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).

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 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.

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.

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.

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.

Tattoos do not affect exercise-induced localised sweat rate or sodium concentration

OBJECTIVES

Skin tattoos have been shown to reduce localised sweat rate and increase sweat sodium concentration ([Na⁺]) when sweating is artificially stimulated. This study investigated whether similar responses are observed with exercise-induced sweating.

DESIGN

Unblinded, within-participant control, single trial.

METHODS

Twenty-two healthy individuals (25.1±4.8 y (Mean±SD), 14 males) with a unilateral tattoo ≥11.4cm² in size, ≥2 months in age, and shaded ≥50% participated in this investigation. Participants undertook 20min of intermittent cycling (4×5min intervals) on a stationary ergometer in a controlled environment (24.6±1.1°C; 64±6% RH). Resultant sweat was collected into absorbent patches applied at two pairs of contralateral skin sites (pair 1: Tattoo vs. Non-Tattoo; pair 2: Control 1 vs. Control 2 (both non-tattooed)), for determination of sweat rate and sweat [Na⁺]. Paired samples t-tests were used to determine differences between contralateral sites.

RESULTS

Tattoo vs. Non-Tattoo: Neither sweat rate (Mean±SD: 0.92±0.37 vs. 0.94±0.43mg·cm^-2·min^-1, respectively; p=0.693) nor sweat [Na⁺] (Median(IQR): 37(32-52) vs. 37(31-45) mM·L^-1, respectively; p=0.827) differed. Control 1 vs. Control 2: Neither sweat rate (Mean±SD: 1.19±0.53 vs. 1.19±0.53mg·cm^-2·min^-1, respectively; p=0.917) nor sweat [Na⁺] (Median(IQR): 29(26-41) vs. 31(25-43)mM·L^-1, respectively; p=0.147) differed. The non-significant differences for sweat rate and [Na⁺] between Tattoo vs. Non-Tattoo were inside the range of the within participant variability (sweat rate CVi=5.4%; sweat [Na⁺] CVi=4.4%).

CONCLUSIONS

Skin tattoos do not appear to alter the rate or [Na⁺] of exercise-induced sweating. The influence of skin tattoos on localised sweat responses may have previously been over-estimated.

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.

Repeated muscle glycogen supercompensation with four days' recovery between exhaustive exercise

OBJECTIVES

To determine if a 4 d period of high carbohydrate intake can supercompensate muscle glycogen and exercise work capacity on back-to-back occasions.

DESIGN

Seven trained cyclists (6 male, VO₂peak: 57 ± 4 mL kg^-1 min^-1) completed a 9-d experimental period, consisting of three intermittent exhaustive cycling trials on days 1 (trial 1), 5 (trial 2) and 9 (trial 3). Following trial 1 cyclists were fed a high carbohydrate diet (˜10 g kg^-1 day^-1) for eight days to assess their capacity to repeatedly supercompensate muscle glycogen with 4 d recovery.

METHODS

A resting muscle biopsy was obtained prior to each trial consisting of 2 min work intervals (90-60% peak power output) interspersed with 2 min recovery (40% peak power output) repeated until exhaustion. Each 72-h period between trial days included two days of low volume cycling and a rest day. Resting muscle glycogen and total work completed was determined for each trial day.

RESULTS

Baseline muscle glycogen on day 1 (583.6 ± 111.0 mmol kg^-1 dry mass) was supercompensated on day 5 (835.1 ± 112.8 mmol kg^-1 dry mass; p = 0.04, d = 2.25) and again on day 9 (848.3 ± 111.4 mmol kg^-1 dry mass; p = 0.01, d = 2.38). Total cycling work capacity increased from trial 1 to trial 2 (+8.7 ± 5.4 kJ kg^-1; p = 0.01; d = 1.41); a large effect was observed in trial 3 compared to trial 1 (+6.4 ± 6.8 kJ kg^-1; p = 0.10; d = 1.10).

CONCLUSIONS

A 4 d high carbohydrate feeding strategy is sufficient to repeatedly supercompensate muscle glycogen content following exhaustive exercise and results in enhanced work capacity.

The effect of different post-exercise beverages with food on ad libitum fluid recovery, nutrient provision, and subsequent athletic performance

This study investigated the effect of consuming either water or a carbohydrate (CHO)-electrolyte sports beverage ('Sports Drink') ad libitum with food during a 4 h post-exercise recovery period on fluid restoration, nutrient provision and subsequent endurance cycling performance. On two occasions, 16 endurance-trained cyclists; 8 male [M] (age: 31 ± 9 y; VO_2max: 54 ± 6 mL·kg^-1·min^-1) and 8 female [F] (age: 33 ± 8 y; VO_2max: 50 ± 7 mL·kg^-1·min^-1); lost 2.3 ± 0.3% and 1.6 ± 0.3% of their body mass (BM), respectively during 1 h of fixed-intensity cycling. Participants then had ad libitum access to either Water or Sports Drink and food for the first 195 min of a 4 h recovery period. At the conclusion of the recovery period, participants completed a cycling performance test consisting of a 45 min fixed-intensity pre-load and an incremental test to volitional exhaustion (peak power output, PPO). Beverage intake; total water/nutrient intake; and indicators of fluid recovery (BM, urine output, plasma osmolality [P_OSM]) were assessed periodically throughout trials. Participants returned to a similar state of net positive fluid balance prior to recommencing exercise, regardless of the beverage provided (Water: +0.4 ± 0.5 L; Sports Drink: +0.3 ± 0.3 L, p = 0.529). While Sports Drink increased post-exercise energy (M: +1.8 ± 1.0 MJ; F: +1.3 ± 0.5 MJ) and CHO (M: +114 ± 31 g; F: +84 ± 25 g) intake (i.e. total from food and beverage) (p's < 0.001), this did not improve subsequent endurance cycling performance (Water: 337 ± 40 W [M] and 252 ± 50 W [F]; Sports Drink: 340 ± 40 W [M] and 258 ± 47 W [F], p = 0.242). Recovery beverage recommendations should consider the post-exercise environment (i.e. the availability of food), an individual's tolerance for food and fluid pre-/post-exercise, the immediate requirements for refuelling (i.e. CHO demands of the activity) and the athlete's overall dietary goals.

