Skills and Expertise
Research Items (69)
Acute exercise can induce either a compensatory increase in food intake or a reduction in food intake, which results from appetite suppression in the post-exercise state. The timing of food choice—choosing for immediate or later consumption—has been found to influence the healthfulness of foods consumed. To examine both of these effects, we tested in our study whether the timing of food choice interacts with exposure to exercise to impact food choices such that choices would differ when made prior to or following an exercise bout. Visitors to a university recreational center were equipped with an accelerometer prior to their habitual workout regime, masking the true study purpose. As a reward, participants were presented with a snack for consumption after workout completion. Participants made their snack choice from either an apple or chocolate brownie after being pseudo-randomly assigned to choose prior to (“before”) or following workout completion (“after”). Complete data were available for 256 participants (54.7% male, 22.1 ± 3.1 years, 24.7 ± 3.7 kg/m2) who exercised 65.3 ± 22.5 min/session. When compared with “before,” the choice of an apple decreased (73.7% vs. 54.6%) and the choices of brownie (13.9% vs. 20.2%) or no snack (12.4% vs. 25.2%) increased in the “after” condition (χ2 = 26.578, p < 0.001). Our results provide support for both compensatory eating and exercise-induced anorexia. More importantly, our findings suggest that the choice of food for post-exercise consumption can be altered through a simple behavioral intervention.
Brown/beige fat plays a crucial role in maintaining energy homeostasis through non-shivering thermogenesis in response to cold temperature and excess nutrition (adaptive thermogenesis). Although numerous molecular and genetic regulators have been identified, relatively little information is available regarding thermogenic dietary molecules. Recently, a growing body of evidence suggests that high consumption of n-3 polyunsaturated fatty acids (PUFA) or activation of GPR120, a membrane receptor of n-3 PUFA, stimulate adaptive thermogenesis. In this review, we summarize the emerging evidence that n-3 PUFA promote brown/beige fat formation and highlight the potential mechanisms whereby n-3 PUFA require GPR120 as a signaling platform or act independently. Human clinical trials are revisited in the context of energy expenditure. Additionally, we explore some future perspective that n-3 PUFA intake might be a useful strategy to boost or sustain metabolic activities of brown/beige fat at different lifecycle stages of pregnancy and senescence. Given that a high ratio of n-6/n-3 PUFA intake is associated with the development of obesity and type 2 diabetes, understanding the impact of n-6/n-3 ratio on energy expenditure and adaptive thermogenesis will inform the implementation of a novel nutritional strategy for preventing obesity.
Exercise Physiology, a section of the journal Frontiers in Physiology In order to monitor their energy requirements, athletes may desire to assess energy expenditure (EE) during training and competition. Recent technological advances and increased customer interest have created a market for wearable devices that measure physiological variables and bodily movement over prolonged time periods and convert this information into EE data. This mini-review provides an overview of the applicability of the SenseWear armband (SWA), which combines accelerometry with measurements of heat production and skin conductivity, to measure total daily energy expenditure (TDEE) and its components such as exercise energy expenditure (ExEE) in athletic populations. While the SWA has been shown to provide valid estimates of EE in the general population, validation studies in athletic populations indicate a tendency toward underestimation of ExEE particularly during high-intensity exercise (>10 METs) with an increasing underestimation as exercise intensity increases. Although limited information is available on the accuracy of the SWA during resistance exercise, high-intensity interval exercise, or mixed exercise forms, there seems to be a similar trend of underestimating high levels of ExEE. The SWA, however, is capable of detecting movement patterns and metabolic measurements even at high exercise intensities, suggesting that underestimation may result from limitations in the proprietary algorithms. In addition, the SWA has been used in the assessment of sleep quantity and quality as well as non-exercise activity thermogenesis. Overall, the SWA provides viable information and remains to be used in various clinical and athletic settings, despite the termination of its commercial sale.
- Sep 2017
Background: The first 2 years of a child's life are a particularly critical time period for obesity prevention. Aim: An increasing amount of research across the world is aimed at understanding factors that impact early childhood obesity and developing interventions that target these factors effectively. With this growing interest, new and interdisciplinary research teams are developing to meet this research need. Due to rapid growth velocity during this phase of the lifespan, typical assessments used in older populations may not be valid or applicable in infants, and investigators need to be aware of the pros and cons of specific methodological strategies. Methods: This paper provides an overview of methodology available to assess obesity-related factors in the areas of anthropometry and body composition, nutrient intake, and energy expenditure in infants aged 0-2 years. Results: Gold standard measures for body composition, such as dual-energy X-ray absorptiometry (DXA) or other imaging techniques, are costly, require highly trained personnel, and are limited for research application. Nutrient intake methodology primarily includes surveys and questionnaires completed via parent proxy report. In terms of energy expenditure, methods of calorimetry are expensive and may not differentiate between different activities. Questionnaires or physical activity sensors offer another way of energy expenditure assessment. However, questionnaires have a certain recall bias, while the sensors require further validation. Conclusions: Overall, in addition to understanding the pros and cons of each assessment tool, researchers should take into consideration the experience of the interdisciplinary team of investigators, as well as the cost and availability of measures at their institution.
Rationale: Natural stable nitrogen isotope ratios (δ(15) N values) are frequently used for the determination of provenance and dietary assessment of recent and ancient humans. Although individual δ(15) N values typically correspond to the dietary δ(15) N composition, they are also affected by metabolic conditions. Preferred matrices for the mesurement of human δ(15) N values have been hair, nail or blood. The goal of this study was to validate a novel approach for the assessment of the δ(15) N values from urinary urea, the principal end-product of human N metabolism. Methods: The method, which involves the precipitation of urea from urine using xanthydrol, was validated using fortified urea solutions. Intra- and inter-individual variance of the δ(15) N values of urinary urea was determined from samples obtained from multiple human subjects. Results: Precipitation with xanthydrol did not alter the δ(15) N values of urea. The mean δ(15) N value in urinary urea from human subjects from Germany was +4.4 ±0.6 ‰, which corresponds to the estimated dietary composition. It falls below previously reported δ(15) N values for human tissue and blood samples. Longitudinal analyses over seven days illustrate short-time changes linked to varying protein intake. Discussion: Our results indicate that δ(15) N values can be measured reliably from human urine and that the method is suitable to monitor rapid dietary and metabolic changes of an individual. Our findings further confirm that urinary urea is depleted in (15) N compared with human tissue but within the range of the δ(15) N composition of the diet.
Brown adipose tissue (BAT) is a specialized fat tissue that has a high capacity to dissociate cellular respiration from ATP utilization, resulting in the release of stored energy as heat. Adult humans possess a substantial amount of BAT in the form of constitutively active brown fat or inducible beige fat. BAT activity in humans is inversely correlated with adiposity, blood glucose concentrations, and insulin sensitivity; this suggests that strategies aimed at BAT-mediated bioenergetics are an attractive therapeutic target in combating the continuing epidemic of obesity and diabetes. Despite advances in knowledge regarding the developmental lineage and transcriptional regulators of brown and beige adipocytes, our current understanding of environmental modifiers of BAT thermogenesis, such as diet, is limited. In this review, we consolidated the latest research on dietary molecules that may serve to promote BAT thermogenesis. Here, we summarized the thermogenic function of selected phytochemicals (e.g., capsaicin, resveratrol, curcumin, green tea, and berberine), dietary fatty acids (e.g., fish oil and conjugated linoleic acids), and all-trans retinoic acid, a vitamin A metabolite. We also delineated the proposed mechanisms whereby these dietary molecules promote BAT activity and/or browning of white adipose tissue. Characterizing thermogenic dietary factors may offer novel insight into revising nutritional intervention strategies aimed at obesity and diabetes prevention and management.
