Energy intake and energy expenditure of pre-professional female contemporary dancers

Patterns of energy availability and carbohydrate intake differentiate between adaptable and problematic low energy availability in female athletes

Background

Problematic low energy availability (EA) is the underlying culprit of relative energy deficiency in sport (REDs), and its consequences have been suggested to be exacerbated when accompanied by low carbohydrate (CHO) intakes.

Objectives

This study compared dietary intake, nutrition status and occurrence of REDs symptoms in groups of female athletes, displaying different patterns of EA and CHO intake.

Methods

Female athletes (n = 41, median age 20.4 years) from various sports weighed and recorded their food intake and training for 7 consecutive days via a photo-assisted mobile application. Participants were divided into four groups based on patterns of EA and CHO intakes: sufficient to optimal EA and sufficient to optimal CHO intake (SEA + SCHO), SEA and low CHO intake (SEA + LCHO), low energy availability and SCHO (LEA + SCHO), and LEA and LCHO (LEA + LCHO). SEA patterns were characterised by EA ≥30 and LEA by EA <30 kcal/kg fat free mass, and SCHO patterns characterised by CHO intake ≥3.0 and LCHO <3.0 g/kg body weight for most of the registered days. Body composition was measured with dual energy x-ray absorptiometry, resting metabolic rate with indirect calorimetry and serum blood samples were collected for evaluation of nutrition status. Behavioural risk factors and self-reported symptoms of REDs were assessed with the Low Energy Availability in Females Questionnaire, Eating Disorder Examination Questionnaire Short (EDE-QS), Exercise Addiction Inventory, and Muscle Dysmorphic Disorder Inventory.

Results

In total, 36.6% were categorised as SEA + SCHO, of which 5/16 were ball sport, 7/10 endurance, 1/7 aesthetic, 2/5 weight-class, and 0/3 weight-class athletes. Of LEA + LCHO athletes (19.5% of all), 50% came from ball sports. Aesthetic and endurance athletes reported the greatest training demands, with weekly training hours higher for aesthetic compared to ball sports (13.1 ± 5.7 vs. 6.7 ± 3.4 h, p = 0.012). Two LEA + LCHO and one SEA + LCHO athlete exceeded the EDE-QS cutoff. LEA + LCHO evaluated their sleep and energy levels as worse, and both LEA groups rated their recovery as worse compared to SEA + SCHO.

Conclusion

Repeated exposures to LEA and LCHO are associated with a cluster of negative implications in female athletes. In terms of nutrition strategies, sufficient EA and CHO intakes appear to be pivotal in preventing REDs.

Female Athlete Triad and Relative Energy Deficiency in Sport (REDs): Nutritional Management

The female athlete triad (TRIAD) is a spectrum of disorders involving low energy availability (LEA), low bone mineral density, and menstrual disorders. It is increasingly common to use the term 'relative energy deficiency in sport' (RED), emphasising the extensive impact of LEA on the body. The aim of this narrative review was to gather original research encompassing female athletes across various sports as well as to collect findings on the potential of a nutrition-focused approach to prevent or treat the aforementioned disorders. A comprehensive search was conducted in PubMed and Scopus. Several challenges were identified regarding the adequacy of the energy availability, protein, and carbohydrate requirements in the diets of female athletes. Moreover, insufficient intake of vitamin D has been observed across all athlete groups studied. This insufficiency also extends to the average requirement for Ca, Mg, the Ca/P ratio, Zn, and Fe. To address those concerns, a nutritional approach is proposed in the latter part of this review. The factors that can improve the absorption of micronutrients have also been discussed. The TRIAD/REDs affect an ever-growing number of women and require appropriate therapeutic management, particularly through nutritional care. Therefore, cooperation within an interdisciplinary team comprising a physician, nutritionist, physiotherapist, and psychologist is crucial.

Investigating pre-professional dancer health status and preventative health knowledge

Introduction

Dance is a highly demanding physical pursuit coupled with pressure to conform to aesthetic ideals. Assessment of health status and preventative health knowledge of pre-professional dancers may help inform educational strategies promoting dancers' health and career longevity. The aim of this research was to establish a baseline understanding of dance students at a single pre-professional institution based on metrics focused on current health, nutrition, lifestyle, and wellbeing while also gauging knowledge of longer-term health implications.

Methods

Adopting a cross-sectional study design, the Dance-Specific Energy Availability Questionnaire was tailored for Australian participants and administered online.

Results

The response rate was 59.5% (69/116 eligible students) and the survey was completed in full by 63 students. Mean BMI was 20 kg/m2, although among females, 47% had a BMI < 20 (range 16 to 25 kg/m2), and at their lowest reported weight BMI was 14 to 25 kg/m2. Over a third had either experienced (31%) or were currently experiencing (3.4%) secondary amenorrhea (period absence ≥ 3 consecutive months). Most dancers did not exclude food groups, however, 24% had been advised to exclude particular foods in the past, mostly by dance teachers. A large percentage used nutritional supplements (68%) with 60% supplementing with iron and more than half (53%) taking two or more supplements. Only 25% had ever utilised a qualified dietitian, although 16% reported a history of eating disorders and 25% reported vegetarian or vegan eating patterns. REDs risk scores ranged from -16 to +16 points with negative scores indicating LEA and higher risk of REDs. The mean score for males was 5.2 (SD = 3.9) and 2.1 (SD = 5.9) for females, with 33.3% producing a negative score.

