdenum (Mo) and Titanium (Ti) serum levels immediately after the exercise, a decrease was detected in Aluminum (Al), Scandium (Sc) and Tungsten (W) serum levels. Except for aluminum, the trace elements we worked on showed statistically meaningful responses (P < 0.05 and P < 0.001). According to the responses of trace elements to the exercise showed us the selection and application of the convenient sport is important not only in terms of sportsman performance but also in terms of future healthy life plans and clinically.

Magnesium enhances exercise performance via increasing glucose availability in the blood, muscle, and brain during exercise

Glucose mobilization and utilization in the periphery and central nervous system are important during exercise and are responsible for exercise efficacy. Magnesium (Mg) is involved in energy production and plays a role in exercise performance. This study aimed to explore the effects of Mg on the dynamic changes in glucose and lactate levels in the muscle, blood and brain of exercising rats using a combination of auto-blood sampling and microdialysis. Sprague-Dawley rats were pretreated with saline or magnesium sulfate (MgSO₄, 90 mg/kg, i.p.) 30 min before treadmill exercise (20 m/min for 60 min). Our results indicated that the muscle, blood, and brain glucose levels immediately increased during exercise, and then gradually decreased to near basal levels in the recovery periods of both groups. These glucose levels were significantly enhanced to approximately two-fold (P<0.05) in the Mg group. Lactate levels in the muscle, blood, and brain rapidly and significantly increased in both groups during exercise, and brain lactate levels in the Mg group further elevated (P<0.05) than those in the control group during exercise. Lactate levels significantly decreased after exercise in both groups. In conclusion, Mg enhanced glucose availability in the peripheral and central systems, and increased lactate clearance in the muscle during exercise.

Effects of rehydration and food consumption on salivary flow, pH and buffering capacity in young adult volunteers during ergometer exercise

Background

The aim of this study was to investigate the influences of rehydration and food consumption on salivary flow, pH, and buffering capacity during bicycle ergometer exercise in participants.

Methods

Ten healthy volunteers exercised on a bicycle ergometer at 80% of their maximal heart rate. These sessions lasted for two periods of 20 min separated by 5-min rest intervals. Volunteers were subjected to one of the following conditions: (1) no water (mineral water) or food consumption, (2) only water for rehydration, (3) water and food consumption, (4) a sports drink only for rehydration, and (5) rehydration with a sports drink and food. Statistical significance was assessed using one-way analysis of variance and Dunnett’s test (p < 0.05).

Results

The salivary pH decreased significantly during and after exercise in conditions 4 and 5. The salivary buffering capacity decreased significantly during exercise and/or after the exercise in conditions 1, 3, 4, and 5.

Conclusions

The results showed that salivary pH and buffering capacity decreased greatly depending on the combination of a sports drink and food.

Effects of magnesium supplementation on testosterone levels of athletes and sedentary subjects at rest and after exhaustion

This study was performed to assess how 4 weeks of magnesium supplementation and exercise affect the free and total plasma testosterone levels of sportsmen practicing tae kwon do and sedentary controls at rest and after exhaustion. The testosterone levels were determined at four different periods: resting before supplementation, exhaustion before supplementation, resting after supplementation, and exhaustion after supplementation in three study groups, which are as follows: Group 1-sedentary controls supplemented with 10 mg magnesium per kilogram body weight. Group 2-tae kwon do athletes practicing 90-120 min/day supplemented with 10 mg magnesium per kilogram body weight. Group 3-tae kwon do athletes practicing 90-120 min/day receiving no magnesium supplements. The free plasma testosterone levels increased at exhaustion before and after supplementation compared to resting levels. Exercise also increased testosterone levels relative to sedentary subjects. Similar increases were observed for total testosterone. Our results show that supplementation with magnesium increases free and total testosterone values in sedentary and in athletes. The increases are higher in those who exercise than in sedentary individuals.

Elements in sera of elite taekwondo athletes: effects of vitamin E supplementation

Many researchers have emphasized the relation between nutrition and development and sustaining performance. Two methods are commonly employed to identify the interaction between physical activity and nutrition. The first consists of administering food with a variety of contents to people engaged in physical activity and observing their performance responses, and the other is concerned with determining the effects of physical activity on nutrition. Therefore, it can be said that there has been a growing interest in the explorations into the relation between exercise and vitamins, minerals, and elements. The present study reports the effects of 6 weeks administration of 300 mg/day vitamin E on the distribution of serum elements in elite taekwondo athletes. Seven male athletes, mean ages 22.1 ± 0.5 years weighing on average 66.4 ± 2.4 kg were included in the study. The athletes had been practicing taekwondo for 10-12 years. Resting blood samples were collected in duplicate before and after supplementation for determination of serum levels of cobalt, boron, cadmium, chromium, nickel, manganese, sulfur, copper, iron, zinc, phosphorus, sodium, potassium, and calcium. Supplementation resulted in significant increases of all elements relative to values before supplementation (p < 0.001), with the exception of boron and sulfur, which remained without change. The results of the present study demonstrate that vitamin E supplementation crucially influences the element and mineral metabolism in elite athletes.

