The Effect of Cannabidiol on Subjective Responses to Endurance Exercise: A Randomised Controlled Trial.

BACKGROUND: Exercise is known to improve health. However, it can be unpleasant, often inducing negative feelings, or 'affect'. Cannabidiol (CBD), a non-intoxicating constituent of the cannabis plant, has been reported to enhance the subjective experience of exercise; specifically, in trained individuals performing fixed-intensity endurance activity. Here, we investigated the effects of CBD on subjective responses to exercise under more ecologically valid conditions; namely, in recreationally active individuals performing self-paced endurance activity. METHODS: A randomised, double-blind, placebo-controlled, crossover trial was conducted at Griffith University between July 17 and August 28, 2023. Griffith University students studying sports nutrition were invited to take part, with eligible volunteers ≥ 18 years of age and able to perform endurance exercise. Participants ingested placebo or 150 mg CBD in two soft-gel capsules 90 min before completing a self-paced 25-lap (10 km) run around an outdoor athletics track (400 m, synthetic). The primary outcomes were affective valence during exercise, assessed on completion of laps 6, 12, 18 and 24 using the 'Feelings Scale', and positive and negative affect, assessed at baseline, pre-run and post-run using the 'Positive and Negative Affect Schedule'. Exercise enjoyment, motivation and self-efficacy, the core features of the 'runner's high' (i.e., euphoria, pain, anxiety, sedation), perceived exertion and run time were also assessed. RESULTS: Fifty-two participants were randomised and 51 were included in the final sample (n = 22 female; 22 [21-25] years). Exercise induced negative affect (i.e., at the time of undertaking) and increased pain. CBD did not counteract either response. In fact, CBD had no significant effects on any of the outcomes measured. In contrast, exercise, once completed, increased positive affect, and decreased negative affect and anxiety. CONCLUSIONS: CBD (150 mg, oral) does not appear to enhance the subjective experience of self-paced endurance exercise in recreationally active individuals. Nor, however, does it appear to compromise it. These findings suggest that CBD use is safe under exercise conditions and unlikely to impede physical activity participation. Our study also reaffirms the powerful mood-enhancing effects of exercise. TRIAL REGISTRATION: Registered with the Australian New Zealand Clinical Trials Registry ( www.anzctr.org.au ) on May 31, 2023 (Trial ID: ACTRN12623000593639).

Day-to-Day Glycemic Variability Using Continuous Glucose Monitors in Endurance Athletes.

OBJECTIVES: The application of continuous glucose monitors (CGMs) to measure interstitial glucose in athletic populations is limited by the lack of accepted athlete-specific reference values. The aim of this study was to develop athlete-specific reference ranges for glycemic variability under standardized diet and exercise conditions. METHODS: A total of 12 elite racewalkers (n = 7 men, 22.4 ± 3.5 years, VO2max 61.6 ± 7.3 mL kg-1 min-1) completed two 4-d trials separated by 4-d. Athletes were provided a high-energy, high-carbohydrate diet (225 ± 1.6 kJ kg-1 day-1, 8.4 ± 0.3 g kg-1 day-1 carbohydrate) and completed standardized daily exercise. The timing of food consumed and exercise undertaken were matched each day across the 4-d trials. Interstitial glucose data were collected via Freestyle Libre 2 CGMs. Glycemic variability was calculated as the mean amplitude of glycemic excursions (MAGEs), mean of daily differences (MODD), and standard deviation (SD). RESULTS: Twenty-four hour MODD, MAGE, and SD for interstitial glucose were 12.6 ± 1.8 mg/dL (0.7 ± 0.1 mmol/L), 36.0 ± 5.4 mg/dL (2.0 ± 0.3 mmol/L), and 16.2 ± 1.8 mg/dL (0.9 ± 0.1 mmol/L), respectively. Twenty-four hour mean glucose (MG; 102.6 ± 5.4 mg/dL [5.7 ± 0.3 mmol/L]) was higher than overnight (91.8 ± 5.4 mg/dL [5.1 ± 0.3 mmol/L]; P < .0001) and was lower in women than men (99.0 ± 3.6 mg/dL [5.5 ± 0.2 mmol/L] vs 104.4 ± 3.6 mg/dL [5.8 ± 0.2 mmol/L]; P = .059, d = 1.4). CONCLUSIONS: This study provides reference indices under standardized diet and exercise conditions for glycemic variability derived from CGMs in endurance athletes which are similar than previously reported for healthy individuals, despite strenuous daily training and a high daily energy and carbohydrate diet.