Little is known about whether athletes follow hydration guidelines. The objective of the present study was to assess fluid status in female soccer players in a hot and humid environment, and to assess the effect of an intervention aimed at preventing players from exercising in a dehydrated state. We hypothesized that following the intervention, players would exhibit improved hydration status, as indicated by greater voluntary fluid intake and improved hydration markers. Ten female collegiate soccer players (20±1yrs., 64±9kg) participated in this seven-week study. Changes in body weight (BW), fluid intake, urine color (UC), and urine specific gravity (USG) were measured periodically over three days. Dehydration was classified as USG ≥1.020g/ml and UC >3. Following a 7- week intervention (to individualize hydration strategies), BW, fluid intake, UC, and USG were again measured on two game days to evaluate the impact of the intervention. Pre-test: five players started exercising dehydrated (USG 1.029g/ml; UC 6). Seven players were dehydrated before the next morning practice session (USG 1.029g/ml; UC 5). Five players had a mean BW loss of 2.5%.Post-test: four players were dehydrated before game 1. Despite hydration guidelines, two players experienced tiredness and cramps during the second half. Six players were dehydrated 4h before game 2 and subsequently received individual rehydration instructions. 2h before game 2, none of the players were dehydrated. No symptoms of tiredness or cramps were reported. Hydration status assessment coupled with an intervention of individualized drinking strategies, can prevent female soccer players from exercising in a dehydrated state.
- Mar 2017
Natural stable isotope ratios (δ(15)N) of humans can be used for nutritional analyses and dietary reconstruction of modern and historic individuals and populations. Information about an individual's metabolic state can be obtained by comparison of tissue and dietary δ(15)N. Different methods have been used to estimate dietary δ(15)N in the past; however, the validity of such predictions has not been compared to experimental values. For a total of 56 meals and 21 samples of 24-h diets, predicted and experimental δ(15)N values were compared. The δ(15)N values were predicted from self-recorded food intake and compared with experimental δ(15)N values. Predicted and experimental δ(15)N values were in good agreement for meals and preparations (r = 0.89, p < .001) as well as for the 24-h diets (r = 0.76, p < .001). Dietary δ(15)N was mainly determined by the amount of fish, whereas the contribution of meat to dietary δ(15)N values was less pronounced. Prediction of human dietary δ(15)N values using standardised food records and representative δ(15)N data sets yields reliable data for dietary δ(15)N intake. A differentiated analysis of the primary protein sources is necessary when relating the proportion of animal-derived protein in the diet by δ(15)N analysis.
Ultra-endurance athletes often accumulate an energy deficit when engaging in ultra-endurance exercise, and upon completion of the exercise, they exhibit endocrine changes that are reminiscent of starvation. However, it remains unclear whether these endocrine changes are a result of the exercise per se or secondary to the energy deficit, and more importantly, whether these changes can be attenuated by increased dietary intake. Our goal was to assess the relationship between changes in key metabolic hormones following ultra-endurance exercise and measures of energy balance. Metabolic hormones as well as energy intake and expenditure were assessed in 14 well-trained male cyclists who completed a 1,230-km ultra-endurance cycling event. After completion of the event, serum testosterone (-67±18%), insulin-like growth factor-1 (IGF-1) (-45±8%), and leptin (-79±9%) were significantly suppressed (p<0.001), and remained suppressed after a 12-h recovery period (p<0.001). Changes in IGF-1 were positively correlated with energy balance over the course of the event (r=0.65, p=0.037), which ranged from a 11,859 kcal-deficit to a 3,593 kcal-surplus. The marked suppression of testosterone, IGF-1, and leptin following ultra-endurance exercise is comparable to changes occurring during acute starvation. The suppression of IGF-1, but not that of other metabolic hormones, was strongly associated with the magnitude of the energy deficit, indicating that athletes who attained a greater energy deficit exhibited a more pronounced drop in IGF-1. Future studies are needed to determine whether increased dietary intake can attenuate the endocrine response to ultra-endurance exercise.
- Nov 2016
Background: Academic success is a key determinant of future prospects for students. Cognitive functioning has been related to nutritional and physical factors. Here, we focus on iron status and aerobic fitness in young-adult female students given the high rate of iron deficiency and declines in fitness reported in this population. Objectives: We sought to explore the combined effects of iron status and fitness on academic success and to determine whether these associations are mediated by cognitive performance. Methods: Women (n = 105) aged 18-35 y were recruited for this cross-sectional study. Data were obtained for iron biomarkers, peak oxygen uptake (VO2peak), grade point average (GPA), performance on computerized attention and memory tasks, and motivation and parental occupation. We compared the GPA of groups 1) with low compared with normal iron status, 2) among different fitness levels, and 3) by using a combined iron status and fitness designation. Mediation analysis was applied to determine whether iron status and VO2peak influence GPA through attentional and mnemonic function. Results: After controlling for age, parental occupation, and motivation, GPA was higher in women with normal compared with low ferritin (3.66 ± 0.06 compared with 3.39 ± 0.06; P = 0.01). In analyses of combined effects of iron status and fitness, GPA was higher in women with normal ferritin and higher fitness (3.70 ± 0.08) than in those with 1) low ferritin and lower fitness (3.36 ± 0.08; P = 0.02) and 2) low ferritin and higher fitness (3.44 ± 0.09; P = 0.04). Path analysis revealed that working memory mediated the association between VO2peak and GPA. Conclusions: Low iron stores and low aerobic fitness may prevent female college students from achieving their full academic potential. Investigators should explore whether integrated lifestyle interventions targeting nutritional status and fitness can benefit cognitive function, academic success, and postgraduate prospects.
Background/objectives: Normal-weight women frequently restrict their caloric intake and exercise, but little is known about the effects on body weight, body composition and metabolic adaptations in this population. Subjects/methods: We conducted a secondary analysis of data from a randomized controlled trial in sedentary normal-weight women. Women were assigned to a severe energy deficit (SEV: -1062±80 kcal per day; n=9), a moderate energy deficit (MOD: -633±71 kcal per day; n=7) or energy balance (BAL; n=9) while exercising five times per week for 3 months. Outcome variables included changes in body weight, body composition, resting metabolic rate (RMR) and metabolic hormones associated with energy conservation. Results: Weight loss occurred in SEV (-3.7±0.9 kg, P<0.001) and MOD (-2.7±0.8 kg; P=0.003), but weight loss was significantly less than predicted (SEV: -11.1±1.0 kg; MOD: -6.5±1.1 kg; both P<0.001 vs actual). Fat mass declined in SEV (P<0.001) and MOD (P=0.006), whereas fat-free mass remained unchanged in all groups (P>0.33). RMR decreased by -6±2% in MOD (P=0.020). In SEV, RMR did not change on a group level (P=0.66), but participants whose RMR declined lost more weight (P=0.020) and had a higher baseline RMR (P=0.026) than those whose RMR did not decrease. Characteristic changes in leptin (P=0.003), tri-iodothyronine (P=0.013), insulin-like growth factor-1 (P=0.016) and ghrelin (P=0.049) occurred only in SEV. The energy deficit and adaptive changes in RMR explained 54% of the observed weight loss. Conclusions: In normal-weight women, caloric restriction and exercise resulted in less-than-predicted weight loss. In contrast to previous literature, weight loss consisted almost exclusively of fat mass, whereas fat-free mass was preserved.European Journal of Clinical Nutrition advance online publication, 26 October 2016; doi:10.1038/ejcn.2016.203.
- Jul 2016
Exercising women with menstrual disturbances frequently display a low resting metabolic rate (RMR) when RMR is expressed relative to body size or lean mass. However, normalizing RMR for body size or lean mass does not account for potential differences in the size of tissue compartments with varying metabolic activities. To explore whether the apparent RMR suppression in women with exercise-associated amenorrhea is a consequence of a lower proportion of highly metabolically active tissue compartments or the result of metabolic adaptations related to energy conservation at the tissue level, RMR and metabolic tissue compartments were compared among exercising women with amenorrhea (AMEN, n=42) and exercising women with eumenorrheic, ovulatory menstrual cycles (OV, n=37). RMR was measured using indirect calorimetry and predicted from the size of metabolic tissue compartments as measured by dual-energy X-ray absorptiometry (DXA). Measured RMR was lower than DXA-predicted RMR in AMEN (1215±31 vs. 1327±18 kcal/d, p<0.001) but not in OV (1284±24 vs. 1252±17, p=0.16), resulting in a lower ratio of measured to DXA-predicted RMR in AMEN (91±2%) vs. OV (103±2%, p<0.001). AMEN displayed proportionally more residual mass (p<0.001) and less adipose tissue (p=0.003) when compared to OV. A lower ratio of measured to DXA-predicted RMR was associated with lower serum total triiodothyronine (ρ=0.38, p<0.001) and leptin (ρ=0.32, p=0.004). Our findings suggest that RMR suppression in this population is not the result of a reduced size of highly metabolically active tissue compartments but due to metabolic and endocrine adaptations at the tissue level that are indicative of energy conservation.