Serum levels of Cu, Se, and Zn in adult rural/urban residents in Ghana: paradigm shift?

Deficiencies in Cu, Se, and Zn impair one or more biochemical functions, and excess are associated with toxicity. Baseline studies on the Ghanaian population are scanty. The study was undertaken to determine whether significant rural/urban differences in the serum levels of Cu, Se, and Zn did exist. Forty males/60 females from rural and 50 males/50 females from urban Ghanaian communities were sampled. Serum Cu, Se, and Zn were determined using flame atomic absorption spectrometry. Cu level for rural and urban subjects was 997 +/- 333 and 979 +/- 290 microg/L, respectively (p = 0.68). However, Cu levels were significantly higher in the rural females (1,063 +/- 367 microg/L) than the rural males (898 +/- 249 microg/L; p = 0.0085). Se levels for rural/urban subjects were 97 +/- 36 and 87 +/- 31 microg/L, respectively (p = 0.03). Zn levels in the rural/urban subjects were 312 +/- 218 and 150 +/- 102 microg/L, respectively (p = 0.002). Additionally, Zn was significantly higher in rural females (428 +/- 204 microg/L) than the urban females (166 +/- 103 microg/L; p = 0.0002). Finally, Zn was significantly higher in rural females (428 +/- 204 microg/L) than males (172 +/- 116 microg/L; p = 0.0028). In conclusion, Cu, Se, and Zn were higher in the rural group compared to the urban group, and the generally low Zn levels were confirmed in another cohort follow-up study.

Magnesium sulfate enhances exercise performance and manipulates dynamic changes in peripheral glucose utilization

The effect of magnesium supplementation on exercise performance remains controversial. In the present study, the effects of magnesium sulfate on exercise performance and blood glucose metabolism were examined. In order to provide a non-invasive measure of continuous exercise, we developed an auto-blood sampling system was coupled to a microdialysis analyzer to detect the dynamic changes in glucose metabolism in conscious and freely moving gerbils subjected to forced swimming. Gerbils were pretreated with saline or magnesium sulfate (90 mg kg(-1), ip) 30 min before exercise. The duration times were significantly increased by 71% in the magnesium sulfate-treated groups (p < 0.01) when compared with those in the control. Another group of gerbils were subjected to blood sampling assay. A catheter was implanted in the jugular vein of each gerbil for collecting blood samples by the computer-aided blood sampler. The basal levels of plasma glucose, lactate, and magnesium were 6,245 +/- 662, 1,067 +/- 309, and 590 +/- 50 microM, respectively, with no significant difference between groups. Plasma glucose, lactate, and magnesium levels increased to 134 and 204%, 369 and 220%, and 155 and 422% of basal levels during swimming in both the control and magnesium sulfate-treated groups, respectively (p < 0.05). Pretreatment with magnesium sulfate elevated glucose and magnesium levels to 175 and 302% of the basal levels (p < 0.05), respectively, whereas pretreatment with magnesium sulfate reduced the lactate levels 150% of the basal level (p < 0.05) during swimming. Furthermore, the magnesium levels increased to about 152-422% of basal levels during forced swimming and the recovery period (p < 0.05). The present study demonstrates that magnesium sulfate improved the duration time of forced swimming exercise. In addition, magnesium raised glucose levels and attenuated lactate levels during forced swimming. These results indicate that positive effects of magnesium supplementation may contribute to the enhancement of exercise performance in athletes.