The impact of moulage on learners' experience in simulation-based education and training: systematic review.

BACKGROUND: Moulage is a technique used to simulate injury, disease, aging and other physical characteristics specific to a scenario, often used in health and emergency worker training, predominantly for simulation-based learning activities. Its use in allied health fields is unclear. Previous work has explored moulage as an adjunct for authentic simulations, however there is opportunity for broadening its scope. AIM: To explore the effects of moulage interventions in simulation-based education and training, for learner experience. A secondary aim was to understand which pedagogical frameworks were embedded in moulage interventions. METHOD: Four electronic databases (PubMed, CINAHL, EmBase, Proquest Central) were systematically searched to December 2022 for studies utilising moulage in simulation-based education experiences. Outcomes were focused on learner satisfaction, confidence, immersion, engagement, performance, or knowledge. Study quality was assessed using the Mixed Methods Appraisal Tool. RESULTS: Twenty studies (n = 11,470) were included. Studies were primarily conducted in medicine (n = 9 studies) and nursing (n = 5 studies) and less frequently across other health disciplines. The findings demonstrated greater learner satisfaction, confidence, and immersion when moulage was used against a comparator group. Minimal improvements in knowledge and performance were identified. One study underpinned the intervention with a pedagogical theory. CONCLUSION: Moulage improves learner experience in simulation-based education or training, but not knowledge or clinical performance. Further research utilising moulage across a broader range of professions is needed. Interventions using moulage should be underpinned by pedagogical theories.

Fluid intake is a strong predictor of outdoor team sport pre-season training performance.

Our aim was to characterize fluid intake during outdoor team sport training and use generalized additive models to quantify interactions with the environment and performance. Fluid intake, body mass (BM) and internal/external training load data were recorded for male rugby union (n = 19) and soccer (n = 19) athletes before/after field training sessions throughout an 11-week preseason (357 observations). Running performance (GPS) and environmental conditions were recorded each session and generalized additive models were applied in the analysis of data. Mean body mass loss throughout all training sessions was -1.11 ± 0.63 kg (~1.3%) compared with a mean fluid intake at each session of 958 ± 476 mL during the experimental period. For sessions >110 min, when fluid intake reached ~10-19 mL·kg-1 BM the total distance increased (7.47 to 8.06 km, 7.6%; P = 0.049). Fluid intake above ~10 mL·kg-1 BM was associated with a 4.1% increase in high-speed running distance (P < 0.0001). Most outdoor team sport athletes fail to match fluid loss during training, and fluid intake is a strong predictor of running performance. Improved hydration practices during training should be beneficial and we provide a practical ingestion range to promote improved exercise capacity in outdoor team sport training sessions.

The Use of Continuous Glucose Monitors in Sport: Possible Applications and Considerations.