Conclusion

Results provide insight to health knowledge and particular issues pertinent for dancers and highlights the need for specific education strategies to promote a preventative health focus for those entering a pre-professional programme. This study also highlights the need for improved awareness of LEA and REDs among all practitioners working with dancers along with cultural and structural changes within the broader dance community to help protect and promote the wellbeing of dancers.

Timing is everything, but does it really matter? Impact of 8-weeks morning versus evening iron supplementation in ballet and contemporary dancers

ABSTRACTThe effectiveness of a morning versus evening oral iron supplement strategy to increase iron stores was explored. Ballet and contemporary dancers with serum ferritin (sFer) < 50μg/L (n = 14), were supplemented daily with 105 mg elemental oral iron in either the morning (FeAM) or evening (FePM) for 8 weeks. A control group (n = 6) with sFer >50μg/L were given no supplement over the same period. Dancers' sFer were measured at baseline and post-intervention. Assessment of daily training load, dietary intake, and menstruation were made. A significant interaction (p < 0.001) showed the within group sFer change over the 8-week intervention in FeAM (+25.9 ± 10.5μg/L) and FePM, (+22.3 ± 13.6μg/L) was significantly different to CON (-30.17 ± 28.7μg/L; both p = 0.001). This change was not different between FeAM and FePM (p = 0.778). sFer levels within FeAM and FePM significantly increased over the 8-weeks; however, they significantly decreased in the CON group (all p < 0.05). Post-intervention sFer levels were no longer different between the three groups (p > 0.05). Training load, dietary intake, and number of menstrual cycles incurred were similar between FeAM and FePM (p > 0.05). Oral iron supplementation in either the morning or evening appears equally effective in increasing sFer levels in dancers with sub-optimal iron status.

Examination of the Cumulative Risk Assessment and Nutritional Profiles among College Ballet Dancers

This study examined female collegiate ballet dancers' (n = 28) Female Athlete Triad (Triad) risk via the Cumulative Risk Assessment (CRA) and nutritional profiles (macro- and micronutrients; n = 26). The CRA identified Triad return to play criteria (RTP: Full Clearance, Provisional Clearance, or Restricted/Medical Disqualified) by assessing eating disorder risk, low energy availability, menstrual cycle dysfunction, and low bone mineral density. Seven-day dietary assessments identified any energy imbalances of macro- and micronutrients. Ballet dancers were identified as low, within normal, or high for each of the 19 nutrients assessed. Basic descriptive statistics assessed CRA risk classification and dietary macro- and micronutrient levels. Dancers averaged 3.5 ± 1.6 total score on the CRA. Based on these scores, the RTP outcomes revealed Full Clearance 7.1%, n = 2; Provisional Clearance 82.1%, n = 23; and Restricted/Medical Disqualification 10.7%, n = 3. Dietary reports revealed that 96.2% (n = 25) of ballet dancers were low in carbohydrates, 92.3% (n = 24) low in protein, 19.2% (n = 5) low in fat percent, 19.2% (n = 5) exceeding saturated fats, 100% (n = 26) low in Vitamin D, and 96.2% (n = 25) low in calcium. Due to the variability in individual risks and nutrient requirements, a patient-centered approach is a critical part of early prevention, evaluation, intervention, and healthcare for the Triad and nutritional-based clinical evaluations.

Energy intake, expenditure and balance, and factors associated with energy balance of young adults (20-39 years): a retrospective cross-sectional community-based cohort study

BACKGROUND

Obesity epidemic presents major challenge to chronic disease prevention. Young adults may be at higher risk due to consumption of energy dense foods/beverages and low physical activity. This study assessed the energy intake, expenditure and balance of 20-39 year-old adults and also evaluated factors associated with energy balance to provide basis for obesity prevention and control.

METHODS

This retrospective cross-sectional cohort study involved 240 respondents selected through multistage random sampling. Data were collected through questionnaire, anthropometry and three 24-h dietary recall. Energy expenditure was assessed as the sum of resting energy expenditure (REE), energy expenditure of activity (EEA) and diet-induced energy expenditure of three days. Frequencies and percentages were employed in analysing general characteristics of the respondents. T-test and analysis of variance were used to assess relationships between and among numerical variables while relationships among categorical variables were evaluated through Chi-square test. Binary and multivariate logistic regression analyses were used to evaluate the factors associated with energy balance.