Purpose: A positive association between cardiorespiratory fitness (CRF) and cognitive function has been demonstrated mainly in children and older adults. Women attending college live in a cognitively-demanding setting where optimal cognition matters but often experience declines in CRF. Our aim was to test whether CRF is associated with executive function in young adult women. Methods: Participants in this cross-sectional study included 120 healthy women aged 18-35 years in a university setting. Each woman completed a maximal treadmill-based exercise test to determine peak oxygen uptake (VO2 peak), computerized tests of executive function, and questionnaires to assess motivation and other factors with potential to influence physical and cognitive performance. Results: Overall CRF was excellent, with a sample mean VO2 peak of 44.6 ml/min/kg. After adjusting for covariates, higher VO2 peak was associated with better performance on attention (P < 0.01), learning/shifting (P < 0.01), working memory (P < 0.01), and problem-solving (P < 0.05) tasks. Likewise, when women were grouped according to ACSM fitness classification, performance on executive function tasks was poorest in women with very poor or poor CRF. Women with superior CRF performed best on executive function tasks, and performance was intermediate in women with fair, good, or excellent CRF. Conclusion: The findings from this cross-sectional study suggest that optimal cognition is related to CRF in young adult women. Future studies are needed to test whether strategies to improve CRF are effective in improving cognitive function.
- Apr 2016
Purpose: To explore the association between cumulative menstrual status and indices of bone health assessed using dual-energy x-ray absorptiometry (DXA), including femoral neck geometry and strength and areal BMD (aBMD), in exercising women. Methods: 101 exercising women (22.0±0.4years, BMI 21.0±0.2kg/m(2), 520±40min/week of self-reported exercise) participated in this cross-sectional study. Women were divided into three groups as follows based on their self-reported current and past menstrual status: 1) current and past regular menstrual cycles (C+P-R) (n=23), 2) current and past irregular menstrual cycles (C+P-IR) (n=56), 3) and current or past irregular cycles (C/P-RIR) (n=22). Current menstrual status was confirmed using daily urinary metabolites of reproductive hormones. DXA was used to assess estimates of femoral neck geometry and strength from hip strength analysis (HSA), aBMD, and body composition. Cross-sectional moment of inertia (CSMI), cross-sectional area (CSA), strength index (SI), diameter, and section modulus (Z) were calculated at the femoral neck. Low CSMI, CSA, SI, diameter, and Z were operationally defined as values below the median. Areal BMD (g/cm(2)) and Z-scores were determined at the lumbar spine, femoral neck, and total hip. Low BMD was defined as a Z-score<-1.0. Chi-square tests and multivariable logistic regression were performed to compare the prevalence and determine the odds, respectively, of low bone geometry, strength, and aBMD among groups. Results: Cumulative menstrual status was identified as a significant predictor of low femoral neck CSMI (p=0.005), CSA (p≤0.024), and diameter (p=0.042) after controlling for confounding variables. C+P-IR or C/P-RIR were four to eight times more likely to exhibit low femoral neck CSMI or CSA when compared with C+P-R. Lumbar spine aBMD and Z-score were lower in C+P-IR when compared with C+P-R (p≤0.003). A significant association between menstrual group and low aBMD was observed at the lumbar spine (p=0.006) but not at the femoral neck or total hip (p>0.05). However, after controlling for confounding variables, cumulative menstrual status was not a significant predictor of low aBMD. Conclusion: In exercising women, the cumulative effect of current and past menstrual irregularity appears to be an important predictor of lower estimates of femoral neck geometry, as observed by smaller CSMI and CSA, which may serve as an another means, beyond BMD, by which menstrual irregularity compromises bone strength. As such, evaluation of both current and past menstrual status is recommended to determine potential risk for relatively small bone geometry at the femoral neck.
- Mar 2016
- Marathon Running: Physiology, Psychology, Nutrition and Training Aspects
Marathon runners can uniquely benefit from nutritional strategies that support their training responses and/or maximize their performance during the actual race. Promising strategies during marathon training include the adequate provision of dietary energy, macronutrients (carbohydrates, protein), and selected micronutrients (e.g., iron) to meet the increased requirements of prolonged distance running. Nutritional and training approaches aimed at increasing fat oxidation rates or facilitating weight loss may be associated with negative effects and should therefore be conducted with care. During the actual marathon race, runners can benefit from carbohydrate loading strategies that serve to maximize pre-race muscle glycogen storage capacity. Consumption of carbohydrates, fluid, and sodium can prevent preemptive fatigue due to nutrient depletion, and caffeine supplementation can provide ergogenic effects during prolonged running. Because the responses to these nutritional interventions can vary substantially among individuals and require fine tuning depending on factors such as performance level, environmental conditions, designated running pace, propensity for gastrointestinal discomfort, and availability of aid stations during the race, marathon runners are highly encouraged to familiarize themselves with these strategies prior to utilizing them in a competitive setting.
Low energy availability, defined as low caloric intake relative to exercise energy expenditure, has been linked to endocrine alterations frequently observed in chronically energy-deficient exercising women. Our goal was to determine the endocrine effects of low energy availability in exercising men. Six exercising men (VO2peak: 49.3 ± 2.4 ml · kg(-1) · min(-1)) underwent two conditions of low energy availability (15 kcal · kg(-1) fat-free mass [FFM] · day(-1)) and two energy-balanced conditions (40 kcal · kg(-1) FFM · day(-1)) in randomised order. During one low energy availability and one balanced condition, participants exercised to expend 15 kcal · kg(-1) FFM · day(-1); no exercise was conducted during the other two conditions. Metabolic hormones were assessed before and after each 4-day period. Following both low energy availability conditions, leptin (-53% to -56%) and insulin (-34% to -38%) were reduced (P < 0.05). Reductions in leptin and insulin were independent of whether low energy availability was attained with or without exercise (P > 0.80). Low energy availability did not significantly impact ghrelin, triiodothyronine, testosterone and IGF-1 (all P > 0.05). The observed reductions in leptin and insulin were in the same magnitude as changes previously reported in sedentary women. Further research is needed to understand why other metabolic hormones are more robust against low energy availability in exercising men than those in sedentary and exercising women.
- Aug 2015
The ingestion of exogenous carbohydrates (CHO) during prolonged endurance exercise, such as long-distance triathlon, is considered beneficial with regards to performance. However, only little is known whether this performance benefit differs among different forms of CHO administration. To this end, the purpose of our study was to determine the impact of CHO ingestion from a semisolid source (GEL) on measures of performance and gastrointestinal comfort when compared to CHO ingestion from a liquid source (LIQ). Nine well-trained triathletes participated in this randomized cross-over study. Each participant completed a 60 min swim, 180 min bike exercise, and a 60 min all out run in a laboratory environment under two conditions, once while receiving 67.2 ± 7.2 g · h-1 of CHO from GEL and once while receiving 67.8 ± 4.2 g · h-1 of CHO from LIQ. The amount of fluid provided was matched among conditions. Respiratory exchange ratio (RER), blood glucose, and lactate as well as gastrointestinal discomfort were assessed at regular intervals during the experiment. The distance covered during the final all-out run was not significantly different among GEL (11.81 ± 1.38 km) and LIQ (11.91 ± 1.53 km; p=0.89). RER, blood glucose and lactate did not differ significantly at any time during the experiment. Seven participants reported gastrointestinal discomfort during GEL, while no athlete reported gastrointestinal discomfort during LIQ (p = 0.016). The present study suggests that administration of GEL does not alter long-distance triathlon performance when compared to LIQ, but GEL seems to be associated with reduced gastrointestinal tolerance. Athletes should consider this as a potential disadvantage of GEL administration during long-distance triathlon.