This review discusses the potential value of tracking interstitial glucose with continuous glucose monitors (CGMs) in athletes, highlighting possible applications and important considerations in the collection and interpretation of interstitial glucose data. CGMs are sensors that provide real time, longitudinal tracking of interstitial glucose with a range of commercial monitors currently available. Recent advancements in CGM technology have led to the development of athlete-specific devices targeting glucose monitoring in sport. Although largely untested, the capacity of CGMs to capture the duration, magnitude, and frequency of interstitial glucose fluctuations every 1-15 min may present a unique opportunity to monitor fueling adequacy around competitive events and training sessions, with applications for applied research and sports nutrition practice. Indeed, manufacturers of athlete-specific devices market these products as a "fueling gauge," enabling athletes to "push their limits longer and get bigger gains." However, as glucose homeostasis is a complex phenomenon, extensive research is required to ascertain whether systemic glucose availability (estimated by CGM-derived interstitial glucose) has any meaning in relation to the intended purposes in sport. Whether CGMs will provide reliable and accurate information and enhance sports nutrition knowledge and practice is currently untested. Caveats around the use of CGMs include technical issues (dislodging of sensors during periods of surveillance, loss of data due to synchronization issues), practical issues (potential bans on their use in some sporting scenarios, expense), and challenges to the underpinning principles of data interpretation, which highlight the role of sports nutrition professionals to provide context and interpretation.

The Impact of a 'Remotely-Delivered' Sports Nutrition Education Program on Dietary Intake and Nutrition Knowledge of Junior Elite Triathletes.

Triathlon is a physically demanding sport, requiring athletes to make informed decisions regarding their daily food and fluid intake to align with daily training. With an increase in uptake for online learning, remotely delivered education programs offer an opportunity to improve nutritional knowledge and subsequent dietary intake in athletes. This single-arm observational study aimed to evaluate the effectiveness of a remotely delivered nutrition education program on sports nutrition knowledge and the dietary intake of junior elite triathletes (n = 21; female n = 9; male n = 12; 18.9 ± 1.6 y). A total of 18 participants completed dietary intake assessments (4-day food diary via Easy Diet DiaryTM) and 14 participants completed an 83-question sports nutrition knowledge assessment (Sports Nutrition Knowledge Questionnaire (SNKQ)) before and after the 8-week program. Sports nutrition knowledge scores improved by 15% (p < 0.001, ES = 0.9) following the program. Male participants reported higher energy intakes before (3348 kJ, 95% CI: 117−6579; p = 0.043) and after (3644 kJ, 95% CI: 451−6836; p = 0.028) the program compared to females. Carbohydrate intake at breakfast (p = 0.022), daily intakes of fruit (p = 0.033), dairy (p = 0.01) and calcium (p = 0.029) increased following nutrition education. Irrespective of gender, participants had higher intakes of energy (p < 0.001), carbohydrate (p = 0.001), protein (p = 0.007), and fat (p = 0.007) on heavy training days compared to lighter training days before and after the program with total nutrition knowledge scores negatively correlated with discretionary food intake (r = −0.695, p = 0.001). A remotely delivered nutrition education program by an accredited sports nutrition professional improved sports nutrition knowledge and subsequent dietary intake of junior elite triathletes, suggesting remote delivery of nutrition education may prove effective when social distancing requirements prevent face-to-face opportunities.

Effects of Different Sources of Low-Dose Caffeine on Mood/Arousal and Cognitive Performance.

In this study we investigated the effects of variously derived sources of low-dose caffeine on mood/arousal and cognitive performance. Twenty-two participants (15 men, 7 women; M age: 28.2, SD = 9.0 years) undertook five randomized, crossover trials in which they consumed either a water control (CON) or 80 mg of caffeine from one of four sources (coffee [COF], energy drink [END], capsule [CAP], and dissolvable mouth strip [STR]). We measured the participants' perceived efficacy of these varied caffeine sources pre-treatment; and we measured mood/arousal at pre-treatment, and again at 15 and 45 minutes post-treatment. We also measured choice reaction-time at 15 and 45 minutes post-treatment, and participants completed the psychomotor vigilance task (PVT) 45 minutes post-treatment. Caffeine increased participant ratings of alertness and decreased their ratings of tiredness irrespective of source (p's < .05), and all sources of caffeine decreased reaction time on the PVT (p's < .05), with ex-Gaussian distributional analysis localizing this to the tau-parameter, indicating lower variability. However, only the COF source was associated with improved 'overall mood' (p's < .05). Participants expected to perform better on the PVT with COF compared to CON, but there were no other significant associations between source expectancy and performance. In sum, a modest dose of caffeine, regardless of source, positively impacted mood/arousal and cognitive performance, and these effects did not appear to be influenced by expectations.

