International journal of sport nutrition and exercise metabolism最新文献

Given the underrepresentation of women in sports and exercise science research, we sought to understand the experiences of female athletes currently involved in applied sports and exercise science research to inform future studies and potentially increase participation rates. Accordingly, we investigated the experiences of 89 female athletes (n = 48 cyclists/triathletes, n = 19 race walkers, n = 22 National Rugby League Indigenous Women's Academy players) who participated in four separate studies of sports performance with different methodological characteristics. Participants completed a questionnaire upon study completion that queried prior research participation, reasons for participating and experiences during the current study. Across all 89 athletes, 81% were first-time research participants, with the primary barriers cited as a perceived lack of opportunities or being unaware of opportunities (93%). Participants rated an interest in the research outcome as the most important aspect influencing their decision to participate (90 ± 14 [out of 100]), followed by the opportunities to receive personalized results (84 ± 20) and education (78 ± 27). Most participants (87%) stated that they would apply the study findings to their sports involvement, while the remaining 13% reported that they required support to understand the application of results. The majority (94%) of participants indicated a willingness to participate in future studies, while the research experience was rated positively at a mean 77 out of 100. Ultimately, our findings uncovered a perceived lack of opportunity as the primary barrier to female athlete research participation. As such, opportunities for women to participate in high-quality studies should be prioritized.

The aim was to verify the effects of 12 weeks of resistance training (RT) performed in the fasted state compared with the fed state on body composition and physical performance in young adults. Participants were randomly assigned into fasting RT group (Fast-RT, n = 15) and fed RT group (Fed-RT, n = 13). Both groups trained two weekly resistance exercise sessions after an overnight fast or between 1 and 2 hr after consumption of a carbohydrate-rich meal, associated with isocaloric nutritional guidance. Assessments of body composition (dual-energy X-ray absorption), quadriceps muscle thickness (ultrasonography), maximum dynamic strength (one repetition maximum test), and muscle power in bench press and knee-extension exercises were performed before and after 12 weeks of intervention. Both Fast-RT and Fed-RT groups showed increases (p time ≤ .01) in quadriceps muscle thickness (1.21 and 1.18 cm, respectively; p group = .371; p Group × Time = .871), maximum dynamic strength (bench press: 10.53 and 4.89 kg, respectively; p group = .251; p Group × Time = .268; knee extension: 28.53 and 29.31 kg, respectively; p group = .919; p Group × Time = .846), and muscle power (knee extension mean power 70% one repetition maximum: 59.28 and 46.21 W, respectively; p group = .833; p Group × Time = .616; knee extension maximal power 70% one repetition maximum: 100.65 and 54.76 W, respectively; p group = .812; p Group × Time = .409). Regardless of food consumption prior to the sessions (fasted state and fed state), RT performed twice weekly across 12 weeks was associated with improvements in muscle hypertrophy and neuromuscular performance in young adults.

The noninvasive and reliable saliva collection method for stress-related endocrine biomarkers analysis has become common in field- and laboratory-based research in the last 15 years. Current guidelines recommend interrupting water consumption 10 min before saliva sampling to avoid inaccurate, diluted concentrations of the biomarkers being examined. However, the impact of saliva dilution on salivary cortisol and testosterone levels has not been examined yet. This was a randomized, crossover experiment. Fourteen active healthy males completed three separate cycle-bout trials, where a set volume of water (250 ml) was consumed 10, 5, or 1 min before saliva sampling. Saliva was collected pre-, post-, and 30 min postexercise. No differences were observed in resting samples in any of the trials (p < .05). However, salivary cortisol increased from pre- to postexercise in the 10 (+52%, p = 0.022) and 5-min trial (+36%, p = .005) only. Salivary testosterone also increased in 10 (+34%, p = .005), 5 (+37%, p < .001), and 1-min trials (+24%, p < .035). This study proposes that consuming water up to 1 min before providing a saliva sample will not dilute the sample, allowing for an accurate determination of salivary cortisol and testosterone concentration levels. Practically, the 10-min fluid abstinence required before saliva sampling in the previous guidelines could be reduced to 1 min; however, if examining the response of salivary cortisol to an exercise trail, a fluid abstinence of 5 min may be more appropriate. This conclusion will allow for less restriction on researchers and participants alike.