- Oct 2014
Objective To determine if reducing the frequency of urinary sample collection from daily to 5, 3, or 2 days per week during a menstrual cycle or 28-day amenorrheic monitoring period provide accurate representations of the reproductive hormone metabolites estrone-1-glucuronide (E1G) and pregnanediol glucuronide (PdG) exposure and mean concentrations.Methods Exercising women presenting with eumenorrhea or exercise-associated menstrual disturbances collected daily urine samples for the assessment of E1G and PdG concentrations. After enzyme immunoassay analysis of the daily samples, E1G and PdG data were systematically removed from each menstrual cycle or amenorrheic monitoring period to mimic three reduced collection frequencies, representing 5, 3, and 2 days per week. Exposure and mean concentration were calculated for both hormones and all four urinary collection frequencies.ResultsE1G and PdG exposure and mean cycle concentrations derived from reduced collection frequencies were not different from daily collection (P > 0.05), independent of whether menstrual cycles and monitoring periods were analyzed together or separately. Bland-Altman analysis indicated acceptable agreement between each reduced collection frequency and daily collection.Conclusions Compared with daily urinary collection, a reduced collection frequency of 5, 3, or 2 days each week provides accurate E1G and PdG profiles of collection periods of various lengths and types of menstrual function. Reduction of urinary sample collection frequency may enable researchers to reduce participant burden and costs, increase compliance, and study a wider range of study populations. Am. J. Hum. Biol., 2014. © 2014 Wiley Periodicals, Inc.
We are concerned that readers of the IOC paper will be confused and misled by the poorly referenced statements and frank (and sometimes dangerous) errors in the paper. The IOC authors should publish a correction of these and other errors noted. Broadening research of low energy availability in other groups, such as the male athlete, athletes of diverse ethnicities and the disabled athlete may help to advance science and may one day warrant introduction of a specific term for whatever serious clinical sequelae of energy deficiency may be discovered in future research on men. Research on the “Female Athlete Triad” has forged a platform from which a broad array of healthcare providers (e.g., physicians, sport dietitians, mental health professionals and athletic trainers) have made great strides in learning how to manage and treat affected women. Research on the “Female Athlete Triad” has also been translated to the lay public such that more and more affected female athletes and exercising women willingly seek education, prevention and treatment. Meanwhile, subsuming the term “Female Athlete Triad” under the umbrella of the term RED-S has the potential to confuse rather than enlighten, and undo decades of work educating and advocating for awareness, prevention and treatment for the Triad. The individual most impacted by the de-emphasis on the Triad will be the female athlete herself. The overwhelming clinical importance of the Female Athlete Triad compared with other conditions under the proposed RED-S umbrella will continue to make a specific reference for the Triad useful for those who deal with it, including physicians, coaches, sport dietitians, athletics trainers, parents and, most importantly, female athletes. As such, efforts promoting awareness, prevention and treatment of the Female Athlete Triad remain critically important and should not be overshadowed by an ill-conceived and poorly defended new construct.
Inactivity and overweight are major health concerns in children and adolescents with disabilities. Methods for the assessment of activity and energy expenditure may be affected negatively by the underlying disability, especially when motor function is impaired. The purpose of this study was to assess the validity of the SenseWear armband in adolescents with cerebral palsy and hemiparesis. Ten volunteers (age: 13.4 ± 1.6 years) were equipped with SenseWear armbands (Model MF, BodyMedia, Pittsburgh, PA) on the hemiparetic and non-hemiparetic side of the body. Energy expenditure was measured at rest and during treadmill exercise (speed range: 0.85 to 2.35 m/s). Indirect calorimetry served as independent reference method. The mean error was between -0.6 and 0.8 kcal/min and there were no significant differences between SenseWear and indirect calorimetry at any speed. Differences between body sides in expenditure (mean: -0.2 to 0.0 kcal/min) and step count (mean: -3.4 to 9.7 steps/min) were not significant. The validity of the SenseWear armband does not appear to be negatively affected by cerebral palsy during laboratory treadmill exercise. Future field studies are necessary to assess the validity and practicability energy expenditure and physical activity in children and adolescents with physical disabilities.
Athletes competing in ultra-endurance events are advised to meet energy requirements, to supply appropriate amounts of carbohydrates (CHO), and to be adequately hydrated before and during exercise. In practice, these recommendations may not be followed because of satiety, gastrointestinal discomfort, and fatigue. The purpose of the study was to assess energy balance, macronutrient intake and hydration status before and during a 1,230-km bike marathon. A group of 14 well-trained participants (VO2max: 63.2 ± 3.3 ml/kg/min) completed the marathon after 42:47 hours. Ad libitum food and fluid intake were monitored throughout the event. Energy expenditure (EE) was derived from power output and urine and blood markers were collected before the start, after 310, 618, 921 km, after the finish, and 12 hours after the finish. Energy intake (EI; 19,749 ± 4,502 kcal) was lower than EE (25,303 ± 2,436 kcal) in 12 of 14 athletes. EI and CHO intake (average: 57.1 ± 17.7 g/h) decreased significantly after km 618 (p<0.05). Participants ingested on average 392 ± 85 ml/h of fluid, but fluid intake decreased after km 618 (p<0.05). Hydration appeared suboptimal before the start (urine specific gravity: 1.022 ± 0.010 g/ml) but did not change significantly throughout the event. The results show that participants failed to maintain in energy balance and that CHO and fluid intake dropped below recommended values during the second half of the bike marathon. Individual strategies to overcome satiety and fatigue may be necessary to improve eating and drinking behavior during prolonged ultra-endurance exercise.
Glycerol is prohibited as a masking agent by the World Anti-Doping Agency and a urinary threshold has recently been recommended. However, little is known about urinary glycerol excretion after exercise, when (1) exogenous glycerol is metabolized increasingly and (2) endogenous glycerol levels are elevated. The purpose of the placebo-controlled cross-over study was to determine the effects of pre-exercise glycerol administration on glycerol metabolism, urinary excretion, and selected blood parameters. After administration of glycerol (G; 1.0 g/kg body weight (BW) + 25 ml fluid/kg BW) or placebo (P; 25 ml fluid/kg), 14 cyclists exercised 90 min at 60% VO(2max) . Samples were taken at 0 h (before administration), 2.5 h (before exercise), 4 h (after exercise) and 6.5 h and additional urine samples were collected until 24 h. Exercise increased endogenous plasma glycerol (0.51 ± 0.21 mmol/l) but peak concentrations were much higher in G (2.5 h: 15.6 ± 7.8 mmol/l). Urinary glycerol increased rapidly (58,428 ± 71,084 µg/ml after 2.5 h) and was significantly higher than in P until 13.6 ± 0.9 h (p < 0.01). In comparison with placebo administration, G caused significantly greater changes in plasma volume and haemoglobin concentrations after 2.5 h. BW and urine production were significantly different between P and G after 2.5 h and post-exercise. Despite exercise-induced increases in endogenous glycerol in the control group, urinary excretion remained well below the previously recommended threshold. In addition, exercise-related glycerol degradation did not appear to negatively affect the detection of exogenously administered glycerol. Copyright © 2013 John Wiley & Sons, Ltd.
- Nov 2013
The use of glycerol in combination with excess fluid can be used to increase total body water. Because glycerol hyperhydration may also be misused to mask the effects of blood doping on doping-relevant parameters, namely haemoglobin and haematocrit, glycerol has been prohibited by the World Anti-Doping Agency since 2010. In order to test this rationale, the purpose of this meta-analysis was to quantify the effects of glycerol hyperhydration on plasma volume, haemoglobin, and haematocrit in comparison to administration of fluid only. Following a literature search, a total of seven studies was included and meta-analyses were performed separately for the effects on plasma volume (5 studies, total n = 54) and on haemoglobin (6 studies, n = 52) and haematocrit (6 studies, n = 52). The meta-analysis revealed that the increase in plasma volume was 3.3% larger (95%-CI: 1.1-5.5%) after glycerol administration when compared to fluid only. Reductions in haemoglobin were 0.2 g/dl (95%-CI: -0.3, 0.0) larger and there was no difference in the changes in haematocrit between glycerol and fluid administration (95%-CI: -0.7-0.8%). In comparison with other plasma-volume expanding agents, glycerol hyperhydration has a very limited potential in increasing plasma volume and altering doping-relevant blood parameters. Copyright © 2013 John Wiley & Sons, Ltd.