Sports Dietitian practices for assessing and managing athletes at risk of low energy availability (LEA).

OBJECTIVES: To characterise the assessment and management practices employed by Sports Dietitians when assessing and managing athletes at risk of low energy availability (LEA). DESIGN: 55 Sports Dietitians participated in an online questionnaire that captured the typical methods used to identify and manage LEA in athletic populations. METHODS: The questionnaire consisted of 27 questions which explored common methods used to identify and manage LEA, as well as dietary methods employed and barriers experienced by Sports Dietitians. RESULTS: Broadly, the top 3 nutrition-related priorities for respondents were nutrition strategies to support training, competition, and recovery while 'LEA' was ranked fifth. 'Dietary intake', 'menstrual function' and 'training load (km/week)' were the primary methods used to assess LEA and respondents were 'confident' in their ability to correctly identify athletes at risk. Among support personnel, coaches were rarely a referral source for management of LEA but did present frequent communication difficulties. Respondents indicated athletes have concerns about undesirable changes in body composition when providing recommendations of increased energy intake for LEA management. CONCLUSIONS: Sport Dietitians appear to recognise and prioritise LEA management in athletes, but assessments are limited to dietary intake and training load (km/week); with collaborative approaches to LEA management lacking. Sports Dietitian may be overconfident in their ability to identify LEA as only a limited number of assessment methods are commonly used. Access to reliable assessments methods and collaborative management approaches are needed to improve athlete care when suspected of LEA.

Effect of Acetaminophen on Endurance Cycling Performance in Trained Triathletes in Hot and Humid Conditions.

PURPOSE: The effect of acetaminophen (ACT, also known as paracetamol) on endurance performance in hot and humid conditions has been shown previously in recreationally active populations. The aim of this study was to determine the effect of ACT on physiological and perceptual variables during steady-state and time-trial cycling performance of trained triathletes in hot and humid conditions. METHODS: In a randomized, double-blind crossover design, 11 triathletes completed ∼60 minutes steady-state cycling at 63% peak power output followed by a time trial (7 kJ·kg body mass-1, ∼30 min) in hot and humid conditions (∼30°C, ∼69% relative humidity) 60 minutes after consuming either 20 mg·kg body mass-1 ACT or a color-matched placebo. Time-trial completion time, gastrointestinal temperature, skin temperature, thermal sensation, thermal comfort, rating of perceived exertion, and fluid balance were recorded throughout each session. RESULTS: There was no difference in performance in the ACT trial compared with placebo (P = .086, d = 0.57), nor were there differences in gastrointestinal and skin temperature, thermal sensation and comfort, or fluid balance between trials. CONCLUSION: In conclusion, there was no effect of ACT (20 mg·kg body mass-1) ingestion on physiology, perception, and performance of trained triathletes in hot and humid conditions, and existing precooling and percooling strategies appear to be more appropriate for endurance cycling performance in the heat.

Free-Living Dietary Intake in Tactical Personnel and Implications for Nutrition Practice: A Systematic Review.

Tactical personnel (including military, law enforcement, and fire and rescue) are responsible for ensuring national and public safety. Dietary intake is an important consideration to support optimal health and performance. The aims of this systematic review were to: (1) describe the reported free-living dietary intake (energy and macronutrients) of tactical personnel, and (2) describe the practical implications of reported dietary intakes to support the physical and dietary requirements of tactical personnel. A systematic search of databases (MEDLINE, EMBASE, CINAHL and Web of Science) was conducted following the PRISMA guidelines. English and full text research articles were identified and screened against inclusion and exclusion criteria. Demographic and dietary intake data were extracted, tabulated, and synthesized narratively. The quality of the studies was assessed using the Academy of Nutrition and Dietetics Quality Criteria Checklist. Twenty-two studies (15 military, 4 law enforcement, and 2 fire and rescue) were eligible to inform this review. The volume of evidence suggested that tactical personnel met dietary protein and exceeded dietary fat recommendations but failed to meet energy and carbohydrate recommendations. Therefore, practical approaches to support optimized energy, fat and carbohydrate intake in tactical personnel is important.