RESULTS

Majority (53.2%) had normal body mass index and this decreased as age increased (P < 0.001); 23.8% had overweight, 21.7% had general obesity, 38.3% had abdominal obesity and 39.2% had high risk waist hip ratio. Total energy intake (TEI) of the respondents was 2416.0 ± 722.728 kcal/day. Males had lower energy intake (kcal/day) of 2398.8 ± 494.761 than females (2431.1 ± 876.664). Male intake contributed less (85.7%) than female intake (110.5%) to recommended energy intake. TEI (kcal/day) was lowest among 25-29 (2285.3 ± 497.793) but highest (2586.0 ± 467.587) among 35-39 year-olds (P < 0.05). Total energy expenditure (TEE) was 2195.5 ± 384.544 kcal/day; a value of 2274.3 ± 385.792 was found among males while the females had a lower value of 2126.6 ± 371.403. TEE (kcal/day) ranged from 2169.4 ± 411.625 in 20-24 to 2248.8 ± 273.534 in 30-34 year-olds. Those with general obesity had higher energy (kcal/day) intake (2733.7 ± 1171.073), expenditure (2431.7 ± 491.666) and balance (302.0 ± 1300.186) than those without obesity (P < 0.01). Energy intake (2573.0 ± 966.553) and expenditure (2226.4 ± 372.621) were significantly higher among those with abdominal obesity than those with normal waist circumference (P < 0.05). Overall positive energy balance of the adults was 220.5 ± 787.271. The females had higher positive energy balance (304.4 ± 921.041) than males (124.5 ± 588.637). Energy balance was lowest (102.5 ± 629.780) among 25-29 and highest (373.5 ± 494.546) in 35-39 year-olds. Most (68.8%) of the participants had positive energy balance. Age (AOR:2.89, 95% C.I.:1.27-6.56) and occupation (AOR:2.30, 95% C.I.:1.05-5.03) increased the likelihood of positive energy balance by 2.

CONCLUSIONS

The study showed lower energy intake among the respondents than the recommended value; females had a value higher than what was recommended, males had less. Majority had positive energy balance and this was mostly found among those with obesity. Age and occupation were factors associated with positive energy balance. Nutrition education, health education and dietary counselling are recommended strategies to control sustained weight gain.

Management of Stress Fractures in Ballet

Stress fractures are highly prevalent in ballet dancers and lead to notable time loss from dancing. Nutritional status, body composition, bone mineral density, and rate of increase in activity are among the components that influence risk for stress fractures. Proper evaluation and management of stress fractures is essential including a review of the causative factors involved in each stress injury. The purpose of this article was to summarize current evidence for risk factors involved in dancers' stress fractures to optimize prevention and treatment. Identified associated factors include low energy availability, low bone mineral density, low fat body composition, abnormal lower extremity biomechanics, genetic factors, and high training loads.

Fat-Free Mass Using Bioelectrical Impedance Analysis as an Alternative to Dual-Energy X-Ray Absorptiometry in Calculating Energy Availability in Female Adolescent Athletes

Energy availability (EA) is calculated by subtracting exercise energy expenditure from energy intake, adjusted for fat-free mass (FFM) obtained using accurate methods, such as dual-energy X-ray absorptiometry (DXA). Unlike DXA, the bioelectrical impedance analysis (BIA) is low in cost, simple and easy to carry out. This study aimed to test the concordance between the calculation of EA using FFM values from four BIA predictive equations and FFM obtained using DXA in female adolescent athletes (n = 94), recruited via social media. Paired Student's t test, Wilcoxon test, Lin's concordance correlation coefficient, root mean square error, limits of agreement, and mean absolute percentage error were used to evaluate agreement between the FFM values obtained by the four SF-BIA predictive equations and DXA. Regression linear analysis was used to determine the relation between FFM values obtained using DXA and the BIA predictive equations. Standardized residuals of the FFM and EA were calculated considering DXA values as reference. The most appropriate model for the FFM (limits of agreement = 4.0/-2.6 kg, root mean square error = 1.9 kg, mean absolute percentage error = 4.34%, Lin's concordance correlation coefficient = .926) and EA (limits of agreement = 2.51/4.4 kcal·kg FFM-1·day-1, root mean square error = 1.8 kcal·kg FFM-1·day-1, mean absolute percentage error 4.24%, Lin's concordance correlation coefficient = .992) was the equation with sexual maturity as a variable, while the equation with the greatest age variability was the one with the lowest agreement. FFM-BIA predictive equations can be used to calculate EA of female adolescent athletes. However, the equation should be chosen considering sex, age, and maturation status. In the case of athletes, researchers should use equations developed for this group.

Dietary Iron and the Elite Dancer

Dancers are an athlete population at high risk of developing iron deficiency (ID). The aesthetic nature of the discipline means dancers potentially utilise dietary restriction to meet physique goals. In combination with high training demands, this means dancers are susceptible to problems related to low energy availability (LEA), which impacts nutrient intake. In the presence of LEA, ID is common because of a reduced mineral content within the low energy diet. Left untreated, ID becomes an issue that results in fatigue, reduced aerobic work capacity, and ultimately, iron deficient anaemia (IDA). Such progression can be detrimental to a dancer’s capacity given the physically demanding nature of training, rehearsal, and performances. Previous literature has focused on the manifestation and treatment of ID primarily in the context of endurance athletes; however, a dance-specific context addressing the interplay between dance training and performance, LEA and ID is essential for practitioners working in this space. By consolidating findings from identified studies of dancers and other relevant athlete groups, this review explores causal factors of ID and potential treatment strategies for dancers to optimise absorption from an oral iron supplementation regime to adequately support health and performance.