Do multi-ingredient protein supplements augment resistance training-induced gains in skeletal muscle mass and strength? A systematic review and meta-analysis of 35 trials

Objective

To determine the effects of multi-ingredient protein (MIP) supplements on resistance exercise training (RT)-induced gains in muscle mass and strength compared with protein-only (PRO) or placebo supplementation.

Data sources

Systematic search of MEDLINE, Embase, CINAHL and SPORTDiscus.

Eligibility criteria

Randomised controlled trials with interventions including RT ≥6 weeks in duration and a MIP supplement.

Design

Random effects meta-analyses were conducted to determine the effect of supplementation on fat-free mass (FFM), fat mass, one-repetition maximum (1RM) upper body and 1RM lower body muscular strength. Subgroup analyses compared the efficacy of MIP supplementation relative to training status and chronological age.

Results

The most common MIP supplements included protein with creatine (n=17) or vitamin D (n=10). Data from 35 trials with 1387 participants showed significant (p<0.05) increases in FFM (0.80 kg (95% CI 0.44 to 1.15)), 1RM lower body (4.22 kg (95% CI 0.79 to 7.64)) and 1RM upper body (2.56 kg (95% CI 0.79 to 4.33)) where a supplement was compared with all non-MIP supplemented conditions (means (95% CI)). Subgroup analyses indicated a greater effect of MIP supplements compared with all non-MIP supplements on FFM in untrained (0.95 kg (95% CI 0.51 to 1.39), p<0.0001) and older participants (0.77 kg (95% CI 0.11 to 1.43), p=0.02); taking MIP supplements was also associated with gains in 1RM upper body (1.56 kg (95% CI 0.80 to 2.33), p=0.01) in older adults.

Summary/conclusions

When MIP supplements were combined with resistance exercise training, there were greater gains in FFM and strength in healthy adults than in counterparts who were supplemented with non-MIP. MIP supplements were not superior when directly compared with PRO supplements. The magnitude of effect of MIP supplements was greater (in absolute values) in untrained and elderly individuals undertaking RT than it was in trained individuals and in younger people.

Trial registration number

CRD42017081970.

Fluid, energy, and nutrient recovery via ad libitum intake of different commercial beverages and food in female athletes

This study investigated the effect of consuming different commercial beverages with food ad libitum after exercise on fluid, energy, and nutrient recovery in trained females. On 4 separate occasions, 8 females (body mass (BM): 61.8 ± 10.7 kg; maximal oxygen uptake: 46.3 ± 7.5 mL·kg^-1·min^-1) lost 2.0% ± 0.3% BM cycling at ∼75% maximal oxygen uptake before completing a 4-h recovery period with ad libitum access to 1 of 4 beverages: Water, Powerade (Sports Drink), Up & Go Reduced Sugar (Lower Sugar (LS)-MILK) or Up & Go Energize (Higher Protein (HP)-MILK). Participants also had two 15-min opportunities to access food within the first 2 h of the recovery period. Beverage intake, total water/nutrient intake, and indicators of fluid recovery (BM, urine output, plasma osmolality), gastrointestinal tolerance and palatability were assessed periodically. While total water intake (from food and beverage) (Water: 1918 ± 580 g; Sports Drink: 1809 ± 338 g; LS-MILK: 1458 ± 431 g; HP-MILK: 1523 ± 472 g; p = 0.010) and total urine output (Water: 566 ± 314 g; Sports Drink: 459 ± 290 g; LS-MILK: 220 ± 53 g; HP-MILK: 230 ± 117 g; p = 0.009) differed significantly by beverage, the quantity of ingested water retained was similar across treatments (Water: 1352 ± 462 g; Sports Drink: 1349 ± 407 g; LS-MILK: 1238 ± 400 g; HP-MILK: 1293 ± 453 g; p = 0.691). Total energy intake (from food and beverage) increased in proportion to the energy density of the beverage (Water: 4129 ± 1080 kJ; Sports Drink: 5167 ± 643 kJ; LS-MILK: 6019 ± 1925 kJ; HP-MILK: 7096 ± 2058 kJ; p = 0.014). When consumed voluntarily and with food, different beverages promote similar levels of fluid recovery, but alter energy/nutrient intakes. Providing access to food and understanding the longer-term dietary goals of female athletes are important considerations when recommending a recovery beverage.

Fluid, energy and nutrient recovery via ad libitum intake of different fluids and food

INTRODUCTION

This study compared the effects of ad libitum consumption of different beverages and foods on fluid retention and nutrient intake following exercise.