Consumer expectation and responses to environmental sustainability initiatives and their impact in foodservice operations: A systematic review.

BACKGROUND: With increasing pressure on the Earth's finite resources, there is significant demand for environmentally sustainable practices in foodservice. A shift to sustainable foodservice operations can decrease its environmental impact and may align with consumer expectations. This systematic review explored consumer expectations (attitudes pre-intervention) and responses (behaviour, cognitive attitudes and affective attitudes post-intervention) towards environmentally sustainable initiatives of foodservice operations. METHODS: A systematic search following PRISMA guidelines was conducted across MEDLINE, EMABASE, CINAHL and Web of Science databases. English and full-text research articles published up to November 2019 were identified. Consumers' expectations and responses to interventions were extracted. The quality of the studies was assessed using the Mixed Methods Appraisal Tool (MMAT). RESULTS: Thirty-three studies were included and, given the heterogeneity of the studies, the results were synthesised narratively. The main outcomes analysed included changes in behaviour and attitudes (cognitive and affective), including knowledge and satisfaction. Intervention strategies were interpreted and categorised into three groups: food waste reduction, single-use item and packaging waste reduction, and initiatives related to menu, messaging and labelling. Most studies resulted in significant pro-environmental changes towards decreasing food waste, decreasing single use-item and packaging waste, as well as engaging consumers in sustainable eating. CONCLUSIONS: There are a range of successful environmentally sustainable strategies that when implemented by foodservices can have a mostly positive impact on consumer attitudes and responses. However, positive consumer attitudes did not always translate to changes in behaviour. Foodservices should carefully consider implementing interventions that support changes in consumer behaviour.

The impact of post-prandial delay periods on ad libitum consumption of a laboratory breakfast meal.

This study examined the impact of varying the holding time following an ad libitum laboratory breakfast on acute dietary behaviour and subsequent intake. Twenty-four participants (20 females (age: 23.4 ± 6.3 years; body mass index: 23.9 ± 3.9 kg·m-2, mean ± SD)) completed 3 trials following a quasi-randomised, crossover design. Each trial (7-day separation) incorporated a defined post-prandial delay (DPD) period of either zero (no delay), 1 or 3 hours following a buffet breakfast consumed over 30 minutes. Dietary intake outcomes included energy, macronutrient and core food group intakes. On completion of the DPD period, participants left the laboratory and recorded all food/beverages consumed for the remainder of the day. One-way repeated-measures ANOVA assessed all outcomes, with post hoc analysis conducted on significant main effects. Energy and carbohydrate intakes were significantly lower on no delay vs. 1-hour (p = 0.014) and 3-hour (p = 0.06) DPD trials (energy intake: 1853 ± 814 kJ vs. 2250 ± 1345 kJ vs. 1948 ± 1289 kJ; carbohydrates: 68 ± 34 g vs. 77 ± 44 vs. 69 ± 43 g; respectively). DPD periods did not influence the time to consume next meal or energy, macronutrient and core food group intakes for the remainder of the day. Delaying participants from leaving a laboratory alters dietary intake at an ad libitum test meal. The post-meal holding period is an important methodological consideration when planning laboratory studies to assess appetite. Novelty: Delaying participants from leaving a laboratory alters dietary intake at ad libitum breakfast meals. The length of the delay period did not affect dietary intake at ad libitum breakfast meals.

Belief in caffeine's ergogenic effect on cognitive function and endurance performance: A sham dose-response study.