Impact of Low Energy Availability on Skeletal Health in Physically Active Adults

For decades researchers reported that pre-menopausal women who engage in extensive endurance exercise and have menstrual dysfunction can develop low bone mineral density (BMD) or osteoporosis. More recently, low energy availability has been recognized as the initiating factor for low BMD in these women. Furthermore, the relationship between low energy availability and poor skeletal health is not exclusive to women engaging in endurance exercise. Rather, both males and females commonly experience endocrine dysfunction resulting from low energy availability and high exercise levels that degrades skeletal health. Consequences to skeletal health can range from short-term changes in bone metabolism and increased risk of bone stress injuries to long-term consequences of low BMD, such as osteoporosis and related fragility fractures. The degree to which low energy availability degrades skeletal health may be dependent on the length and extent of the energy deficit. However, the complex relationships between under-fueling, short- and long-term skeletal consequences and the factors that mediate these relationships are not well described. In this review, we discuss the consequences of low energy availability on sex hormones and skeletal health in two highly-active populations-athletes and military trainees-and provide a summary of existing knowledge gaps for future study.

The relationship between rigorous perception of one's own body and self, unhealthy eating behavior and a high risk of anorexic readiness: a predictor of eating disorders in the group of female ballet dancers and artistic gymnasts at the beginning of their career

BACKGROUND

A group that is particularly exposed to eating disorders are young sportswomen who practice aesthetic disciplines, for whom it is important to keep a slim figure. Hence, the purpose of the study was to present the assessment of perception of one's own body and self as well as nutritional behavior in the group of ballet dancers and artistic gymnasts (BGA, n = 60) aged 10-12 against the background of the peer group (K, n = 60) and to determine the relationship between the studied elements, as well as anorexic readiness risk assessment to help diagnose premorbid stage of eating disorders with full symptoms.

METHODS

Anthropometric measurements (height, body weight) and the assessment of adipose tissue were performed. Using a questionnaire, data on physical activity, perception of one's own body and self, and selected eating behaviors were collected.

RESULTS

Underweight was observed in nearly half of the girls from the BGA group and the content of adipose tissue was significantly lower. Girls from the BGA group were characterized by overestimation of body size (p = 0.032), the need to improve their appearance/body (p = 0.025) and wanting to be the best in many areas of life (p = 0.002) significantly more often than in the K group. Moreover, they significantly more often limited the consumption of fats and carbohydrates (p = 0.044) and felt angry with themselves after too large of a meal (p = 0.050). It was shown that unhealthy eating behavior in the BGA group was significantly associated with rigorous self-perception (r = 0.42; p < 0.001). Students from the BGA group were more often exposed to a higher risk of anorexic readiness (p = 0.001). In a detailed analysis, it was found that eating behaviors, such as fasting, limiting the consumption of fats and carbohydrates, and avoiding eating under stress, were associated with feelings of dissatisfaction with oneself, the belief that appearance is extremely important in achieving life success and the need to improve appearance.

CONCLUSION

The obtained research results can be used as a source of information for specialists (including dietitians and psychologists), for the preparation of educational and repair programs in the group of ballet dancers or artistic gymnasts aged 10-12, including nutritional education and psychological care.

Collegiate Male Athletes Exhibit Conditions of the Male Athlete Triad

The primary purpose of this study was to determine prevalence of the Male Athlete Triad (MAT) conditions: low energy availability (EA), low bone mineral density (BMD), and low testosterone in male collegiate athletes from different sports. Participants included 44 collegiate male athletes (age, 20.4 ± 0.2 yr; BMI, 25.3 ± 1.3 kg/m2) from seven sports (cross country, soccer, basketball, wrestling, track, golf, and baseball). Resting metabolic rate, three-day food intake, seven-day exercise energy expenditure, body composition, and reproductive and metabolic hormones were assessed. Of the total participants, 15% had low EA, 0% had low BMD, 28% had low total testosterone (TT), and 80% had low calculated free testosterone (cFT). There were no significant correlations between EA, BMD, TT, and cFT. Insulin and sex hormone binding globulin (SHBG) were below and on the upper end of the reference range for healthy male adults, respectively. Insulin was negatively correlated with total (r = -0.330, p = 0.043) and lumbar spine BMD z-scores (r = -0.413, p = 0.010). Low TT and low cFT were the most prevalent MAT conditions among all athletes. Further research should investigate the relationship between insulin and SHBG and the role of these hormones in the MAT. Novelty Bullets • Assessment of energy availability alone is not sufficient to identify physiological disturbances in collegiate male athletes. • Low total and/or free testosterone may be present in some collegiate male athletes, regardless of BMD status. • Low insulin and high SHBG concentration may portray the presence of conditions of the MAT in male collegiate athletes.

Amateur ballet practicing, body image and eating behaviors: a comparative study of classical ballet dancers, gym users and sedentary women

BACKGROUND

Ballet dancers are a risk group for body image (BI) distortion, dissatisfaction and eating disorders (ED), but few studies have investigated these aspects in amateur adult practitioners. This study aimed to evaluate if amateur female adult classical ballet dancers presented different BI and behaviors for ED than gym users and sedentary women.