Effects of acute swimming exercise on some elements in rats

The objective of the present study is to explore the effects of acute swimming exercise on plasma levels of some elements in rats, immediately after the exercise, and 24 and 48 h later. The study included 40 adult male rats of Spraque Dawley species, which were equally allocated to four groups. Group 1: General Control Group; Group 2: Swimming Group, the group that was decapitated immediately after 30-min acute swimming exercise; Group 3: Swimming Group, the group that was decapitated 24 h after 30-min acute swimming exercise; Group 4: Swimming Group, the group that was decapitated 48 h after 30-min acute swimming exercise. Plasma copper (Cu), iron (Fe), magnesium (Mg), phosphorus (P), selenium (Se), zinc (Zn) levels were determined according to atomic emission method in the blood samples collected from the animals by decapitation method. Measurements conducted immediately after acute swimming exercise (group 2) showed a significant decrease in Se and Zn levels (p < 0,01) and a significant increase in P levels (p < 0,01), when compared to group 1. Measurements carried out 24 h after the exercise (group 3) demonstrated a significant increase in all parameters except for Mg, in comparison to groups 1 and 2 (p < 0,01). It was seen in the measurements made 48 h after the exercise (group 4) that all parameters were restored to control values. The results of our study show that acute swimming exercise significantly changes plasma Cu, Fe, P, Se, and Zn levels.

Adrenocorticotropic hormone and cortisol levels in athletes and sedentary subjects at rest and exhaustion: effects of magnesium supplementation

The effects of a 1-month exercise program and magnesium supplementation on the adrenocorticotropic hormone and cortisol levels were studied in young tae-kwon-do and sedentary subjects both at rest and exhaustion. The hormone levels were compared before and after supplementation with 10 mg of magnesium (as magnesium sulfate) per kilogram of body weight. Both exercise and magnesium supplements caused significant increases of the adrenocorticotropic hormone (p < 0.05). The cortisol levels were increased in training subjects receiving supplements (p < 0.05) but not so in subjects that either trained or received magnesium supplements in an independent manner. The cortisol levels measured in resting individuals were higher in the supplemented and non-supplemented athletes than those in sedentary subjects (p < 0.05). The results of this study show that exercise and/or magnesium supplementation causes a rise of the adrenocorticotropic hormone, whereas cortisol is increased only as a result of combined exhaustion and magnesium supplements.

Effects of magnesium sulfate on dynamic changes of brain glucose and its metabolites during a short-term forced swimming in gerbils

This investigation examined the acute effects of magnesium on the dynamic changes of brain glucose, lactate, pyruvate and magnesium levels in conscious gerbils during forced swimming. Gerbils were pretreated with saline (control group) and magnesium sulfate (90 mg kg(-1), intraperitoneal injection) before a 15 min forced swimming period. The basal levels of glucose, pyruvate, lactate, and magnesium in brain dialysates were 338 +/- 18, 21 +/- 2, 450 +/- 39, and 2.1 +/- 0.1 microM, respectively, with no significant difference between groups. Magnesium levels were found slightly higher (but not significant) in the magnesium-treated group. However, brain glucose and pyruvate levels in the control group decreased to about 50 and 60% of the basal level (P = 0.01) after swimming, respectively. Pretreatment with magnesium sulfate immediately increased glucose levels to about 140% of the basal level, and increased pyruvate levels to about 150% of the basal level during forced swimming (P = 0.01). Both glucose and pyruvate levels returned to the basal level after 30 min of the recovery. The lactate levels of the control group increased to about 160% of the basal level (P = 0.01) during swimming, whereas pretreatment with magnesium sulfate attenuated lactate levels to 130% of the basal level (P = 0.01). Magnesium supplementation may be beneficial because it provides an additional glucose source and may also promote the recovery of energy substrates in the brain during and after forced exercise. In order to achieve optimal physical performance, further investigation as to dosage of magnesium supplementation is needed.

Hand Strike-Induced Hemolysis and Adaptations in Iron Metabolism in Basque Ball Players

INTRODUCTION

Basque ball players (BBPs) make repeated hand strikes to the ball which involves continuous mechanical trauma.

OBJECTIVE

The aim of this work is to describe the hematological variations and changes in iron metabolism occurring in BBPs as a result of acute and continuous practice of this special sport native to Northern Spain.

METHODS

40 healthy male subjects volunteered to participate in this study: 11 subjects who exercise moderately (control group) but do not play Basque ball sport and 29 professional BBPs were studied in two situations: before a match (BM group) and after a match (AM group). The following hematological parameters were determined: red blood cell count (RBC), hemoglobin and hematocrit; MCV, MCH and MCHC. The following variables were measured in serum: iron, ferritin, transferrin, transferrin saturation, proteins, and lactate dehydrogenase (LDH). Proteins and hemoglobin were determined in urine.

RESULTS

The BM group showed lower hematocrit, MCV, hemoglobin and serum transferrin levels, and higher LDH than controls. The AM group showed higher RBC, hemoglobin, serum proteins, iron, transferrin and LDH levels, lower plasma volume, and higher urine hemoglobin and protein levels than the BM group.