- Oct 2013
Wie von diversen Fachgesellschaften empfohlen, lasst sich ein bei Sportlern eventuell erhohter Nahrstoffbedarf uber eine ausgewogene Ernahrung abdecken, sodass Nahrungserganzungsmittel (NEM) nur nach einer individuellen Nutzen-Risiko-Analyse eingesetzt werden [18, 34]. Einerseits konnen Nahrungserganzungsmittel, z. B. auf Reisen, bei extremen Unvertraglichkeiten, bei besonderen Ernahrungsgewohnheiten oder in Gewichtsreduktionsphasen dazu beitragen, die Zufuhr einzelner Nahrstoffe zu verbessern. Fur einige wenige Substanzen sind auch positive Effekte auf die Leistungsfahigkeit beschrieben. Allerdings besteht auch die Gefahr gesundheitlicher Nebenwirkungen und zumindest fur Leistungssportler ein nicht zu vernachlassigendes Dopingrisiko.
- Sep 2013
Dietary analysis using δ(15) N values of human remains such as bone and hair is usually based on general principles and limited data sets. Even for modern humans, the direct ascertainment of dietary δ(15) N is difficult and laborious, due to the complexity of metabolism and nitrogen fractionation, differing dietary habits and variation of δ(15) N values of food items. The objective of this study was to summarize contemporary regional experimental and global literature data to ascertain mean representative δ(15) N values for distinct food categories. A comprehensive data set of more than 12,000 analyzed food samples was summarized from the literature. Data originated from studies dealing with (1) authenticity tracing or origin control of food items, and (2) effects of fertilization or nutrition on δ(15) N values of plants or animals. Regional German food δ(15) N values revealed no major differences compared with the mean global values derived from the literature. We found that, in contrast to other food categories, historical faunal remains of pig and poultry are significantly enriched in (15) N compared to modern samples. This difference may be due to modern industrialized breeding practices. In some food categories variations in agricultural and feeding regimens cause significant differences in δ(15) N values that may lead to misinterpretations when only limited information is available. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.
- Aug 2013
Fragestellung: Einerseits wird in der Literatur Leistungssport als Risikofaktor für Essstörungen betrachtet, andererseits werden Sport und körperliche Aktivität eine präventive Wirkung auf psychische Störungen und Essstörungen zugeschrieben. Für Studierende mit einem starken Sportbezug ist bisher unklar, welcher Einfluss überwiegt. Daher war es das Ziel der Untersuchung, Sportstudenten und Studierende anderer Studiengänge hinsichtlich des Auftretens von Verhalten, welches mit Essstörungen assoziiert wird, zu vergleichen. Material und Methodik: An der Befragung nahmen 221 Studierende der Sporthochschule Köln sowie 225 Studierende des Fachs BWL und 287 Studierende naturwissenschaftlicher Studiengänge der Universität Köln teil. Der anonyme Onlinefragebogen umfasste Fragen des Eating Disorder Inventory-2 nach Schlankheitsstreben, bulimieassoziiertem Verhalten und Unzufriedenheit mit dem eigenen Körper sowie zum Ess- und Trainingsverhalten. Ergebnisse: Sportstudenten wiesen ein signifikant geringeres Schlankheitsstreben auf als BWL-Studenten. Die Unzufriedenheit mit dem eigenen Körper war sowohl bei BWL- als auch naturwissenschaftlichen Studenten signifikant höher als bei Sportstudenten, während männliche Sportstudenten signifikant höhere Werte in der Bulimieskala erzielten. Schlussfolgerung: Die vorliegende Untersuchung zeigt, dass Sportstudenten trotz eines höheren Anteils an Leistungssportlern nicht vermehrt von Verhaltensweisen berichten, die mit Essstörungen assoziiert werden, als Studierende ohne Sportbezug. Geschlechterübergreifend zeichneten sich Sportstudenten durch ein höheres Maß an Zufriedenheit mit dem eigenen Körper aus.
The exercise-induced metabolic stress can be influenced by the mode of recovery and is associated with acute hormonal responses. Therefore, it is hypothesized that active recovery between high intensity intervals reduces the metabolic stimulus and therefore the hormonal response compared to passive recovery. 12 male cyclist/triathletes performed four 30s all-out intervals, either with active (A) or passive (P) recovery between each bout. Human growth hormone (hGH), testosterone and cortisol, vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF) and macrophage migration inhibitory factor (MIF) were determined pre, 0', 30', 60' and 180' after both interventions. Metabolic stimuli and perturbations were characterized by lactate, blood gas (pH, BE, HCO3(-), PO2, PCO2), and spirometric analysis. Both interventions caused a transient increase in circulating levels of cortisol, testosterone, testosterone/cortisol-ratio, hGH, VEGF and HGF. Transient differences between A- and P-recovery were found only for testosterone and HGF directly after exercise, despite significant differences in metabolic disturbances (lactate, acid base status). Based on the data of testosterone, hGH and the testosterone/cortisol-ratio, as well as on the data of VEGF and HGF it appears that this kind of exercise protocol may promote anabolic processes and may lead to pro-angiogenic conditions independent of the mode of recovery. However transient differences between A- and P-recovery were shown for testosterone and HGF. In contrast, cortisol and hGH, which are known to be sensitive for metabolic perturbations (e.g. pH) showed no differences. Therefore, it is proposed that if a certain threshold for metabolic perturbations is exceeded, a hormonal response is induced, which does not differ between A- and P-recovery.
Previous intervention studies suggest that leptin, insulin, insulin-like growth factor 1 (IGF-1), and triiodthyronine (T3) are sensitive markers of inadequate energy intake in relation to exercise expenditures. Because of limitations in metabolic hormone measurements, self-reported energy availability (EA) based on food and activity records may present an alternative for characterizing energy status in young athletes. The purpose of the current study was to assess whether self-reported EA is related to leptin, insulin, IGF-1, and T3 in 352 young athletes. Sex, body composition, sport participation, and acute weight changes were considered as confounding variables. Multiple linear regression revealed that EA was negatively associated with leptin (p < 0.05) but not with insulin, IGF-1, or T3. Female athletes with low EA (<30 kcal·kg(-1) fat-free mass (FFM)) had higher leptin concentrations (5.0 ± 4.7 ng·mL(-1)) and more body fat (18.3% ± 5.1%) than did females with normal EA (leptin, 3.1 ± 2.4 ng·mL(-1); body fat, 15.8% ± 4.2%; both, p < 0.001). Athletes reporting acute weight loss (>1 kg·week(-1)) had a lower EA (18.9 ± 7.4 kcal·kg(-1) FFM) than did weight-stable athletes (30.0 ± 11.2 kcal·kg(-1) FFM) or athletes reporting weight gain (>1 kg; 49.7 ± 13.1 kcal·kg(-1) FFM). IGF-1 and T3 were also reduced in athletes who lost weight (p < 0.01). This cross-sectional study reveals a lack of association between self-reported EA and metabolic hormones indicative of energy status in young athletes. Further studies are needed to investigate whether self-reported EA and metabolic hormones are in better agreement when measured repeatedly.
- Jun 2013
In the last years, mainly 2 high-intensity-training (HIT) protocols became common: First, a Wingate-based "all-out" protocol and second, a 4×4 min protocol. However, no direct comparison between these protocols exists, and also a comparison with high-volume-training (HVT) is missing. Therefore, the aim of the present study was to compare these 3 endurance training protocols on metabolic, hormonal, and psychological responses. Twelve subjects performed: 1) HVT [130 min at 55% peak power output (PPO)]; 2) 4×4 min at 95% PPO; 3) 4×30 s all-out. Human growth hormone (hGH), testosterone, and cortisol were determined before (pre) and 0', 30', 60', 180' after each intervention. Metabolic stimuli and perturbations were characterized by lactate, blood gas (pH, BE, HCO3 -, pO2, PCO2), and spirometric analysis. Furthermore, changes of the person's perceived physical state were determined. The 4×30 s training caused the highest increases in cortisol and hGH, followed by 4 × 4 min and HVT. Testosterone levels were significantly increased by all 3 exercise protocols. Metabolic stress was highest during and after 4×30 s, followed by 4×4 min and HVT. The 4×30 s training was also the most demanding intervention from an athlete's point of view. In conclusion, the results suggest that 4×30 s and 4×4 min promote anabolic processes more than HVT, due to higher increases of hGH, testosterone, and the T/C ratio. It can be speculated that the acute hormonal increase and the metabolic perturbations might play a positive role in optimizing training adaptation and in eliciting health benefits as it has been shown by previous long term training studies using similar exercise protocols.