METHODS

This is a cross-sectional study where classical ballet dancers (n = 19) were compared to gym users (n = 19) and sedentary women (n = 19). Body mass index (BMI) was assessed, and a figure rating scale was applied to assess BI distortion/dissatisfaction. The body shape questionnaire (BSQ) was used to measure BI concern. The eating attitudes test (EAT-26) and the bulimic investigatory test, Edinburgh (BITE) were used for behaviors toward anorexia and bulimia.

RESULTS

BMI was significantly lower in ballet dancers than gym users and sedentary women (F, p = .04). BI distortion did not differ among the studied groups. BI dissatisfaction was lower (X², p = .041) in ballet dancers (75.0%) and gym users (70.6%) compared to sedentary women (100%). Correspondence analysis showed ballet dancers were mostly not concerned with BI, which was not observed among the other groups. The EAT-26 did not differ between the studied groups. The BITE score was lower (Tukey's post hoc test, p = .005) in the ballet dancers [mean 5.3 (5.6)] compared to the sedentary women [mean 10.9 (4.8)].

CONCLUSIONS

Data suggest that amateur classical ballet practicing is associated to better BI and fewer behaviors for ED in the studied population. The lower BMI in ballet dancers might explain these findings, and further studies should explore these associations.

Prevalence of Normal Weight Obesity and Health Risk Factors for the Female Collegiate Dancer

ABSTRACT

Brown, AF, Alfiero, CJ, Brooks, SJ, Kviatkovsky, SA, Smith-Ryan, AE, and Ormsbee, MJ. Prevalence of normal weight obesity and health risk factors for the female collegiate dancer. J Strength Cond Res 35(8): 2321-2326, 2021-The purpose of this study was to investigate the prevalence of normal weight obesity (NWO) and evaluate the relationship between NWO and health risk factors in a collegiate dancer population. Reanalysis of data of female dancers (N = 42) from 2 larger studies was used to assess prevalence and health risk factors of NWO. Dancers completed a dual-energy x-ray absorptiometry scan to assess fat mass (FM), lean mass (LM), and visceral adipose tissue (VAT) and a 3-day food record. Normal weight obesity was defined as a body mass index (BMI) of 18.5-24.9 kg·m-2 and body fat (BF) ≥30%. Twenty-five (60%) dancers were classified as normal weight lean (NWL), and 17 dancers (40%) were classified as NWO. Significant differences were observed for BMI (NWL: 21.1 ± 1.7, NWO: 23.1 ± 1.6, p < 0.001), LM (NWL: 71.0 ± 2.9%, NWO: 62.5 ± 2.7%, p < 0.001), %BF (NWL: 24.8 ± 3.1%, NWO: 33.9 ± 2.6%, p < 0.001), and VAT (NWL: 130.6 ± 43.0 g, NWO: 232.3 ± 70.8 g, p < 0.001) between NWL and NWO. A significant difference was observed for carbohydrate intake (NWL: 4.7 ± 1.8 g·kg-1, NWO: 3.7 ± 1.0 g·kg-1, p = 0.020) between groups. Significant positive correlations with FM were observed between carbohydrate (kcal, p = 0.048), fat (kcal, p = 0.018; g·kg-1, p = 0.040), and total calories (p = 0.019) in NWO. Normal weight obesity in collegiate dancers may be more prevalent than previously perceived and may be significantly related to important health risk factors. The current study demonstrates the need for body composition assessments and emphasizing on promoting overall health in collegiate dancers.

Measuring the Exercise Component of Energy Availability during Arduous Training in Women

INTRODUCTION

Low energy availability (EA) may impede adaptation to exercise, suppressing reproductive function and bone turnover. Exercise energy expenditure (EEE) measurements lack definition and consistency. This study aimed to compare EA measured from moderate and vigorous physical activity from accelerometry (EEEmpva) with EA from total physical activity (EEEtpa) from doubly labeled water in women. The secondary aim was to determine the relationship of EA with physical fitness, body composition by dual-energy x-ray absorptiometry, heart rate variability (HRV), and eating behavior (Brief Eating Disorder in Athletes Questionnaire [BEDA-Q]).

METHODS

This was a prospective, repeated-measures study, assessing EA measures and training adaptation during 11-month basic military training. Forty-seven women (23.9 ± 2.6 yr) completed three consecutive 10-d assessments of EEEmvpa, EEEtpa, and energy intake (EI). EA measures were compared using linear regression and Bland-Altman analyses; relationships of EA with fat mass, HRV, 1.5-mile run times, and BEDA-Q were evaluated using partial correlations.

RESULTS

EA from EEEmvpa demonstrated strong agreement with EA from EEEtpa across the measurement range (R2 = 0.76, r = 0.87, P < 0.001) and was higher by 10 kcal·kg-1 FFM·d-1. However, EA was low in absolute terms because of underreported EI. Higher EA was associated with improved 1.5-mile run time (r = 0.28, P < 0.001), fat mass loss (r = 0.38, P < 0.001), and lower BEDA-Q score (r = -0.37, P < 0.001) but not HRV (all P > 0.10).

CONCLUSION

Accelerometry-based EEE demonstrated validity against doubly labeled water during multistressor training, the difference representing 10 kcal·kg-1 FFM·d-1 EEE from nonexercise activity. Beneficial physical but not autonomic adaptations were associated with higher EA. EAmvpa and BEDA-Q warrant consideration for low EA assessment and screening.

