Energy expenditure of swimmers during high volume training

Energetics of a World-Tour Female Road Cyclist During a Multistage Race (Tour de France Femmes)

Despite the increased popularity of female elite road cycling, research to inform the fueling requirements of these endurance athletes is lacking. In this case study, we report for the first time the energetics of a female world-tour cyclist competing in the 2023 Tour de France Femmes, an 8-day race of the Union Cycliste Internationale. The 29-year-old athlete presented with oligomenorrhea and low T3 before the race. Total daily energy expenditure assessed with the doubly labeled water technique was 7,572 kcal/day (∼4.3 physical activity levels), among the highest reported in the literature to date for a female. Crank-based mean maximal power was consistent with female world-tour cyclists (5 min, mean 342 W, 4.8 W/kg; 20 min 289 W, 4.1 W/kg). The average daily energy intake measured with the remote food photography method (Stage Days 1-7) was 5,246 kcal and carbohydrate intake was 13.7 g/kg (range 9.7-15.9 g/kg), and 84 g/hr during stages, and an average fat intake of 15% of daily energy intake. An estimated 2,326 kcal/day energy deficit was evidenced in a 2.2 kg decrease in body mass. Notwithstanding the high carbohydrate intake, the athlete was unable to match the energy requirements of the competition. Despite signs of energy deficiency preexisting (oligomenorrhea and low T3), and other further developing during the race (weight loss), performance was in line with that of other world-tour cyclists and a best personal performance was recorded for the last stage. This case study emphasizes the need for further research to inform energy requirements for female athletes' optimal performance and health.

International Society of Sports Nutrition Position Stand: Effects of essential amino acid supplementation on exercise and performance

Position Statement: The International Society of Sports Nutrition (ISSN) presents this position based on a critical examination of literature surrounding the effects of essential amino acid (EAA) supplementation on skeletal muscle maintenance and performance. This position stand is intended to provide a scientific foundation to athletes, dietitians, trainers, and other practitioners as to the benefits of supplemental EAA in both healthy and resistant (aging/clinical) populations. EAAs are crucial components of protein intake in humans, as the body cannot synthesize them. The daily recommended intake (DRI) for protein was established to prevent deficiencies due to inadequate EAA consumption. The following conclusions represent the official position of the Society: 1. Initial studies on EAAs' effects on skeletal muscle highlight their primary role in stimulating muscle protein synthesis (MPS) and turnover. Protein turnover is critical for replacing degraded or damaged muscle proteins, laying the metabolic foundation for enhanced functional performance. Consequently, research has shifted to examine the effects of EAA supplementation - with and without the benefits of exercise - on skeletal muscle maintenance and performance. 2. Supplementation with free-form EAAs leads to a quick rise in peripheral EAA concentrations, which in turn stimulates MPS. 3. The safe upper limit of EAA intake (amount), without inborn metabolic disease, can easily accommodate additional supplementation. 4. At rest, stimulation of MPS occurs at relatively small dosages (1.5-3.0 g) and seems to plateau at around 15-18 g. 5. The MPS stimulation by EAAs does not require non-essential amino acids. 6. Free-form EAA ingestion stimulates MPS more than an equivalent amount of intact protein. 7. Repeated EAA-induced MPS stimulation throughout the day does not diminish the anabolic effect of meal intake. 8. Although direct comparisons of various formulas have yet to be investigated, aging requires a greater proportion of leucine to overcome the reduced muscle sensitivity known as "anabolic resistance." 9. Without exercise, EAA supplementation can enhance functional outcomes in anabolic-resistant populations. 10. EAA requirements rise in the face of caloric deficits. During caloric deficit, it's essential to meet whole-body EAA requirements to preserve anabolic sensitivity in skeletal muscle.

Contributing Factors to Low Energy Availability in Female Athletes: A Narrative Review of Energy Availability, Training Demands, Nutrition Barriers, Body Image, and Disordered Eating

Relative Energy Deficiency in sport is experiencing remarkable popularity of late, particularly among female athletes. This condition is underpinned by low energy availability, which is a byproduct of high energy expenditure, inadequate energy intake, or a combination of the two. Several contributing factors exist that may predispose an athlete to low energy availability, and therefore a holistic and comprehensive assessment may be required to identify the root causes. The focus of the current narrative review is to discuss the primary contributing factors as well as known risk factors for low energy availability among female athletes to help practitioners increase awareness on the topic and identify future areas of focus.

