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PubMed2005

Effects of short-term normobaric hypoxia on haematology, muscle phenotypes and physical performance in highly trained athletes.

This study aimed to determine the impact of short-term normobaric hypoxia on physiology and performance in highly trained athletes. Twelve (7 male and 5 female) athletes were randomly assigned into two groups and spent 8 h per night for two consecutive nights a week over 3 weeks under either short-term normobaric hypoxia (simulating 3636 m altitude, inspired O2=13%) or in normobaric normoxia in a single-blind study. Following a 3 week washout period, athletes were then exposed to the other condition. Athletes were tested for maximal oxygen consumption and time to exhaustion on an electromagnetically braked cycle ergometer before and after each treatment in addition to being tested for anaerobic performance (Wingate test) on a modified Monark cycle ergometer. Blood samples were taken throughout the experiment and vastus lateralis muscle biopsies were taken before and after each treatment. Increases in red blood cell count, haematocrit, haemoglobin, platelet number and erythropoietin concentration were observed following short-term normobaric hypoxia. Except for a modest decrease in phosphofructokinase activity following short-term normobaric hypoxia, no changes were observed in muscle enzyme activities, buffer capacity, capillary density or morphology. No performance measures were changed following short-term normobaric hypoxia or normobaric normoxia. Although short-term normobaric hypoxia exposure increased levels of a number of haematological parameters, this was not associated with improved aerobic or anaerobic performance in highly trained athletes.

Altitude↗

PubMed2005

Reduced ventricular flow propagation velocity in elite athletes is augmented with the resumption of exercise training.

Chronic exercise induces physiological enlargement of the left ventricle ('athlete's heart'), but the effects of current and long-term exercise training on diastolic function have not been investigated. Echocardiography and Doppler imaging were used to assess left ventricular (LV) dimensions and indices of diastolic filling in 22 elite athletes at the end of their 'off-season' (baseline) and, subsequently, following 3 and 6 months of training. Twelve matched controls were also studied at baseline, 3 and 6 months. Compared to controls at baseline, athletes exhibited significantly higher LV mass (235.7 +/- 7.1 g versus 178.1 +/- 14.5 g, P < 0.01) and reduced flow propagation velocity (V(P): 50.21 +/- 1.7 versus 72.2 +/- 3.6 cm s(-1), P < 0.01), a measure of diastolic function. Three months of training further increased LV mass in athletes (253.2 +/- 7.1 g; P < 0.01 versus baseline), and significantly increased their V(P) (66.7 +/- 2.5 cm s(-1); P < 0.05 versus baseline). These trends for increased mass and diastolic filling persisted following 6 months of training (LV mass 249.0 +/- 8.7 g P < 0.05 versus baseline; V(P) 75.7 +/- 3.0 cm s(-1); P < 0.01 versus baseline, and P = 0.01 versus 3 months). This study suggests that following a period of relative inactivity the rate of ventricular relaxation during early diastole may be slowed in athletes who exhibit ventricular hypertrophy, whilst resumption of training increases the speed of ventricular relaxation in the presence of further hypertrophy of the left ventricle.

Adaptation, Physiological↗

PubMed1991

Nutrition assessment of athletes: a model for integrating nutrition and physical performance indicators.

Athletes, like all people, have special nutritional needs based on their age, lifestyle, health status, level of physical activity, physical conditioning, and type of sport. The diets of many athletes are inadequate due to overly restrictive eating habits, nutrition misinformation, dietary fads, and/or obsession with weight and food. There is a growing need for sports nutrition counseling and education to help athletes improve their eating habits. However, before attempting to develop intervention strategies, sports nutritionists should assess the metabolic changes that take place during exercise and how these changes affect nutrition status. In addition, it is important to consider how psychosocial factors may influence an athlete's eating habits and his/her ability to make positive changes. A two-pronged model is introduced that can be used as a guide for the practitioner in interpreting relevant data and integrating physiological and psychological considerations for the design of individualized nutrition care plans for athletes.