Effects of acute heat stress on salivary metabolites in growing pigs: an analysis using nuclear magnetic resonance-based metabolomics profiling

Heat stress (HS) causes adverse impacts on pig production and health. A potential biomarker of HS is required to predict its occurrence and thereby better manage pigs under HS. Information about the saliva metabolome in heat-stressed pigs is limited. Therefore, this study was aimed to investigate the effects of acute HS on the saliva metabolome and identify metabolites that could be used as potential biomarkers. Growing pigs (n = 6, 3 boars, and 3 gilts) were raised in a thermal neutral (TN; 25°C) environment for a 5-d adaptation period (CON). After adaptation, the pigs were first exposed to HS (30°C; HS30) and then exposed to higher HS (33°C; HS33) for 24 h. Saliva was collected after adaptation, first HS, and second HS, respectively, for metabolomic analysis using ¹H-nuclear magnetic resonance spectroscopy. Four metabolites had significantly variable importance in the projection (VIP > 1; p < 0.05) different levels in TN compared to HS groups from all genders (boars and gilts). However, sex-specific characteristics affected metabolites (glutamate and leucine) by showing the opposite results, indicating that HS was less severe in females than in males. A decrease in creatine levels in males and an increase in creatine phosphate levels in females would have contributed to a protective effect from protein degradation by muscle damage. The results showed that HS led to an alteration in metabolites related to energy and protein. Protection from muscle damage may be attributed to the alteration in protein-related metabolites. However, energy-related metabolites showed opposing results according to sex-specific characteristics, such as sex hormone levels and subcutaneous fat layer. This study had shown that saliva samples could be used as a noninvasive method to evaluate heat-stressed pigs. And the results in this study could be contributed to the development of a diagnostic tool as a noninvasive biomarker for managing heat-stressed pigs.

Deep Learning to Predict Energy Expenditure and Activity Intensity in Free Living Conditions using Wrist-specific Accelerometry

Wrist-worn accelerometers are more comfortable and yield greater compliance than hip-worn devices, making them attractive for free-living activity assessments. However, intricate wrist movements may require more complex predictive models than those applied to hip-worn devices. This study developed a novel deep learning method that predicts energy expenditure and physical activity intensity of adults using wrist-specific accelerometry. Triaxial accelerometers were worn by 119 participants on their wrist and hip for two weeks during waking hours. A deep learning model was developed from week 1 data of 60 participants and tested using week 2 data for: (i) the remaining 59 participants (Group UT), and (ii) participants used for training (Group TR). Estimates of physical activity were compared to a reference hip-specific method. Moderate-to-vigorous physical activity predicted by the wrist-model was not different to the reference method for participants in Group UT (5.9±3.1vs. 6.3±3.3 hour/week) and Group TR (6.9±3.7 vs. 7.2±4.2 hour/week). At 60-s epoch level, energy expenditure predicted by the wrist-model on Group UT was strongly correlated with the reference method (r=0.86, 95%CI: 0.84-0.87) and closely predicted activity intensity (83.7%, 95%CI: 80.9-86.5%). The deep learning method has application for wrist-worn accelerometry in free-living adults.

Nutritional Concerns for the Artistic Athlete

Performing artists are similar to sports athletes, with repeated patterns of training and performing. This requires that artistic athletes manage the dynamic interaction between energy/nutrient/fluid utilization and provision to assure long, healthful, and successful careers. Although sports athletes have an abundance of science-based nutritional guidance available, there are few nutrition-focused resources available to artistic athletes, which can result in failure to optimally satisfy the artistic athlete's individual nutritional needs. The purpose of this article is to review common nutritional issues faced by artistic athletes and to present science-based nutrition strategies that can aid in lowering nutrition-associated health and performance risks.

Low Energy Availability in Athletes 2020: An Updated Narrative Review of Prevalence, Risk, Within-Day Energy Balance, Knowledge, and Impact on Sports Performance

Low energy availability (EA) underpins the female and male athlete triad and relative energy deficiency in sport (RED-S). The condition arises when insufficient calories are consumed to support exercise energy expenditure, resulting in compromised physiological processes, such as menstrual irregularities in active females. The health concerns associated with longstanding low EA include menstrual/libido, gastrointestinal and cardiovascular dysfunction and compromised bone health, all of which can contribute to impaired sporting performance. This narrative review provides an update of our previous review on the prevalence and risk of low EA, within-day energy deficiency, and the potential impact of low EA on performance. The methods to assess EA remain a challenge and contribute to the methodological difficulties in identifying “true” low EA. Screening female athletic groups using a validated screening tool such as the Low Energy Availability in Females Questionnaire (LEAF-Q) has shown promise in identifying endurance athletes at risk of low EA. Knowledge of RED-S and its potential implications for performance is low among coaches and athletes alike. Development of sport and gender-specific screening tools to identify adolescent and senior athletes in different sports at risk of RED-S is warranted. Education initiatives are required to raise awareness among coaches and athletes of the importance of appropriate dietary strategies to ensure that sufficient calories are consumed to support training.