Dietary Macronutrient and Micronutrient Intake over a 7-Day Period in Female Varsity Ice Hockey Players

This study examined the energy, macronutrient, and micronutrient intakes of female ice hockey players over a 7-d period including game, practice, and rest days. Twenty-three female varsity players (19.0 ± 1.1 yr, 167.1 ± 6.5 cm, 67.0 ± 8.0 kg) volunteered for the study. Average total daily energy expenditure (TDEE) was estimated over the 7-day period. Average 7-day energy intake (EI) and TDEE were 2354 ± 353 and 2304 ± 204 kcal. The majority (n = 19) of athletes had an EI ≥ 90% of their estimated TDEE. Macronutrient intake was 52% carbohydrate (CHO), 32% fat, and 16% protein of total EI, although CHO intake was slightly below recommendations (5 g/kg BM/d) on game and practice (4.8 ± 1.4 and 4.5 g/kg BM/d) days. Game day EI was greater than practice and rest days. Recommended micronutrient intakes were not met by most athletes for iron, calcium, vitamin D, and potassium, and intakes were similar between game, practice, and rest days. In summary, the average EI for female varsity ice hockey players appeared adequate to meet their energy needs over a weekly cycle of game, practice, and rest days. However, these female athletes would benefit from increasing CHO intake on game and practice days and selecting foods that are rich in vitamins and minerals.

Using physical activity levels to estimate energy requirements of female athletes

[Purpose]

The goal of this study was to review data on physical activity level (PAL), a crucial index for determining estimated energy requirement (EER), calculated as total energy expenditure (TEE, assessed with doubly labeled water [DLW]) divided by resting metabolic rate (RMR, PAL = TEE/RMR) in female athletes and to understand the methods of assessing athletes’ EERs in the field.

[Methods]

For the PAL data review among female athletes, we conducted a PubMed search of the available literature related to the DLW method. DLW studies measuring TEE and RMR were included for the present review.

[Results]

Briefly, the mean PAL was 1.71 for collegiate swimmers with moderate training, which was relatively low, but the mean PAL was 3.0 for elite swimmers during summer training camp. This shows that PAL can largely vary even within the same sport depending on the amount of training, and the differences in PAL were remarkable depending on the sport. Aside from the DLW method, there is currently no research tool related to athletes’ EERs that can be used in the field.

[Conclusion]

Briefly, the mean PAL was 1.71 for collegiate swimmers with moderate training, which was relatively low, but the mean PAL was 3.0 for elite swimmers during summer training camp. This shows that PAL can largely vary even within the same sport depending on the amount of training, and the differences in PAL were remarkable depending on the sport. Aside from the DLW method, there is currently no research tool related to athletes’ EERs that can be used in the field.

Comparison of Conventional and Individualized 1-MET Values for Expressing Maximum Aerobic Metabolic Rate and Habitual Activity Related Energy Expenditure

The maximum aerobic metabolic rate can be expressed in multiple metabolically equivalent tasks (MET), i.e., METmax. The purpose was to quantify the error when the conventional (3.5 mL∙kg⁻¹∙min⁻¹) compared to an individualized 1-MET-value is used for calculating METmax and estimating activity energy expenditure (AEE) in endurance-trained athletes (END) and active healthy controls (CON). The resting metabolic rate (RMR, indirect calorimetry) and aerobic metabolic capacity (spiroergometry) were assessed in 52 END (46% male, 27.9 ± 5.7 years) and 53 CON (45% male, 27.3 ± 4.6 years). METmax was calculated as the ratio of VO₂max over VO₂ during RMR (METmax_ind), and VO₂max over the conventional 1-MET-value (METmax_fix). AEE was estimated by multiplying published MET values with the individual and conventional 1-MET-values. Dependent t-tests were used to compare the different modes for calculating METmax and AEE (α = 0.05). In women and men CON, men END METmax_fix was significantly higher than METmax_ind (p < 0.01), whereas, in women END, no difference was found (p > 0.05). The conventional 1-MET-value significantly underestimated AEE in men and women CON, and men END (p < 0.05), but not in women END (p > 0.05). The conventional 1-MET-value appears inappropriate for determining the aerobic metabolic capacity and AEE in active and endurance-trained persons.