Adult↗

PubMed1993

Nutrient intake of female elite athletes suffering from eating disorders.

This study assessed the nutrient intake and eating behavior in Norwegian female elite athletes suffering from eating disorders (ED) who met the criteria for anorexia nervosa (AN), anorexia athletica (AA), or bulimia nervosa (BN). The subjects included 7 AN, 43 AA, 42 BN, and 30 controls. Three-day and 24-hr food records were used to assess energy and nutrient intake. Results revealed that a significant number of AN and AA athletes have diets too low in energy and nutrients, the mean intake for energy and CHO being lower than recommended for active females. A significant number did not reach the protein level recommended for athletes. In addition, there were low intakes of several micronutrients, most notably calcium, vitamin D, and iron. The energy and nutritional inadequacy, combined with the use of purging, are of major concern since the athletes in this study were relatively young. It is unknown whether the abnormal eating pattern is a consequence of ED or is typical of top level athletes.

Adolescent↗

PubMed1993

How to help the athlete with bulimia: practical tips and a case study.

Surveys suggest that 8 to 41% of athletes may struggle with binge/purge and bulimic eating behaviors. Many of these athletes with bulimia struggle alone, receiving no professional help for recovery. This article offers effective counseling strategies for nutrition professionals who want to help bulimic athletes. Through a case study of a triathlete who binges, and then purges through compulsive exercise, a nutrition care plan is discussed that addresses the food and weight concerns commonly expressed by athletes with bulimia. The priorities of the care plan are to reduce preoccupation with weight, establish a pattern of regular eating, and address the underlying causes of the binges. The case demonstrates that nutrition counseling is only one part of the treatment program, and emphasizes the importance of developing a team of health professionals to assist athletes with bulimia.

Adult↗

PubMed1994

Self-esteem: its application to eating disorders and athletes.

Self-esteem, a hierarchical and multifactorial perception, can be described as the extent to which a person feels positive about himself or herself. Social factors such as life satisfaction, sex, age, and strongly held values can affect self-esteem. Low self-esteem is a well-recognized trait of those with eating disorders and may be associated with a heightened self-awareness. Body dissatisfaction, common among women in Western society, may enhance this awareness. Athletes, especially those with eating disorders, are perfectionists and have acute body awareness and a sense of loss of control. Control is a crucial issue with these athletes. Before any nutrition counseling starts, readiness to listen should be assessed in conjunction with a mental health professional. Various tools are available to assess the eating disordered athlete's self-esteem, body image, and eating behavior. Nutrition counseling can help the athlete overcome an eating disorder by clarifying misconceptions and focusing on the role of nutrition in promoting health and athletic performance.

Body Image↗

PubMed1995

Indicators of vitamin and mineral status in athletes' blood: a review.

This review examines the hypothesis that vitamin and mineral status in athletes is inadequate for optimal sports performance. The review is based on indicators determined from blood and on studies published since 1980. Most of the studies did not find micronutrient status in athletes to be different from untrained controls. The serum ferritin concentration in females was lower than in males (27 vs. 78 micrograms.L-1), and the prevalence of low serum ferritin concentration was higher in female athletes than in untrained female controls (37 vs. 23%). Supplementation of water-soluble vitamins and iron was associated with an improvement in the corresponding indicators. Excluding a few studies with mildly anemic subjects, improvements in indicators of micronutrient status were not associated with enhanced athletic performance. Consequently, the levels of indicators of micronutrient status seen in athletes' blood were apparently compatible with optimal physical performance.

Female↗

PubMed1996

Nutritional aspects of amenorrhea in the female athlete triad.

Female athletes experience a high incidence of menstrual abnormalities. This has critical health consequences because amenorrheic athletes are at greater risk of developing osteopenia and bone injury compared to normally menstruating athletes or nonathletic normally cycling females. Female performers and athletes are also at risk for developing disordered eating behaviors. There appears to be a connection between menstrual dysfunction, athletic training, and disordered eating, but how they relate is not fully understood. In this paper we explore how low calorie intakes, nutritional inadequacies, vegetarianism, low body fat stores, and specific training behaviors may contribute to the abnormal menstrual patterns seen in this population. Recommendations for the detection and prevention of eating and training problems and consequent menstrual abnormalities are included.