METHODS

Ten endurance trained males (mean±SD; Age=25.3±4.9years, VO₂max=63.0±7.2mL·kg·min^-1) performed four trials employing a counterbalanced, crossover design. Following 60min of exercise (matched for energy expenditure and fluid loss) participants consumed either water (W1 and W2), a sports drink (Powerade® (P)) or a milk-based liquid meal supplement (Sustagen Sport® (SS)) over a four hour recovery period. Additionally, participants had access to snack foods on two occasions within the first 2h of recovery on all trials. All beverages and food were consumed ad libitum. Total nutrient intake, urine volume, USG, body weight as well as subjective measures of gastrointestinal tolerance and thirst were obtained hourly. Plasma osmolality was measured pre, post, 1 and 4h after exercise.

RESULTS

Total fluid volume ingested from food and beverages in W1 (2.28±0.42L) and P (2.82±0.80L) trials were significantly greater than SS (1.94±0.54L). Total urine output was not different between trials (W1=644±202mL, W2=602±352mL, P=879±751mL, SS=466±129mL). No significant differences in net body weight change was observed between trials (W1=0.01±0.28kg, W2=0.08±0.30kg, P=-0.02±0.24kg, SS=-0.05±0.24kg). Total energy intake was higher on P (10,179±1484kJ) and SS (10,577±2210kJ) compared to both water trials (W1=7826±888kJ, W2=7578±1112kJ).

CONCLUSION

With the co-ingestion of food, fluid restoration following exercise is tightly regulated and not influenced by the choice of either water, a carbohydrate-electrolyte (sports drink) or a milk-based beverage.

Timing of post-exercise carbohydrate ingestion: influence on IL-6 and hepcidin responses

PURPOSE

Carbohydrate ingestion prior and during exercise attenuates exercise-induced interleukin-6. This investigation examined if an analogous effect was evident for interleukin-6 and hepcidin response when carbohydrates were ingested post-exercise.

METHODS

In a crossover design, 11 well-trained endurance athletes completed two experimental trials. Participants completed an 8 × 3 min interval running session at 85 % vVO2peak followed by 5 h of monitored recovery. During this period, participants were provided with two 1.2 g kg(-1) carbohydrate beverages at either an early feeding time (immediately post-exercise and 2 h post-exercise) or delayed feeding time (2 h post-exercise and 4 h post-exercise). Venous blood samples were collected pre-, immediately post-, 3 and 5 h post-exercise. Samples were analysed for Interleukin-6, serum iron, serum ferritin and hepcidin.

RESULTS

Interleukin-6 was significantly elevated (p = 0.004) immediately post-exercise compared to baseline for both trials. Hepcidin levels were significantly elevated at 3 h post-exercise (p = 0.001) and 5 h post-exercise (p = 0.002) compared to baseline levels in both trials, with no significant difference between the two conditions and any time point. Serum iron was significantly increased from baseline to immediately post-exercise (p = 0.001) for both trials, with levels decreasing by 3 h (p = 0.025) and 5 h post-exercise (p = 0.001). Serum ferritin levels increased immediately post-exercise compared to baseline (p = 0.006) in both conditions.

CONCLUSIONS

The timing and ingestion of post-exercise carbohydrate ingestion do not appear to impact post-exercise interleukin-6 and hepcidin responses; this is likely a result of the interval running task inducing an inflammatory response and subsequent up-regulation of hepcidin.

Systematic review: Carbohydrate supplementation on exercise performance or capacity of varying durations

This systematic review examines the efficacy of carbohydrate (CHO) supplementation on exercise performance of varying durations. Included studies utilized an all-out or endurance-based exercise protocol (no team-based performance studies) and featured randomized interventions and placebo (water-only) trial for comparison against exclusively CHO trials (no other ingredients). Of the 61 included published performance studies (n = 679 subjects), 82% showed statistically significant performance benefits (n = 50 studies), with 18% showing no change compared with placebo. There was a significant (p = 0.0036) correlative relationship between increasing total exercise time and the subsequent percent increase in performance with CHO intake versus placebo. While not mutually exclusive, the primary mechanism(s) for performance enhancement likely differs depending on the duration of the exercise. In short duration exercise situations (∼1 h), oral receptor exposure to CHO, via either mouthwash or oral consumption (with enough oral contact time), which then stimulates the pleasure and reward centers of the brain, provide a central nervous system-based mechanism for enhanced performance. Thus, the type and (or) amount of CHO and its ability to be absorbed and oxidized appear completely irrelevant to enhancing performance in short duration exercise situations. For longer duration exercise (>2 h), where muscle glycogen stores are stressed, the primary mechanism by which carbohydrate supplementation enhances performance is via high rates of CHO delivery (>90 g/h), resulting in high rates of CHO oxidation. Use of multiple transportable carbohydrates (glucose:fructose) are beneficial in prolonged exercise, although individual recommendations for athletes should be tailored according to each athlete's individual tolerance.

Influence of post-exercise hypoxic exposure on hepcidin response in athletes

PURPOSE

To assess the influence of a simulated altitude exposure (~2,900 m above sea level) for a 3 h recovery period following intense interval running on post-exercise inflammation, serum iron, ferritin, erythropoietin, and hepcidin response.