Glycerol is prohibited as an ergogenic aid by the World Anti-Doping Agency (WADA) due to the potential for its plasma expansion properties to have masking effects. However, the scientific basis of the inclusion of Gly as a "masking agent" remains inconclusive. The purpose of this study was to determine the effects of a hyperhydrating supplement containing Gly on doping-relevant blood parameters. Nine trained males ingested a hyperhydrating mixture twice per day for 7 days containing 1.0 g·kg(-1) body mass (BM) of Gly, 10.0 g of creatine and 75.0 g of glucose. Blood samples were collected and total hemoglobin (Hb) mass determined using the optimized carbon monoxide (CO) rebreathing method pre- and post-supplementation. BM and total body water (TBW) increased significantly following supplementation by 1.1 ± 1.2 and 1.0 ± 1.2 L (BM, P < 0.01; TBW, P <0.01), respectively. This hyperhydration did not significantly alter plasma volume or any of the doping-relevant blood parameters (e.g., hematocrit, Hb, reticulocytes and total Hb-mass) even when Gly was clearly detectable in urine samples. In conclusion, this study shows that supplementation with hyperhydrating solution containing Gly for 7 days does not significantly alter doping-relevant blood parameters.
- Dec 2011
Die Einnahme von Nahrungsergänzungsmitteln (NEM) ist in der Bevölkerung und besonders bei Sportlern weit verbreitet. Die Gründe dafür sind z. T. unterschiedlich, liegen aber im Wesentlichen im Bereich von Erhaltung und Unterstützung der Gesundheit, Optimierung der Regeneration und Verbesserung der Leistungsfähigkeit. Unabhängig davon, ob ein NEM diesen Erwartungen gerecht wird, sollte sich jeder Konsument bewusst sein, dass in den vergangenen Jahren immer wieder NEM entdeckt wurden, die nicht deklarierte Substanzen (wie Ephedrin, Koffein, anabol-androgene Steroide, Sibutramin, Methylhexanamin) enthielten. Bei Sportlern, die dem Dopingkontrollsystem unterliegen, kann die Einnahme solcher NEM zu einem positiven Dopingbefund führen. Zudem besteht das potenzielle Risiko ernsthafter gesundheitlicher Konsequenzen. Generell sollte daher die Einnahme von NEM zurückhaltend und auf Basis einer individuellen Nutzen-Risiko-Abwägung erfolgen und auf NEM aus risikoarmen Quellen zurückgegriffen werden.
During prolonged periods of high energy expenditure (EE), restricted food intake can lead to a loss of body mass. This case study describes the preexpedition support for an unsupported 3-wk crossing of the Atacama Desert in Chile. The goals were to simulate the energy requirements of walking under varying conditions and to predict energy intake and EE to evaluate whether the expected weight loss was in acceptable limits. The expeditionist (male, 35 yr, 197 cm, basal weight 80 ± 0.5 kg) was a well-trained endurance athlete with experience of multiple expeditions. During the simulation, he walked on a treadmill at speeds of 2-7 km/hr under varying conditions of inclination (0%, 7.5%), backpack weight (0 kg, 30 kg), and altitude (sea level, simulated altitude of 3,500 m). Under all conditions, the lowest EE was observed at 5 km/ hr. Based on the simulation data, we predicted an average EE of 4,944 kcal/day for the expedition. Because energy intake was restricted to 2,249 kcal/day, we expected the expeditionist to lose considerable weight and consequently advised him to gain 5 kg of body-fat reserves. During the actual desert crossing, he covered a distance of 26 ± 7 km/day at an average speed of 3.8 ± 0.4 km/hr. Daily EE (4,817 ± 794 kcal/day) exceeded energy intake (1,771 ± 685 kcal/day), and the negative energy balance was in agreement with the actual weight loss of 10.5 kg, which was most notable in the lower trunk.
- Nov 2011
Since 2010, glycerol has been ruled a masking agent by the World Anti-Doping Agency and consequently its administration is prohibited in sports. A detection method is available but little is known about the urinary excretion following administration. Fourteen well-trained cyclists (27.0 ± 5.4 years; O2max: 63.9 ± 8.5 ml/kg/min) were administered glycerol (1 g/kg body mass + 25 ml water/kg body mass) and placebo (25 ml water/kg) in a cross-over study. Blood and urine samples were collected before administration and after 2.5, 4, and 6.5 h. Urine samples were further collected up to 24 h post-administration. Following glycerol administration, urinary glycerol increased from 10.9 ± 15.5 to 50581 ± 23821 µg/ml within 2.5 h. In the placebo group, urinary glycerol did not exceed 26.8 ± 31.3 µg/ml. Urinary concentrations in the glycerol group were significantly higher than in the placebo group for 16.9 ± 1.0 h. In comparison to placebo, glycerol caused a larger increase in body weight (0.69 ± 0.42 vs. 0.27 ± 0.44 kg; p < 0.05) and a reduced urine output (972 ± 379 vs. 1271 ± 387 ml; p < 0.05). Reductions in haemoglobin and haematocrit were significantly greater after glycerol (−0.60 ± 0.28 g/dl; -1.7 ± 0.7%) than after placebo administration (−0.29 ± 0.39 g/dl; -0.9 ± 1.1%). The study shows that glycerol administration was detectable in urine for several hours. Even though there were significant reductions in haemoglobin and haematocrit after 2.5 h, the plasma expansion by glycerol appeared rather marginal in comparison to placebo. Copyright
- Oct 2011
During prolonged periods of high energy expenditure, restricted food intake can lead to a loss of body mass. In this case study we describe the pre-expedition support for an unsupported three-week crossing of the Atacama Desert (Chile). Our goals were to simulate the energy requirements of walking under varying conditions and to predict energy intake and energy expenditure in order to evaluate whether the expected weight loss was in acceptable limits. The expeditionist (male, 35 years, 197 cm, basal weight: 80 ± 0.5 kg) was a well-trained endurance athlete with experience of multiple expeditions. During the simulation, he walked on a treadmill at speeds between 2 and 7 km·h-1 under varying conditions such as inclination (0%, 7.5%), backpack weight (0 kg, 30 kg) and altitude (sea-level, simulated altitude of 3500 m). Under all conditions, the lowest energy expenditure was observed at 5 km·h-1. Based on the simulation data, we predicted an average energy expenditure of 4944 kcal·d-1 for the expedition. Since energy intake was restricted to 2249 kcal·d-1, we expected the expeditionist to lose considerable weight and consequently advised him to gain 5 kg of body fat reserves. During the actual desert crossing, the expeditionist covered a distance of 26 ± 7 km·d-1 at an average speed of 3.8 ± 0.4 km·h-1. Daily EE (4817 ± 734 kcal·d-1) exceeded energy intake (1873 ± 761 kcal·d-1) and the negative energy balance was in agreement with the actual weight loss of 10.5 kg, which was most notable in the lower trunk.
The aim of the study was to determine the cardiorespiratory and metabolic characteristics during intense and moderate table tennis (TT) training, as well as during actual match play conditions. Blood lactate concentration (Lac), heart rate (HR, beats per minute [bpm]), oxygen uptake (VO2), and energy expenditure (EE) in 7 male participants of the German junior national team (age: 14 ± 1 y, weight: 60.5 ± 5.6 kg height; 165 ± 8 cm) were examined during six training sessions (TS) and during an international match. The VO2 was measured continuously with portable gas analyzers. Lac was assessed every 1 to 3 min during short breaks. Mean (peak) values for Lac, HR, VO2, and EE during the TS were 1.2 ± 0.7 (4.5) mmol·L-1, 135 ± 18 (184) bpm, 23.5 ± 7.3 (43.0) mL·kg-1· min-1, and 6.8 ± 2.0 (11.2) METs, respectively. During match play, mean (peak) values were 1.1 ± 0.2 (1.6) mmol·L-1, 126 ± 22 (189) bpm, 25.6 ± 10.1 (45.9) mL·kg-1·min-1, and 4.8 ± 1.4 (9.6) METs, respectively. For the first time, cardiorespiratory and metabolic data in elite junior table tennis have been documented demonstrating low cardiorespiratory and metabolic demands during TT training and match play in internationally competing juniors.