Amenorrhea↗

PubMed2003

Copper status of collegiate female athletes involved in different sports.

Copper status was assessed in 70 female collegiate athletes aged 18 to 25 years participating in cross country track, tennis, softball, swimming, soccer, basketball, and gymnastics during the 2000-2001 season. A group of 8 college-aged females, 20 to 23 years of age, who were not collegiate athletes, served as controls. Mean copper intakes including supplements did not differ significantly among the controls and athletic teams. Mean copper intakes including supplements as micrograms/day and percent recommended dietary allowance (RDA) were as follows: controls 1071 +/- 772 microg (119 +/- 86%), cross country track 1468 +/- 851 microg (163 +/- 95%), tennis 1099 +/- 856 microg (122 +/- 95%), softball 654 +/- 420 microg (73 +/- 47%), swimming 1351 +/- 1060 g (150 +/- 118%), soccer 695 +/- 368 microg (77 +/- 41%), and gymnastics 940 +/- 863 microg (104 +/- 96%). Forty-one percent of athletes and 29% of controls failed to consume two thirds of the RDA for copper. Mean serum copper and ceruloplasmin concentrations were within the normal range and did not differ significantly among the controls (117 +/- 22 microg/dl, 445 +/- 122 mg/L) and cross country track (98 +/- 17 microg/dl, 312 +/- 59 mg/L), tennis (140 +/- 84 microg/dl, 424 +/- 244 mg/L), softball (95 +/- 30 microg/dl, 310 +/- 77 mg/L), swimming (98 +/- 25 microg/dl, 312 +/- 40 mg/L), soccer (93 +/- 15 microg/dl, 324 +/- 54 mg/ L), basketball (85 +/- 10 microg/dl, 280 +/- 62 mg/L), and gymnastics (96 +/- 21 microg/dl, 315 +/- 68 mg/L) teams. Copper status of female collegiate athletes appears to be adequate in this cross-sectional assessment.

Adolescent↗

PubMed2004

Nutritional supplement use among college athletes and their sources of information.

A survey was conducted to examine the source of information and usage of nutritional supplements in 115 male and 88 female varsity athletes at a Division I university. The survey asked each athlete to define supplement, and report supplement use and type, source of information, and reasons for use. Supplement use frequencies were determined, and comparisons were made between gender and sport. Eighty-nine percent of the subjects had or were currently using nutritional supplements. Many athletes did not consider sports drinks and calorie replacement products as supplements. Females were more likely to take calcium and multivitamins, and males had significant intake for ginseng, amino acids, glutamine, hydroxy-methyl-buterate (HMB), weight gainers, whey protein, and Juven. The most frequently used supplements overall were energy drinks (73%), calorie replacement products of all types (61.4%), multivitamin (47.3%), creatine (37.2%), and vitamin C (32.4%). There was also significant supplement use noted per sport. Females were more likely to obtain information from family members regarding supplementation, and males from a store nutritionist, fellow athletes, friends, or a coach. Female athletes were more likely to take supplements for their health or because of an inadequate diet, while men reported taking supplements to improve speed and agility, strength and power, or for weight/muscle gain.

Adult↗

PubMed2004

Nutrient intakes and dietary behaviors of male and female collegiate athletes.

The purpose of this study was to assess the dietary intakes and behaviors of male and female collegiate athletes. Athletes (n =345) at a NCAA Division I university completed an anonymous questionnaire. T-tests, chi(2) statistic, and ANOVA were used to assess gender and sport differences. Multiple linear regression was used to assess gender differences in nutrient intakes, controlling for energy intake and to examine the relationships between desired weight change, dietary behaviors, and nutrient intakes. Only 15 % and 26 % of athletes had adequate intakes of carbohydrate and protein, respectively, based on recommendations for athletes. Males were more likely to exceed the Dietary Guidelines for fat, saturated fat, cholesterol, and sodium than females. Sixty-two percent of female athletes wanted to lose at least 5 lbs compared to 23 % of males. The desire to lose weight was associated with decreased energy and macronutrient consumption, but not with inadequate micronutrient intakes.