METHODS

In a cross-over design, ten well-trained male endurance athletes completed two 8 × 3 min interval running sessions at 85 % of their maximal aerobic velocity on a motorized treadmill, before being randomly assigned to either a hypoxic (HYP: F IO2 ~0.1513) or a normoxic (NORM: F IO2 0.2093) 3 h recovery period. Venous blood was collected pre- and immediately post-exercise, and after 3 and 24 h of recovery. Blood was analyzed for interleukin-6, serum iron, ferritin, erythropoietin, and hepcidin.

RESULTS

Interleukin-6 was significantly elevated (p < 0.01) immediately post-exercise compared to baseline (NORM: 1.08 ± 0.061 to 3.12 ± 1.80) (HYP: 1.32 ± 0.86 to 2.99 ± 2.02), but was not different between conditions. Hepcidin levels were significantly elevated (p < 0.01) at 3 h post-exercise for both conditions when compared to baseline (NORM: 3.25 ± 1.23 to 7.40 ± 4.00) (HYP: 3.24 ± 1.94 to 5.42 ± 3.20), but were significantly lower (p < 0.05) in the HYP trial compared to NORM. No significant differences existed between HYP and NORM for erythropoietin, serum iron, or ferritin.

CONCLUSION

Simulated altitude exposure (~2,900 m) for 3 h following intense interval running attenuates the peak hepcidin levels recorded at 3 h post-exercise. Consequently, a hypoxic recovery after exercise may be useful for athletes with compromised iron status to potentially increase acute dietary iron absorption.

Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling

We determined the effects of varying daily carbohydrate intake by providing or withholding carbohydrate during daily training on endurance performance, whole body rates of substrate oxidation, and selected mitochondrial enzymes. Sixteen endurance-trained cyclists or triathletes were pair matched and randomly allocated to either a high-carbohydrate group (High group; n = 8) or an energy-matched low-carbohydrate group (Low group; n = 8) for 28 days. Immediately before study commencement and during the final 5 days, subjects undertook a 5-day test block in which they completed an exercise trial consisting of a 100 min of steady-state cycling (100SS) followed by a 7-kJ/kg time trial on two occasions separated by 72 h. In a counterbalanced design, subjects consumed either water (water trial) or a 10% glucose solution (glucose trial) throughout the exercise trial. A muscle biopsy was taken from the vastus lateralis muscle on day 1 of the first test block, and rates of substrate oxidation were determined throughout 100SS. Training induced a marked increase in maximal citrate synthase activity after the intervention in the High group (27 vs. 34 micromol x g(-1) x min(-1), P < 0.001). Tracer-derived estimates of exogenous glucose oxidation during 100SS in the glucose trial increased from 54.6 to 63.6 g (P < 0.01) in the High group with no change in the Low group. Cycling performance improved by approximately 6% after training. We conclude that altering total daily carbohydrate intake by providing or withholding carbohydrate during daily training in trained athletes results in differences in selected metabolic adaptations to exercise, including the oxidation of exogenous carbohydrate. However, these metabolic changes do not alter the training-induced magnitude of increase in exercise performance.

Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling

We determined the effects of varying daily carbohydrate intake by providing or withholding carbohydrate during daily training on endurance performance, whole body rates of substrate oxidation, and selected mitochondrial enzymes. Sixteen endurance-trained cyclists or triathletes were pair matched and randomly allocated to either a high-carbohydrate group (High group; n = 8) or an energy-matched low-carbohydrate group (Low group; n = 8) for 28 days. Immediately before study commencement and during the final 5 days, subjects undertook a 5-day test block in which they completed an exercise trial consisting of a 100 min of steady-state cycling (100SS) followed by a 7-kJ/kg time trial on two occasions separated by 72 h. In a counterbalanced design, subjects consumed either water (water trial) or a 10% glucose solution (glucose trial) throughout the exercise trial. A muscle biopsy was taken from the vastus lateralis muscle on day 1 of the first test block, and rates of substrate oxidation were determined throughout 100SS. Training induced a marked increase in maximal citrate synthase activity after the intervention in the High group (27 vs. 34 micromol x g(-1) x min(-1), P < 0.001). Tracer-derived estimates of exogenous glucose oxidation during 100SS in the glucose trial increased from 54.6 to 63.6 g (P < 0.01) in the High group with no change in the Low group. Cycling performance improved by approximately 6% after training. We conclude that altering total daily carbohydrate intake by providing or withholding carbohydrate during daily training in trained athletes results in differences in selected metabolic adaptations to exercise, including the oxidation of exogenous carbohydrate. However, these metabolic changes do not alter the training-induced magnitude of increase in exercise performance.

Influence of chronic dietary carbohydrate supplementation on plasma cytokine responses to exercise