This study aimed to determine if belief in caffeine's ergogenic potential influences choice reaction time (CRT) and/or running performance. Twenty-nine healthy individuals (23.7 ± 5 years, 16 males) completed two trials (one week apart). Before the trials, participants indicated their "belief" in caffeine's ergogenic effects and previous "experience" using caffeine for performance. On arrival, participants randomly received either sham "Low (100mg; LD)" or "High (300mg; HD)" dose caffeine capsules 30-min before commencing the CRT test, followed by a 10km run. Paired samples t-tests determined differences between trials for CRT latency (Ex-Gaussian analysis; µ-, σ- and τ-) and running performance using the entire cohort and sub-groups exhibiting strong "beliefs"+/-"experience". Sham caffeine dose did not influence CRT (µ-, σ- and τ-respectively, LD: 400 ± 53ms vs. HD: 388 ± 41ms; LD: 35 ± 18ms vs. HD: 34 ± 17ms; LD: 50 ± 24ms vs. HD: 52 ± 19ms, all p's > 0.05). Neither belief (n = 6), nor belief + experience (n = 4), influenced this effect. Furthermore, caffeine dose did not influence run time (LD: 49.05 ± 3.75min vs. HD: 49.06 ± 3.85min, p = 0.979). Belief (n = 9) (LD: 48.93 ± 3.71min vs. HD: 48.9 ± 3.52min, p = 0.976), and belief + experience (n = 6) (LD: 48.68 ± 1.87min vs. HD: 49.55 ± 1.75min, p = 0.386) didn't influence this effect. A dose-response to sham caffeine ingestion was not evident on cognitive or endurance performance in healthy individuals, regardless of their convictions about caffeine's ergogenicity.

The effectiveness of nutrition education programmes on improving dietary intake in athletes: a systematic review.

Nutrition education programmes for athletes aim to enhance nutrition knowledge and more importantly support positive dietary change to enhance performance, health and well-being. This systematic review assessed changes in the dietary intakes of athletes in response to nutrition education programmes. A search was conducted which included studies providing quantitative dietary intake assessment of athletes of any calibre aged between 12 and 65 years in response to a nutrition education programme. Standardised differences (effect sizes) were calculated (when possible) for each dietary parameter. The search yielded 6285 papers with twenty-two studies (974 participants (71·9 % female)) eligible for inclusion. Studies described athletes competing at high school (n 3) through to college level or higher (n 19). Study designs were either single arm with an intervention-only group (twelve studies; n 241) or double arm including an intervention and control group (ten studies; n 689). No control groups received an alternative or 'sham' intervention. Face-to-face lectures (9/22) and individual nutrition counselling (6/22) were the most common education interventions. Non-weighed, 3-d diet records (10/22) were the most frequently utilised dietary assessment method. Although 14/22 studies (n 5 single and n 9 double) reported significant change in at least one nutrition parameter, dietary changes were inconsistent. Poor study quality and heterogeneity of methods prohibit firm conclusions regarding overall intervention success or superior types of educational modalities. Of note, carbohydrate intakes 'post-intervention' when assessed often failed to meet recommended guidelines (12/17 studies). Given the substantial investment made in nutrition education interventions with athletes, there is a need for well-designed and rigorous research to inform future best practice.

Metabolic Cost of Paddling on Different Commercially Available Kayak Ergometers.