CONCLUSIONS

Basque ball playing induces hemolysis and increases the plasma capability to quench free iron, but its clinical consequences on iron metabolism do not seem to be enough to take an iron intake proportional to the caloric intake. In order to prevent, in the long term, the development of anemia in these peculiar sportsmen, it would be useful that medical teams observe urine blood losses and oxidative stress in these BBPs.

Alterations of ionized Mg2+ in human blood after exercise

Magnesium (Mg) is the second most abundant intracellular cation with modulating properties in a number of metabolic processes, e.g. in glycolysis, and intracellular signalling processes, e.g. regulation of ion channels and transporters. There are conflicting data available about the regulation of Mg in blood cells during exercise. Moreover, there are no data available about changes of the metabolic important fraction of ionized Mg(2+) both in blood and in blood cells during exercise. The present study investigated the changes of ionized Mg(2+) and total Mg concentration in different compartments after a stepwise treadmill ergometer test. Intracellular ionized Mg(2+) of thrombocytes and erythrocytes was determined by the magnesium sensitive fluorescent dyes mag-fura-2 and Mag-Green using fluorescence spectroscopy and flow cytometry, respectively. Ionized Mg(2+) in blood/serum was measured by an ion-sensitive microelectrode. Total cellular and serum Mg concentration were investigated using atomic absorbance spectroscopy and photometry, respectively. The present results shown that at the end of the ergometer test, ionized Mg(2+) in both blood and serum and total serum Mg decreased. In contrast, intracellular concentration of ionized Mg increased in both thrombocytes and erythrocytes. Total intracellular Mg was unchanged making a Mg(2+) shift between the intra- and extracellular compartment unlikely. The present study therefore demonstrated opposite changes of the ratio [ionized Mg(2+)]/[total Mg] in the intracellular and the extracellular compartment after anaerobic exercise. In in vitro experiments, similar changes of ionized Mg(2+) in both compartments could be mimicked by application of weak acids like propionic and lactic acid. It is concluded changes in the fraction of ionized Mg(2+) should be high enough to influence intracellular signalling and metabolic processes.

Urine nandrolone metabolites: false positive doping test?

The aim of this review is to analyse the studies on nandrolone metabolism to determine if it is possible for an athlete to test positive for nandrolone without having ingested or injected nandrolone.

Aspectos nutricionais do futebol de competição

O futebol envolve exercícios intermitentes e a intensidade do esforço físico depende do posicionamento do atleta, qualidade do adversário e importância do jogo. Pretende-se rever as principais alterações metabólicas desses atletas com prováveis implicações nutricionais e/ou na conduta dietética para melhor desempenho. O gasto energético de um jogador de futebol é estimado em 1.360kcal/jogo. As atividades do segundo tempo são 5% menores que as do primeiro, com variações diretamente relacionadas com os níveis do glicogênio muscular pré-jogo. Em jogadores de elite o consumo das reservas de glicogênio muscular, durante o jogo, varia de 20% a 90%, dependendo de fatores como: condicionamento físico, intensidade do esforço, temperatura ambiente e composição dietética pré-competição. Desidratação e hipertermia são aceleradores do consumo de glicogênio e, assim, da fadiga muscular, perceptível, particularmente, no segundo tempo, quando o atleta evita sprints, caminha mais do que corre e reduz a distância percorrida. A hidratação e suprimento glicídico constituem, então, os principais ergogênicos nutricionais para os futebolistas. Por ser uma modalidade esportiva sem intervalos regulares, o futebol não permite a reposição hidroeletrolítica periódica. Por isso, recomenda-se que o atleta inicie o jogo bem hidratado, ingerindo meia hora antes 500ml de líquido contendo polímeros de glicose (5%-8%). O aumento do desempenho físico é verificado com a ingestão de dietas contendo 312g de carboidrato quatro horas antes do jogo e, para a normalização do glicogênio muscular, após o jogo, recomenda-se oferta de dieta contendo 7-10g/kg/24h com maior consumo nas duas primeiras horas. Os futebolistas encontram-se sob risco constante de deficiências latentes de micronutrientes pelo desgaste muscular, perdas intestinais, sudorese intensa, viagens constantes, mudanças de fuso horário e cardápios. Para o caso específico dos futebolistas, os maiores desbalanceamentos parecem ocorrer pelo elevado consumo de proteínas, gorduras e álcool e baixa ingestão de carboidratos.