This study examined the influence of 28 days of dietary carbohydrate (CHO) supplementation on plasma cytokine responses to cycle ergometry. Sixteen highly trained male cyclists and triathletes (age: 30.6+/-5.6 y; VO2max: 64.8+/-4.7 mL x kg(-1) x min(-1); mean+/-SD) participated in the study. One group (n=8) consumed a higher-CHO (8.5+/-1.7 g x kg(-1) body mass.day (-1)) diet for 28 days; a second group (n=8) consumed a moderate-CHO diet (5.3+/-0.4 g x kg (-1) x day (-1)). Total daily energy intakes were similar between the two groups. Cytokine responses to cycle ergometry were assessed prior to and again following the dietary intervention period. The cycle ergometry protocol involved 100 min steady state cycling at 70% VO2max followed by a time trial of approximately 30 min. Athletes were provided with 15 mL x kg (-1) x h (-1) of water during each trial. Blood samples were collected pre-, immediately post- and 1 h post-exercise for determination of plasma glucose and pro-inflammatory (IL-6, IL-8) and anti-inflammatory (IL-10, IL-1ra) cytokine concentrations. Cytokine responses to cycle ergometry were not substantially altered following the 28-day higher-CHO diet. In contrast, following the 28-day moderate-CHO diet, there were approximately 30-50% reductions (p=0.08-0.11) in anti-inflammatory cytokine responses post-exercise. These findings suggest that increased dietary CHO content alone does not effectively attenuate the pro-inflammatory cytokine response to exercise, however, there may be a small reduction in the anti-inflammatory cytokine response.

Influence of chronic dietary carbohydrate supplementation on plasma cytokine responses to exercise

This study examined the influence of 28 days of dietary carbohydrate (CHO) supplementation on plasma cytokine responses to cycle ergometry. Sixteen highly trained male cyclists and triathletes (age: 30.6+/-5.6 y; VO2max: 64.8+/-4.7 mL x kg(-1) x min(-1); mean+/-SD) participated in the study. One group (n=8) consumed a higher-CHO (8.5+/-1.7 g x kg(-1) body mass.day (-1)) diet for 28 days; a second group (n=8) consumed a moderate-CHO diet (5.3+/-0.4 g x kg (-1) x day (-1)). Total daily energy intakes were similar between the two groups. Cytokine responses to cycle ergometry were assessed prior to and again following the dietary intervention period. The cycle ergometry protocol involved 100 min steady state cycling at 70% VO2max followed by a time trial of approximately 30 min. Athletes were provided with 15 mL x kg (-1) x h (-1) of water during each trial. Blood samples were collected pre-, immediately post- and 1 h post-exercise for determination of plasma glucose and pro-inflammatory (IL-6, IL-8) and anti-inflammatory (IL-10, IL-1ra) cytokine concentrations. Cytokine responses to cycle ergometry were not substantially altered following the 28-day higher-CHO diet. In contrast, following the 28-day moderate-CHO diet, there were approximately 30-50% reductions (p=0.08-0.11) in anti-inflammatory cytokine responses post-exercise. These findings suggest that increased dietary CHO content alone does not effectively attenuate the pro-inflammatory cytokine response to exercise, however, there may be a small reduction in the anti-inflammatory cytokine response.

Pre-exercise carbohydrate status influences carbohydrate-mediated attenuation of post-exercise cytokine responses

Most studies investigating the effects of acute carbohydrate (CHO) ingestion on post-exercise cytokine responses have involved fasted athletes. This study characterised the effects of acute CHO beverage ingestion preceded by consumption of a CHO-containing pre-exercise meal. Sixteen highly-trained male cyclists/triathletes (age: 30.6 +/- 5.6 y; V O (2max): 64.8 +/- 4.7 ml . kg . min (-1) [mean +/- SD]) undertook two cycle ergometry trials involving randomised consumption of a 10 % CHO beverage (15 mL . kg (-1) . hr (-1)) or water (H (2)O). Trials were undertaken 2 h after a breakfast providing 2.1 g CHO . kg (-1) body mass (BM) (48 kJ . kg (-1) BM) and consisted of 100 min steady state cycle ergometry at 70 % V O (2max) followed by a time trial of approximately 30 min duration. Blood samples were collected pre-, post- and 1 h post-exercise for measurement of Interleukin (IL)-6, IL-8, IL-10 and IL-1ra. Time-trial performance was not substantially different between CHO and H (2)O trials (4.5 %, p = 0.42). Neither IL-6 nor IL-8 responses were substantially reduced in the CHO compared to the H (2)O trial. There was a substantial reduction in IL-10 (32 %, p = 0.05) and IL-1ra (43 %, p = 0.02) responses at 1 h post-exercise with CHO compared to H (2)O ingestion. In conclusion, the previously shown attenuating effects of CHO ingestion during exercise on cytokine responses appear reduced when athletes consume a CHO-containing pre-exercise meal.

Maximising performance in triathlon: applied physiological and nutritional aspects of elite and non-elite competitions

Triathlon is a sport consisting of sequential swimming, cycling and running. The main diversity within the sport of triathlon resides in the varying event distances, which creates specific technical, physiological and nutritional considerations for athlete and practitioner alike. The purpose of this article is to review physiological as well as nutritional aspects of triathlon and to make recommendations on ways to enhance performance. Aside from progressive conditioning and training, areas that have shown potential to improve triathlon performance include drafting when possible during both the swim and cycle phase, wearing a wetsuit, and selecting a lower cadence (60-80 rpm) in the final stages of the cycle phase. Adoption of a more even racing pace during cycling may optimise cycling performance and induce a "metabolic reserve" necessary for elevated running performance in longer distance triathlon events. In contrast, drafting in swimming and cycling may result a better tactical approach to increase overall performance in elite Olympic distance triathlons. Daily energy intake should be modified to reflect daily training demands to assist triathletes in achieving body weight and body composition targets. Carbohydrate loading strategies and within exercise carbohydrate intake should reflect the specific requirements of the triathlon event contested. Development of an individualised fluid plan based on previous fluid balance observations may assist to avoid both dehydration and hyponatremia during prolonged triathlon racing.