Female Collegiate Dancers Body Composition, Macronutrient and Micronutrient Intake Over Two Academic Years: A Longitudinal Analysis

Collegiate dancers face unique challenges to maintain a lean aesthetic, optimal diet, and a high-performance level due to the various stressors in college. The purpose of this study was to examine changes in body composition (BC) and diet over two years. Participants (N = 17, 19.6 ± 1.6 years) completed two laboratory sessions per semester. Sessions included height and weight, BC, dietary intake, and a health history questionnaire. Regardless of rigorous dance training and variations in the academic calendar, no significant changes in BC or diet were observed within semesters of over two years. BMI was normal (24.9 ± 4.1 kg/m²) with fat mass exceeding 30% at all timepoints. Fat mass was negatively correlated with carbohydrate, fat, and protein intake (g/kg/day; r = -0.291, p = 0.004; r = -0.372, p < 0.0001; r = -0.398, p < 0.0001; respectively). Energy intake was within the recommended daily allowance (2040 ± 710 kcal/day), however may be insufficient for an active dance population. Protein (1.1 ± 0.5 g/kg), carbohydrate (3.7 ± 1.6 g/kg), calcium (835 ± 405 mg/day), iron (17 ± 15 mg/day), and potassium (1628 ± 1736 mg/day) intake fell below recommendations for an active population. Alterations in dance training and the demands of the academic calendar may be contributing to suboptimal dietary intake and BC in female collegiate dancers.

Cross-validation of prediction equations for estimating body composition in ballet dancers

Introduction

In sports related to low body weight, such as classical ballet, the assessment of body composition is important for monitoring performance and health status. This study aimed to cross-validate anthropometry and bioelectrical impedance (BIA) predictive equations for estimating body composition of non-professional classical ballet dancers, using dual-energy-X-ray absorptiometry (DXA) as a reference method.

Materials and methods

Thirty-seven female non-professional classical dancers (median age of 19 years), at intermediate/advanced level, were evaluated in a cross-sectional study. Body composition was evaluated by DXA, anthropometry and tetrapolar BIA. Twenty different predictive equations of anthropometry (n = 8) and BIA (n = 12) were used to estimate Body Fat (BF) and Fat-Free Mass (FFM), testing their validity against DXA using the Bland-Altman statistics.

Results

For BF estimated by anthropometry equations, just one equation showed agreement with DXA (r = 0.852, p < 0.0005; p = 0.600 for one sample T-test). According to the Bland-Altman analysis, this equation also showed validity, with the absence of proportional bias. Regarding the predictive BIA equations tested, none were valid for our study group.

Conclusion

Only one of the anthropometric equations, the one proposed by Durnin and Womerley (1974), but none of the BIA equations analyzed, was valid for the evaluation of body composition of the studied classical dancers. Our results emphasize the importance of previous cross-validation of existing equations or the development of specific equations for body composition assessment in specific populations.

Assessment of Dietary Intake, Energy Status, and Factors Associated With RED-S in Vocational Female Ballet Students

Elite ballet dancers are at risk of health issues associated with Relative Energy Deficiency in Sport (RED-S). This study determined the nutritional status, estimated energy status, and assessed factors related to RED-S in vocational female ballet students. Using a cross-sectional study design, we measured dietary intake (food diaries and 24 h dietary-recall) and energy expenditure (accelerometry) in vocational female ballet students (n = 20; age: 18.1 ± 1.1 years; body mass index: 19.0 ± 1.6 kg·m²; body fat: 22.8 ± 3.4%) over 7 days, including 5 weekdays (with dance training) and 2 weekend days (without scheduled dance training). Furthermore, we assessed eating behaviors, menstrual function, risk of RED-S (questionnaires), and body composition (dual x-ray absorptiometry). Energy and macronutrient intakes of vocational ballet students were similar during weekdays and weekend days (P > 0.050), whereas total energy expenditure was greater on weekdays than weekend days (P < 0.010; 95% CI: 212, 379). Energy balance was lower on weekdays (-425 ± 465 kcal·day^-1) than weekend days (-6 ± 506 kcal·day^-1, P = 0.015; 95% CI: -748, -92). Exercise energy expenditure was greater on weekdays (393 ± 103 kcal·day^-1) than weekend days (213 ± 129 kcal·day^-1; P < 0.010; 95% CI: 114, 246), but energy availability was similar between time periods (weekdays 38 ± 13 kcal·kg FFM·day^-1; weekend days 44 ± 13 kcal·kg FFM·day^-1; P = 0.110). Overall, 35% of participants had an energy intake <1,800 kcal·day^-1, 44% had reduced energy availability (30-45 kcal·kg FFM·day^-1), and 22% had low energy availability (<30 kcal·kg FFM·day^-1). Menstrual dysfunctions were reported in 40% of participants; 15 and 25% reported oligomenorrhea and secondary amenorrhea, respectively; while 65% were classified at risk of RED-S (based on the Low Energy Availability in Females Questionnaire). All participants had adequate bone health (bone mineral density Z-score: 1.1 ± 0.9 SD), but 20% had <85% expected body weight. The observation of an energy deficit in vocational female ballet students was primarily attributed to an inability to plan energy intake and thereby meet higher energy requirements during ballet training weekdays. Screening for factors associated with RED-S and tailoring education programs to inform energy and nutrition requirements for health and training are recommended in elite young ballet students.