Within-Day Amino Acid Intakes and Nitrogen Balance in Male Collegiate Swimmers during the General Preparation Phase

A higher protein intake is recommended for athletes compared to healthy non-exercising individuals. Additionally, the distribution and quality (i.e., leucine content) of the proteins consumed throughout the day should be optimized. This study aimed to determine the nitrogen balance and distribution of protein and amino acid intakes in competitive swimmers during the general preparation phase. Thirteen swimmers (age: 19.7 ± 1.0 years; VO₂max: 63.9 ± 3.7 mL·kg-1·min-1, mean ± standard deviation) participated in a five-day experimental training period. Nutrient intakes were assessed using dietary records. Nitrogen balance was calculated from the daily protein intake and urinary nitrogen excretion. The intake amounts of amino acids and protein at seven eating occasions were determined. The average and population-safe intakes for zero nitrogen balance were estimated at 1.43 and 1.92 g·kg-1·day-1, respectively. The intake amounts of protein and leucine at breakfast, lunch, and dinner satisfied current guidelines for the maximization of muscle protein synthesis, but not in the other four occasions. The population-safe protein intake level in competitive swimmers was in the upper range (i.e., 1.2⁻2.0 g·kg-1·day-1) of the current recommendations for athletes. The protein intake distribution and quality throughout the day may be suboptimal for the maximization of the skeletal muscle adaptive response to training.

Total energy expenditure in elite open-water swimmers

This study aimed to examine the total energy expenditure (TEE) and physical activity level (PAL) of elite open-water swimmers. Our study group included 5 world-class competitive open-water swimmers. TEE was measured using the doubly labeled water method for 1 week. The TEE was 4549 ± 1185 kcal/day. The PAL was 3.22 ± 0.46. Our results may provide a reference to optimize energy requirement support.

The antidepressant fluoxetine acts on energy balance and leptin sensitivity via BDNF

Leptin and Brain Derived Neurotrophic Factor (BDNF) pathways are critical players in body weight homeostasis. Noninvasive treatments like environmental stimulation are able to increase response to leptin and induce BDNF expression in the brain. Emerging evidences point to the antidepressant selective serotonin reuptake inhibitor Fluoxetine (FLX) as a drug with effects similar to environmental stimulation. FLX is known to impact on body weight, with mechanisms yet to be elucidated. We herein asked whether FLX affects energy balance, the leptin system and BDNF function. Adult lean male mice chronically treated with FLX showed reduced weight gain, higher energy expenditure, increased sensitivity to acute leptin, increased hypothalamic BDNF expression, associated to changes in white adipose tissue expression typical of “brownization”. In the Ntrk2^tm1Ddg/J model, carrying a mutation in the BDNF receptor Tyrosine kinase B (TrkB), these effects are partially or totally reversed. Wild type obese mice treated with FLX showed reduced weight gain, increased energy output, and differently from untreated obese mice, a preserved acute response to leptin in terms of activation of the intracellular leptin transducer STAT3. In conclusion, FLX impacts on energy balance and induces leptin sensitivity and an intact TrkB function is required for these effects to take place.

Nutritional needs in the professional practice of swimming: a review

[Purpose]

Swimming requires developing a high aerobic and anaerobic capacity for strength and technical efficiency. The purpose of this study was to establish the nutritional requirements and dietary strategies that can optimize swimming performance.

[Methods]

Several related studies retrieved from the databases, Dialnet, Elsevier, Medline, Pubmed, and Web of Science, through keyword search strategies were reviewed.

[Results]

The recommended carbohydrate intake ranges between 6-10-12 g/kg/d, protein 2 g/kg/d, and fat should surpass 20-25% of the daily intake.

[Conclusion]

Performance can be optimized with a hydration plan, as well as adequate periodization of supplements, such as caffeine, creatine, sodium bicarbonate, B-alanine, beetroot juice, Vitamin D, bovine colostrum, and HMB.

Monitoring Energy Expenditure Using a Multi-Sensor Device-Applications and Limitations of the SenseWear Armband in Athletic Populations

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.