This study tested the hypothesis that delaying consumption of a carbohydrate-rich breakfast by 2 hr would impair prolonged high-intensity intermittent exercise performance in the afternoon. Fifteen intermittent games players (mean ± SD: age: 24 ± 6 years; V˙O2peak: 46 ± 6 ml·kg-1·min-1) completed a randomized, single-blind, placebo-controlled crossover study with two trials (EARLY and DELAY) matched for dietary intake. In EARLY, participants consumed a high-carbohydrate (semisolid) breakfast shake (2 g/kg BM maltodextrin, 1 ml/kg BM orange squash, 0.15 g/kg BM xanthan gum, 0.067 g/kg BM artificial sweetener, and 6 ml/kg BM water) at 8 a.m., followed by a taste and texture matched, but energy depleted, placebo shake 2 hr later. In DELAY, the order of these shakes was reversed. Three hours following a high-carbohydrate lunch (888 ± 107 Kcal, 145 ± 28 g carbohydrate), participants completed a 90-min intermittent cycling test, consisting of two 40-min halves, with 10 min of rest in between. Each half involved 18 repeated 2-min blocks of steady-state cycling (100 s; 35% Wmax), followed by 15 s of unloaded pedaling and a 6-s all-out sprint. There were no differences in peak power (first half: mean difference [95% confidence interval]: 6.6 [-10.9, 24.1] W, d = 0.03 and second half: 8.5 [-6.5, 23.6] W, d = 0.04) or mean power (first half: mean difference: 6.4 [-10.7, 23.5] W, d = 0.03 and second half: mean difference: 7.3 [-6.5, 21.3] W, d = 0.04) during the sprints between the DELAY and EARLY conditions. In contrast with our hypothesis, these data provide no evidence that delaying consumption of a carbohydrate-rich breakfast by 2 hr impairs prolonged high-intensity intermittent exercise performance in the afternoon.

A better understanding of the practical and methodological challenges inherent in accurately tracking female hormonal status would enhance the clarity of research findings in exercise metabolism. The purpose of this study was to conduct an objective assessment of the quality of existing literature in this area and to provide a general overview of the practical conditions and issues encountered in studies investigating substrate metabolism during exercise in women, both in those using (HC+) or not using (HC-) hormonal contraceptives. Forty-four articles were identified through systematic reviews, meta-analyses, and searches on PubMed/MEDLINE. A quality assessment framework was developed and applied using a double-blind scoring approach. The loss/exclusion of data between baseline and final analyses per study was quantified, and the main challenges were highlighted. A higher mean global score was observed in studies conducted among HC+ women (81%) than those among HC- women (46%). Although the dropout rates were rarely mentioned in HC+ women articles, the mean rate of participant/data loss in HC- groups was 22.1%. The rate of HC- participant loss was positively correlated with the global score (r = .504, p = .02). High-quality research may be easier to achieve in studies involving HC+ women compared with those involving HC- women. Studies on HC- women seem to face more practical challenges, such as tracking the menstrual cycle and targeting specific (sub)phases of the menstrual cycle, along with technical and feasibility limitations. Thus, although the framework for designing such studies exists, the quality assessment of the available literature emphasizes its challenge in terms of research implementation.

Exercise perturbs various aspects of gastrointestinal integrity and function, which may lead to performance impeding gastrointestinal symptoms (GIS) and/or precipitate clinical issues warranting medical management. This study aimed to determine the impact of prebiotic supplementation on gastrointestinal integrity and functional status in response to exertional heat stress (EHS). Sixteen endurance athletes completed two trials of 3-hr running at 60% V˙O2max in 30 °C at baseline (T1) and following an 8-week supplementation period (T2), with 16 g/day prebiotic (PREBIOTIC) or matched placebo (PLACEBO). Blood samples were collected pre-EHS and post-EHS and in recovery for determination of stress response (cortisol), intestinal epithelial injury (intestinal fatty acid binding protein), bacterial endotoxemia (sCD14), and systemic inflammation (C-reactive protein). GIS and feeding tolerance variables were assessed throughout the EHS. Orocecal transit time was determined via a lactulose challenge given at 2.5 hr into EHS. Plasma cortisol (combined mean: +252 ng/ml), intestinal fatty acid binding protein (+800 pg/ml), and sCD14 (+487 ng/ml) concentrations increased in response to EHS in T1 (p ≤ .05), but not for C-reactive protein (+0.8 μg/ml; p > .05), in both PREBIOTIC and PLACEBO. PREBIOTIC supplementation resulted in a blunted intestinal fatty acid binding protein response on T2 (+316 pg/ml) compared with an increase (+1,001 ng/ml) in PLACEBO (p = .005). Lower sCD14 was observed at T2 (2,799 ng/ml) versus T1 (3,246 ng/ml) in PREBIOTIC only (p = .039). No intervention effects were observed for C-reactive protein. No difference within or between PREBIOTIC and PLACEBO at T1 and T2 was observed for orocecal transit time, GIS, and feeding tolerance. In conclusion, 8 weeks of prebiotic supplementation modestly attenuates EHS associated perturbations to intestinal integrity, but does not further impair gastrointestinal transit and/or exacerbate EHS associated GIS or feeding tolerance.