Functional food science and substrate metabolism

The present review addresses the role of food constituents in the aetiology of metabolic conditions and chronic diseases, mostly related to energy metabolism and substrate regulation, such as obesity and non-insulin-dependent diabetes mellitus. Second, attention is paid to malnutrition, a major cause of mortality and morbidity in developing countries, which may be a cause of concern in Europe because of the increasing number of elderly people in the population. Finally, the role of diet during exercise, a condition of enormous substrate demands, is evaluated. Based on a critical evaluation of the existing knowledge in the literature, implications for future research in relation to functional foods are discussed.

Effects of zinc supplementation on vertebral and femoral bone mass in rats on strenuous treadmill training exercise

The hypothesis that a zinc (Zn) deficit may cause osteopenia in athletes is well founded. In rats exposed to strenuous exercise, we evaluated the effect of a zinc supplement on femoral and vertebral bone mass determined by dual-energy X-ray absorptiometry. Four lots of 93-day-old female Wistar rats were studied. A control group of 30 rats were not manipulated (Zn- Ex- group). The experimental group of 40 rats was fed a diet supplemented with an additional 20% of Zn/kg of feed; this group was divided into two groups of 20 rats each, one that did not exercise (Zn+ Ex-) and one that did (Zn+ Ex+). A group of 15 rats exercised but did not receive a zinc supplement (Zn- Ex+ group). Training consisted of treadmill running for 5 out of 7 days over an 11-week period. Initial speed, running time, and treadmill speed were increased gradually. Analysis of variance with the Bonferroni/Dunn test showed that the length, weight, bone mineral content (BMC), and bone mineral density (BMD) of the femur were less in the Zn- Ex+ group than in the others (p < 0.008), and the weight, BMC, and BMD of the fifth lumbar vertebra also were lower in the Zn- Ex+ group than in the others (p < 0.008). These findings confirm the adverse effects of strenuous exercise (treadmill running) on bone tissue in rats and the effectiveness of zinc supplementation in preventing it.

Compartmental shifts of calcium and magnesium as a result of swimming and swimming training in rats

To describe accurately the mineral changes (Ca and Mg) provoked by swimming, the aims of this study were to analyze those tissues that, with regard to their mineral content, can better classify individuals performing both swimming until exhaustion and swimming as training and to know the shifts of these minerals between different tissues after a single session of swimming until exhaustion and after training. Wistar rats were distributed into 12 groups, six male and six female (N = 10): 1) control rest group (CR); 2) trained rest group (TR); 3) control exercise group (CE); 4) trained exercise group (TE); 5) control recovery group (CER) and 6) trained recovery group (TER). The most informative tissues of Ca and Mg compartmental shifts during exercise have been determined. Discriminant analysis selected heart Ca, muscle Ca and bone Ca, bone Mg, erythrocyte Mg, and serum Mg as the most significant variables. The animals were classified by means of two canonical axes: the first one relates to training situation and sex, and the second one shows the special characteristics of trained male rats. Another independent discriminant analysis applied to male and female groups separately showed that the first canonical axis (control/trained) is basically defined by heart Ca, bone Ca, and erythrocyte Mg (male), and by heart Ca, bone Ca, and bone Mg (female), while the second axis, related to the exercise situations, is defined by the serum Mg levels in both sexes. We think that discriminant analysis is a statistical method capable of explaining physiological processes and classifying individuals performing exercises of different length. It suggests that the homeostasis of Ca and Mg is somewhat different for males and females. Serum magnesium must be considered to distinguish exercise situations. The analysis of these tissues could inform us about the mineral status of the rats and then we could correct possible deficiencies in our research. In this work we have only found different mineral redistributions among tissues. The trained animals have a better mineral recovery capacity than the untrained ones. Training has a different physiological repercussion in male and female rats on the basis of their respective maximal swimming times after training and their mineral behavior.

Nutrition for improved sports performance. Current issues on ergogenic aids

Several nutritional modifications have been used by athletes to improve performance. Recent attention has focused on high fat diets, branched-chain amino acids, creatine, carnitine, bicarbonate and phosphate loading, and caffeine. Of these, only caffeine, which is present in food but has no known nutritional value, appears on the list of substances banned by the International Olympic Committee (IOC). While there is a theoretical basis for each of these diet manipulations to enhance performance, there are insufficient data to state unequivocally that high fat diets, branched-chain amino acids, carnitine or phosphate loading are effective. Caffeine has been found to enhance endurance performance, while creatine and bicarbonate loading were generally found to benefit short term strenuous exercise. Acute ingestion of these diet manipulations appears safe, although some, like caffeine and bicarbonate, can cause gastrointestinal disturbances or other problems in certain individuals. Long term use of high fat diets may have negative consequences on health. The safety of long term use of these diet manipulations has not been established.