Variability in estimation of self-reported dietary intake data from elite athletes resulting from coding by different sports dietitians

A routine activity for a sports dietitian is to estimate energy and nutrient intake from an athlete's self-reported food intake. Decisions made by the dietitian when coding a food record are a source of variability in the data. The aim of the present study was to determine the variability in estimation of the daily energy and key nutrient intakes of elite athletes, when experienced coders analyzed the same food record using the same database and software package. Seven-day food records from a dietary survey of athletes in the 1996 Australian Olympic team were randomly selected to provide 13 sets of records, each set representing the self-reported food intake of an endurance, team, weight restricted, and sprint/power athlete. Each set was coded by 3-5 members of Sports Dietitians Australia, making a total of 52 athletes, 53 dietitians, and 1456 athlete-days of data. We estimated within- and between- athlete and dietitian variances for each dietary nutrient using mixed modeling, and we combined the variances to express variability as a coefficient of variation (typical variation as a percent of the mean). Variability in the mean of 7-day estimates of a nutrient was 2- to 3-fold less than that of a single day. The variability contributed by the coder was less than the true athlete variability for a 1-day record but was of similar magnitude for a 7-day record. The most variable nutrients (e.g., vitamin C, vitamin A, cholesterol) had approximately 3-fold more variability than least variable nutrients (e.g., energy, carbohydrate, magnesium). These athlete and coder variabilities need to be taken into account in dietary assessment of athletes for counseling and research.

A short-term, high-fat diet up-regulates lipid metabolism and gene expression in human skeletal muscle

BACKGROUND

Dietary fatty acids may be important in regulating gene expression. However, little is known about the effect of changes in dietary fatty acids on gene regulation in human skeletal muscle.

OBJECTIVE

The objective was to determine the effect of altered dietary fat intake on the expression of genes encoding proteins necessary for fatty acid transport and beta-oxidation in skeletal muscle.

DESIGN

Fourteen well-trained male cyclists and triathletes with a mean (+/- SE) age of 26.9 +/- 1.7 y, weight of 73.7 +/- 1.7 kg, and peak oxygen uptake of 67.0 +/- 1.3 mL x kg(-1) x min(-1) consumed either a high-fat diet (HFat: > 65% of energy as lipids) or an isoenergetic high-carbohydrate diet (HCho: 70-75% of energy as carbohydrate) for 5 d in a crossover design. On day 1 (baseline) and again after 5 d of dietary intervention, resting muscle and blood samples were taken. Muscle samples were analyzed for gene expression [fatty acid translocase (FAT/CD36), plasma membrane fatty acid binding protein (FABPpm), carnitine palmitoyltransferase I (CPT I), beta-hydroxyacyl-CoA dehydrogenase (beta-HAD), and uncoupling protein 3 (UCP3)] and concentrations of the proteins FAT/CD36 and FABPpm.

RESULTS

The gene expression of FAT/CD36 and beta -HAD and the gene abundance of FAT/CD36 were greater after the HFat than after the HCho diet (P < 0.05). Messenger RNA expression of FABPpm, CPT I, and UCP-3 did not change significantly with either diet.

CONCLUSIONS

A rapid and marked capacity for changes in dietary fatty acid availability to modulate the expression of mRNA-encoding proteins is necessary for fatty acid transport and oxidative metabolism. This finding is evidence of nutrient-gene interactions in human skeletal muscle.

Effect of different protocols of caffeine intake on metabolism and endurance performance

Competitive athletes completed two studies of 2-h steady-state (SS) cycling at 70% peak O(2) uptake followed by 7 kJ/kg time trial (TT) with carbohydrate (CHO) intake before (2 g/kg) and during (6% CHO drink) exercise. In Study A, 12 subjects received either 6 mg/kg caffeine 1 h preexercise (Precaf), 6 x 1 mg/kg caffeine every 20 min throughout SS (Durcaf), 2 x 5 ml/kg Coca-Cola between 100 and 120 min SS and during TT (Coke), or placebo. Improvements in TT were as follows: Precaf, 3.4% (0.2-6.5%, 95% confidence interval); Durcaf, 3.1% (-0.1-6.5%); and Coke, 3.1% (-0.2-6.2%). In Study B, eight subjects received 3 x 5 ml/kg of different cola drinks during the last 40 min of SS and TT: decaffeinated, 6% CHO (control); caffeinated, 6% CHO; decaffeinated, 11% CHO; and caffeinated, 11% CHO (Coke). Coke enhanced TT by 3.3% (0.8-5.9%), with all trials showing 2.2% TT enhancement (0.5-3.8%; P < 0.05) due to caffeine. Overall, 1) 6 mg/kg caffeine enhanced TT performance independent of timing of intake and 2) replacing sports drink with Coca-Cola during the latter stages of exercise was equally effective in enhancing endurance performance, primarily due to low intake of caffeine (approximately 1.5 mg/kg).