Iron depletion seems to occur more frequently among athletes than in the general population and may affect performance capacity. Only little information is available about the prevalence of iron status abnormalities in young elite athletes and whether iron depletion is associated with gender, sport, age or nutrition- and exercise-related factors in this group. Hence, diet, exercise and haematological data from 193 elite athletes (96 males, 97 females; 16.2 ± 2.7 years) from 24 different sports were analyzed retrospectively. Most female athletes failed to meet the recommended daily allowance for iron, even though dietary iron density was higher than in males (5.75 ± 0.78 vs. 6.17 ± 0.98 mg/1,000 kcal; P = 0.001). Iron depletion (serum ferritin < 35 μg/L) occurred in 31% of male and 57% of female athletes (P < 0.001). Low haemoglobin (males: <13 g/dL; females: <12 g/dL) and haematocrit (males: <40%; females: <36%) values were equally prevalent in both genders [haemoglobin: 7.3% (males), 6.2% (females); haematocrit: 13.5% (males); 15.5% (females)]. In females, reduced ferritin levels were associated with a lower dietary iron density (5.9 ± 0.8 vs. 6.6 ± 1.1 mg/1,000 kcal; P = 0.002). Males with iron depletion had a significantly higher estimated energy expenditure (48.7 ± 7.0 vs. 44.4 ± 7.6 kcal/kg/day; P = 0.009).
High-intensity interval training (HIIT) in junior and adult soccer has been shown to improve oxygen uptake (VO₂) and enhance soccer performance. The main purpose of this study was to examine the short term effects of a 5-week HIIT vs. high-volume training (HVT) program in 14-year-old soccer players regarding the effects on VO₂max and 1,000-m time (T₁₀₀₀) and on sprinting and jumping performance. In a 5-week period, 19 male soccer players with a mean (SD) age of 13.5 ± 0.4 years performed HIIT at close to ~90% of maximal heart rate. The HVT intensity was set at 60-75% of maximal heart rate. VO₂max increased significantly (7.0%) from pre to post in HIIT but not after HVT. T₁₀₀₀ decreased significantly after HIIT (~-10 vs. ~-5 seconds in HVT). Sprint performance increased significantly in both groups from pre to posttesting without any changes in jumping performance.
- Jan 2011
The correct assessment of individual energy requirements of athletes remains a challenge. Available literature indicates that accelerometry-based sensors underestimated energy expenditure in athletes, especially during high-intensity exercise. The goal of our study was to evaluate two commercially available devices (Actiheart; SenseWear Pro3) during high-intensity running and to identify potential sources of error.Twenty-nine male endurance- and strength-trained athletes participated in an incremental running exercise, which started at 2.8 m · s. Running speed was increased by 0.4 m · s every 5 minutes until 4.8 m · s or individual exhaustion were reached. Energy expenditure was measured with indirect calorimetry (IC) and both sensors were worn according to the manufacturers’ instructions. Twelve participants also conducted a step test in order to individually recalibrate the Actiheart data.The Actiheart monitor underestimated energy expenditure (EE) for all speeds by 1.1 to 8.3 kcal · min and showed a weak correlation with IC (r=0.61). Following individual recalibration there were no significant differences to IC but validity correlation did not improve (r=0.56). Heart rate was assessed correctly with the Actiheart when compared to a Polar 610 recorder. Activity counts increased only between 2.8 and 3.6 m · s but plateaued thereafter. SenseWear significantly underestimated EE for all speeds by 1.0 to 9.5 kcal min and was moderately correlated with IC (r=0.66). Longitudinal and transversal acceleration increased significantly between 2.8 and 4.4 m · s and were correlated with running speed (0.63
- Dec 2010
The correct assessment of energy expenditure (EE) in athletes is important to ensure that dietary energy intake is sufficient. In general, athletes are individuals with especially high levels of total EE (TEE) and exercise-related EE (ExEE). The SenseWear Pro3 Armband (SWA) is a multisensor device for the individual assessment of EE, but data on the validity for higher exercise intensities are missing. The aim of the study was to validate the SWA for the assessment of TEE and ExEE in endurance athletes. The SWA was worn by 14 male endurance athletes for 7 d during a regular training period, and TEE was measured in parallel with the doubly labeled water method. Two controlled exercise trials (treadmill running=2.4-4.8 m·s, stationary bicycling=140-380 W) were performed, during which indirect calorimetry was used to assess ExEE. TEE assessed with the SWA and TEE measured with the doubly labeled water method were significantly correlated (r=0.73, P<0.01), but there were a proportional bias and considerably wide limits of agreement (-1368 to 1238 kcal·d). The error of TEE assessed with the SWA was related to the athletes' individual lactate thresholds (P<0.05). During running and bicycling, ExEE was significantly underestimated for most exercise intensities, and the underestimation increased with exercise intensity (P<0.001). According to our results, the SWA does not provide valid results of TEE and ExEE in endurance athletes because of the underestimation of EE at higher exercise intensities. It seems necessary to develop exercise-specific prediction equations to improve EE measurements in athletes.
The assessment of nutrition and activity in athletes requires accurate and precise methods. The aim of this study was to validate a protocol for parallel assessment of diet and exercise against doubly labelled water, 24-h urea excretion, and respiratory gas exchange. The participants were 14 male triathletes under normal training conditions. Energy intake and doubly labelled water were weakly associated with each other (r = 0.69, standard error of estimate [SEE] = 304 kcal x day(-1)). Protein intake was strongly correlated with 24-h urea (r = 0.89) but showed considerable individual variation (SEE = 0.34 g kg(-1) x day(-1)). Total energy expenditure based on recorded activities was highly correlated with doubly labelled water (r = 0.95, SEE = 195 kcal x day(-1)) but was proportionally biased. During running and cycling, estimated exercise energy expenditure was highly correlated with gas exchange (running: r = 0.89, SEE = 1.6 kcal x min(-1); cycling: r = 0.95, SEE = 1.4 kcal x min(-1)). High exercise energy expenditure was slightly underestimated during running. For nutrition data, variations appear too large for precise measurements in individual athletes, which is a common problem of dietary assessment methods. Despite the high correlations of total energy expenditure and exercise energy expenditure with reference methods, a correction for systematic errors is necessary for the valid estimation of energetic requirements in individual athletes.
- Aug 2009
The carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope ratios of human hair can be used for the interpretation of dietary habits and nutritional status in contemporary or past populations. Although the results of bulk or segmental isotope ratio analysis of human hair have been used for the reconstruction of an individual's diet for years, only limited data of controlled dietary changes on the carbon and nitrogen isotopic composition of human hair are available. Hair of four individuals, two males and two females, who participated in a dietary change experiment for 28 days was segmentally analysed for delta(13)C and delta(15)N. The dietary change included a change from C3 to C4 plant enriched diets and a simultaneous replacement of terrestrial animal products by marine products. This resulted in an increase in delta(13)C(diet) of +8.5 to +9.9 per thousand and in delta(15)N(diet) of +1.5 to +2.2 per thousand. All subjects showed significant increases in delta(13)C(hair) and delta(15)N(hair) during the dietary change period, although no subject reached a new steady state for either carbon or nitrogen. The change in delta(15)N(hair) was faster than the change in delta(13)C(hair) for all individuals. The magnitude of change of the isotopic composition during the dietary change period could be attributed to the degree of physical activity of the individuals, with a higher physical activity resulting in a faster change.