Total Energy Expenditure, Energy Intake, and Body Composition in Endurance Athletes Across the Training Season: A Systematic Review

BACKGROUND

Endurance athletes perform periodized training in order to prepare for main competitions and maximize performance. However, the coupling between alterations of total energy expenditure (TEE), energy intake, and body composition during different seasonal training phases is unclear. So far, no systematic review has assessed fluctuations in TEE, energy intake, and/or body composition in endurance athletes across the training season. The purpose of this study was to (1) systematically analyze TEE, energy intake, and body composition in highly trained athletes of various endurance disciplines and of both sexes and (2) analyze fluctuations in these parameters across the training season.

METHODS

An electronic database search was conducted on the SPORTDiscus and MEDLINE (January 1990-31 January 2015) databases using a combination of relevant keywords. Two independent reviewers identified potentially relevant studies. Where a consensus was not reached, a third reviewer was consulted. Original research articles that examined TEE, energy intake, and/or body composition in 18-40-year-old endurance athletes and reported the seasonal training phases of data assessment were included in the review. Articles were excluded if body composition was assessed by skinfold measurements, TEE was assessed by questionnaires, or data could not be split between the sexes. Two reviewers assessed the quality of studies independently. Data on subject characteristics, TEE, energy intake, and/or body composition were extracted from the included studies. Subjects were categorized according to their sex and endurance discipline and each study allocated a weight within categories based on the number of subjects assessed. Extracted data were used to calculate weighted means and standard deviations for parameters of TEE, energy intake, and/or body composition.

RESULTS

From 3589 citations, 321 articles were identified as potentially relevant, with 82 meeting all of the inclusion criteria. TEE of endurance athletes was significantly higher during the competition phase than during the preparation phase (p < 0.001) and significantly higher than energy intake in both phases (p < 0.001). During the competition phase, both body mass and fat-free mass were significantly higher compared to other seasonal training phases (p < 0.05).

CONCLUSIONS

Limitations of the present study included insufficient data being available for all seasonal training phases and thus low explanatory power of single parameters. Additionally, the classification of the different seasonal training phases has to be discussed. Male and female endurance athletes show important training seasonal fluctuations in TEE, energy intake, and body composition. Therefore, dietary intake recommendations should take into consideration other factors including the actual training load, TEE, and body composition goals of the athlete.

Total energy expenditure assessment in elite junior basketball players: a validation study using doubly labeled water

An accurate assessment of total energy expenditure (TEE) during a competitive season is required. We aimed to validate TEE estimated by self-reported energy intake (EI) and the dietary reference intake (DRI) method in 19 elite basketball players (aged 16-18 years) using doubly labeled water (DLW) as the reference method. The DRI models and EI from dietary records over a 7-day period were simultaneously assessed for TEE estimation. Resting energy expenditure was assessed by indirect calorimetry. Fat and fat-free mass (FFM) were determined by a 4-compartment model (body volume by air displacement plethysmography, bone mineral by DXA, and water by deuterium dilution). Fat and FFM ranged from 4 to 19 kg and from 47 to 81 kg, respectively. The physical activity level ranged from 2.2 to 3.7 with a mean value of 2.8 ± 0.4. Total energy expenditure from DLW (17,598 ± 3,298 kJ·d) was significantly underestimated by EI (11,274 ± 2,567 kJ·d), whereas no differences were found using DRI (17,008 ± 3,206 kJ·d). The EI and DRI methods explained TEE from DLW by 34% (p = 0.057) and 44% (p = 0.002), respectively, and wide limits of agreement were observed. Our findings suggested that EI is not a valid tool for TEE assessment. The DRI method may be valid at a group level but inaccurate for estimating individual TEE in young players during a demanding competitive season period.

Effect of different seasonal strength training protocols on circulating androgen levels and performance parameters in professional soccer players

OBJECTIVE

To examine the effects of three seasonal training programs, largely different in strength volume, on androgen levels and performance parameters in soccer players.

DESIGN

Sixty-seven soccer players, members of three different professional teams, participated in the study. Strength intensity of the training programs were assessed as high (for Team-A, n=23), moderate (for Team-B, n=22), and low (for Team-C, n=22). Blood samples were analyzed for total-testosterone, free-testosterone, and the metabolic product of activate testosterone 3a-androstendiol glucuronade (3a-Diol-G). Players were tested for maximal oxygen consumption (VO2max), squad-jump (SJ), countermovement-jump (CMJ), 10 m and 20 m sprint performance prior at the beginning of the pre-season period, at the middle (mid-point), and at the end of the competition period (end-point).