Body mass changes and voluntary fluid intakes of elite level water polo players and swimmers

Calculated sweat rates (measured by body mass changes) and voluntary fluid intakes were monitored in elite level water polo players and swimmers during normal exercise sessions to determine fluid requirements to maintain fluid balance, and the degree of fluid replacement of these athletes. Data were collected from training and competition sessions for male water polo players (n = 23) and training sessions only for swimmers (n = 20 females; n = 21 males). The calculated average sweat rate and fluid intake rate during training sessions for male water polo players was 287 ml/h and 142 ml/h, respectively, with a rate of 786 ml/h and 380 ml/h during matches. During training sessions for male swimmers, the calculated average sweat rate and fluid intake rate per kilometre was 138 ml/km and 155 ml/km, respectively; and for female swimmers, 107 ml/km and 95 ml/km. There was a wide individual variation in fluid intake and sweat loss of both water polo players and swimmers. Dehydration experienced by athletes in this study was less than typically reported for "land-based" athletes. Errors inherent in the technique used in this study are acknowledged and may be significant in the calculation of reported sweat losses and levels of fluid balance in aquatic athletes.

Adaptations to short-term high-fat diet persist during exercise despite high carbohydrate availability

PURPOSE

Five days of a high-fat diet produce metabolic adaptations that increase the rate of fat oxidation during prolonged exercise. We investigated whether enhanced rates of fat oxidation during submaximal exercise after 5 d of a high-fat diet would persist in the face of increased carbohydrate (CHO) availability before and during exercise.

METHODS

Eight well-trained subjects consumed either a high-CHO (9.3 g x kg(-1) x d(-1) CHO, 1.1 g x kg(-1) x d(-1) fat; HCHO) or an isoenergetic high-fat diet (2.5 g x kg(-1) x d(-1) CHO, 4.3 g x kg(-1) x d(-1) fat; FAT-adapt) for 5 d followed by a high-CHO diet and rest on day 6. On day 7, performance testing (2 h steady-state (SS) cycling at 70% peak O(2) uptake [VO(2peak)] + time trial [TT]) of 7 kJ x kg(-1)) was undertaken after a CHO breakfast (CHO 2 g x kg(-1)) and intake of CHO during cycling (0.8 g x kg(-1) x h(-1)).

RESULTS

FAT-adapt reduced respiratory exchange ratio (RER) values before and during cycling at 70% VO(2peak); RER was restored by 1 d CHO and CHO intake during cycling (0.90 +/- 0.01, 0.80 +/- 0.01, 0.91 +/- 0.01, for days 1, 6, and 7, respectively). RER values were higher with HCHO (0.90 +/- 0.01, 0.88 +/- 0.01 (HCHO > FAT-adapt, P < 0.05), 0.95 +/- 0.01 (HCHO > FAT-adapt, P < 0.05)). On day 7, fat oxidation remained elevated (73 +/- 4 g vs 45 +/- 3 g, P < 0.05), whereas CHO oxidation was reduced (354 +/- 11 g vs 419 +/- 13 g, P < 0.05) throughout SS in FAT-adapt versus HCHO. TT performance was similar for both trials (25.53 +/- 0.67 min vs 25.45 +/- 0.96 min, NS).

CONCLUSION

Adaptations to a short-term high-fat diet persisted in the face of high CHO availability before and during exercise, but failed to confer a performance advantage during a TT lasting approximately 25 min undertaken after 2 h of submaximal cycling.

Guidelines for daily carbohydrate intake: do athletes achieve them?

Official dietary guidelines for athletes are unanimous in their recommendation of high carbohydrate (CHO) intakes in routine or training diets. These guidelines have been criticised on the basis of a lack of scientific support for superior training adaptations and performance, and the apparent failure of successful athletes to achieve such dietary practices. Part of the problem rests with the expression of CHO intake guidelines in terms of percentage of dietary energy. It is preferable to provide recommendations for routine CHO intake in grams (relative to the body mass of the athlete) and allow flexibility for the athlete to meet these targets within the context of their energy needs and other dietary goals. CHO intake ranges of 5 to 7 g/kg/day for general training needs and 7 to 10 g/kg/day for the increased needs of endurance athletes are suggested. The limitations of dietary survey techniques should be recognised when assessing the adequacy of the dietary practices of athletes. In particular, the errors caused by under-reporting or undereating during the period of the dietary survey must be taken into account. A review of the current dietary survey literature of athletes shows that a typical male athlete achieves CHO intake within the recommended range (on a g/kg basis). Individual athletes may need nutritional education or dietary counselling to fine-tune their eating habits to meet specific CHO intake targets. Female athletes, particularly endurance athletes, are less likely to achieve these CHO intake guidelines. This is due to chronic or periodic restriction of total energy intake in order to achieve or maintain low levels of body fat. With professional counselling, female athletes may be helped to find a balance between bodyweight control issues and fuel intake goals. Although we look to the top athletes as role models, it is understandable that many do not achieve optimal nutrition practices. The real or apparent failure of these athletes to achieve the daily CHO intakes recommended by sports nutritionists does not necessarily invalidate the benefits of meeting such guidelines. Further longitudinal studies of training adaptation and performance are needed to determine differences in the outcomes of high versus moderate CHO intakes. In the meantime, the recommendations of sports nutritionists are based on plentiful evidence that increased CHO availability enhances endurance and performance during single exercise sessions.