Adult↗

PubMed2004

Dietary intake and nutritional practices of elite Greek aquatic athletes.

To investigate whether aquatic athletes follow optimal dietary intake, 58 athletes, all members of the Greek national swimming and water polo teams, were tested. Dietary intake was assessed at the nutrient, food, and food group level using the 24-h recall method and a food frequency questionnaire. Mean energy intake for males and females was 14.3 and 8.5 MJ, respectively. Mean carbohydrate consumption for male and female athletes was 4.5 g/kg and 3.8 g/kg of body weight, respectively. Fat intake was 153 g for males and 79 g for females. A significant number of the athletes (71% of the males, 93% of the females) did not meet the Dietary Reference Intakes for at least one of the antioxidant vitamins. The data suggest that athletes of both genders consumed too much fat and too little carbohydrate. Insufficient fruit and vegetable intake was related to low intake of antioxidants.

Adolescent↗

PubMed2005

Untangling the Links among Athletic Involvement, Gender, Race, and Adolescent Academic Outcomes.

Although previous research has established that high school sports participation may be associated with positive academic outcomes, the parameters of the relationship remain unclear. Using a longitudinal sample of nearly 600 Western New York adolescents, this study examined gender- and race-specific differences in the impact of two dimensions of adolescent athletic involvement ("jock" identity and athlete status) on changes in school grades and school misconduct over a two-year interval. Female and black adolescents who identified themselves as "jocks" reported lower grades than those who did not, whereas female athletes reported higher grades than female nonathletes. Jocks also reported significantly more misconduct (including skipping school, cutting classes, having someone from home called to the school for disciplinary purposes, and being sent to the principal's office) than nonjocks. Gender moderated the relationship between athlete status and school misconduct; athletic participation had a less salutary effect on misconduct for girls than for boys.

Journal Article↗

PubMed2004

Mutations in the hereditary haemochromatosis gene HFE in professional endurance athletes.

BACKGROUND: Hereditary haemochromatosis, a disease that affects iron metabolism, progresses with a greater or lesser tendency to induce iron overload, possibly leading to severe organ dysfunction. Most elite endurance athletes take iron supplements during their active sporting life, which could aggravate this condition. OBJECTIVE: To determine the prevalence and discuss potential clinical implications of mutations of HFE (the gene responsible for hereditary haemochromatosis) in endurance athletes. METHODS: Basal concentrations of iron, ferritin, and transferrin and transferrin saturation were determined in the period before competition in 65 highly trained athletes. Possible mutations in the HFE gene were evaluated in each subject by extracting genomic DNA from peripheral blood. The restriction enzymes SnaBI and BclI were used to detect the mutations 845G-->A (C282Y) and 187C-->G (H63D). RESULTS: Our findings indicate a high prevalence of HFE gene mutations in this population (49.2%) compared with sedentary controls (33.5%). No association was detected in the athletes between mutations and blood iron markers. CONCLUSIONS: The findings support the need to assess regularly iron stores in elite endurance athletes.

Adult↗

PubMed2004

Objective evaluation of small bowel and colonic transit time using pH telemetry in athletes with gastrointestinal symptoms.