RESULTS

All performance parameters increased significantly until mid-point in all teams (p<0.001). However, performance was further increased only in Team-A only for jumping and sprinting ability between end-point vs mid-point (p<0.001). An effect of the training program of Team-A on TT levels was evident exhibiting significant differences between at all point-measurements (baseline/mid-point:p=0.024, baseline/end-point:p<0.001, mid/end-point:p=0.008), while a marginally significant effect (p=0.051) was detected within Team-B and a non-significant effect in Team-C. Similar results were obtained for 3a-Diol-G in Team-A (p=0.001) where significant differences were found between end-point to both baseline (p=0.001) and mid-point (p=0.038). No differences were detectable for FT. A borderline significant negative correlation was observed between 3a-Diol-G and VO2max in Team-B at mid-point. No other correlations were evident between performance and hormonal parameters.

CONCLUSION

Our findings suggest that the volume of strength training combined with intensive soccer training caused an elevation of circulating TT and 3a-Diol-G levels in parallel to the induction of performance capacity. It is our opinion that the elevation of endogenous androgens as a result of the volume of strength training indicates that the only method to improve athletic performance is hard training. There are no substitutes or shortcuts. If the organism needs more androgens it will produce them endogenously.

Maximal sustained levels of energy expenditure in humans during exercise

Migrating birds have been able to sustain an energy expenditure (EE) that is five times their basal metabolic rate. Although humans can readily reach these levels, it is not yet clear what levels can be sustained for several days.

PURPOSE

The study's purposes were 1) to determine the upper limits of human EE and whether or not those levels can be sustained without inducing catabolism of body tissues and 2) to determine whether initial body weight is related to the levels that can be sustained.

METHODS

We compiled data on documented EE as measured by doubly labeled water during high levels of physical activity (minimum of five consecutive days). We calculated the physical activity level (PAL) of each individual studied (PAL = total EE / basal metabolic rate) from the published data. Correlations were run to examine the relationship between initial body weight and body weight lost with both total EE and PAL.

RESULTS

The uppermost limit of EE was a peak PAL of 6.94 that was sustained for 10 consecutive days of a 95-d race. Only two studies reported PALs above 5.0; however, significant decreases in body mass were found in each study (0.45-1.39 kg·wk(-1) of weight loss). To test whether initial weight affects the ability to sustain high PALs, we found a significant positive correlation between TEE and initial body weight (r = 0.46, P < 0.05) but no correlation between PAL and body weight (r = 0.27, not statistically significant).

CONCLUSIONS

Some elite humans are able to sustain PALs above 5.0 for a minimum of 10 d. Although significant decreases in body weight occur at this level, catabolism of body tissue may be preventable in situations with proper energy intake. Further, initial body weight does not seem to affect the sustainability of PALs.

Energy expenditure and dietary intake during high-volume and low-volume training periods among male endurance athletes

The primary purpose of this study was to examine dietary intake in endurance-trained athletes during a week of high-volume and a week of low-volume training while measuring exercise energy expenditure (EEE), resting metabolic rate (RMR), and nonexercise activity thermogenesis (NEAT). In addition, compliance with current American College of Sports Medicine/American Dietetic Association nutrition and performance recommendations for macronutrients was evaluated. Energy expenditure and dietary intake were measured in 15 male endurance athletes during 2 nonconsecutive weeks resembling a high-volume and a low-volume training period. Anthropometric measurements were taken and percentage body fat was determined at the beginning and end of each week of training. Total daily energy expenditure (TDEE) was calculated by summing RMR, NEAT, and EEE. Dietary intake was assessed with an online food-frequency questionnaire completed at the end of each week of data collection. Despite significant differences between TDEE and energy intake, no difference in body composition between the beginning and end of either week of training was observed, suggesting underreporting of caloric intake. Further, no changes in total caloric intake or macronutrient intake occurred even though TDEE increased significantly during the high-volume training. Reported carbohydrate intake (4.5 g·kg(-1)) and fiber intake (25 g·day(-1)) were below recommendations, whereas fat intake (1.3 g·kg(-1)) was slightly above recommendations. In summary, no short-term dietary adjustments occurred in response to differences in training regimen. Because these athletes were generally consuming a Western diet, they may have required some support to achieve desirable intakes for health and performance.