Evaluation of iron metabolism indices and their relation with physical work capacity in athletes

OBJECTIVE

To evaluate the relation between iron status and physical working capacity, and to assess the effect of oral iron treatment on these variables, in athletes with borderline iron status.

METHODS

Blood haemoglobin (Hb), packed cell volume (PCV), red blood cell count (RBC), serum iron, total iron binding capacity (TIBC), and ferritin determinations were compared in 71 male and 18 female athletes participating in various sports and in matched male (n = 11) and female (n = 8) controls. The first aim was to assess the relations between these variables and performance in a physical work capacity test (PWC170). Oral iron treatment (175-350 mg ferrous fumarate daily) was provided for three weeks to six male and five female athletes with borderline Hb concentrations, to determine the effects of such treatment on both iron status and performance.

RESULTS

Among females, handball players had the lowest serum ferritin concentrations (P < 0.05), the highest TIBC values, and lowest PWC170 scores (P < 0.01); runners had the highest ferritin concentrations and PWC170 scores (P < 0.01). There were significant correlations (P < 0.01) between PWC170 and PCV, serum ferritin, and transferrin saturation of female athletes. Hb, serum iron, serum ferritin, and transferrin saturation increased with iron treatment in both males (P < 0.01) and females (P < 0.05).

CONCLUSIONS

Serum ferritin determination may prove a valuable addition to the screening of athletes and may indicate the need for iron treatment, even though a causal effect on improvement of work capacity may not be present.

Effect of magnesium supplementation and training on magnesium tissue distribution in rats

The aim of this work is to study the effect of training and Mg supplementation on body pools of Mg and on Mg tissue distribution. Forty male Wistar rats were divided into four groups (n = 10): control group (C); trained group (T); Mg-supplemented group (+Mg); and trained and Mg-supplemented group (+MgT). The Mg supplement (1000 ppm of Mg) was given in the drinking water for 21 d. The training consisted of swimming during 60% of maximal swimming time obtained in the first session to exhaustion, during 3 wk (5 d a week). The variables measured were: erythrocytes (RBC), hemoglobin (Hb), hematocrit (Hto), total proteins (TP), and Mg in serum, RBC, liver, muscle, bone, and kidney. There was less Mg in liver, muscle, and erythrocyte in trained animals than in control or supplemented animals (T vs C, +MgT vs C and +MgT vs +Mg) (p < 0.01). Trained animals (T and +MgT) showed higher Mg kidney rates than the untrained ones (p < 0.01). There was less bone Mg in control (C) and in supplemented and trained (+MgT) groups than in trained (T) and in supplemented (+Mg) animals (p < 0.01). Serum Mg showed a decreasing concentration profile in the following order: +Mg, +MgT, T, C (p < 0.01). We conclude that Mg supplementation improves bone and serum Mg levels, but this does not affect Mg status in soft tissues. Maintained exercise leads to a diminution of Mg in the aforementioned soft tissues that is not noticeable in serum, probably provoked by an increase of renal excretion.

Trace mineral requirements for athletes

This paper reviews information pertaining to zinc, copper, chromium, and selenium requirements of athletes. Exercise increases zinc loss from the body, and dietary intake for some athletes, especially females, may be inadequate. Blood copper levels are altered by exercise, but there is no information to suggest that copper ingestion or status is compromised in athletes. Studies have shown that urinary chromium excretion is increased by exercise, but whether this leads to an increased requirement is still unknown. There is concern that athletes may not ingest sufficient quantities of chromium; however, there are inadequate data to confirm this. The limited data that exist show that athletes do not have altered selenium status. There is no conclusive evidence that supplementation with any of these trace minerals will enhance performance. A diet containing foods rich in micronutrients is recommended. However, for those athletes concerned that their diets may not be sufficient, a multivitamin/mineral supplement containing no more than the RDA may be advised.

Diet and athletic performance

Inadequate diet inhibits optimal performance in otherwise well-trained athletes. Controversy exists regarding specific dietary requirements, particularly in the areas of protein and vitamin/mineral supplementation. This article reviews energy substrate utilization, provides an overview of nutrient requirements during exercise, discusses ergogenic aids, and where possible, makes specific dietary recommendations for athletes.