Little is known about the prevalence and motives of supplement use among elite young athletes who compete on national and international levels. Therefore, the current survey was performed to assess information regarding the past and present use of dietary supplements among 164 elite young athletes (16.6 +/- 3.0 years of age). A 5-page questionnaire was designed to assess their past and present (last 4 weeks) use of vitamins, minerals, carbohydrate, protein, and fat supplements; sport drinks; and other ergogenic aids. Furthermore, information about motives, sources of advice, supplement sources, and supplement contamination was assessed. Eighty percent of all athletes reported using at least 1 supplement, and the prevalence of use was significantly higher in older athletes (p < .05). Among supplement users, minerals, vitamins, sport drinks, energy drinks, and carbohydrates were most frequently consumed. Only a minority of the athletes declared that they used protein/amino acids, creatine, or other ergogenic aids. Major motives for supplement use were health related, whereas performance enhancement and recommendations by others were less frequently reported. Supplements were mainly obtained from parents or by athletes themselves and were mostly purchased in pharmacies, supermarkets, and health-food stores. Among all athletes, only 36% were aware of the problem of supplement contamination. The survey shows that supplement use is common and widespread among German elite young athletes. This stands in strong contrast to recommendations by leading sport organizations against supplement use by underage athletes.
- Nov 2008
Recently published news regarding food safety in China caused some world-wide disturbance and uncertainty among top athletes and their supporting staff. According to an article in The New York Times, a member of the U.S. Olympic team discovered oversized chicken breast when visiting it Supermarket in Beijing China. More interesting, the chicken contained considerable amounts of anabolic steroids. which were reported to be large enough to cause a failed doping test after ingesting the meat (Shpigel. 2008). Based on this case report it appears necessary to assess the danger posed to our (Olympic) athletes by foods and especially meat products oil a more general basis. More important, our athletes are involved in worldwide travel during the competitive season. Therefore we must consider not Only Our athletes' local food choices but also the wide variety of foods and regional delicacies our athletes might be confronted with in foreign Countries.
- Jul 2008
Since 1999 several groups have analyzed nutritional supplements with mass spectrometric methods (GC/MS, LC/MS/MS) for contaminations and adulterations with doping substances. These investigations showed that nutritional supplements contained prohibited stimulants as ephedrines, caffeine, methylenedioxymetamphetamie and sibutramine, which were not declared on the labels. An international study performed in 2001 and 2002 on 634 nutritional supplements that were purchased in 13 different countries showed that about 15% of the nonhormonal nutritional supplements were contaminated with anabolic-androgenic steroids (mainly prohormones). Since 2002, also products intentionally faked with high amounts of ‘classic’ anabolic steroids such as metandienone, stanozolol, boldenone, dehydrochloromethyl-testosterone, oxandrolone etc. have been detected on the nutritional supplement market. These anabolic steroids were not declared on the labels either. The sources of these anabolic steroids are probably Chinese pharmaceutical companies, which sell bulk material of anabolic steroids. In 2005 vitamin C, multivitamin and magnesium tablets were confiscated, which contained cross-contaminations of stanozolol and metandienone. Since 2002 new ‘designer’ steroids such as prostanozol, methasterone, androstatrienedione etc. have been offered on the nutritional supplement market. In the near future also cross-contaminations with these steroids are expected. Recently a nutritional supplement for weight loss was found to contain the β2-agonist clenbuterol. The application of such nutritional supplements is connected with a high risk of inadvertent doping cases and a health risk. For the detection of new ‘designer’ steroids in nutritional supplements, mass spectrometric strategies (GC/MS, LC/MS/MS) are presented. Copyright
- Mar 2008
In several studies it has been demonstrated that products containing pharmaceutically active ingredients are marketed as dietary supplements. Most of these products contain anabolic steroids. Recently products for weight loss containing active drugs have also appeared on the market. In the present case a healthy male ordered the product 'Anabolic burner' via the Internet. The product was received from a German dispatcher and paid by bank transfer to a German bank account. After ingesting one tablet he reported tremor and delivered a urine sample. This urine was found to contain 2 ng/mL of clenbuterol utilizing LC-MS/MS analysis. Additionally the product itself was analyzed with GC-MS for clenbuterol, yielding a content of about 30 microg per tablet. The beta-2 agonist clenbuterol is only legally available on prescription and is classified as prohibited doping substance in sports. The present case for the first time confirms the presence of clenbuterol in a dietary supplement. It again demonstrates the common problem with products on the supplement market, where non-licensed pharmaceuticals and doping substances are easily available. The ingestion of these products containing additions of therapeutic drugs can lead to side effects and/or interactions with conventional medicines.
To investigate whether the administration of the zinc-containing nutritional supplement ZMA causes an increase of serum testosterone levels, which is an often claimed effect in advertising for such products; to monitor the urinary excretion of testosterone and selected steroid hormone metabolites to detect potential changes in the excretion patterns of ZMA users. Fourteen healthy, regularly exercising men aged 22-33 years with a baseline zinc intake between 11.9 and 23.2 mg day(-1) prior to the study. Supplementation of ZMA significantly increased serum zinc (P=0.031) and urinary zinc excretion (P=0.035). Urinary pH (P=0.011) and urine flow (P=0.045) were also elevated in the subjects using ZMA. No significant changes in serum total and serum free testosterone were observed in response to ZMA use. Also, the urinary excretion pattern of testosterone metabolites was not significantly altered in ZMA users. The present data suggest that the use of ZMA has no significant effects regarding serum testosterone levels and the metabolism of testosterone in subjects who consume a zinc-sufficient diet.
- Sep 2007
According to the rules of national and international sport authorities the presence of a forbidden substance in equine as well as in human sports is controlled under the policy of zero tolerance. That means that the qualitative identification of a banned substance leads to a positive doping case regardless of its quantity, except for a few threshold substances. These rules apply also to therapeutics, which are in common use in routine veterinary management of competition horses. Veterinarians must be aware of the specific detection time of a given therapeutic to avoid an unintentional doping case. Detection times for betamethasone and flumethasone are mainly dependent on the dosage, the formulation and on analytical capabilities. In the present study single intravenous injections of 4.5 to 6.0 ml of Acutol® (4.2 to 5.5 μg/kg flumethasone) and intra-articular injections (and an intra-muscular injection in one horse, respectively) of 2.0 to 5.0 ml of Celestovet® (50 bis 138 μg/kg betamethasone) were administered. For both medications ten different horses were used. Concentrations of betamethasone and flumethasone were determined by a sensitive high performance liquid chromatography-tandem mass spectrometry method. In the Celestovet® study concentrations of betamethasone were still above the limit of detection 45 days after the administration. However, 48 hours after the injection of Acutol® concentrations of flumethasone were below the limit of detection of the employed analytical method.
- Feb 2007
In numerous studies it has been demonstrated that several nutritional supplements contain prohormones not declared on the label. In the current study two products (effervescent tablets) containing high amounts of the 17-methylated anabolic androgenic steroids metandienone (product 1: 16.8 mg/tablet) and stanozolol (product 2: 14.5 mg/tablet) were identified. Additionally in both products norandrostenedione was detected, in product 2 with minor amounts of several other steroids. The substances identified can cause enormous health risks. In addition, the use of the analyzed tablets can lead to positive doping results for metabolites of the respective steroids in sports. This study again shows the insufficient surveillance of the production and trade of dietary supplements. Consumers should be aware of the enormous health and doping risks connected with the use of such products. For GC-MS identification of the analytes the trimethylsilyl derivatives of the steroids and the mixed N-t-butyldimethylsilyl,O-trimethylsilyl derivatives were used. The quantitation of metandienone, norandrostenedione, and stanozolol was performed using HPLC-DAD.
At the end of 2005, a German drug surveillance authority confiscated nutritional supplements (effervescent tablets) from a German manufacturer, which contained among other steroids high amounts of metandienone (about 15 mg/tablet) and stanozolol (about 17 mg/tablet). These anabolic steroids were not declared on the labels. Additionally the drug surveillance authority confiscated other nutritional supplements like vitamin C-, multivitamin-, calcium-and magnesium – tablets, which were produced from the same manufacturer on the same production line within the same time interval. The LC/MS/MS analyses showed cross-contaminations of the vitamin C-, multivitamin-and magnesium-tablets with metandienone and stanozolol. These cross-contaminated products were produced for the sale in ordinary German and Spanish groceries and drug stores.