Differences in energy expenditure between high- and low-volume training

Several studies have examined energy expenditure in various sports but there is a lack of research on the contribution of exercise and habitual activity during different training periods. This study examined changes in total daily energy expenditure (TDEE) and its components during high- and low-volume training periods. Further, changes in time spent in sedentary, light, moderate and vigorous activity in response to different training volumes were explored. Energy expenditure was measured in 15 male endurance athletes during 2 non-consecutive weeks - 1 week of high volume (>13 hours) training and another week of low volume (<7 hours) training. The SenseWear Pro 3 Armband, individual heart-rate-oxygen consumption regression and indirect calorimetry was used to measure non-exercise activity thermogensis (NEAT), exercise energy expenditure (EEE) and resting metabolic rate, respectively. Time spent at different intensities was assessed using previously established MET cutpoints. TDEE as well as EEE increased significantly with higher training volume, while no difference in NEAT occurred. Further, significantly less time was spent in sedentary activities during the high-volume week. These results suggest that highly trained athletes do not compensate for increased training volume and reduce sedentary activities to allow for more training time.

Energy intake and expenditure during a 6-day cycling stage race

Energy intake (EI) and energy expenditure (EE) are relatively easy to measure accurately over short periods in a laboratory setting, but less so during a multi-day competition. Our goal was to measure EI and EE as accurately as possible during a 6-day, 10-stage cycling race. We prepared all meals and supplements, assessed EI (weighed diet-records) and macrontrient intake, total EE (doubly labelled water), resting metabolic rate (respiratory gas exchange), exercise EE (power meters), and body mass. Body composition was measured several days before and after racing (dual x-ray absorptiometry). Body mass remained stable over the course of the race. The mean EI (27.3+/-3.8 MJ/day) nearly matched EE (27.4+/-2.0 MJ/day). The majority (62%) of EE was exercise EE. Macronutrient intake was within or exceeded the recommendations. Lean body mass increased and fat mass decreased in most of our participants. Our study indicates that EI can match high EE with adequate macronutrient intake during multi-day cycle racing and may be facilitated by appropriate foods being available at appropriate times. This optimization of nutritional provision supports positive changes in body composition.

Nutritional concerns for the child and adolescent competitor

With exercise for sports competition in children and adolescents, acute nutrient needs will change. Fluid intake to ensure the replacement of water and minerals (electrolytes) lost in sweat is important. Energy needs also increase because of the elevated energy expenditure with physical activity. Arguably carbohydrate is the recommended source of training needs, although research has yet to be done to show performance benefits in young athletes on a high-carbohydrate diet. In the majority of sports, an increased intake of food naturally occurs to accommodate the day-to-day nutrient needs of young athletes, and unlike non-athlete, young competitors typically come closer to meeting their requirements for micronutrients. Nonetheless, certain athletic groups may be at risk for shortfalls in their diet. Compared to athletes in team sports, participants in weight-control sports may be at greater risk of failing to meet requirements for energy, protein, and some micronutrients. Endurance athletes, particularly female distance runners, may have intake deficits for the minerals iron and calcium. Acute issues such as heat illness and chronic concerns that include impaired growth and development, and the risk of injuries that include stress fractures may be an outcome of inadequate nutrition during physical training.

Physiological and Metabolic Aspects of Very Prolonged Exercise with Particular Reference to Hill Walking