BACKGROUND: Gastrointestinal (GI) disturbances are often reported by long distance runners and are more common in women, particularly after prolonged high intensity exercise. OBJECTIVES: To determine whether these symptoms could be associated with alterations in GI motility. METHODS: Small bowel and colonic transit were measured using pH telemetry in a group of 11 female athletes (age 22 to 53 years), six of whom experienced lower GI symptoms during exercise. Subjects participated in two experimental sessions: a control measurement, where small bowel transit was estimated during a rest period (R) of six hours; and an exercise session (E), where small bowel transit was measured during a one hour period of high intensity exercise (cross country running) at >70% VO(2)max. Colonic transit was estimated indirectly from determinations of whole gut transit time by radio-opaque marker. RESULTS: Small bowel transit time was 3.5 to 10.6 h (R) and 3.0 to 8.7 h (E) in asymptomatic athletes, versus 4.0 to 6.6 h (R) and 4.6 to 7.3 h (E) in symptomatic athletes (NS). Colonic transit time was 35.0 to 62.5 h (R) and 30.5 to 70.9 h (E) in asymptomatic athletes versus 20.4 to 42.9 h (R) and 21.5 to 67.2 h (E) in symptomatic athletes (NS). CONCLUSIONS: Small bowel and colonic transit times were similar in the two groups in the rest and exercise sessions. The diarrhoea seen in this study did not result from accelerated colonic transit. Other mechanisms must be sought.

Adult↗

PubMed2005

Nutritional supplement practices in UK junior national track and field athletes.

METHODS: The nutritional supplementation practices of 32 national track and field athletes competing at the 2004 World Junior Championships were studied using an anonymous questionnaire. Information was sought on the prevalence and type of supplement used, the reasons for use, knowledge of supplements, and sources of information. RESULTS: Use of supplements was widespread with 62% of respondents declaring supplement use. Prevalence in female athletes (75%) was higher than in males (55%) but was not statistically significant. No differences were found for age, training volume, or type of event. Seventeen different supplements were taken, with each athlete using an average of 2.4 products, multivitamins and minerals being the most popular. Reasons for using supplements were for health (45%), to enhance the immune system (40%), and to improve performance (25%). Of all respondents 48% believed they had an average knowledge of supplements, but three quarters felt that they required further information. Those not using supplements were more likely to think supplements were associated with health risks than those taking them (p = 0.03). Most athletes (72%) have access to a sports dietician but underutilise this resource. Coaches (65%) had the greatest influence on supplementation practices, with doctors (25%) and sports dieticians (30%) being less important. CONCLUSIONS: Supplementation practices were widespread among the population studied. The findings of this investigation could be used to enable the sports dietician and physician to identify common misconceptions held by adolescent athletes regarding nutritional supplements and to implement educational programs, which should include members of the non-medical support team.

Adolescent↗

PubMed1994

Athletic footwear affects balance in men.

Stable equilibrium during locomotion is required for both superior performance of sports and prevention of injuries from falls. A recent report indicated that currently available athletic footwear impairs stability in older men. Since this discovery, if confirmed, seems important to both competitive athletes and the physically active general public, we performed an experiment using similar methods on a younger population. We tested the hypothesis that midsole thickness is negatively, and hardness positively related to dynamic equilibrium, in 17 healthy adult men (mean(s.d.) age 33(11.13) years) via a balance beam method. Subjects walked along a 9-m long beam at 0.5 m s-1 once barefoot and six times wearing identical pairs of experimental shoes which differed only in midsole hardness and thickness which spanned the respective ranges currently available in footwear. Falls from the beam (balance failures) were quantified. Balance failures varied significantly in relation to midsole hardness and thickness, and there was a strong trend toward interaction of these variables (P = 0.09). Midsole hardness was positively related to stability, and midsole thickness was negatively related, which confirms the previous report. Hence, shoes with thick-soft soles, similar to modern athletic footwear and 'walking shoes', destabilize men, and shoes with thin-hard soles provide superior stability. The pair with the poorest stability (A 15-thick; 12.34 balance failures per 100 m) produced 217% more balance failures than those associated with the best stability (A 50-thin; 3.89 balance failures per 100 m). Since most types of athletic footwear and many other shoes incorporate midsoles with hardness and thickness associated with poor stability, we conclude that both athletic performance and public safety could be enhanced through stability optimized footwear.

Adult↗

PubMed1996

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.

Adult↗