PURPOSE: To compare the metabolic cost of paddling on different commercially available kayak ergometers using a standardized kayak incremental exercise protocol. METHODS: Six male sprint kayak athletes undertook an incremental exercise protocol on 3 different kayak ergometers utilizing a randomized counterbalanced pair-matched design. RESULTS: Mean maximal aerobic power on the WEBA ergometer (265 [14] W) was significantly higher than on the Dansprint (238 [9] W) and KayakPro® (247 [21] W, P < .01, effect size [ES] = 0.80). At the fifth stage, absolute oxygen consumption on the WEBA (3.82 [0.25] L·min-1) was significantly lower (P < 0.05, ES = 0.20) than KayakPro and Dansprint (4.10 [0.28] and 4.08 [0.27] L·min-1, respectively). Blood lactate concentration response at the sixth stage was significantly lower for the WEBA (3.5 [0.8] mmol·L-1), compared with KayakPro and Dansprint (5.4 [1.2] and 5.6 [1.5] mmol·L-1, P = .012, ES = 0.20). Stroke rate was significantly higher, without any effect of pacing during the submaximal stages for the Dansprint, compared with the WEBA (P < .001, ES = 0.28) and KayakPro (P < .001, ES = 0.38). A pacing effect was present at the maximal stage for all ergometers. CONCLUSIONS: This study demonstrated that paddling on different kayak ergometers when controlling power output elicits different metabolic and work outputs. It is recommended that scientists and coaches avoid testing on different ergometers and regularly calibrate these devices. Moreover, when an ergometer has been calibrated against a first principle device, it is necessary to consider calibration of various drag settings, due to their impact on stroke rate. Further research should explore the relationship between drag settings and stroke rate.

Sports nutrition for the recreational athlete.

BACKGROUND: Recreational sports participation provides many potential health benefits. However, some athletes experience medical problems associated with, or exacerbated by, a mismanagement of the relationship between their diet and sporting endeavours. OBJECTIVE: The aim of this article is to highlight recent developments in clinical sports nutrition, with a focus on providing evidence-based advice and resources for the management of common medical presentations. DISCUSSION: A low dietary energy intake relative to exercise energy demands (ie low energy availability) may result in an array of medical issues. An evidence-based framework for advice on sports supplements is available.

Sports Dietitians Australia Position Statement: Nutrition for Exercise in Hot Environments.

It is the position of Sports Dietitians Australia (SDA) that exercise in hot and/or humid environments, or with significant clothing and/or equipment that prevents body heat loss (i.e., exertional heat stress), provides significant challenges to an athlete's nutritional status, health, and performance. Exertional heat stress, especially when prolonged, can perturb thermoregulatory, cardiovascular, and gastrointestinal systems. Heat acclimation or acclimatization provides beneficial adaptations and should be undertaken where possible. Athletes should aim to begin exercise euhydrated. Furthermore, preexercise hyperhydration may be desirable in some scenarios and can be achieved through acute sodium or glycerol loading protocols. The assessment of fluid balance during exercise, together with gastrointestinal tolerance to fluid intake, and the appropriateness of thirst responses provide valuable information to inform fluid replacement strategies that should be integrated with event fuel requirements. Such strategies should also consider fluid availability and opportunities to drink, to prevent significant under- or overconsumption during exercise. Postexercise beverage choices can be influenced by the required timeframe for return to euhydration and co-ingestion of meals and snacks. Ingested beverage temperature can influence core temperature, with cold/icy beverages of potential use before and during exertional heat stress, while use of menthol can alter thermal sensation. Practical challenges in supporting athletes in teams and traveling for competition require careful planning. Finally, specific athletic population groups have unique nutritional needs in the context of exertional heat stress (i.e., youth, endurance/ultra-endurance athletes, and para-sport athletes), and specific adjustments to nutrition strategies should be made for these population groups.

Influence of Periodizing Dietary Carbohydrate on Iron Regulation and Immune Function in Elite Triathletes.