Hill walking is a popular recreational activity in the developed world, yet it has the potential to impose severe stress simultaneously upon several regulatory systems. Information regarding the physiological strain imposed by prolonged walking outdoors in adverse climatic conditions was reported almost four decades ago and recent research has extended some of this work. These data indicate that once the walker fatigues and starts to slow or stops walking altogether, the rate of heat production falls dramatically. This decrease alone predisposes to the development of hypothermia. These processes, in adverse weather conditions and/or during periods when the level of exertion is low (with low heat production), will be accelerated. Since the majority of walkers pursue this activity in groups, the less fit walkers may be more susceptible to fatigue when exercising at a higher relative intensity compared with their fitter counterparts. The best physiological offset for hypothermia is to maintain heat production by means of exercise, and so fatigue becomes a critical predisposing factor; it is as important to facilitate heat loss, especially during periods of high exertion, as it is to maintain heat production and preserve insulation. This can be partly achieved by clothing adjustments and consideration of the intensity of exercise. Failure to provide adequate energy intake during hill walking activities has been associated with decreased performance (particularly with respect to balance) and impaired thermoregulation. Such impairments may increase susceptibly to both fatigue and injury whilst pursuing this form of activity outdoors. The prolonged low to moderate intensity of activity experienced during a typical hill walk elicits marked changes in the metabolic and hormonal milieu. Available data suggest that during hill walking, even during periods of acute negative energy balance, blood glucose concentrations are maintained. The maintenance of blood glucose concentrations seems to reflect the presence of an alternative fuel source, a hormonally induced increase in fat mobilisation. Such enhancement of fat mobilisation should make it easier to maintain blood glucose by decreasing carbohydrate oxidation and promoting gluconeogenesis, thus sparing glucose utilisation by active muscle. During strenuous hill walking, older age walkers may be particularly prone to dehydration and decreased physical and mental performance, when compared with their younger counterparts. In summary, high rates of energy expenditure and hypohydration are likely to be closely linked to the activity. Periods of adverse weather, low energy intake, lowered fitness or increased age, can all increase the participants' susceptibility to injury, fatigue and hypothermia in the mountainous environment.

Water Turnover and Changes in Body Composition during Arduous Wildfire Suppression

INTRODUCTION

Our lab has recently documented the total energy expenditure during arduous wildfire suppression using the doubly labeled water methodology. The elevated rates of isotopic elimination indicate an arduous working environment that may often compromise energy balance and overall hydration.

PURPOSE

The purpose of this investigation was to determine the effects of arduous wildfire suppression on water turnover and changes in body composition in wildland firefighters (WLFF).

METHODS

WLFF (N = 14) were studied during a 5-d period of arduous fire suppression work. A comparison group (N = 13) of recreationally active college students (RACS) was also studied. Water turnover was measured from rates of 2H elimination (rH2O). Urine osmolality, specific gravity, and skinfold measures were also collected.

RESULTS

WLFF demonstrated a decrease in nude body weight (pre = 71.9 +/- 10.4 kg, post = 70.9 +/- 10.2 kg, P = 0.0001) and total body water (pre = 42.9 +/- 7.2 kg, post = 42.0 +/- 6.7 kg, P = 0.0046). RACS maintained total body water and body weight during the experimental period. Isotope (2H2O) dilution demonstrated that rH2O was significantly higher for the WLFF (rH2O = 6.7 +/- 1.4 and 3.8 +/- 1.0 L.24 h-1 for the WLFF and RACS, respectively).

CONCLUSION

These results demonstrate an arduous work environment that threatens hydration, energy balance, and perhaps normal glycogen status.

Methodology of dietary assessment in athletes: concepts and pitfalls

PURPOSE OF REVIEW

Evaluation of an athlete's diet is important in both clinical practice and research. The main purpose of this review is to provide health professionals with guidance regarding the special issues that are likely to be encountered when assessing the dietary intake of sportspersons.

RECENT FINDINGS

A number of methods may be used for the dietary assessment of individuals and/or groups of athletes, including retrospective (diet recall, food-frequency questionnaire, and diet history) and prospective (diet record, duplicate portion) techniques. A 3-4-day estimated diet record is the most widely used approach, but collection of single or multiple diet recalls is also common. Care must be taken, however, to ensure that days of diet monitoring accurately reflect usual food consumption during the period of interest. Under-reporting of habitual energy intake is widespread among athletes, and its magnitude should be carefully addressed when interpreting the results of dietary assessment. Other issues, specifically related to sportspersons, that are often neglected include adequacy of standard portion sizes, frequency of snacking, fluid intake, supplement use, weight-control practices, and seasonality of sport activities and food consumption.

SUMMARY

There are subtle methodological differences in the dietary assessment of athletes and non-athletes, which, when taken into consideration, may substantially increase the quality of intake data and optimise the outcome of dietary intervention.

Total energy expenditure during arduous wildfire suppression

PURPOSE

The purpose of this investigation was to determine the total energy expenditure (TEE) by using the doubly labeled water (DLW) methodology during 5 d of wildfire suppression in Montana, California, Florida, Washington, and Idaho.