Athletes often experience poor sleep quality and quantity which may hinder physical performance and cognitive function. Presleep nutritional strategies may be an alternative to pharmacological interventions to improve sleep. The aim of this study was to examine the effect of two different doses of a nutritional intervention (both containing high Glycemic Index carbohydrate, whey, tryptophan, theanine, and 5'AMP) versus placebo on objective and subjective sleep, next-morning physical performance, cognitive function, and postural sway. Seventeen healthy, trained adult males completed three double-blind trials in a randomized, counterbalanced, crossover design. Participants were allocated to conditions using a Latin Square design. A (a) low-dose, (b) high-dose, or (c) placebo drink was provided 90 min before sleep each night. Polysomnography was used to measure objective sleep parameters. Cognitive function, postural sway, and subjective sleep quality were assessed 30 min after waking. Physical performance was assessed using a 10-min maximal effort cycling time trial each morning. All data were analyzed using linear mixed effects models and effect sizes were calculated using Cohen's d. This study was registered prospectively as a clinical trial with Australian New Zealand Clinical Trials Registry (registration number: NCT05032729). No significant main effects or improvements were observed in objective or subjective sleep parameters, physical performance, cognitive function, or postural sway. The low-dose intervention appeared to reduce N3 sleep duration compared with placebo (-13.6 min). The high-dose intervention appeared to increase N1 sleep duration compared with placebo (+7.4 min). However, the magnitude of changes observed were not likely to cause meaningful reductions in sleep quality and quantity.

This study aimed to assess the effects of caffeine ingestion incorporated into an ice slushy on cycling time-trial (CTT) performance in hot, humid conditions. Nine moderately trained recreational male cyclists or triathletes ingested 6.8 g/kg crushed ice with either 6% carbohydrate concentration only (CON) or 6% carbohydrate concentration and 3 mg/kg caffeine (CAF) consumed over a 30 min period prior to exercise in a single-blind, counterbalanced design. Postingestion, participants completed a CTT equating 1,200 kJ of work (∼40 km) in a climate-controlled chamber (33 °C and 60% relative humidity). Experimental sessions were separated by 7 days. During each CTT, rectal temperature, cycling time, heart rate, blood lactate, and ratings of perceived exertion and thermal sensation were measured at set intervals of work. The 1,200 kJ CTT was completed faster in CAF (4,716 ± 785 s) compared with CON (4,911 ±755 s) (p < .05); and split times were completed faster in CAF compared with CON from the 800 to 1,200 kJ timepoints of the CTT. Precooling lowered rectal temperature similarly in both CAF (-0.6 ± 0.2 °C) and CON (-0.6 ± 0.1 °C) (p > .05). No differences were observed between CAF and CON for heart rate, rating of perceived exertion, rating of perceived thermal sensation, or blood lactate across the measured time points (p > .05). Precooling with the combination of a carbohydrate-based ice slushy and caffeine resulted in improved CTT performance in hot conditions compared with a carbohydrate-based ice slushy alone. Therefore, the addition of caffeine to ice slushies might be considered by endurance athletes competing in the heat for enhanced performance gains.

Gut-training has been shown to improve gastrointestinal tolerance, circulatory glucose availability, and exercise performance. The study aimed to investigate the effects of a repetitive feeding-challenge using fat versus carbohydrate (CHO) on markers of gastrointestinal function, glucose availability, and subsequent performance when challenged with a high-CHO load (87 g/hr) during exercise. Forty-four endurance athletes (mean ± SD [9 females and 35 males]: body mass: 71.2 ± 9.2 kg, height: 173.6 ± 7.0 cm, V˙O2max: 55.0 ± 6.1 ml·kg-1·min-1) completed a preintervention gut-challenge trial (T1), involving a 2 hr run (60% V˙O2max) while taking a CHO gel every 20 min (87 g/hr, 10% w/v), followed by a 1 hr self-paced distance test with ad libitum water. Participants were then randomized to a fat (fat feeding-challenge [FFC]; 20 g nut butter, 124 kcal, 11 g fat, 3 g protein, and 3 g CHO) or CHO supplement (CHO feeding-challenge [CFC]; 47 g CHO gel: 123 kcal, 29 g CHO) group to complete a 7-day repetitive feeding-challenge (1 hr exercise and supplement intake every 20 min with 290 ml water), followed by a gut-challenge retrial (T2). FFC did not differ from CFC in terms of resting orocecal transit time, feeding tolerance, or substrate oxidation during T1 and T2. Peak breath hydrogen was lower in FFC than CFC (p = .028) at T2. Total (FFC: 27%, p = .005 vs. CFC: 38%, p = .001) and upper gastrointestinal symptoms severity (FFC: 26%, p = .013 vs. CFC: 40%, p < .001) during exercise was reduced similarly between groups from T1 to T2. FFC covered more distance in T2 (11.51 ± 2.02 vs. 11.08 ± 2.02 km, p = .013), but not significantly different to CFC (p = .341). A repetitive feeding-challenge with fat does not enhance nor worsen gastrointestinal and fueling outcomes compared with a CHO repetitive feeding-challenge.