Sleeping with low carbohydrate (CHO) availability is a dietary strategy that may enhance training adaptation. However, the impact on an athlete's health is unclear. This study quantified the effect of a short-term "sleep-low" dietary intervention on markers of iron regulation and immune function in athletes. In a randomized, repeated-measures design, 11 elite triathletes completed two 4-day mixed cycle run training blocks. Key training sessions were structured such that a high-intensity training session was performed in the field on the afternoon of Days 1 and 3, and a low-intensity training (LIT) session was performed on the following morning in the laboratory (Days 2 and 4). The ingestion of CHO was either divided evenly across the day (HIGH) or restricted between the high-intensity training and LIT sessions, so that the LIT session was performed with low CHO availability (LOW). Venous blood and saliva samples were collected prior to and following each LIT session and analyzed for interleukin-6, hepcidin 25, and salivary immunoglobulin-A. Concentrations of interleukin-6 increased acutely after exercise (p < .001), but did not differ between dietary conditions or days. Hepcidin 25 increased 3-hr postexercise (p < .001), with the greatest increase evident after the LOW trial on Day 2 (2.5 ± 0.9 fold increase ±90% confidence limit). The salivary immunoglobulin-A secretion rate did not change in response to exercise; however, it was highest during the LOW condition on Day 4 (p = .046). There appears to be minimal impact to markers of immune function and iron regulation when acute exposure to low CHO availability is undertaken with expert nutrition and coaching input.

Effect of Drinking Rate on the Retention of Water or Milk Following Exercise-Induced Dehydration.

This study investigated the effect of drinking rate on fluid retention of milk and water following exercise-induced dehydration. In Part A, 12 male participants lost 1.9% ± 0.3% body mass through cycle exercise on four occasions. Following exercise, plain water or low-fat milk equal to the volume of sweat lost during exercise was provided. Beverages were ingested over 30 or 90 min, resulting in four beverage treatments: water 30 min, water 90 min, milk 30 min, and milk 90 min. In Part B, 12 participants (nine males and three females) lost 2.0% ± 0.3% body mass through cycle exercise on four occasions. Following exercise, plain water equal to the volume of sweat lost during exercise was provided. Water was ingested over 15 min (DR15), 45 min (DR45), or 90 min (DR90), with either DR15 or DR45 repeated. In both trials, nude body mass, urine volume, urine specific gravity and osmolality, plasma osmolality, and subjective ratings of gastrointestinal symptoms were obtained preexercise and every hour for 3 hr after the onset of drinking. In Part A, no effect of drinking rate was observed on the proportion of fluid retained, but milk retention was greater (p < .01) than water (water 30 min: 57% ± 16%, water 90 min: 60% ± 20%, milk 30 min: 83% ± 6%, and milk 90 min: 85% ± 7%). In Part B, fluid retention was greater in DR90 (57% ± 13%) than DR15 (50% ± 11%, p < .05), but this was within test-retest variation determined from the repeated trials (coefficient of variation: 17%). Within the range of drinking rates investigated the nutrient composition of a beverage has a more pronounced impact on fluid retention than the ingestion rate.

Body composition of elite Olympic combat sport athletes.

Physique traits of a range of elite athletes have been identified; however, few detailed investigations of Olympic combat sports (judo, wrestling, taekwondo and boxing) exist. This is surprising given the importance of body composition in weight category sports. We sought to develop a descriptive database of Olympic combat sport athletes, compare variables relative to weight division and examine differences within and between sports. Additionally, we investigated the appropriateness of athletes' self-selected weight classes compared to an internationally recognised classification system (the NCAA minimum wrestling weight scheme used to identify minimum 'safe' weight). Olympic combat sport athletes (56♂, 38♀) had body mass (BM), stretch stature and dual-energy X-ray absorptiometry derived body composition assessed within 7-21 days of competition. Most athletes were heavier than their weight division. Sport had an effect (p < .05) on several physique traits, including; lean mass, lean mass distribution, stretch stature and BMI. BM was strongly positively correlated (r > 0.6) with; fat free mass, fat mass and body fat percentage, however, was not predictive of total mass/weight division. The Olympic combat sports differ in competitive format and physiological requirements, which is partly reflected in athletes' physique traits. We provide reference ranges for lean and fat mass across a range of BM. Lighter athletes likely must utilise acute weight loss in order to make weight, whereas heavier athletes can potentially reduce fat mass.