METHODS

Seventeen wildland firefighters (from three Interagency Hot Shot crews, N = 8 men, height = 177 +/- 7 cm, weight = 74.6 +/- 6.4 kg, age = 24.5 +/- 1.8 yr; N = 9 women, height = 170 +/- 7 cm, weight = 65.2 +/- 8.0 kg, age = 25.0 +/- 1.3 yr) served as subjects. Before wildland fire suppression, each subject was given an oral dose of 2H2O and H218O (approximately 0.23 g 2H2O.kg estimated TBW-1 and 0.39 g H218O.kg estimated TBW-1). Urine samples were collected between 0400 and 0600 daily. TEE was calculated using the two-point method for days 1-3 and 1-5, with the TEE for days 4-5 calculated by extrapolation. Urine samples from other crew members not participating in the DLW protocol were collected at the same times and used to adjust calculations of isotopic elimination for background shifts.

RESULTS

TEE was 17.4 +/- 3.7 and 17.5 +/- 6.9 MJ.d-1 during days 1-3 and 4-5, respectively. The energy expenditure associated with physical activity (EEA) was 8.8 +/- 3.0 and 8.9 +/- 6.1 MJ.d-1 for days 1-3 and 4-5, respectively.

CONCLUSION

The current data demonstrate consistently high daily energy expenditure in the wildland firefighter. These data also demonstrate that the doubly labeled water methodology is an appropriate methodology for the measure of TEE during unpredictable field operations if adjustments are made for changes in background enrichment and elevated water turnover.

Relationship of high energy expenditure and variation in dietary intake with reporting accuracy on 7 day food records and diet histories in a group of healthy adult volunteers

OBJECTIVES

To assess the accuracy of reporting from both a diet history and food record and identify some of the characteristics of more accurate reporters in a group of healthy adult volunteers for an energy balance study.

DESIGN

Prospective measurements in free-living people.

SETTING

Wollongong, Australia.

SUBJECTS

Fifteen healthy volunteers (seven male, eight female; aged 22-59 y; body mass index (BMI) 19-33 kg/m(2)) from the local community in the city of Wollongong, Australia.

INTERVENTIONS

Measurement of energy intake via diet history interview and 7 day food records, total energy expenditure by the doubly labelled water technique over 14 days, physical activity by questionnaire, and body fat by dual-energy X-ray absorptiometry.

RESULTS

Increased misreporting of energy intake was associated with increased energy expenditure (r=0.90, P<0.0001, diet history; r(S)=0.79, P=0.0005, food records) but was not associated with age, sex, BMI or body fat. Range in number of recorded dinner foods correlated positively with energy expenditure (r(S)=0.63, P=0.01) and degree of misreporting (r(S)=0.71, P=0.003, diet history; r(S)=0.63, P=0.01, food records). Variation in energy intake at dinner and over the whole day identified by the food records correlated positively with energy expenditure (r=0.58, P=0.02) and misreporting on the diet history (r=0.62, P=0.01).

CONCLUSIONS

Subjects who are highly active or who have variable dietary and exercise behaviour may be less accurate in reporting dietary intake. Our findings indicate that it may be necessary to screen for these characteristics in studies where accuracy of reporting at an individual level is critical.

The validity of self-reported energy intake as determined using the doubly labelled water technique

In the 1980s the development of the doubly labelled water (DLW) technique made it possible to determine the validity of dietary assessment methods using external, independent markers of intake in free-living populations. Since then, the accuracy of self-reported energy intake (EI) has been questioned on a number of occasions as under-reporting has been found to be prevalent in many different populations. This paper is a review of investigations using the DLW technique in conjunction with self-reported EI measures in groups including adults, children and adolescents, obese persons, athletes, military personnel and trekking explorers. In studies where a person other than the subject is responsible for recording dietary intake, such as parents of young children, EI generally corresponds to DLW determined energy expenditure. However, in instances where the subjects themselves report their intake, EI is generally under-reported when compared with energy expenditure. It was originally believed that this phenomenon of under-reporting was linked to increased adiposity and body size, however, it is now apparent that other factors, such as dietary restraint and socio-economic status, are also involved. This paper therefore aims to present a more comprehensive picture of under-reporting by tying in the findings of many DLW studies with other studies focusing particularly on the characteristics and mechanisms for under-reporting. Awareness of these characteristics and mechanisms will enable researchers to obtain more accurate self-reports of EI using all dietary recording techniques.