Effect of fat adaptation and carbohydrate restoration on metabolism and performance during prolonged cycling

For 5 days, eight well-trained cyclists consumed a random order of a high-carbohydrate (CHO) diet (9.6 g. kg(-1). day(-1) CHO, 0.7 g. kg(-1). day(-1) fat; HCHO) or an isoenergetic high-fat diet (2.4 g. kg(-1). day(-1) CHO, 4 g. kg(-1). day(-1) fat; Fat-adapt) while undertaking supervised training. On day 6, subjects ingested high CHO and rested before performance testing on day 7 [2 h cycling at 70% maximal O(2) consumption (SS) + 7 kJ/kg time trial (TT)]. With Fat-adapt, 5 days of high-fat diet reduced respiratory exchange ratio (RER) during cycling at 70% maximal O(2) consumption; this was partially restored by 1 day of high CHO [0.90 +/- 0.01 vs. 0.82 +/- 0.01 (P < 0.05) vs. 0.87 +/- 0.01 (P < 0.05), for day 1, day 6, and day 7, respectively]. Corresponding RER values on HCHO trial were [0. 91 +/- 0.01 vs. 0.88 +/- 0.01 (P < 0.05) vs. 0.93 +/- 0.01 (P < 0.05)]. During SS, estimated fat oxidation increased [94 +/- 6 vs. 61 +/- 5 g (P < 0.05)], whereas CHO oxidation decreased [271 +/- 16 vs. 342 +/- 14 g (P < 0.05)] for Fat-adapt compared with HCHO. Tracer-derived estimates of plasma glucose uptake revealed no differences between treatments, suggesting muscle glycogen sparing accounted for reduced CHO oxidation. Direct assessment of muscle glycogen utilization showed a similar order of sparing (260 +/- 26 vs. 360 +/- 43 mmol/kg dry wt; P = 0.06). TT performance was 30.73 +/- 1.12 vs. 34.17 +/- 2.48 min for Fat-adapt and HCHO (P = 0.21). These data show significant metabolic adaptations with a brief period of high-fat intake, which persist even after restoration of CHO availability. However, there was no evidence of a clear benefit of fat adaptation to cycling performance.

Safety of commercial air travel following myocardial infarction

BACKGROUND

Travelers occasionally suffer myocardial infarction (MI) while abroad. Existing guidelines recommend a 4- to 24-week convalescent period following MI before air travel should be permitted.

HYPOTHESIS

Air travel may be undertaken safely in the early post-MI period.

METHODS

The aeromedical transport records of two international medical assistance companies over a 3-yr period were reviewed. We identified 209 patients who suffered MI; 13 transported by private air ambulance were excluded. We reviewed the aeromedical transports of the remaining 196 adults carried on commercial aircraft between 3-53 d post-MI to investigate the safety of air travel in this group. Data were recorded regarding patient age; sex; location of MI; complications of MI; presence of medical escort; duration of flight(s); use of oxygen, medications, or cardiac monitoring during transport; and development of symptoms in flight.

RESULTS

Within 7 d of their acute MI 3 patients (2%) were transported; 87 (44%) between days 8-14 post-MI; 65 (33%) between days 15-21; 27 (14%) between days 22-28; and 14 (7%) more than 28 d post-MI. Some 187 patients (95%) were transported without incident; 9 (5%) patients experienced symptoms requiring evaluation by the escorting physician. Of the 9, 6 problems occurred in patients being transported less than 14 d post-MI. Symptoms resolved spontaneously or immediately after physician intervention in all but one case.

CONCLUSION

International aeromedical transport of patients may be safely accomplished 2-3 wk after an acute MI when an accompanying physician is present. Recommendations for delaying travel more than 4 wk after infarction are not supported by clinical experience and should be revised.

Body weight changes and voluntary fluid intakes during training and competition sessions in team sports

Fluid losses (measured by body weight changes) and voluntary fluid intakes were measured in elite basketball, netball, and soccer teams during typical summer and winter exercise sessions to determine fluid requirements and the degree of fluid replacement. Each subject was weighed in minimal clothing before and immediately after training, weights, and competition sessions; fluid intake, duration of exercise, temperature and humidity, and opportunity to drink were recorded. Sweat rates were greatest during competition sessions and significantly lower during weights sessions for all sports. Seasonal variation in dehydration (%DH) was not as great as may have been expected, particularly in sports played indoors. Factors influencing fluid replacement during exercise included provision of an individual water bottle, proximity to water bottles during sessions, encouragement to drink, rules of the game, duration and number of breaks or substitutions, and awareness of personal sweat rates. Guidelines for optimizing fluid intakes in these three sports are provided.

Delayed presentation of unstable cervical spine injury with minimal symptoms

Emergency physicians are less likely to suspect the presence of a severe or unstable cervical spine injury in patients who have been ambulatory since the traumatic episode. We present the case of a man with multiple cervical fractures and a 75% anterior subluxation of C6 and C7 who did not seek medical care for six weeks after falling from a height. Previous reports of delayed or occult cervical spine injuries are reviewed. Physicians must aggressively search for injuries whenever a history of neck pain is present or a strong mechanism of injury exists, even if the patient has been ambulatory for days or weeks following the injury.

Acute cholecystitis in the emergency department

Acute cholecystitis is a frequent consideration in patients presenting to the emergency department with the challenging complaint of upper abdominal pain. It is estimated that 20% of American adults have gallstones, and of these a large percentage (about one-third) will at some point develop acute cholecystitis. The epidemiology and associated risk factors of acute cholecystitis are briefly reviewed along with the pathogenesis and clinical presentation of the disease. Finally, an approach to the diagnosis in the emergency department and suggested management is discussed including a comparison of the strengths and weaknesses of ultrasonography and hepatobilary scintigraphy.