Wrist-specific accelerometry methods for estimating free-living physical activity

OBJECTIVES

To compare accelerometry-derived estimates of physical activity from 9 wrist-specific predictive models and a reference hip-specific method.

DESIGN

Prospective cohort repeated measures study.

METHODS

110 participants wore an accelerometer at wrist and hip locations for 1 week of free-living. Accelerometer data from three axes were used to calculate physical activity estimates using existing wrist-specific models (3 linear and 6 artificial neural network models) and a reference hip-specific method. Estimates of physical activity were compared to reference values at both epoch (≤60-s) and weekly levels.

RESULTS

9044h were analysed. Physical activity ranged from 7 to 96min per day of moderate-to-vigorous physical activity (MVPA). Method of analysis influenced determination of sedentary behaviour (<1.5 METs), light physical activity (1.5 to <3 METs) and MVPA (>3 METs) (p<0.001, respectively). All wrist-specific models produced total weekly MVPA values that were different to the reference method. At the epoch level, Hildebrand et al. (2014) produced the strongest correlation (r=0.69, 95%CI: 0.67-0.71) with tightest ratio limits of agreement (95%CI: 0.53-1.30) for MVPA, and highest agreement to predict MVPA (94.1%, 95%CI: 94.0-94.1%) with sensitivity of 63.1% (95%CI: 62.6-63.7%) and specificity of 96.0% (95%CI: 95.9-96.0%).

CONCLUSIONS

Caution is required when comparing results from studies that use inconsistent analysis methods. Although a wrist-specific linear model produced results that were most similar to the hip-specific reference method when estimating total weekly MVPA, modest absolute and relative agreement at the epoch level suggest that additional analysis methods are required to improve estimates of physical activity derived from wrist-worn accelerometers.

Pitfalls of Conducting and Interpreting Estimates of Energy Availability in Free-Living Athletes

The human body requires energy for numerous functions including, growth, thermogenesis, reproduction, cellular maintenance, and movement. In sports nutrition, energy availability (EA) is defined as the energy available to support these basic physiological functions and good health once the energy cost of exercise is deducted from energy intake (EI), relative to an athlete’s fat-free mass (FFM). Low EA provides a unifying theory to link numerous disorders seen in both female and male athletes, described by the syndrome Relative Energy Deficiency in Sport, and related to restricted energy intake, excessive exercise or a combination of both. These outcomes are incurred in different dose–response patterns relative to the reduction in EA below a “healthy” level of ∼45 kcal·kg FFM−1·day−1. Although EA estimates are being used to guide and monitor athletic practices, as well as support a diagnosis of Relative Energy Deficiency in Sport, problems associated with the measurement and interpretation of EA in the field should be explored. These include the lack of a universal protocol for the calculation of EA, the resources needed to achieve estimates of each of the components of the equation, and the residual errors in these estimates. The lack of a clear definition of the value for EA that is considered “low” reflects problems around its measurement, as well as differences between individuals and individual components of “normal”/“healthy” function. Finally, further investigation of nutrition and exercise behavior including within- and between-day energy spread and dietary characteristics is warranted since it may directly contribute to low EA or its secondary problems.

Validity of Dietary Assessment in Athletes: A Systematic Review

Dietary assessment methods that are recognized as appropriate for the general population are usually applied in a similar manner to athletes, despite the knowledge that sport-specific factors can complicate assessment and impact accuracy in unique ways. As dietary assessment methods are used extensively within the field of sports nutrition, there is concern the validity of methodologies have not undergone more rigorous evaluation in this unique population sub-group. The purpose of this systematic review was to compare two or more methods of dietary assessment, including dietary intake measured against biomarkers or reference measures of energy expenditure, in athletes. Six electronic databases were searched for English-language, full-text articles published from January 1980 until June 2016. The search strategy combined the following keywords: diet, nutrition assessment, athlete, and validity; where the following outcomes are reported but not limited to: energy intake, macro and/or micronutrient intake, food intake, nutritional adequacy, diet quality, or nutritional status. Meta-analysis was performed on studies with sufficient methodological similarity, with between-group standardized mean differences (or effect size) and 95% confidence intervals (CI) being calculated. Of the 1624 studies identified, 18 were eligible for inclusion. Studies comparing self-reported energy intake (EI) to energy expenditure assessed via doubly labelled water were grouped for comparison (n = 11) and demonstrated mean EI was under-estimated by 19% (-2793 ± 1134 kJ/day). Meta-analysis revealed a large pooled effect size of -1.006 (95% CI: -1.3 to -0.7; p < 0.001). The remaining studies (n = 7) compared a new dietary tool or instrument to a reference method(s) (e.g., food record, 24-h dietary recall, biomarker) as part of a validation study. This systematic review revealed there are limited robust studies evaluating dietary assessment methods in athletes. Existing literature demonstrates the substantial variability between methods, with under- and misreporting of intake being frequently observed. There is a clear need for careful validation of dietary assessment methods, including emerging technical innovations, among athlete populations.